Cumulative impact studies in the Louisiana coastal zone: eutrophication, land loss final report to Louisiana State Planning Office

[From the U.S. Government Printing Office, www.gpo.gov]

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CUMULATIVE IMPACT STUDIES
IN THE LOUISIANA COASTAL ZONE
EUTROPHICATION
",".At,. Wo..
."i. I LAND LOSS
..of" tit. EDITED BY N. J.CRAIG & J.W. DAYJR.

FINAL REPORT TO
LOUISIANA STATE PLANNING OFFICE
Wt'. 30 JUNE 1977
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Cumulative Impact Studies

in the Louisiana Coastal Zone

0 Eutrophication

0 Land Loss

F N TOF COMMERCE NOAA
F F40 CES CENTER
J L 1)
"()uTH HOBSON AVENUE
TON , SC 29405-2413
Edited by N. J. Craig and J. W. Day Jr.

Contributors, N. J. Craig 9 J. W. Day Jr.
* P. Kemp e A. Seaton * W. G. Smith 9
P"0VertY Of CSC 4Lib0razy R. E. Turner

LOUISIANA STATE UNIVERSITY
CENTER FOR WETLAND RESOURCES
BATON ROUGE, LA 70803

Final Report to
Louisiana State Planning Office

30 June 1977

The preparation of this report was financed
sn part through a grant from the U.S. De-
partment of Commerce under the provisions
of the Coasta2Z Zone Management Act of 6Z972.

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Part 1 9 Eutrophication
I by N. J. Craig, J. W. Day Jr.,
A. Seaton, P. Kemp, W. G. Smith
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CONTENTS
Part I

List of figures Vii
List of tables Viii

Abstract ix

Introduction
Eutrophication 2
Definition and background 2
Differential effects in the coastal zone 3
Eutrophication and the nursery zone 3
Range of the nursery zone 4
Seasonal effects of eutrophication 6
Sources of eutrophication 6
Indices of eutrophication: phosphorus loading
and trophic state index to
Barataria Basin Z5
Description of area
Nursery grounds in Barataria
Sources of eutrophication 16
Salinity increase and phosphorous loading 16
Trophic state index 24

Lake Pontchartrain 35
Phosphorus loading for Lake Pontchartrain 35
Natural vs. Artificial P input 38
Phosphorus input--past, present, and future 40
Sources of nutrient enrichment 42
Conclusion 43

Terrebonne Basin 44
Description 44
Sources of eutrophication 45
Present estimates of phosphorus input 45
Water quality 49
Conclusion 49

Atchafalaya Basin 51
Description 5Z
Nutrient input and loading rate 52
Nutrient sources 54
Water quality 54
Conclusion 55

Calcasieu Basin 55
Nutrient analysis 55
Sources of Eutrophication 56
Phosphorus loading into Calcasieu Lake 56
Water quality 57
Conclusion 58

Management Guidelines 58
Basin Concept 59
Point and Nonpoint Sources 59
Overland Flow from Point Source Treatment 60
Nonpoint Source Techniques 61
Agricultural Management Suggestions 6,1
Management for Urban Runoff 54
Canals and Eutrophications 64
Determination of Trophic Status 65
Conclusions 66

References 67
Figures after page 74
Acknowledgments 15Y

LIST OF FIGURES

1. Barataria Basin's three areal divisions. 75
2. Estimated phosphorus loading rate (g/m2/yr) and salinity levels (ppt)
at various locations in Barataria 1898-1910. Conch range illustrates
southern limit of oyster production. 76
3. Phosphorus loading rate (g/m2/yr) and salinity levels (ppt) at various
locations in Barataria Basin, 1961-1974. Conch range illustrates
southern limit of oyster production. 77
4. Estimated phosphorus loading rate (g/m2/yr) and salinity levels Opt)
at various locations in Barataria Basin for year 2000.- Conch range
illustrates southern limit of oyster production. 78

5. The relationship between the areal water load (qs) and phosphorus
retention (Rp) in fifteen southern Ontario lakes. 79

6. Barataria Basin--Location of the 23 water quality stations. 80

7. Secchi depth (top) and phosphorus concentrations (bottom) at various
brackish and saline stations in the Barataria Basin. See text for
discussion. Solid squares and circles are clean water stations (group
2, Fig. 9). Open circles are intermediate (group 3a, Fig. 9). Open
squares and stars are eutrophic stations (group 3b, Fig. 9). 81

8. Schematic classification of brackish and saline stations in the Barataria
Basin according to water quality. 82

9. Graphic representation of the results of factor analysis and cluster
analysis. Dashed lines enclose cluster groupings. 83

10. Lake Pontchartrain Basin. 84

11. Population growth in Lake Pontchartrain drainage area. 85

12. Major freshwater and phosphorus sources of Lake Pontchartrain. 86

13. Terrebonne Basin: Area I & Area 11. 87

14. Current closure of oyster grounds in Terrebonne Basin. 88

15. Atchafalaya Basin. 89

16. Calcasieu Basin. 90

17. The variation in phosphate concentration at one station (Burton Landing)
on the Calcasieu River and the variation in total phosphorus concentration
at this and three additional stations along the river. Data is graphed
for the water years 1970-1975. It should be noted that total phosphorus
is measured on a phosphorus basis, whereas the phosphate concentration is
graphed on a phosphate basis. There appear to be relatively high values
of P during late summer, perhaps largely due to the low river flow rates
at that time (Johnston 1977). 9z

Vii

18. Yield of sugar cane (lbs/acre) compared to amount of total nitrogen
and phosphorus added (lbs/acre). 92
19. Uptake rates over time for nitrogen and P205 in sugar cane.

LIST OF TABLES

1. Critical concentrations and critical loading rates for nitrogen
and phosphorus. 11

2. Permissible loading levels2for total nitrogen and total phosphorus
(biochemically active) g/m /yr (Vollenweider 1968).

3. Amount of phosphorus discharged from present municipal sewage locations
in Barataria Basin. 20

4. Hajor freshwater sources of Lake Pontchartrain. 36

5. P-concentrations in freshwater sources input to Lake Pontchartrain. 37

6. Phosphorus loading in freshwater sources input to Lake Pontchartrain. 37

7. Total phosphorus input under predevelopment conditons. 39

8. Artificial P input from sources into Lake Pontchartrain. 39

9. Per capita artificial P-input. 40

10. Phosphorus loading into Lake Pontchartrain over time. 41

11. Artificial nutrient sources for Lake Pontchartrain. 42

Viii

ABSTRACT

Eutrophication is a widespread problem throughout the coastal zone

of Louisiana. It leads to poor water quality, development of nuisance

algal blooms, decline in desirable commercial and sports fishery species,

and diminished recreational usefulness of water bodies. The major cultural

sources of nutrients leading to eutrophication are urban runoff, domestic

sewage, and agricultural runoff.

Basins across the coastal zone were examined for water quality. Lake

Pontchartrain Basin, Barataria Basin, Terrebonne Basin, Atchafalaya Basin,

and Calcasieu Basin all had serious problems of eutrophication.

Eutrophication can be controlled and is reversible. If direct introduction

of nutrient-laden water into aquatic bodies is eliminated, the water bodies

will eventually return to a less eutrophic state. The length of time for

this to take place depends on the duration and intensity of historical nutrient

input. Land treatment (overland flow) offers a viable means of treatment of

nutrient wastes.

The understanding and solution of the problem of eutrophication in the

coastal zone must be considered within the context of the hydrologic unit.

The whole drainage basin or watershed must be considered the fundamental unit

of study.

We have outlined a methodology (trophic state analysis) which we believe

can be used to classify water bodies in the coastal zone according to trophic

status.

INTRODUCTION

The coastal zone of Louisiana contains approximately 7.5 million

acres of wetland and water bodies. The wetlands include fresh swamp,

and fresh,, brackish, and saline marshes. These wetlands are inter-

spersed with numerous shallow lakes, bays, sounds, and ponds which are

extensively interconnected by rivers, bayous, passes, and canals. These

systems are unified by hydrology and their health depends on water

quality.

In many areas across the coastal zone, water quality is deteri-

orating to critical levels. Many of the lakes in the coastal zone are

eutrophic or rapidly approaching eutrophy. This is the*cumulative

result of numerous interacting factors, many of which are cultural.

Domestic wastes are becomming an increasing problem due to inadequate

treatment and population growth. Additionally, urban runoff is a

significant source of pollution from our cities. Concreted, impermeable

areas increase the surface runoff into storm sewers, allowing direct

introduction of the waste from our streets into receiving water bodies.

Agricultural runoff results in large quantities of nutrients from

sediment erosion, fertilizers, and animal manure entering lakes via

drainage canals. Wastes from industrial sites are also sources of high

nutrient input. Natural sources of nutrients are precipitation, water-

fowl waste, detritus, and sediment recycling.

The objectives of this paper are:

1) To develop quantitative indices for measuring eutrophication

based on data from the Barataria Basin. These indices include

a trophic state index, phosphorus loading rates, and bio-

logical indicators of eutrophication.

2) To apply these indices to other areas of the coast in order to

determine the trophic status in the coastal zone.

3) To indicate areas where data is insufficient to determine

trophic conditions.

4) To suggest management guidelines which could have significant

ameloriative impact.

EUTROPHICATION

Definition and Background

Eutropbication can be defined as the natural or artificial addition

of nutrients to water bodies and the effects of these added nutrients

(Rohlich 1969). Although eutrophication is a natural process, it has

been accelerated in many cases by the activities of people. It often

results in undesirable changes in water quality, causing destabilization

of natural cDmmunities, with the advent of algal blooms leading to the

development of obnoxious species, and, eventually, to anoxic conditions.

The classic terms 'oligotrophic,' 'mesotrophic,' and 'eutrophic'

are used in reference to the trophic status of lakes. The typical

oligotrophic lake is clear, deep, and nutrient deficient, while a

eutrophic lake is shallow, nutrient-rich, with frequent algal blooms.

In Louisiana,, however, the spectrum of trophic states ranges from meso-

trophic to hypereutrophic because the coastal wetland systems are

naturally shallow and evolved with high nutrient loading. There seem

to be no natural oligotrophic water bodies in the Louisiana coastal

zone.

Bayous and streams in the coastal zone follow.the same trophic

stages as lakes because of similar characteristics. Most streams are

shallow and sluggish and have biological and chemical characteristics

comparable as lakes. Only certain physical factors such as wave-

induced turbulence are significantly different. The effects of pro-

longed eutrophication result in similar changes in community structure,

such as anerobic benthic communities, blue-green phytoplankton, and

pollution tolerant fish species.

Differential Effects in Coastal Zone

Eutrophication can occur from fresh to marine conditions; therefore,

all environmental units (swamp, and fresh, brackish.and saline marshes)

are susceptible. The effects of eutrophication are similar in all

areas, although the characteristic species recognized as biological

indicators may be different. Microcystis, Anabaena, Anabaenopsis, and

Spirulina are common eutrophic freshwater phytoplankton. Brackish and

saline forms tend to be small, such as Monodus, Nanochloris, and

Stichococcus.

In general, the upper basins (freshwater areas) tend to be more

susceptible to eutrophication. This is due to three factors. First,

flushing is less in the fresh areas than near the coast because there

is little or no tidal action in these areas. Second, the bulk of.

cultural enrichment occurs in fresh or slightly brackish areas. Finally,

the "nutrient trap" of brackish waters tends to lower nutrient levels

in the lower basin.

Eutrophication and the-Nursery Zone

It has been well documented that estuaries serve as nursery grounds

for most commercially important Gulf of Mexico crustaceans and fishes.

Examples of marine species using the estuaries as nursery grounds are

the croaker (Micropogon.undulatus), sand sea trout (Cynoscian arenarius),

sea catfish (Arius felis), menhaden (Brevoortia patronus , shrimp

(Penaeus sp.), striped mullet (Mugil cephalus), bay whiff (Citarichthyes

spilopterus), and the blue crab (Callinectes sapidus) (Day et al. 1973).

The nursery ground is generally defined as an area from the mesohaline

(5 ppt to 18 ppt) to lower portion of the polyhaline (18 ppt to 30 ppt),

where juvenile stages of various marine species spend the fast-growing

phase of their life. Recent work has shown that some freshwater areas

are important nursery zones (Hinchee, CWR, unpublished). Our use of the

term will be inclusive of those species, such as the oyster, which spend

their entire life in the nursery zone.

The effects of eutrophication on the nursery zone in other coastal

areas has been well documented (New York: Rhyther 1954; Galtsoff 1956;

Barlow et al. 1963; Jeffries 1962, 1964; Dean and Haskin 1964; Chesapeake

Bay area: Brehmer 1964, 1967; Massman et al. 1962; Fournier 1966;

Sharpiro and Riberie 1965. North Carolina: Odum and Chestnut 1970;

Kuenzler and Chestnut 1971. Fjords: Braarud 1945. Biscayne Bay: Lynn

and Yang 1960; McNulty et al. 1960; McNulty 1961. Louisiana: Craig and

Day 1976. The West Coast: Welch 1968; Gibbs and Isaac 1968; Riesh 1960;

Hume et al. 1962).

Range of th@ Nursery Zone

The exact extent of the nursery zone in Louisiana has not been

delineated. Although a large proportion of commercial fishes and

crustaceans are known to be estuarine dependent, their use of the

Louisiana marsh-estuarine system as nursery grounds has been rarely

quantitatively documented.

Two major studies of the use of Louisiana marsh areas (as opposed

to open bays and lakes) as nursery grounds were of brackish marshes on

Marsh Island (Herke 1971) and intermediate marshes bordering Lake

Pontchartrain in St. Charles Parish (Hinchee, unpublished). Although

some marine nektonic species are known to migrate throughout the entire

coastal area, including fresh marsh and swamp-forest zones, there is

presumed to be a rapid decline in use of wetland areas by marine larval

and juvenile forms as salinity drops below brackish levels. The

distribution of many nursery ground species is apparently strongly

influenced by their minimum salinity tolerance, and this tolerance often

decreases as the fish grow (i.e., juvenile fish can tolerate lower

salinities; Herke 1971).

It has been long assumed that larval brown shrimp, Penaeus aztecus,

require relatively high salinities (10-15 ppt; see St. Amant et al. 1965).

There is now some evidence, however, that in Louisiana juvenile brown

shrimp as well as juveniles of other important species actually migrate

into low-salinity waters for much of their development (Herke 1971,

Wagner 1973, Crowe 1973, Hinchee unpublished). In Galveston Bay, Tex.,

Parker (1970) found brown shrimp abundant from salinities of 0.9 to

30.8 ppt, with shrimp being very abundant at salinities lower than 5 ppt.

Work in upper Trinity Bay marshes (Baldauf et al. 1970) showed these

areas to be important nursery grounds. An ecological study of the

Calcasieu lobe and river in southwestern Louisiana is presently being

carried out by W. Stickle of the LSU Zoology Department. Preliminary

results show that juvenile forms are abundant in low-salinity waters.

The nursery areas of white shrimp, Penaeus setiferus, are unknown and

could also be low-salinity areas (Herke 1971).

Seasonal Effects of Eutrophication

Normally algal blooms and oxygen problems associated with eutro-

phication will occur in the warmer months of the year. In Lac des

Allemands there are extensive blue-green algae blooms consisting mainly

of.Microcystis, Anabaena, Anabaenopsis, and Spirulina from April into

October (Day et al. 1977). A study of Great South Bay/Moriches Bay

complex in New York shows heavy growths of algae develop in early spring

and persist through the summer and fall with the months from May to

September having optimal temperature range for the bloom algae,

Nanochloris and Stichococcus (Rhyther 1954).

Other studies have shown algal blooms occurring during winter

months. In North Carolina, intense Monodus blooms occurred from November

through April in brackish ponds fertilized with secondary SE@wage wastes.

The warm inonths of May through September were nonbloom pericds

(Kuenzler and Chestnut 1971). The size, density, and ecology were

similar to the forms found in Great South Bay.

The effects of prolonged eutrophication are permanent, regardless

of time of seasonal blooms, because they lead to similar changes in community

structure (such as blue-green phyroplankton, anaerobic bentbic commu-

nities, and pollution-tolerant fish species).

Sources of Eutrophication

The primary nutrient sources of eutrophication in the coastal zone

are municipal. sewage, industrial wastes, urban runoff, drainage from

agricultural land, and natural sources (detrital, waterfowl -waste, pre-

cipitation, sediment recycling). Uttormark et al. (1974) notes when

considering the flow of nutrients, in a strict sense, there -are no

sources or sinks, rather, a multitude of cyclic pathways along which

nutrients are transported. Sources are points along tbese.-nutrient

pathways.

The sources mentioned above fall into roughly two categories:

point and diffuse (nonpoint) sources. A point source is a location at

which nutrients are released in quantity and concentration compatible

with practical means of nutrient removal. A diffuse source is an area

from which nutrients are exported in a manner not-compatible with

practical means of nutrient removal. These are important concepts for

management purposes (Uttormark et al. 1974). Municipal sewage effluent

and industrial wastes are point sources, while urban-storm and agri-

cultural runoff are diffuse sources. The specific contributors of

nutrients in municipal sewage are mainly human waste and detergents, and in

agricultural runoff, chemical fertilizers, animal excretion, and erosion

of topsoil.

Domestic Waste

Domestic wastes, stemming from point sources, could conceivably be

controlled by proper waste treatment. Inadequate treatment is an

increasing problem in the coastal zone as urban centers grow. In many

urban areas (Houma, Jefferson parish, N.O.) numerous sewage

bypasses periodically dump raw sewage into lakes and waterways. Even if

secondary treatment (removal of BOD) were completely implemented,

effluents from secondary treatment plants would still lead to eutro-

phication because of high inorganic N and P level. It is unlikely that

tertiary treatment plants (for removal of inorganic nutrients) will ever

be built because of high costs (see Meo et al. 1975).

Urban Runoff

Urban runoff is rich in nutrients from lawn fertilizers, animal

excretion, leaves, and sediment erosion. All of the filth from our

streets--residue from gasoline stations, exhaust fumes settling from

cars, litter--drain into storm sewer system allowing direct introduction

into receiving streams and canals. (Urban runoff is also high in

toxins and heavy metals.) Concreted, impermeable areas increase the

amount of surface runoff. Thompson (1970), in a-study of land drainage

in metropolitan Detroit, indicated that erosion from areas under develop-

ment contributed 155 metric tons of sediment per hectare per year

compared with an overall average erosion rate of approxCmately 7 metric

tons per hectare per year for the metropolitan area. Surburban resi-

dential development, where land is stripped for subdividing, and road

construction can account for significantly large amounts of sediment

even if tOtELl acreage under construction is low (Uttormark et al. 1974).

Agricultural. Runoff

Agricultural runoff is a major contributor to the nutrient enrich-

ment of water bodies in the coastal zone. The amount of nutrients in

runoff and the quantity of runoff itself depends on type of farming,

soil retention capacity, and fertilizer practices. A signi:Eicant part

of fertilizers applied to crops reaches natural waters (Holt et al.

1970, Kunishi et al. 1972, and Gilliam and Terry 1973). According to

Gilliam and'Terry (1973), the.,portion of fertilizer recovered in yield

is roughly 50 percent. The main nutrient inputs from agricultural

runoff in Louisiana seem to be nitrogen from sugarcane and phosphorus

from sugarcane and rice. For sugarcane grown on Recent alluvial soils

in Louisiana, only 38 percent of the nitrogen and 59 percent of the

phosphorus is recovered in the yield (Hinchee unpublished).

C. Hopkinson (CWR unpublished) determined amounts of phosphorus in

runoff due to sediment erosion and fertilizer excess for crops in the

coastal zone. The amount of phosphorus lost due to sediment erosion is

4.3 lb P/acre (average for all crops). The input of P due to fertilizer

excess is 10 lb P/acre for sugarcane, 145 lb P/acre for vegetables and

orchards, 54 lb P/acre for corn, and 12 lb P/acre-for rice.

Industrial Waste

Industrial wastes are point sources of high nutrient input.

Wastes from industry often have the added deleterious effect of highly

toxic byproducts and heavy metals. Most industry in the coastal zone is

situated on the major rivers and bayous for transportation purposes and

also because of large water requirement in these industries. Industries

often have insufficient wastewater treatment and generally treatment is

not updated as expansion occurs (Burk and Associates, Inc. 1973; Page

et al. 1976; and Frileux 1971).

Natural Factors

The natural factors affecting nutrient enrichment of water bodies

are the hydrology of the particular basin, (i.e., turnover time of

lake), size of drainage basin, type of soil in basin, type of bottom

sediments, geochemistry of basin, and climate (i.e., precipitation and

thermal structure) (Brezonik 1969).

Natural sources of nutrients are waterfowl waste, detritus, lichens,

sediment recycling. Precipitation introduces nutrients into the system

but the source of the nutrients in the rain may be cultural. Precipita-

tion is often considered a transport vector rather than a source (Uttormark

et al. 1974).

Indices of Eutrophication: Phosphorus
Loading an Trophic State Index

Phosphorus Loading

Historically, indices for eutrophication have included such things

as pounds of BOD; change in community structure using key fish,

benthic, and plankton species;- diversity; productivity; nutrients; and

secchi depth. In current trophic studies of lakes, more attention is

given to the nutrients, phosphorus, and nitrogen, the widely recognized

limiting factors in lakes. As a general rule, increased nitrogen and

phosphorus will lead to increased plant production, i.e., algal blooms,

etc. Although no strict guidelines for nutrient input to in-lake con-

centrations are available, several rigorous studies have determined

tentative values for critical concentrations and loading rates for

nitrogen and phosphorus (See Tables I and 2).

TABLE 1. CRITICAL CONCENTRATIONS AND CRITICAL
LOADING RATES FOR NITROGEN AND PHOSPHORUS.

A. Reference: Rate LOADING
Permissible Dangerous
.(up -to) .(In excess of)
N P N P

Shannon & Brezonik Volumetric .86 .12 1.51 .22
(1971) (g/m3/yr)

Ib id Areal 2.0 .28 3.4 .49
(g/m2/yr)

Vollenweider (1968) Areal 1.0 .07 2.0 .13
for lakes <5m (g/m2/yr)

TABLE 2. PERMISSIBLE LOADING LEVELS FOR TOTAL NITROGEN
AND TOTAL PHOSPHORUS (BIOCHEMICALLY ACTIVE)
g/m2/yr (VOLLENWEIDER 1968).

LOADING
Mean Depth Up To Permissible Dangerous
(up to) (in'exces6 of)
N P N P

5m 1.0 0.07 2.0 0.13

lom 1.5 0.10 3.0 0.20

50m 4.0 0.25 8.0 0.50

loom 6.0 0.40 12.0 0.80

150m 7.5 0.50 15.0 1.00
200m 9.0 0.60 18.0 1.20

Phosphorus loading was selected as an appropriate measure of

nutrient enrichment for the following reasons:

1) In many aquatic systems, phosphorus availability has been

shown to be an important factor governing primary produc-

tivity, and thus potential eutrophication. While loading

is not an absolute measure of availability to plants, it is

directly related and provides a good estimate until a

detailed budget is available showing rates of export and

loss to the sediments.

2) Phosphorus, rather than nitrogen, has been used as a

III--racer" of artificial nutrient enrichment, because it has

a simpler chemical behavior and is better conserved in an

aquatic system. Nitrogen moves through four oxidation
states (NH4_@-N, NO3-N, NO 2-N, Org-N) and is subject to fixa-

tion by algae from the large atmospheric pool and to loss

through denitrification. Phosphorus has only two forms,
orthophosphate (P04 3-_P) and organic -P,and it is not

exchanged with the atmosphere.

While future research may show nitrogen rather than phosphorus to be

the limiting nutrient in some of the areas in this study, it can be

assumed that loading rates for each will be positively related. When

streams or canal waters are contaminated with domestic waste or

fertilizer runoff, they are generally rich in both phosphorus and

nitrogen. Thus, we are using P loading as an index of all the factors

which lead to eutrophication.

Trophic State Index

The measurement of the eutrophic conditions or the trophic state

of a water body has been a difficult concept to define quantitatively.

As previously mentioned, numerous techniques have been developed as

indices of eutrophication, such as species diversity, primary produc-

tivity, and plant nutrient levels. The concept of eutrophication,

however, is multidimensional and interdependent, begging a broader

approach than can be conceived when utilizing only-one or two components

of the system. Brezonik and Shannon (1971) developed a technique

for Florida freshwater lakes that quantifies the trophic state of the

water by combining seven indications of water quality into one term

or factor. Qualitative speculation can be tested with multivariate

analysis techniques in the form of a quantitative index of the trophic

state of water bodies. This trophic state index can be utilized in

predicting water quality levels through estimates of nitrogen and

phosphorus loadings.

Trophic state indices (TSI) have been developed for freshwater

lakes in Florida (Brezonik and Shannon 1971) and freshwater rivers

and lakes in North Carolina (Weiss and Kuenzler 1976). A similar index

has not been developed for an estuarine area. As fresh water enters

estuarine conditions, changes in the physical and chemical parameters

cause large amounts of nutrients to be deposited in sediments. Currents

plume and decrease in speed upon entering the estuary, causing the

nutrient-rich particulate matter to settle to the bottom (Hobbie 1976).

Clay particles which are in colloidal suspension in freshwater, clump when

entering brackish waters. These large particles and flakes sink,

carrying with them absorbed nutrients. In addition the back and forth

action of the tide allows more time for nutrients to be incorporated

into biological and chemical cycles. These processes collectively are

the common Inutrient trap' of estuaries. These unique processes require

a different selection and interpretation of parameters (variables) than

in fresh waiter to form an estuarine trophic state index.

Multivariate Analysis. The trophic index is developed by use of

the! multivariate technique, factor analysis (also-referred to as

Principle Component Analysis). A multidimensional phenomenon such as

eutrophication is difficult to invision. A simplification @procedure is

needed that will identify major patterns of eutrophication from a

multitude of' descriptive variables, such as nitrogen, phosphorus,

secchi depth, chlorophyll a. Once these variables have been

selected, data is collected from a variety of lakes, bayous, and canals.

The levels of variables differ

each area forms an axis and the combination of these axes describes a

multidimensional space. The response of all areas to a specific vari-

able is plotted as a single point. When each variable has been iden-

tified in this manner, the variables with similar response are clustered

together. In factor analysis, these clusters of variables are called

patterns or factors. The factor is composed of a weighted score or

factor loading for each variable designating its relative contribution

to the factor. These are then applied to each variable within an area

by multiplying its factor loading by each variable and adding to other

variables in that area. In this way, each area will be represented

by one score and can be interpreted as a relative index number for

eutrophication.

BARATARIA BASIN

The examination of eutrophication in the Barataria Basin was

approached by two methods. The first approach was to estimate phos-

phorus loading of various waterbodies within the basin. The cumu-

lative impact of eutrophication and salinity intrusion on the nursery

grounds of the basin were assessed. The second was a more thorough

approach leading to the development of a trophic state index. Both

studies compliment and substantiate each other.

Description of Area

The Barataria Basin is an interdistributary bay-wetland system

bordered by Bayou Lafourche, the Mississippi River, and the Gulf of

Mexico. The coastal wetlands of the basin, extending from the fresh

swamp of the upper basin to the saline marsh bordering the coast,

serve as water storage reservoirs, nursery areas, chemical trans-

formation factories, and sources of organic matter and nutrients.

Barataria Basin is responsible for about 45 percent of Louisiana's

total commercial fishery harvest, including menhaden, trout, croaker,

crab, shrimp, oyster, catfish, and crawfish (Lindall et al. 1972).

For 1974, this was approximately $39.6 million dockside value (U.S.

Nat. Mar. Fish. Serv. 1975).

Nursery Grounds in Barataria

The nursery grounds in Barataria extend from the upper estuarine

areas such as Lake Salvador and Lake Cataouatche to Barataria-Caminada
Z5

Bay area. For the oyster (Crassostrea virginica Gmelin), the upper

reaches of Barataria Bay/Little Lake complex have become more and more

dependable as culture grounds (Van Sickle et al. 1976). Juvenile blue

crabs (Callinectes sapidus) spend part of their life cycle in upper

estuarine areas such as Lake Salvador (Jaworski 1972). The overlap of

the different nursery grounds of the various species gives the general

range of the nursery zone--A broad zone from Barataria Bay

Salvador will include the most important nurseries.

Sources of Eutrophication

The specific sources of eutrophication in the Barataria Basin are

sewage, urban runoff, drainage from agricultural land, and natural

sources. The upper basin is heavily loaded by agricultural. runoff from

sugarcane (.46%), soybeans (9%), fallow (crop failure and crop rotation,

35%), and other cr ops such as corn, vegetables, and wheat ('10%)

(Hopkinson unpublished). The urban runoff and municipal sewage from

westbank New Orleans and surrounding suburban areas input high nutrient

loads into Lake Cataouatche, Lake Salvador, and the intraccastal

waterway.

This encroachment of eutrophication from the upper basin

into brackish nursery grounds could seriously threaten the

commercial fisheries of the Barataria Basin.

Salinity Inrease and Phosphorus-Loading

Salinity Increase in Barataria

There ELre trends toward increased salinity in much of the coastal

zone of Louisiana (Lindall et al. 1972, Pollard 1973). These changes

reflect seVE@ral factors: (1) Leveeing of the Mississippi River

resulting in loss of freshwater input to the upper basins; (2) land

loss and inlet widening; and (3) specific projects such as the

Mississippi River Gulf Outlet and the Barataria Waterway.

Two ecological effects of the salinity changes in Barataria

Bay are changes in the position of vegetation zones and oyster

producing areas. The saline-brackish marsh and brackish-fresh marsh

boundaries are moving inland.

A historical examination of oyster leases shows a movement of the

prime producing areas into the upper estuaries. In 1910 oyster reefs

were located in the southern half of Barataria Bay, the northern half

having never produced oysters because of low salinity (Van Sickle et al.

1976). By 1947 the northern half of Barataria Bay was a reliable area

for natural spatfall (settlement of oyster larvae). By the 1950s,

the upper bay leases had become the most valuable (Van Sickle et al.

1976). In the low rainfall years of the 1960s there was natural oyster

growth in Little Lake and by 1975 there were 4,000 acres of water

bottoms leased in Little Lake (Van Sickle et al. 1976). The optimum

salinity range for oysters is 5-15 ppt (Galtsoff 1964), so as salinity

increases, oysters naturally move inland. The seaward range of oyster

production is limited by predation by the conch (Thais haemestoma),

which cannot survive salinities below 10 to 15 ppt. Oyster fishermen

have noted conchs in upper bay areas more and more frequently in

previous years.

Salinity Data, 1898-1910. Van Sickle et al. (1976) note, "the

salinity for the area of Grand Terre usually lies within the poly-

haline, 18 to 30 ppt." For our purposes an average of this range was

taken to represent salinity at the southern end of Barataria Bay. The

salinity for St. Mary's Point, the northern end of the bay, was esti-

mated to boa approximately 6 ppt around 1898-1910 (Van Sickle et al.

1976). Little Lake was considered fresh around the turn of the century

because it harbored a continuous population of largemouth bass (Moore

and Pope 1910).

Salin-ty Data, 1961-1974. The salinity data for St. Mary's Point,

Grand Terre, and Lafitte were averaged over the years 1961-1974 from

annual averages of salinity for each year. Approximate salinity levels

for the three stations were Grand Terre, 20 ppt; St. Mary's Point,

13 ppt; and Lafitte, 3 ppt (Van Sickle et al. 1976).

Salinity Projection for Year 2000. The salinity for the year 2000

was based on the predicted increase of salinity of 0.009 ppt/month at

St.. Mary's 'Point (Van Sickle et al. 1976). This value was used for Lake

Salvador and Little Lake.

Phosphorus-Loading

. DescriDtion of Barataria Basin's Areal Divisions. For quantifi-

cation of phosphorus-loading, the Barataria Basin was divided into three

areas (See Fig. 1): the upper basin (Area 1) is bounded by the Mississippi

River, Bayou Lafourche, and Highway 90; Area 2 is bounded by Highway 90,

Bayou Lafourche, the Intracoastal Canal, and the Mississippi River

levee; Area 3, the lower basin, is bounded by the Intracoastal Waterway,

Bayou Lafourche, the Gulf, and the Mississippi River. The major water

bodies are Lac des Allemands (Area 1); Lake Salvador and Lake Cataouatche

(Area 2); Little Lake, Bay L'ours, Round Lake, Bayou Perot, Bayou

Rigolettes, Barataria Bay, and Caminada Bay (Area 3).

Present. Estimate of Phosphorus Input. Area 1: The current total
input of phosphorus into Lac des Allemands (Area 1) is 4.3 I:,/m2/yr

(Butler 1975). Area 2: The current phosphorus loading rate for Lake
Salvador is 0.97 g/m2/yr and 1.6 g/m2/yr for Lake Cataouatche. These

were obtained by summing estimated inputs of P from municipal sewage,

urban runoff, agriculture, and the upper basin. P input was calculated

from Table 3. The amount of phosphorus in urban runoff from the West

Bank of New Orleans entering Lake Cataouatche is 14 metric tons. This

was computed by multiplying the West Bank population of the New Orleans

area, 153,939 (U.S. Dept. of Commerce 1970) by the average

amount of P04= in storm water runoff produced per person per year on the

East Bank (90 g/yr; Stern and Stern 1969). P input from the upper basin

(Area 1) is 154 metric tons. Agricultural input of P into Area 2 was

estimated to be 43 metric tons/yr. We assumed that the ratio of P input

to area of agricultural land in the upper basin (281 metric tons/187
mi2' Butler 1975) held for Area 2. The P input of the upper basin

includes P exported as detritus from wetland, as well as from agri-

culture, therefore our estimate for Area 2 would include both sources.

We believe that agriculture represents the primary source in Area 1

(Day, CWR, unpublished). Agricultural land area in the basin was

digitized with a Calmagraphic 11 digitizing system from USGS 1:250,000

scale map. Revisions of the USGS 1:250,000 scale maps from NASA high

altitude color infrared photographs were used to update areas of

agricultural land.

Total P input to Area 2 for Lake Salvador and Lake Cataouatche was

computed as fol:

Lake Salvador Lake Cataouatche

upper basin 154 metric tons urban runoff 14 metric tons
sewage 0.3 metric tons sewage 33 metric tons
agriculture 21.5 metric tons agriculture 22 metric tons
175.8 metric tons 69 metric tons

TABLE 3. AMOUNT OF PHOSPHORUS DISCHARGED FROM PRESENT
MUNICIPAL SEWAGE LOCATIONS IN BARATARIA BASIN.

Pg/yr (106 P lbs/yr

Lafourche 0.05 .000.11
Marrero 17.90 .039
Bridge City 2.56 .006
Westwego 7.67 .014
Donaldsonville 5.11 .011
Avondale Homes 2.56 .006
Harvey 3.68 .008
Terrytown #1 4.55 .010
Terrytown #2 50.30 .1107
Southwood West and
Timberlane Subdivision 0.31 .00068
Live Oak Manor 0.41 .000902
Florahzae Subdivision 0.20 .00044
Floral Acres Subdivision 0.26 .000572
Ascension Sewer District 0.38 .0001336
St. James Sewer District 0.38 .000836
St. James Sewer District 1.38 .000836
Lakewood West Subdivision 1.23 .0024706
Grand Isle 1.73 .0038
Lafourche Sewer District #2 0.28 .00062
Golden Meadow 2.07 .004-5
Larose .21 .00046

The average discharge of untreated, primary or secondarily
treated sewage from present municipal sewage discharge loca-
tions I-or Barataria Bay Basin (Burk and Assoc., Inc. 1.973)
was multiplied by an average of the typical range of phos-
phat:e concentrations in domestic untreated, primary and
secondary sewage (Echelberger et al. 1969).

TYpical ranges of phosphate concentrations in
various hydrological lake inputs

inplIt Source Orthophosphate_(mg/l as P)

Domestic Wastewater

1. Untreated 1.0 10.0
2. Primary 0.5 9.0
3. Secondary 0.1 7.5
4. Tertiary 0.03- 0.30

The areas for Lake Salvador and Lake Cataouatche, 182 x 106M2 and
43 x 106 , respectively, were digitized. The total area of the water

bodies was divided into the total phosphorus input to give a P
loading of 97 g/m2/yr for Lake Salvador and 1.6 g/m2/yr for Lake

Cataouatche.

Phosphorus Input for Years 1898-1910. For the years 1898-1910,

the phosphorus loading was assumed to be below eutrophic conditions,
i.e., less than 0.4 g/m2/yr (Vollenweider 1968, Brezonik and Shannon

1971; See Fig. 2).

Projected Phosphorus for Year 2000. The phosphorus-loading levels

for the year 2000 are based on projections for urban development in the

Barataria Basin. We assumed the ratio of the present amount of phos-

phorus entering Lake Salvador-Lake Cataouatche from the area of urban

development existing today would hold for future phosphorus levels in

relation to projected urban development areas. (The areas for both

time periods were digitized with a Calmagraphic 11 digitizing system

from a USGS 1:250,000 scale map.) We assumed close to maximum develop-

ment along the Mississippi River in Area 2 and the completion of the

Bayou des Familles development project. In Area 3 we assumed con-

struction of the Lafitte-Larose Highway below the Intracoastal Waterway

and subsequent development of areas between. Phosphorus input to

Barataria Bay was calculated by amount of phosphorus loading owing to

development divided by phosphorus retention capacity of Little Lake.

These are obviously rough estimates, but they serve to point out the

consequences of continued development in the wetland.

Phosp orus Retention Capacity in Lac des Allemands, Ltke

Salvador, ad Lake Cataouatche. The phosphorus retention capacity

(percent of P input retained) for Lake Salvador was calculated in two

ways. Onemethod was to assume that the ratio of phosphorus retention
of Lac des Allemands, 127 metric tons, to its area, 65 km2' would be

applicable -to Lake Salvador. Using this ratio we estimated that Lake

Salvador could retain 440 metric tons of phosphorus. A second method

was to use the relationship between areal water load (qs) and phosphorus

retention (Rp) (Kirchner and Dillian 1975, See Fig. 2). The areal water
load of a body of water (m yr-1) is calculated as its outflow volume
(m3/yr) divided by its surface area (m2). The outflow was estimated by

assuming the only hydrologic input to the upper basin is rain, and that

two thirds of the water is lost to evapotranspiration (Day et al. 1977).

The areal water load (qs) for Lake Salvador is approximately 3.0 which

gives a Rp of .95 or almost 100 percent phosphorus retention. Using

this method, Rp for Lac des Allemands is about 0.55 (qs=9.2), which is

approximately the value measured by Day et al. The phosphorus retention

capacity for Lake Cataouatche is approximately 0.95 (qs=3.1').

Nursery Grounds: Past, Present, and Future

The data on past, present, and estimated future phosphorus loading

and salinity levels at various locations in the Barataria Basin are

summarized in Figs. 2, 3, and 4. For the years 1898-1910, there was no

eutrophication in the upper basin and high salinity was limited to

southern Barataria Bay (Fig. 2). This is indicative of a healthy

nursery zone.

From 1961-1974 eutrophic conditions began to effect the upper

-nursery zone. Although no strict upper limit of the nursery ground

can be delineated, Jaworski's citing of the decline of annual crab

landings in Lake Salvador because of eutrophication may corroborate

the decline of the nursery zone shown in Fig. 3.

If present trends continue, by the year 2000 there will be a

drastic decline and perhaps destruction of the nur sery zone in Barataria

Basin (See Fig. 4).

The projection of eutrophication. increases into the future (for

the year 2000) shows the extreme importance of limiting any future

development below the Intracoastal Waterway. Future development in

Area 2 (Fig. 1) will greatly increase eutrophication of Lake Salvador,

further stressing nursery grounds there. Lake Salvador may be capable

of absorbing the increased phosphorus loading rate, but the upper limit

of phosphorus retention capacities is not known. Below Lake Salvador

a bottleneck exists in Bayou Perot and Bayou Rigolettes. Saltwater

intrusion has resulted in oyster leases in Little Lake. Recently, in

years of low rainfall, oyster leases have been productive at the extreme

north end of Little Lake. Accompanying the saltwater intrusion are conchs

that limit the oysters southerly. Development below the buffer zone of

Lake Salvador, such as development along the proposed Lafitte-Larose

Highway, will create eutrophic conditions in Little Lake and cause the

area of healthy oyster grounds to be degraded or destroyed. This

eutrophic situation coupled with rising salinity could sharply delimit

the entire nursery zone, seriously affecting commercial fisheries for

other species such as crab, shrimp, and fish.

Trophic State Index

Over the past two years we have carried out an investigation of

water quality at 23 stations covering the length of the Barataria Basin.

The following discussion of basin chemistry and trophic state analysis

is based on. the data collected during this transect.

Description of Chemistry in the Basin

The chemical interactions and water quality of the Barataria Basin

are the result of interactions of vegetation type, changes in salinity,

and cultural factors. In the freshwater swamps, organic acids rich in

tannins and lignands from decaying vegetation produce characteristic

coffee-colored water. This dark water draining from the swamp contains

high total -hosphorus and organic nitrogen concentrations but very low

inorganic nitrogen (i.e., ammonium, nitrate, nitrite). Lour inorganic

nitrogen may be the result of rapid denitrification and uptake by

bacteria. Clean bayous are characteristically clear, dark, and sluggish.

Heavy agricultural runoff from sugarcane fields results in murky water

and altered nutrient conditions. This is now the most common condition

of swamp bayous.

The swamps grade into freshwater marshes and lakes. Lac des

Allemands, the uppermost lake in the Basin, receives especially high

quantities of agricultural runoff from various bayous. This has caused

accumulation of nutrients and dense algal blooms (Day et al. 1977).

Some phosphorus is stored in the sediments and some nitrogen denitrified.

In Lac des Allemands, the sediments are likely near saturation and their

capacity as a nutrient sink is greatly diminished. This allows sig-

nificant quantities of phosphorus and nitrogen to be flushed out of the

lake into Bayou des Allemands (Day et al. 1977).

Saline water has intruded into Bayou des Allemands occasionally

as evidenced by the recovery of live Rangia clams in thebbottom sediments

north of U.S. Highway 90. The bayou appears to retain some of the in-

coming nutrient material. Phosphorus and total organic nitrogen

decrease from the upper bayou to below the town of des Allemands.

This consistent drop in nutrient levels may well be a result

of salinity. As previously explained, salts will neutralize suspended

clays, causing them to precipitate, carrying many adsorbed nutrient

forms.

Another significant source of nutrients to Bayou des Allemands

is drainage canals such as the Burchell Canal which drains the Simoneaux

ponds. It has the highest particulate organic nitrogen levels of the

stations sampled and fairly high chlorophyll a values.

Bayou des Allemands flows into Lake Salvador where there is a large

drop in nutrient concentrations. There is low phosphorus, total

organic nitrogen, and resultant high secchi depths. This drop is due

to several factors including the large volume of the lake, sorption of

nutrients by sediments, increasing salinity, and incomplete mixing of

the lake. All of these factors combine to make Salvador a fairly clean

water body.

Lake Cataouatche, northeast of Lake Salvador, receives most of its

drainage from urban, industrial, and agricultural areas on the

Mississippi River natural levee. High nutrient and chlorophyll a con-

centrations are common. The most significant nutrient present is

nitrate, an indication of direct agricultural and urban runoff. Nitrate

is three times greater than in Lake Salvador, while particulate organic

nitrogen is six times greater.
25

Canals consistently have high nutrient values, especially in

phosphorus and nitrate. Bayou Segnette and-the Gulf Intracoastal Waterway

receive drZLinage from the west bank of the New Orleans metro area,

carrying sewage, industrial wastes, and urban runoff. Bayou Barataria

receives drainage from Lakes Salvador and Cataouatche, and Bayou Segnette

and the GIVW. The water quality in Bayou Barataria at Lafitte may

further be influenced by extensive commercial and private boat traffic,

as well as local sewage discharges.

South of Lafitte, Bayou Barataria previously flowed into Bayou

Rigolettes. This flow has been altered by the dredging of the Barataria

Waterway, producing a deeper channel that allows the enriched bayou

waters to bypass natural waterways and flow directly into tipper

Barataria Bay. Bayou Rigolettes is now largely isolated from upper

basin runoff and characterized by very low nutrient levels and high

water clarity.

In contrast to Bayou Rigolettes, Bayou Perot is somewhat more

enriched and seems to be receiving enriched waters from Bayou des

Allemands that have flowed along the western shore of Lake Salvador.

Bayous Rigolettes and Perot flow into Little Lake, which is charac-

terized by low nutrients and chlorophyll, and high water clarity. Most

of the phosphorus appears to be adsorbed by the sediments and probably

not exported.

Little Lake flows into Upper Barataria Bay, contributing clean,

filtered water. The Barataria Waterway, another major contributor to

the bay, functions like a drainage pipe for waters from Bayou Barataria.

The waterway at Manila (Mile 29) has higher nutrients, chlorophyll, and

turbidity than Little Lake.
26

Barataria and Caminada bays are large enough so that the effect of

the upper basin drainage is still minimal. Caminada receives water from

a smaller and more isolated basin than Barataria. Ho and Barrett

(1977) showed that Barataria has twice the nutrient levels of Caminada,

reflecting upbasin influences.

Trophic State Analysis

Initial results from the multivariate analysis suggested a source-

sink process could explain the existing water quality. This means that

the various water bodies were functioning principally as either sources

of nutrients, intermediate filtration areas, or nutrient sinks.

Practically all areas of the freshwater swamp are highly eutrophic and

serve as sources of nutrients. Canals draining agricultural areas, such

as the St. James Canal (Fig. 6), contribute the highest nutrient levels

in the entire freshwater area. The few remaining clean bayous are an indi-

cation that previously the swamp functioned as a nutrient sink. Lac des

Allemands under natural, unaltered conditions was probably able to

retain most incoming nutrient loads in its sediments and cycling process.

It appears now to have reached its capacity as a sink and is an in-

effective filtration area. Empirical (Day et al. 1977) and theoretical

(Kirchner and Dillon 1974) calculations show that about half of input

nutrients are exported to the lower basin.

The brackish and saltwater areas display clear-cut examples of a

source-sink process. Phosphorus and secchi depth data provide a good

illustration of chemical changes occurring between the various water

bodies (See Fig. 7). Relatively high phosphorus enters the Burchell

Canal and then into Bayou des Allemands. Secchi depth is extremely low

in both areas. As this enriched water enters Lake Salvador, phosphorus

out of the urater colum and secchi depth is high, indicating Lake

Salvador is functioning primarily as a sink. The other stations that

are clearly sinks are Bayou Rigolettes (17), Little Lake (21), Barataria

Bay (24), and Caminada Bay (25). Intermediate filtration areas include

Bayou des Allemands, Bayou Barataria (16), Bayou Perot (18), and upper

Barataria Bay at Manila (23). These water bodies'have not reached their

capacity as sinks, but are inefficient in retaining all of the*nutrients

either because of high loading or rap id flushing. Natural tidal

channels dra-ining brackish and saline marshes also-contribute*nutrients

to open water areas and thus serve as natural intermediate filtration

areas.

Active sources of nutrients include Lake Cataouatche *(13), Bayou

Segnette (10, and the Gulf Intracoastal Waterway (15). Nutrients,

chlorophyll, and water clarity all indicate that these areas are highly

eutrophic (Fig. 8).

Results of Cluster Analysis

Cluster analysis is a statistical technique which can be useful in

the elucidation of eutrophication. It involves progressively combining

da ta from various water bodies into smaller and smaller groups according

to the degree of similarity among data variables as in Brezonik and

Shannon 19 7.1. In this study the stations were grouped according to

their trophic states, as defined by the following variables: total

phosphorus, total organic nitrogen, chlorophyll a, secchi depth, dissolved

oxygen, and ammonium.

The cluster analysis partitioned the various stations into three

gr6ups (Fig. 9). One group consisted of the cleanest stations in the

basin. A second group contained primarily freshwater eutrophic stations,

while in the third group were mainly brackish and saline stations with
some degree of eutrophication. 28

The clean stations had relatiVely low nutrient and chlorophyll a

concentrations and clear water (group 2). They are mainly brackish

stations (Lake Salvador, Bayou Rigolettes*, Little Lake,'Barataria Bay,

and Caminada Pass) but one was a natural swamp stream. These stations

are active nutrient sinks as indicated'earlier by graphs of phosphorus

and secchi depth (Fig. 7).

The second group contained all freshwater stations (group 1). Most

waters in the upper basin are highly eutrophic and-most of the'stations

clustered into a fairly homogeneous group. It is difficult to pick

out any patterns within this cluster mainly because of the similar

water quality of the stations.

There is a range of eutrophic conditions included within, the last

cluster (group 3). This range is reflected by separate subclusters.

One subgroup contains highly eutrophic brackish stations (Lake

Cataouatche, Bayou Segnette Waterway, the Intracoastal Waterway, and

Lower Bayou des Allemands) as well as one swamp station (3b). The

swamps station is the only one where we have never observed measurable

salinity. All of these stations exhibit high nutrient and chlorophyll

concentrations and low water clarity. This group of stations is very

similar to the eutrophic fresh stations and serve as sources of nutrients.

A second group in this cluster consists of stations of intermediate

trophic status (3a). The stations within this subcluster appear to

function as intermediate filtration areas, absorbing nutrients but

unable to remove them from the water column as efficiently as the active

sinks. Stations included in this grouping are Bayou Barataria, Bayou

Perot, and the Barataria Waterway. It is interesting to note that a

natural brackish marsh tidal pond is included here. This gives some

indication of the trophic status of natural marsh areas.

In summary, by the use of cluster analysis we have effectively

separated various areas of the basin by trophic status. This method

also differentiated most fresh from saline areas. We conclude that with

further refinement, this methodology will prove very useful in clas-

sification of various water bodies in the coastal zone in terms of

trophic status.

Phosphorus Retention

Calculation of P retention according to Kirchner and Dillon (1974)

indicates that both Lake Salvador and Lake Cataouatche should retain
over 95 percent of P input. P loading rates of 0.97 and 1.6 g P m2/yr-1

for Salvador and Cataouatche, respectively, are both higher than the

critical value of 0.4. However, there is a striking difference in

trophic status of the two lakes. Cataouatche is characterized by high

nutrients and chlorophyll levels, and turbid waters. Salvador, on the

other hand, has lower nutrient and chlorophyll a levels and clearer

water.. Lake Salvador is relatively clean while Cataouatche seems

highly eutrophic. How then can the similar P loading and retention be

reconciled with the different trophic status of the two lakes. We

believe difference in circulation patterns, history.of phorphorus

input, and oxidation condition of the sediments can explain these

findings.

The bulk of nutrient input to Salvador is from Bayou des Allemands

at the western end of the lake. The principal outlet from the lake

seems to be Bayou Perot. Winds from the NW, N, E, and SE would tend to

hold water entering from Bayou des Allemands in the western part of the

lake or push it towards Bayou Perot. Only SW winds would tend to mix

this water cover the whole lake. Predominant winds in Louisiana are
30

from the SE or N and NW. Therefore, water entering the lake from Bayou

des Allemands would generally tend not to mix over the whole lake but

flow in the western part of Lake Salvador towards Bayou Perot. Water

clarity, nutrient, and chlorophyll a measurements in these water bodies

support this hypothesis.

By contrast, Lake Cataouatche has no one major inlet or outlet.

Three important inlets are the Louisiana Cypress Lumber canal from the

NW, Bayou Veret (NE), and Bayou Segnette (SE). In addition, there are

several smaller inlets. There are two outlets into Lake Salvador and

one via the Bayou Segnette Waterway. Because of the number of inlets,

smaller size, and shallow depth of the lake, prevailing winds would tend

to mix entering water throughout the lake.

There is also a significant difference in the nutrient loading

history of the two lakes. We believe that Cataouatche has received high

nutrient loads for a longer period of time. Canals were first con-

structed into the lake in the second half of the 19th century. Because

the lake is close to agricultural and urban areas on the west bank of

the Mississippi, it has received the bulk of drainage from these areas

and has acted as a buffer for Lake Salvador. By contrast, the agri-

cultural areas on the east bank of Bayou Lafourche are separated from

Lake Salvador by a larger expanse of marsh. Also, the upper basin which

presently serves as the major source of nutrient input to Lake Salvador

probably was relatively unimportant as recently as 1020 years ago

(Butler 1975). Thus it seems that Cataouatche has received significant

nutrient loading over a much longer period of time.

Another significant difference between the two lakes is the nature

of the bottom sediments. Even though salinities in the two

lakes are similar, Salvador supports extensive populations of Rangia

clams while Cataouatche does not (Bahr, CWR, unpublished). Visual

observation of sediment samples indicates more extensive anaerobic

conditions in Lake Cataouatche.

We believe an examination of these factors can resolve the con-

flicts in our findings. Sediments generally tend to act as a sink for

phosphorus (Syers et al. 1973 review the literature on phosphate c

chemistry and lake sediments.). However, sorption studies have shown

that some sediments, for example those from Lake Wingia (a eutrophic

lake in Wisconsin), are virtually saturated with inorganic P (Williams

et al. 1970). Release of P04 overlying water occurs if the concentra-

tion of interstitial P exceeds that of overlying water (Stumm and

Leckie 1971.). In addition, P release is much higher if anaerobic

conditions exist in the sediments (Syers et al. 1973, Patrick and Khalid

1974).

Thus the application of the P retention index of Kirchner and

Dillon must. include an appreciation of the conditions of the sediments.

So long as sediments can absorb more P, then the relationship holds. We

believe that this situation holds for Lake Salvador; For Lake Cataouatche,

sediments have become saturated. In addition, anaerobic conditions in

Cataouatche favor release of P. Thus it seems that although there is an

appreciable amount of P entering Lake Salvador, most is confined to the

western end of the lake and the sediments are still an active sink.

Cataouatche, on the other hand, has a long history of high nutrient

loads and the saturated sediments are probably acting as a source of P.

In fact, Syers et al. postulated that "advanced eutrophication enhances

release of sediment inorganic P, and it is possible that eutrophic lakes

will perpetuate a eutrophic condition" for some time if external sources

of P were eliminated.

Factor Analysis

Another statistical tool used in classifying the stations according

to trophic status is multivariate factor analysis. Factor analysis is a

means by which the regularity and order in phenomena can be discerned.

As phenomena co-occur in space or in time, they are patterned; as these

co-occurring phenomena are independent of each other, there are a number

of distinct patterns. The phenomena we are dealing with in this report

are water quality variables. "What factor analysis does is this: it

takes many measurements and qualitative observations and resolves them

into distinct patterns of occurrence" (Rummel 1968). These patterns are

called factors. Factor analysis is discussed in detail by Rummel (1968)

and applied to trophic state analysis of Florida Lakes by Brezonik and

Shannon (1971).

Factor analysis was run using the following water quality indi-

cators: ammonium, total phosphorus, total organic nitrogen, dissolved

oxygen, chlorophyll a, and secchi depth. The first factor or pattern

accounted for 49 percent of the total variation among the twenty-three

sampling stations. When two factors were considered, 76 percent of the

variation was accounted for. The most important parameters in the first

factor were phosphorus, chlorophyll, total organic nitrogen, and secchi.

For the second factor, the most significant variables were ammonium and

dissolved oxygen.

Factor- scores of the various stations are plotted in Fig. 9 with

the groupings from the cluster analysis enclosed in envelopes. It

should be stressed that this graph presents the results of two separate

methods; factor analysis and cluster analysis. Factor one seems to be

related to level of nutrient input. The freshwater stations (Cluster 1)

have the highest nutrients while the clean stations (Cluster 2) have the

lowest input. Factor 2 may be related to salinity. Generally, fresher

stations have negative scores. For example, station 3, although grouped

with the clean station, has a much different score on factor 2 than the

other stations, perhaps because it is fresh.

A gradient of trophic status is most pronounced for brackish

stations. The most eutrophic stations (Cluster 3b) fall toward the

right and top area of the graph while the cleanest stations (Cluster 2

with the exception of station 3) are located toward the left and bottom.

Stations of intermediate eutrophy (Cluster 3a) are located between the

other two groups. For the fresh area, there seems to be no intermediate

stations; only highly eutrophic (Cluster 1) and clean (station 3). Had

we sampled intermediate fresh stations, they would likely fall between

station 3 and Cluster 1.

Clearly, both cluster analysis and factor analysis are an effective

means of classifying water bodies according to trophic status. To apply

this technique for the whole coastal zone, the greatest need is for a

comparable set of data for all major water bodies. In the past, dif-

ferent parameters have been measured at different sites, and the methods

of analysis have not been the same. We believe that we have identified

a suitable set of variables, which, if analyzed in the same manner,

could be used in classifying the trophic status of water bodies in -the

coastal zone.
34

LAKE PONTCHARTRAIN

Lake Pontchartrain is a large, shallow, oligohaline water body

located immediately north of New Orleans, La. (see Fig. 10). It

is part of an estuarine lake and bay system in which water entering

from the Gulf of Mexico mixes with fresh water moving out of a water-

shed encompassing 13,000 square kilometers. It is part of Hydrologic

Unit I of the coastal zone. Over the past 50 years, human population

in this drainage area has trebled. While all sections have shown

growth, a large percentage of the residential development incurred by

the increase has been located in reclaimed wetland adjacent to the

lake.

As a consequence of the rapid settlement, many of the natural

streams and drainage canals which bring fresh water into Lake

Pontchartrain now also serve as conduits for domestic wastes and fer-

tilizer residues rich in nitrogen and phosphorus. These inputs have

caused a decline in water quality throughout the lake and are responsible

for increased incidence of eutrophic conditions.

An increasingly urban and environmentally conscious public is

demanding the preservation of Lake Pontchartrain as a commercial,

recreational, and aesthetic resource of high importance. Here we will

use phosphorus loading as an index of eutrophication in Lake

Pontchartrain.

Phosphorus Loading for Lake Pontchartrain

Phosphorus loading for Lake Pontchartrain was calculated using

the following equation:
Loading = All sources (Flow X concentration of P) = g/m2/yr
35 Surface area of Lake

Flow is the sum of major f reshwater sources into Lake Pontchartrain.

These data were gathered from various sources (Table 4). Pass Manchac,

rain, and rLorthshore rivers account for the bulk of freshwater input.

The New Orleans area contributes less than 5 percent.

TABLE 4. MAJOR FRESHWATER SOURCES OF LAKE PONTCHARTRAIN

109m3 yr -1 % Total H,)O Supply

Pass Manchac 5.10 54%

Tangipahoa River 1.53 16%

Rain-Evaporation on Lake 1.42 15%

Tchefuncte River 0.72 7.6%

Bayous Lacombe and Liberty 0.34 -1.6%

New Orleans Metropolitan 0.40 4.2%
Street Runoff

TOTAL 9.51

Streamflow data: U.S. Army Engineers 1962
Lake areas: Barrett 1970
Net rainfal.'I: Gagliano et al. 1973
Magnitude ol New Orleans Street Runoff: Ponlius et al. 1973, Cramer 1974.

The avo---rage P concentrations in each of the freshwater- inputs

(Table 5) account for seasonal flow variations. For example, if

nutrient values are elevated during the spring when flow rate,3 are

high,'the weighted yearly average.will be greater than the mean of all

samples taken at regular intervals throughout the year. The poor

water quality of urban street r unoff is obvious.

TABLE 5. P-CONCENTRATIONS IN FRESHWATER
SOURCES INPUT TO LAKE PONTCHARTRAIN
P-concentration (9/0)

Pass Manchac 0.14

Tangipahoa 0.18

Tchefuncta River 0.10

Bayous Lacombe and Liberty 0.10

New Orleans Street Runoff (2.30 average)

Orleans Parish 1.09

Jefferson Parish 3.50

Pourier and Rogers 1975, Stern and Atwell 1968, Stern and Stern 1969,
Kemp and Root, CWR, unpublished; USGS 1975, USGS 1976, Tarver and
Dugas 1973.

The total quantity of phosphorus from each source was obtained

by multiplying flow times concentrations (Table 6).

TABLE 6. PHOSPHORUS LOADING IN FRESH WATER
SOURCES INPUT TO LAKE PONTCHARTRAIN
P-input (108g/yr) % Total P-input

Pass Manchac 7.14 34%

Tangipahoa 2.75 13%

Aeolian (Rain and dustfall) 1.13 6%

Tchefuncta 0.72 3%

Bayous Lacombe and Liberty 0.34 2%

Jefferson Parish Street Runoff 7.00 32%

Orelans Parish Street Runoff 2.18 10%
TOTAL 2.13 x 109

Pourier and Rogers 1975, Stem and Atwell 1968, Stern and Stern 1969,
Kemp and Root, CWR, unpublished; USGS 1975, USGS 1976, Tarver and
Dugas 1973.
37

While New Orleans metropolitan street runoff is less than 5 percent of fresh-

water input, it represents over 43 percent of total phosphorus input because

of high concentrations of phosphorus in the runoff. Jefferson Parish,

with a smaller population,accounts for almost 33 percent of total P input.

This may be due to two factors. First, as we stated earlier, developing

suburban areas contribute a far greater per capita urban runoff load.

Second, durj@ng heavy rains much raw sewage is allowed to bypass treat-

ment plants. By contract, most sewage from Orleans parish is pumped

to the Mississippi River.

From the total P input and the area of the lake, P loading was

calculated as follows:

Total Loading = 2.13 X 109 g/yr-1 = 1.32 g P m-2yr-1
1.61 X 109 my

This level of loading indicates that the lake is, on the average,

eutrophic. We shall have more to say about this later.

Natural vs. Artificial P-input

To determine what percentage of the total phosphorus loading is

natural and how much is the result of artificial enrichment, we

estimated the loading under predevelopment conditions. We did this by

assuming a direct relationship between current loading and average

phosphorus concentra'tions and also assumed that predevelopment phos-

phorus concentration in Lake Pontchartrain would be approximately

that found j@n Caminada Bay, a relatively uncontaminated part of the

southern BarELtaria estuary (Ho 1971).

TABLE 7. TOTAL PHOSPHORUS INPUT UNDER
PREDEVELOPMENT CONDITIONS

Current loading Natural loading
Current Avg. Conc. Natural Avg. Conc.

1.32 g/m 2 /yr x (Ho 1971)
.1 g/m3 .0@4g/m7

X = .53 g/m3/yr Natural P loading.

We assumed that under natural conditions the amount of phosphorus

entering the lake through each tributary stream would be proportional

to the amount of water flow. To calculate the percent of current

phosphorus loading attributable to development in the watershed, the

following formula is used:

% Artificial Current P Total P input Fraction of total
P from input from - under X H20 input to
source source predevelopment lake from each
conditions source

The artificial input from each freshwater source is given in Table 8.

Practically all P from the New Orleans Metropolitan area is artificial.

TABLE 8. ARTIFICIAL P INPUT FROM
SOURCES INTO LAKE PONTCHARTRAIN

% of total
Artificial P input (g/yr) input from source
Pass Manchac 2.55 X 10 8 36%
Tangipahoa 1.39 X 10 8 51%

Tchefuncte 0.40 X107 6%

Bayous Lacombe & Liberty ru0 0%
New Orleans Street Runoff 8.84 X10 8 96%
TOTAL 1.28 X109

Phosphorus nput - Past, Present, and.Future

In order to project trophic state Lake Pontchartrain into the

future, a common denominator of both basin development and nutrient

enrichment is needed. Population is a good index of both.. Dividing

the figures for artificial nutrient loading developed in Table 8 by the

number of people in each subunit of the watershed, yields per capita

phosphorus input (See Table 9). The size of this figure is dependent on

the type of development and the waste management used in each drainage

area. Areas with high agricultural or suburban development have the

highest per capita P input.

TABLE 9. PER CAPITA ARTIFICIAL P - INPUT

Per Capita Multiplier
Drainage Basin Use (kg/person)

Pass Manchac Urban, Suburban, 0.74
Agricultural, Natural

Tangipahoa Agricultural, Natural 2.03

New Orleans

Orleans Parish Urban 0.36

Jefferson Parish Suburban 1.77

When used in conjunction with population projections based on

present growth rates, the per capita multiplier allows the prediction of

future loading rates using the following formula:

Total P loading = Population X per capita multiplier
area of lake

Projections predict a stable population in the City of New Orleans,

while the suburban areas of both New Orleans and Baton Rouge are predicted

to grow rapidly (See Fig. 11).

These data indicate that Lake Pontchartrain is, on the average,

eutrophic now and will become excessively so by the end of the century.

Artificial phosphorus input will rise from 57 percent at present to 73

percent by the year 2000. However, as in the case of Lake Salvador,

this data must be interpreted in light of other physical, chemical, and

biological data (See Table 10 for past, present, and future nutrient

loading).

First, the lake is not uniformly eutrophic. The most extreme area

is the south shore adjacent to the metropolitan area. This area is

characterized by high nutrient and coliform levels and pollution indica-

tive species. The southwestern part of the lake from Jefferson Parish

to Pass Manchac seems also to be eutrophic. The northshore and eastern

end of the lake are fairly clean because of low nutrient input and more

rigorous tidal flushing.

Thus there is a gradient in eutrophic conditions from south and

west to north and east. This gradient is due to differential inputs of

nutrients and rates of flushing. Phosphorus retention by the sediments

is probably also high in the south and west portion of the lake.

TABLE 10. PHOSPHORUS LOADING INTO LAKE PONTCHARTRAIN OVER TI'.N9
Total P-loading (g/m2/yr) % Artificial

1900 .64 17%

1920 .70 24

1940 .83 36

1960 1.05 50

1970 1.23 57

1990 1.72 70

2000 1.93 73

Sources of Nutrient Enrichment

The data shows that substantial artificial nutrient enrichment is

entering the lake from four major sources. The ranking of these

sources is in Table 11.

TABLE 11. ARTIFICIAL NUTRIENT SOURCES FOR LAKE
PONTCHARTRAIN
% Total artificial
Artificial P-input (g/yr) input to lake
Jefferson Parish 8
Street Runoff 6.88 x 10 54%

Pass Manchac 2.55 X 10 20%
Orleans Parish .1.96 8
Street Runoff x 10 15%
Tangipahoa River 1.39 X 108 11%

Figure 12 gives a visual presentation of the relative importance

of each iipu.t as a water source and as a nutrient source.

Jefferson Parish, west of New Orleans, contributes 2 percent of the

total freshwater input and yet is the origin of 54 percent of the cul-

turally derived phosphorus entering the lake. In contrast, the City of

New Orleans, with a higher population, produces only 15 percent. The

difference lies in the handling of sewage. In Orleans, sewage is

collected, and pumped into the Mississippi River. Water drained

by Lake Pontchartrain outfall canals is strictly street runoff. When

Jefferson was developed, no city sewage lines were installed. Initially,

waste treatment was handled with individual septic tanks. These were

placed in great density in an area in which the water table is almost at

the surface. Canals dug to drain suburban subdivisions took on the

character of raw sewage conduits. While city sewage is now being

emplaced, outfall canal water quality is still extremely poor. The

waste containment problem is far from solved. Domestic sewage must be

prevented from reaching outfall canals. Treatment of outfall canal

waters prior to discharge would be impractical because of the volume

passed during storms and the expense involved in nutrient removal.

The best alternative is to provide a complete sewage collection system

designed to deal with the unique engineering problems created by the

settling of reclaimed wetland soil. Wastes could-be vented to a treat-

ment plant for ultimate disposal in the Mississippi River. The discharge

of secondarily treated waste water from Jefferson Parish would probably

not appreciably lower water quality in what is already a grossly

polluted river. The effect on Lake Pontchartrain would be significant,

however,as nutrient input from Jefferson would drop 70 percent. The lake

would return to a 1960 nutrient loading.

Conclusion

Census figures show that the Lake Pontchartrain watershed is

growing in population faster than any other part of the state of

Louisiana. Much of the anticipated development appears likely to occur

in reclaimed wetlands east and west of New Orleans. This will be

mainly suburban construction of the type currently found in Jefferson

Parish. This development is characterized by an extremely

high per capita phosphorus discharge (Table 9). If New Orleans East

and the St. Charles Parish swamp is converted to suburban residential

use without adequate environmental safeguards, eutrophication will,

within 30 years, destroy most of the desirable aesthetic, recreational,

and commercial values of Lake Pontchartrain. The species shift and

water quality decay which are associated with system eutrophy will also

have an indeterminate deleterious effect on the large offshore fishery

which harvests lakedependent menhaden and shrimp.

TERREBONNE EASIN

Description

The Terrebonne Basin (Hydrologic Unit V) which lies west of the

Barataria Basin, is bordered by Bayou Lafourche, the Atchafalaya Basin

Protection levee, the lower Atchafalaya River, and the Gulf of Mexico
(see Fig. 13). The basin is rich in wetland areas with 484 km 2 of fresh
swamp in the northern basin gradiating into marshes (521 m2) bordering

the Gulf (Gane, CWR, unpublished).

To quantify eutrophication we divided the Terrebonne Basin into

two areas (see Fig. 13). Area I extends north to the Assumption-Iberville

parish line and is bordered on the south by Assumption-Lafourche-Terrebonne

parish line. A previous study of the Lake Verret watershed extended the

northern boundary beyond the Terrebonne Basin coastal zone boundary

(USDA 1976). By close examination of aerial photographs, we determined

that the bayous and canals from Iberville Parish bypass the Lake Verret,

Grassy Lake, and Lake Palourde area almost entirely and for this reason

our study area was reduced. In Area I, commercial, residential, and

agricultural land is limited primarily to the natural levees of the

Mississippi River and the various bayous. The ratio of high land to

swamp is 1:2. Chemical industries are prevalent in the northernmost

parishes of the area.

Area II is bounded by the Atchafalaya, the southern Assumption

parish line, Bayou Lafourche, and the Gulf. Exclusive of the: large

bays and sounds, Area II contains 398 km2 of waterways and waterbodies

(Chabreck 1972). Area II is predominantly fresh, brackish and saline

marsh. The ratio of high land, swamp, and marsh is 1:1.5:5. Shellfish-

eries and petroleum production are important in this area.

Sources of Eutrophication

The sources of eutrophication in Terrebonne are similar to those

of the other basins. In the upper basin, agricultural runoff primarily

from sugarcane fields into the different water bodies results in high

nutrient levels. From the available data, industrial waste seems to

be the source of extremely high phosphorus inputs, particularly in the

Lake Verret region. Municipal sewage from the Houma area is also a

source of high nutrient input and is creating serious problems for the

shell fisheries in the marshes below. Much of Houma's sewage bypasses

any treatment, thus raw sewage is entering the estuary via canals and

bayous from Houma. Although the marsh has the ability to absorb much

of this-nutrient input, the high coliform levels have caused

more and more closures of oyster grounds since 1966 (current closures

are shown in Figure 14). These waters are monitored by the La. Dept.

of Health in compliance with National Shellfish Sanitation Program

(HEW) (Van Sickle, CWR, unpublished).

Present Estimates of Phosphorus Input

Area I. The current P-input into Lake Verret was obtained by

summing estimated inputs from industrial discharge, municipal sewage,

and agricultural runoff. Urban runoff was not considered significantly

important because the area lacks any true urban centers. P-input from

domestic sewage of Napoleonville and Pierre Part was determined on

a per capita basis (P 3lb/capita/yr). Industrial discharge was

determined from given phosphorus concentrations and flow data for the

industries within Area I (Pollution Control Engineers 1975). Agri-

cultural land in the Lake Verret watershed was determined by existing

land use figures (Pollution Control Engineers 1975). Agricultural

input was calculated by assuming an export of 2.0 kg of P per acre

of agricultural land (Hopkinson, CWR, unpublished). Total ihosphorus
P

input into Area I:

sewage 2 metric tons

industry 254 metric tons

agriculture 127 metric tons

383 metric tons

The total area of Lake Verret (59.3 km2) was divided into the total
phosphorus input to give a P-loading of 6.46 g/m2/yr. This level of

phosphorus loading indicates a hypereutrophic condition in Lake Verret,

however, this may not be the case. This brings up problems asso-

ciated with the sole use of P loading as an indicator of eutrophica-

tion. The proper use of P loading should be correlated with such factors

as hydrology, nutrient concentration, and biological indicators.

The hydrology in this upper basin, as opposed to other hydrologic

units addressed in this study, is unclear. Because of this it is

difficult to determine if runoff from specific agricultural areas and

industrial sites actually have complete input into Lake Verret or bypass

the lake partially or entirely.

It is apparent from other data sources that water quality in Area I

is being degraded by runoff from agricultural fields, etc. There is a

large amount of sediment erosion taking place. Total sheet and gully

erosion amounts to 1,486,000 tons per year. It is calculated that

903,000 tons of sediment are deposited in the split ditch system that

is part of the sugarcane culture of the area. Deposition in Grand

Bayou is approximately 29,000 tons/year. Field ditches other than

sugarcane ditches collect 113,000 tons/year of sediment. Northern

Lake Verret collects 20,000 tons/year. The remainder (293,000 tons/

year) is deposited in main channels, other portions of the swamp, and

Lake Natchez. Lake Natchez is rapidly filling from this sediment

input (USGS 1976).

Water quality data from 1974-1975 at Bayou Sigur (Station 5),

Grand Bayou (Station 4), Lake Verret (Station 3), Grassy Lake (Station 2),

and Lake Palourde (Station 1) are given below:

Nitrogen-ammonia N-Nitrate Phosphate-P
Station mg/1) (mg/1) (mg/1)

1 .26 .16 .13

2 .30 .12 .12

3 .66 .10 .07

4 1.30 .48 .22

5 3.80 .88 1.99

(USGS 1976)

This data indicates high levels of nutrients in Bayou Sigur and

Grand Bayou which directly drain the sugarcane fields in Area I. It

seems that some of this nutrient-laden water becomes diluted when it

enters Lake Verret and probably phosphorus is taken up in the sediment

as in Lake Salvador. The northern end of Lake Verret is characterized

by thick grass beds of Certophyllum, Nais, and Nitella (Paille, CWR,

unpublished). These disappear by the middle of Lake Verret.

Lake Verret, like Lake Pontchartrain and Lake Salvador, secms to be

characteriZed by several separate trophic states. In addition, the

sediment dE!POSition data 'reported indicates that much P may be

filtered by the swamp deposited sediments. The waters in Lake Palourde

are relatively low in nutrients (USGS 1976). This is also supported

by 1975 fish population data. Both Grand Bayou and Bayou Sigur have

low-oxygen, pollution tolerant species such as channel catfish, spotted

gar, and sbad and almost no game fish. Lake Verret has much higher

population of game fish including bass, white and black crappie,

bluegills, and sunfish (USGS 1976). It is apparent that the waters

in bayous and channels adjacent to cultivated areas are limiting to

fisheries.

Area II. The total phosphorus input for Area II was determined

by the same methods as for Area I for sewage, agriculture, and industry.

In addition, urban runoff from Houma was included. The total phos-

phorus input is as follows:

Agriculture--123 metric tons
Sewage ------- 63 metric tons
Industry ----- 317 metric tons
Urban runoff- 3 metric tons

TOTAL 506 metric tons

It is difficult to calculate a loading rate for Area II because

we were unable to obtain accurate area measurements for water bodies

and waterways receiving nutrient input. In addition, because of the

complex hydrology, it was impossible to determine which waters were

actually receiving wastes. Although we were unable to define the

extent of eutrophication using P loading, the large P input: coupled

with other-water quality data points to widespread eutrophi'cation in

Lower Terrebonne Basin.

Water Quality

Many of the bayous and bays in Area II have poor water quality

primarily from municipal sewage wastes from the Houma area and from

industrial waste. Bayou Terrebonne is a problem area, with low dissolved

oxygen and high levels of sulfate. The Intracoastal Waterway near Houma

has extremely high coliform levels due to the sewage bypass system of

Houma. The Houma Navigation Canal shunts wastewater discharge from

Houma into the marshes east of Caillou Lake and Lake Mechant, altering

water quality by increasing nutrient and coliform levels. Four League

Bay has coliform counts averaging consistently and substantially above

the limit of 70 set by the National Shellfish Sanitation Program and

adopted by the Louisiana Stream Control Commission. The same holds true

for Bayou du Large, Lake Mechant, and Lake de Cade. Lake Caillou, Bay

junop, Grand Bayou du Large, and Lower Bayou du Large have average

coliform counts within established limits (Pollution Control Engineers

1975). Only the larger bays adjacent to the Gulf are generally clean.

As previously mentioned, this has caused a large area of oyster grounds

to be closed (Fig. 14).

Conclusion

The bayous and canals draining agriculture and receiving industrial

waste in Area I are eutrophic and this high nutrient input has caused

Lake Verret to become eutrophic, possibly hypereutrophic in parts.

In Area 11, many of the bayous and bays have degraded water quality

due to municipal sewage primarily from Houma and industrial waste. This

has seriously impacted the shellfisheries of the basin.

For the basin there is expected to be an overall growth of approxi-

mately 60 percent in the next 20 years (1975-1995), with increased

industrial growth. Much of this growth is projected to occur in the

southern part of the basin in the vicinity of Houma (Pollution Control

Engineers 1975). Unless adequate and,precautionary management measures

are taken the entire basin's water quality could be severely degraded

and unable to support any type of healthy fishery.

ATCHAFALAYA BASIN

Description

The Atchafalaya Basin is located in south central Louisiana to the

west of the Barataria and Terrebonne basins (see Fig. 15). From the

junction of the Old River segment of the Mississippi River, the Atchafalaya

flows 141 miles (227 km) to the Gulf. It is the largest distributary of

the Mississippi River, which drains approximately one-third of the

United States. The Old River control structure limits the diversion of

the Mississippi River flow into the Atchafalaya to 30 percent. A small

additional flow from the Red River inputs into the Atchafalaya. The

Atchafalaya Floodway which includes a large part of the natural Atchafalaya

Basin between its dikes is an interesting case with regard to water

quality in Louisiana. It is the only part of the vast Lower Mississippi

River floodplain which still regularly receives floodwater. As pointed

out by van Beek et al. (1977), "The artificially achieved shrinkage of

the floodplain area has impressed its impact on the ecosystem of the

Atchafalaya Floodway primarily through increased flux of riverborne

materials entering the area."

The Floodway allows water to rise much higher than it would natu-

rally in the spring. Flooding is even more prolonged than would result

simply from the amplication of the floods due to the presence of numerous

navigation, pipeline, and well location canals. These watercourses

continue to allow flow of water into the deeper swamp and remnant lake

basins even during relatively low stage condition of the Atchafalaya

River and its various principal distributaries. The

increased flux of sediment borne by the river water has produced

chronic sedimentation problems which constantly reduce the storage

capacity and thereby the utility of the floodway.

Nutrient Input and Loading Rate

Of special interest is the increased flux of nutrien ts through

the floodway. In the lower lying swamp basins water covers the swamp

floor for -the greater part of most years.I In thes e are extensive and

chronic stands of water hyacinth. This situation has been described

in detail by van Beek et al. (1974). They considered the extensive
50 km2) stand of water hyacinth which persisted from year to year

in the area of the floodway known as Buffalo Cove as evidence of

eutrophication. Buffalo Cove is typical of other areas in the lower

basin. These stands are not only much more extensive than those seen

in other basins of Louisiana known to be undergoing eutrophication,but

the hyacinths are of the more robust,taller form typical of more

strongly flowing water conditions.

These chronic stands of water hyacinth are reflective of the large

nutrient input into the Atchafalaya River. The mean nutrient concen-

trations in the Atchafalaya River at Simmesport are 1.53 mg/l of total

N and 0.18 mg/1 of total P (USGS 1976). The combined mean concentrations

of total N and P from Buffalo Cove, the mainstream, and Duck Lake/Flat

Lake/Little Bayou Sorrel are 1.86 mg/l and .21 mg/l, respectively.

These concentrations are high and comparable to other eutrophic areas

in the coastal zone. The nutrient levels in th e Buffalo Cove region

may actually be higher than what is reflected by the concentrations in

the water. The stands of hyacinth are able to assimilate nutrients

and hold them within their biomass. Thus the concentrations of

nutrients in the water at a given time are not always an adequate

measure of whether the system is or will become eutrophic. The

nutrients in flux through the system and stored in various components

of the system besides the water must be considered. This is illus-

trated in Hutchinson's (1969) statement, "By a eutrophic system, I

mean one in which the total potential concentration of nutrients is

high; there may happen to be an extremely low concentration in the

water because the supply at that moment is locked up somewhere else

in the system--in sediments or in bodies of organisms... the stationary

concentrations of the assimilable form of any nutrient thus will be of

little interest in such a system; what is important is the total

available supply in all forms and the rate at which it undergoes

circulation." The high nutrient concentrations in the water at

Buffalo Cove in addition to the extensive hyacinth stands points to

hypereutrophic conditions in that area.

Th e flux of nutrients into the Atchafalaya Basin are high and show

the importance of high water flow through the basin: 30,000 m tons

P/yr and 264,000 m tons N/yr (obtained by multiplying the mean annual
flow of the Atchafalaya, 1.42 x 10 11m3/yr by the respective concen-

trations) (Garrett et al. 1969). The loading rate of phosphorus is
9 g p/m2/yr (calculated by dividing the area of the lower basin, below

1-10, by total nutrient flux). This is an extremely high loading rate.

Therefore, both nutrient concentrations and loading rate indicate

eutrophic conditions.

This is correlated with the extensive stands of water hyacinths

mentioned and also with large pulses of undesirable blue-green algae

in the mainstream of the basin (USGS 1976, Bryan 1975). Bryan notes

that these pulses of Ahacystis and Anabaena may be the first indicators

of the environmental consequences of prolonged enrichment of swamp

habitats.

Nutrient Sources

The nutrients in the Atchafalaya originate from several sources.

The first is from within Louisiana via the Red River drainage. This

river receives agricultural runoff and inputs from all major urban areas

in North Louisiana (Alexandria, Shreveport, and Monroe). A second

source is the Mississippi River. There are no in puts from Louisiana

to the river north of Old River; thus, the nutrient levels reflect

conditions outside of Louisiana. Finally there are local sources

within the upper basin. For example, there are 147,000 acres of soy-

beans within the basin which obviously have some nutrient input. At

this time it is impossible to separate the various input from. these

sources.

Water Qual ty

The high nutrient input into the basin results in detE@riorating

water quality. The large amount of organic matter introduced into the

water from debris shed from water hyacinths creates a high biological

oxygen demand. This is particularly extreme after winter dieback of

the hyacinth. In warmer months this leads to widespread anoxic condi-

tions and destruction of aquatic fauna. Freezes in January 1977

killed extensive areas of water hyacinth, leading to poor

quality conditions in the spring and reduced harvests of fish and

crawfish.
54

Conclusion

The -nutrient concentrations, flux, and loading rates coupled with

other trophic indicators, point to eutrophic conditions in the Atchafalaya

Basin. This is not surprising because much of this water has nutrient

input from northern Louisiana agriculture and municipalities and from

a large area outside of Louisiana. There is additional local nutrient

input. The large nutrient input results in extensive, chronic stands

of water hyacinth which often result in high biological oxygen demand,

anoxic conditions,and destruction of aquatic fauna.

CALCASIEU BASIN

The Calcasieu Basin lies within the Chenier Plain of southwestern

Louisiana and drains an area of approximately 3,000 square miles (see

Fig. 17). The headwaters of the Calcasieu River occur near Leesville

in Vernon Parish, and the river flows in a southwesterly direction

through Oakdale to the head of Calcasieu Lake near the border of

Calcasieu and Cameron parishes. Several tributaries enter the Calcasieu

River in the upland terrace area. Calcasieu Lake, covering an area of

approximately 100 square miles, was originally part of the Calcasieu

River and was formed by the growth of bars and beaches across the mouth

of the river (Fisk 1948).

Nutrient Analysis

Johnson (1977) found several trends in the available water data

for the Calcasieu Basin. Phosphorus appears in the saltwater areas of

the Calcasieu River at higher levels than observed upstream. Nitrogen

has higher concentration in freshwater areas. This may result from

phosphorus retention and recycling by the sediments in the estuarine

area. Phosphorus shows relatively high values in late summer (see

Fig. 17) (Johnson 1977). Similar variations have been observed in

Barataria Basin and may be due to pulses of detritus, relatively low

river flow rates allowing more concentration of the element, and pulses

from man-made sources such as agriculture.

Sources o-f-Eutrophication

From calculated nutrient flux values, the total annual phosphorus

flux into the study area by stream and river flow for 1976 is 236

metric tons from the upper basin. Both the high values of nutrient

export peaks and their time of occurrence point to agricultural runoff

as the source of the nutrient pulse. The high nutrient export values

coincide with the months in which farmers in the area normally drain

their rice fields after the application of fertilizers in order to apply

herbicides (Johnson 1977). Another source of P is Lake Charles muni-

cipal waste, with an annual export of approximately 178 metric tons (3

lb of P/capita/yr, [Kemp and Mackenthun 1969]). Urban runoff for Lake

Charles is estimated at 13 metric tons (90 g/capita/yr [Stem and Stern]).

Approximately 20 percent of phosphorus and 40 percent of nitrogen input

seems to be generated by industrial waste, but available data on indus-

trial waste is so scarce that we are unable to estimate safely (Johnson

1977).

Phosphorus Loading into Calcasieu Lake

The total phosphorus loading for Calcasieu Lake was computed as

follows:

Sewage 178 metric tons
Agriculture 236 metric tons
Urban runoff 13 metric tons
427 metric tons

The total area of Calcasieu Lake 173 x 106M 2 (Barrett 1970) was
divided into total phosphorus input giving a P loading of 2.5 g/m2/yr.

If industrial input is significant this number may actually be higher.

Water Quality
The high phosphorus loading of 2.5 g/m2 /yr is indicative of

eutrophic conditions in Calcasieu Lake and throughout much of the

drainage basin. Other investigations by federal and state regulatory

groups have shown deteriorating water quality in Calcasieu Lake and

surrounding waters. Water quality standards are being violated for

many parameters in the basin. Examination of water quality has shown

that the application of secondary treatment and point source standards

may be inadequate to obtain water quality objectives in much of the

Calcasieu River Basin. Areas that are water quality limited are Mill

Creek, the Calcasieu River from Oakdale to the saltwater barrier above

Lake Charles, the Calcasieu River from the saltwater barrier to the Gulf,

the Houston River to the Calcasieu River, and Bayou D'Inde (John Givens,

La. Stream Control Commission, personal communication). The Calcasieu

River has a low assimilative capacity for wastes due to its low flow

rate. Its maximum flow is approximately 120,000 cubic feet per second,

and under low flow conditions currents may actually reverse due to

tidal influences. The Louisiana Stream Control Commission calculated

the assimilative capacity of a portion of the Calcasieu River as
compared to actual effluent (Kaiser 1976). Actual Effluent
Assimilative Capacity (Thousands of
lbs/day)

Biochemical Oxygen Demand 7.5 59.3

Ammonia 2.8 35.5*

*Estimate for industry only.

This table includes only municipal sewage and industrial waste.

Conclusion

The P-loading rates, coupled with other data, point to eutrophic

conditions throughout the entire Calcasieu Basin, from the upper

Calcasieu Basin to the Gulf. The data also seems to indicate that the

majority of nutrient input is agricultural in origin, and much of this

is from fertilizer runoff. Municipal sewage from Lake Charles also

introduces a substantial nutrient input. Insufficient data is

available to calculate industrial waste input.

MANAGEMENT MIDELINES

The coastal zone of Louisiana is rich in wetlands and water bodies

and a major factor influencing the health of these estuarine systems

is water quality. There are conflicting demands placed on our

estuaries; they are extremely fertile areas, a vast source of fisheries,

and major navigation areas and harbors. Because of this the estuaries

attract large populations which use them as waste repositories. Although

the coastal zone is a very resilient natural area, the effect of man

is being felt. Water quality throughout large parts of the coastal

zone is becoming seriously degraded; unless mitigation steps are

taken, this can have far reaching effects on fisheries and quality of

life in the coastal environment. This report is an analysis of avail-

able water quality data in such a way as to direct attention of

decision-makers to points where their action can have rapid and

significant ameliorative impact on the widespread and deletExious

problem of eutrophication in the coastal zone.

Basin Concept

The fundamental concept when dealing with the problem of eutro-

phication is that the whole drainage basin must be considered rather

than a single lake or bayou. Eugene Odum (1971) states this precisely:

IlWhen man increases soil erosion or introduces quantities of

organic material (sewage, industrial wastes) at rates that cannot be

assimilated, the rapid accumulation of such materials may be destruc-

tive to the system. The phrase 'cultural eutrophication' (=cultural

enrichment) is becoming widely used to denote organic pollution resulting

from man's interests... The cause of and the solutions for water pollu-

tion are not to be found by looking only into the water; it is usually

the bad management of the watershed that is destroying our water

resources. The entire drainage or catchment basin must be considered

as the management unit."

To control eutrophication, the influx of nutrients must be

limited. Although there is concern over which nutrient sources should

or can be controlled and by what methods, water quality improvement

will never result if the continuous flux of nutrients is excessive

(Uttormark et al. 1974).

Point and Nonpoint Sources

The categories point and nonpoint sources are important manage-

ment concepts. A point source is a location at which nutrients are

released in quantity and concentration compatible with practical means

of nutrient removal. A diffuse, nonpoint source is an area from which

nutrients are exported in a manner not compatible with practical means

of nutrient removal. Municipal sewage effluent and industrial wastes

are point sources, while urban-storm and agricultural runoff are diffuse

sources (Uttormark et al. 1974).

Overland Flow for Point Source Treatment

Point sources such as municipal sewage can be alleviated by proper

treatment. However, secondary waste treatment does not rid the water of

nutrients; and tertiary treatment, which does, is prohibitively ex-

pensive. Fortunately, the marshes themselves can a .ct as tertiary

treatment using the overland flow method. If water from sewage, agri-

culture, an urban runoff were allowed to flow slowly through wetlands,

the productivity of the swamp and marsh could be increased and nutrients

absorbed by the soil-plant system. Meo (1974) measured a phosphorus

removal rate by the soil-plant system during overland flow treatment of
4.73 g/m2. Plant productivity of the area treated was increased by 50

percent (see also Meo et al. 1975, Turner et al. 1976). In Barataria
Basin, for example, in Area 1, 5.9 x 10 4 of marshlands (14.57 acres or 7

percent of marsh in Area I) would be required for overland flow treat-

ment to remove phosphorus now being put in to that area. If this were

done, the productivity of the marsh could be potentially increased by
7.2 percent. In Area 11, 7.2 x 107m2 of marshlands (17,784 acres or 8

percent of total marsh in Area II) would be required for overland flow

treatment to remove phosphorus; the productivity of the marsh could be

potentially kicreased by about 6.4 percent. (This approach is appli-

cable for the other hydrologic basins as well.)

An equivalent value of marsh treatment can be obtained by com-

parison with present tertiary treatment costs. Tertiary treatment can

remove from 0.03-0.30 mg/l of P from municipal wastewater, but the costs

are very high. For a 1 MGD treatment plant, tertiary treatment costs

between $0.42-$1.23/1000 gallons P removal. For overland flow, the cost

is about $0.17/1000 gallons treated. For wastewater with an average

concentration of 7.5 mg P/l, the savings for P removal using overland

flow is about $0.9-$3.8/g P. Removal of P presently put into

Barataria Basin using present tertiary technology would cost between 5.6

and 23.6 million dollars per year more than overland flow.

Nonpoint Source Techniques

For diffuse, nonpoint sources, nutrient abatement depends on tech-

niques to prevent excessive nutrients from directly entering water

bodies. Runoff from mismanaged lands such as agricultural areas,

highway construction, and suburban areas inputs excessive levels of

nutrient due to sediment erosion and, in the case of agriculture,

fertilizers.

Agricultural Management Suggestions

Hinchee (unpublished) has suggested several solutions to lessen the

problem associated with agricultural runoff. One suggestion is to

promote sheet flow of runoff water across swamps and marshes or, in

other words, use overland flow treatment. Another is to limit fertilizer

application. This could have a considerable effect, since according to

Golden and Ricaud (1963, cited by Hinchee, unpublished) sugarcane

production would drop only 17.6 percent if no fertilizers were added.

Figure 18 demonstrates this clearly. Currently, a farmer figures his

rate of fertilizer application according to return on his investment.

It may be that the ecological damage done by the addition of fertilizers

to sugarcane exceeds the value of slightly increased yield.

If fertilizers are to be used, they should be used as sparingly as

possible. WDrk done by Jones and Zwerman (1972) showed that the level

of nitrogen in agricultural runoff was proportional to the amount of

nitrogen fertilizer added (Hinchee, unpublished).

The timing of fertilizer application is critical. If fertilizer is

applied at times of maximum uptake, runoff is limited (Fig. 19).

Figure 19 shows uptake rates over time for nutrients in sugarcane. It

shows clearly that maximum uptake occurs in June through August, there-

fore this is the optimal time for fertilizer application. The practice

of fall and winter fertilizing is a definite cause of loss of fertilizers

from fields ZLt the expense of the farmer and the natural system (Hinchee,

unpublished).

Water management can also be used to minimize nutrient runoff.

Gambrell, Gilliam, and Weed (1974) suggest that by maintaining a high

water table, denitrification is increased, minimizing runoff. A study

done by the Department of Agronomy, College of Agriculture and Life

Sciences, Cornell University (1971) showed that phosphorus runoff was

proportional to the quantity of runoff water more so than to the phos-

phorus added. This would indicate that minimizing runoff would lower

nutrient loss to natural waters. Both of these could be applied to

sugarcane which is heavily drained. Some of this draining is necessary

for growth, especially in late winter (Breaux, et al. 1972). However,

it may be possible to limit runoff at other times. It may also be

possible to allow rice runoff to dry off, decreasing phosphorus loss.

The type of fertilizer may be important. The study done by the

Cornell Department of Agronomy and Life Sciences states that the use of

manure significantly reduces nutrient runoff. This is a practice which

could also solve some animal waste disposal problems.

The method of application of fertilizer may also be important.

Calvert and Phung (1971) and Calvert (1975) have shown that in citrus

groves deeper tilling reduced both nitrogen and phosphorus runoff by

53-74 percent and 76-86 percent, respectively. It was also shown that

adding lime to the soil could reduce runoff.

It should be realized that all of these methods were worked out

in areas other than coastal Louisiana and may not all be applicable.

Research in these areas in Louisiafla is badly needed. Extension

agents and other government farm advisors need to be more aware of this

problem. Fall and winter fertilization is an example of what appears

to be bad advice given to farmers.

Below is a list of guidelines. It is realized that these are a

first attempt and need future modification.

1. Reduce fertilizer use to lower levels, or where possible,
eliminate fertilizer use.

2. Time fertilizer application to correspond to times of
maximum uptake, eliminate fall and winter fertilizing.

3. Reduce the drainage of fields, allow the soils to remain
wet to promote denitrification and evaporation.

4. Use manure to condition ooil and to replace chemical
fertilizers.

5. Plow fertilizer as deeply into the soil as possible.

(Hinchee, unpublished).

Management for Urban Runoff

Urban runoff, a nonpoint source, must be controlled from the

standpoint of reducing nutrients entering the waters. (There is still

the problem of toxins and heavy metals input into receiving waters.)

Urban erosion from road construction and urban-suburban development

supplies significant amounts of sediment even though total acreage

under construction may be low (Uttormark et al. 1974). Efforts should

be made by highway departments and developers to reduce this to a minimum.

Other sources of nutrient input is from lawn fertilizers, animal

population, and leaves. Lawns often require nitrogen,but generally

there is no need for additional phosphorus. The use of fertilizers

with little or no phosphorus could be encouraged. Leachate from

leaves has an input into receiving waters,but much of this could be

prevented by not burning or storing leaves in storm gutters (Uttormark

et al. 1974).

Canals and Rutrophication

Canals are an important factor accelerating the eutrophication

process by shunting nutrient-laden water from agricultural and urban

areas directly into water bodies. Water movement through a hydrologic

basin is characteristically sluggish, and the nutrients can be taken

up by wetland vegetation. The canals "short circuit" this flow of

water and consequently the' level of nutrients in the water increases

until blooms of 'weed' plants such as water hyacinth choke waterways

and lakes and produce conditions for massive fish kill. Canals also

serve as conduits for saltwater intrusion which is tied to the problem

of land loss. Salinity intrusion into fresh areas via canals often

kills the marsh causing it to break up and form ponds. Saltwater

intrusion is also causing a shift in the nursery. ground to the north

where the fisheries could feel the brunt of eutrophication. Preven-

tion of saltwater intrusion may not be possible but may be lessened

by limiting the number of canals that extend through the various marsh

types.

Determination of Trophic Status

To determine the trophic status of water bodies several tech-

niques can be utilized. Ideally, nutrient loadings would be determined

by direct measurements and definite sources and contributions pointed

out. The costs of doing this is almost prohibitive and less costly

methods have been developed for use in assessing management alternatives

and establishing priorities (Uttormark et al. 1974). Nutrient loading,

specifically phosphorus loading, is such a technique. The amount of

phosphorus input from various sources such as municipal sewage, agri-

cultural runoff, urban runoff, and industrial waste can be quantified.

With this information and the size of the lake, phosphorus loading can

be calculated. It is important, however, that the P-loading be done in

correlation with other trophic indicators such as nutrient concentra-

tions, hydrology, and biological indicators. Because the lakes and

bayous in Louisiana are naturally high in nutrients, it may be that
the critical loading level of P is higher than 0.4 g/m2/yr and actually
closer to 0.8-1.0 g/m2/yr).

The application of P-retention index (Kirchner and Dillion 1975)

must include an appreciation of the complex internal nutrient cycles

in the lake sediments, the condition of the sediments (aerobic or

anaerobic), history of nutrient loading, depth of water in lake, etc.

To determine the trophic status of a water body using the trophic

state index, certain standardized parameters must be taken (total

phosphorus, total organic nitrogen, secchi depth, chlorophyll a-,

ammonium, dissolved oxygen) and analyzed by methods presented in

Strickland and Parsons (1968). It is important that the water quality

collected by the different agencies throughout the state be consisten t

in parameters and analytical methods. In some areas in the coastal

zone, such as White Lake and Grand Lake, there is very insufficient

data available. As the trophic state index for the estuaries of

Louisiana becomes completed, it will be correlated with phosphorus

loading and biological indices.

Conclusions

1) Eutrophication is a widespread problem throughout the coastal

zone of Louisiana. It leads to poor water quality, develop-

ment of nuisance algal blooms, decline in desirable commercial

and sports fishery species, and diminished recreational

usefulness of water bodies.

2) The major cultural sources of nutrients leading to eutro-

phication are urban runoff, domestic sewage, and

agricultural runoff.

3) Eutrophication can be controlled and is reversible. If

direct introduction of nutrient-laden water into aquatic

bodies is eliminated, the water bodies will eventually

return to a less eutrophic state. The length of time for

this to take place depends on the duration and intensity

of historical nutrient input. We believe that land treat-

ment in wetlands (overland flow) offers a viable means of

treatment of nutrient wastes.

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Rhyther, J. 11. 1954. The ecology of plankton blooms in Moriches Bay
and Great South Bay, Long Island, N.Y. Biol. Bull. 106:198-209.

Rohlich, G. A. 1969. Eutrophication: Causes, Consequences, Correctives.
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Rummel, R. J. 1968. Understanding factor analysis. J. Conflict
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Sharpiro, J., and R. Riberio. 1965. Algal growth and sewage effluent
in the Potomac estuary. J. Water Pol. Cont. Fed. 37(7)::1034-1043.

St. Amant, L. S., J. G. Brown, and T. B. Ford. 1966. Studies of the
brown shrimp, Penaeus aztecus, in Barataria Bay, La., 1962-1965.
Pages 1-17 in Proc., 18th Ann. Sess., Gulf Caribbean Fish. Inst.

Stern, D. H., and B. H. Atwell. 1968. A summer limnological. study of
Lake Pontchartrain, La. La. Water Resources Res. Inst., Tech.
Report No. 3, Louisiana State University, Baton Rouge.

Stern, D. H., and M. S. Stern. 1969. Physical, chemical, bacterial, and
plankton dynamics of Lake Pontchartrain. La. Water Resources
Research Inst., Tech. Report No. 4. Louisiana State University,
Baton Rouge.

Strickland, J. D. H., and T. R. Parsons. 1968. A practical handbook
of seawater analysis. Fish. Res. Bd. Can. Bull. 167.
Stumm, W. and J. Leckie. 1971. Phosphate exchange with sediments: Its
role in the productivity of surface waters. Presented at the 5th
International Water Pollution Research Conf.

Syers, J. K.$ R. Harris, and D. Armstrong. 1973. Phosphate chemistry in
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Tarver, J. W., and R. J. Dugas. 1973. A study of the clam, Rangia cuneata
in Lakes Pontchartrain and Maurepas, La. La. Wildlife and Fish. Comm.
Tech. Bull. 5.

Thompson, J. R. 1970. Soil erosion in the Detroit metropolitan area.
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Turner, R.E., J. W. Day Jr., M. Meo, P. Payonk, J. R. Stone, T. B. Ford,
W. G. Smith. 1976. Aspects of land-treated waste applications in
Louisiana wetlands- Pages 147-'167 in Proc., Nat. Symp. on Freshwater
Wetlands and Sewage Effluent Disposals. Ann Arbor, Mich.

U.S. Army Corps of Engineers. 1962. Prototype data collection program
for model study of Lake Pontchartrain, La., and vicinity. U.S.
Army Engineers, New Orleans District.

U.S. Dept. of Agriculture. 1976. Agricultural statistics. U.S.
Government Printing Office, Washington, D.C.

U.S. Dept. of Commerce. Bureau of census. 1970. Census Tracts--New
Orleans, La. Standard Metropolitan Statistical Area.

U.S. Geological Survey. 1975. Water resources data for Louisiana.
Water Year 1975. Water Data Report LA-75-1.

U.S. Geological Survey. 1976. Water resources data for Louisiana.
Water Year 1976. Water Data Report LA-76-1.

U.S. Nat'l. Mar. Fish. Serv. 1975. Louisiana Landings, Annual Summary,
1974. U.S. Government Printing Office, Washington, D.C. (Its
current Fish. Stat. No. 6722).

Uttormark, P. D., J. D. Chapin, and K. M. Green. 1974. Estimating
nutrient loadings of lakes from non-point sources. Wisconsin Univer-
sity Water Resources Center, Madison, Wisc.

van Beek, J. L., W. G. Smith, and Philip Light. 1974. Water Management
Plan, Buffalo Cove Swamp. Report of Coastal Environments, Inc., to
the Atchafalaya Basin Division, La. State Dept. Public Works.

van Beek, J. L*, W, G. Smith, and J. W. Smith. 1977. Plans and concepts
for multi-use management of the Atchafalaya Basin, La. Environmental
Protection Agency, Socioeconomic Environmental Studies Series
(in press).

Van Sickle, V. R., B. B. Barrett, and T. B. Ford. 1976. Barataria Basin:
Salinity changes and oyster distribution. Lduisiana State Univer-
sity Center for Wetland Resources, Baton Rouge, La. Sea Grant
Publ. No. LSU-T-76-002.

Vollenweider, R. A. 1968. Scientific fundamentals of the eutrophication
of lake and flowing waters with particular reference to nitrogen and
phosphorous as factors in eutrophication. Tech. Report, DAS/CSI,
68-27. OECD, Paris, France.

Wagner, P. 1973. Seasonal biomass, abundance, and distribution of
estuarine dependent fishes in the Caminada Bay system of Louisiana.
Ph.D. diss., Louisiana State University, Baton Rouge.

Weiss, C. M.,, and E. J. Kuenzler. 1976. The Trophic State of North
Carolina Lakes. Water Resources Research Inst., UniverSity Of
North Carolina at Chapel Hill. Report No. 119.

Welch, E. B. 1968. Phytoplankton and related water-quality conditions
in an enriched estuary. J. Water Pol. Cont. Fed. 40(3):1711-1727.

Williams, J., J. Syers, R. Harris, and D. Armstrong. 1970. Adsorp-
tion and desorption of inorganic phosphorus by lake sediments in
a 0.1M NaCl system. Envir. Sci. Technol. 4:517-519.

= = = = m m m m m -M = = = m =

91*00 90'30 90,00'

30 @0

If.

... .. .........

A
Q

..Jo

iP
Highway 90
Intracoastal Waterway

Area 1

Area 2

Area 3

0 5 10 15 20 M

0. 5 10 15 20 25 30 Krn

Fig. 1. Barataria Basin's three areal divisions.

1898-1910

-30-00

-25.00

4.0 20.00

limit f M
3.0 -15.00
conc s

C@
E 2.0 -10.00

5.00
1.0

_j
- - - - - - - - - - ---- -- - - - - - - - - -
A Lac des Lake Salvador Lafitte Little Lake Barataria Bay X
Allemands

Fig. 2. Estimated phosphorus-loading rate (g/m2/yr) and salinity levels (ppt) at various locations
in Barataria Basin, 1898-1910. Conch range illustrates southern limit of oyster production.
'
im't of
I
conchs

............

-35.00
1961-1974

-30.00

-25.00

4.0 -20.00

limit of -15.00
3-or conchs

-------------

-10.00
2.01-
- ---------------L--------------

-5-00

A Lac des Lake Salvador Lafitte Little Lake Barataria Bay A:
Allemands
Fig. 3. Phosphorus-loading rate (g/m2/yr) and salinity levels (ppt) at various locations in Barataria
Basin, 1961-1974. Conch range illustrates southern limit of oyster production.

2000

- 30.00

- 25.00

20.00
4.0 2.

3 -15.00
-or
- ----------------------
N
E 2.01- -10.00
N ---------------------

10 -5.00

%4
A Lacdes Lake Salvador Witte Little Lake Barataria Bay
Allemands

Fig. 4. Estimated phosphorus-loading rate (g/m2/yr) and salinity levels (ppt) at various loc ations
in Barataria Basin for year 2000. Conch range illustrates southern limit of oyster production.
------------- ---------

1.0

.8-

.6-

.4-

.2-

0
0 40 80 120 1@0 200 240
qS m yr
Fig. 5. The relationship between the areal water load (qs) and
phosphorus retention (Rp) in fifteen southern Ontario lakes.

90,30' 90*ccr

30000
rc,@,S@ 18 Bay
8.
19 Omi
7 20 Littl
21 Littl
22 Joh
13@6

Saline 23 Bar
Fresh 1 Bayou Citamon 24 Bar
25 Cary
2 Omitted 912
3 Stream Flowing into Bayou
Chevreuil U
-4 Bayou Chevreui(
7
5 St. James Canal 4
6 Bayou Chevreuil
?L
7 Lac Des Allemands
8 Lac Des Allemands Recreational Development
29@30 9 Bayou Des Allemands A
10 Burchell Canal (Old Oil Development)
ZI 2
*Simoneaux Ponds
Brackish 11 Bayou Des Allemands 23 A
12 Lake Salvador
13 Lake Cataouatche
V,
7E .5 4*
31 2
14 Bayou Segnette Canal
15 !ntracoasta! Waterway
16 Bayou Barataria
17 Bayou Rigolettes

P25

0 5 10 15 20 Mi.

0 5 10 15 20 25 30 Km.

Fig. 6. Location of the 23 water-quality stations in Barataria Basin.

80
secchi depth

20-

12 14 16 18 20 22 24
Station

total phosphorus
.25-

.20

.01-

.05 ----F-T-T-7-T-T-T-F-T-7-T-T-F-r- -I-1--
10 12 14 16 18 20 22 24
Station
Fig. 7. Secchi depth (top) and phosphorus con-
centrations (bottom) at various brackish and
saline stations in the Barataria Basin. See
text for discussion. Solid squares and 3
circles are clean water stations (group 2,
Fig. 9). Open squares and stars are eutro-
phic stations (group 3b, Fig. 9).

,%0(%

to jlp
01300,\s e\s
. 'A

'c' 0 -cb -

01V es @;;s6

Ca Wo
t\D
rp
Active Source
Saturated Sink 10
Burchell Canal
Bayou des Allemands
Gulf Intracoastal Active Sink
Waterway S
Bayou Segnette Canal ource
Lake Cataouatchie Lake Salvador
Bayou Perot Potential Sink
Barataria Bay Bayou Rigolettes
Barataria Waterway -Little Lake
Uttle Lake Oil Field Carninada Pass
john the Fool Bayou

Fig. 8. Schematic classification of brackish and saline stations in the
Barataria Basin according to water quality.
0

/-3

IN
1-1 3b
/*15 N,

*14
-4

*9
Factor 1
*18 1*16
tk-17 22
24* 012 *23 *20 -5

-13 010
*25 3a
-21 C\I

0
2

Fig. 9. Graphic representation of the results of factor analysis and cluster analysis. Dashed lines
enclose cluster groupings.

At S p

La ke Ponrchartra-

v e
7A
30,00

lir

q
--19 30
0,

0 5
70 W. f, 4

'a 0 '5 2D @5.' 3DK- 09-)

Fig. 10. Lake Pontchartrain Basin.

22.0-

20.0- Suburbs of New Orleans

18.0- City of New Orleans
Population Served by Maurepas
Complex
16.0-
Population Served by V,
00-@ Tangipahoa River
14.0-

(L
u') 12.0-

T-
X
C 10.0-
0
-I.-
cz
=1 8.0-
CX

6.0-

4.0- ........

2.0-
........ ...

1.0 MM
1900 1920 1940 1960 1970 1990 2000

Time Projection
Fig. 11. Population growth in Lake Pontchartrain drainage area.

60- 60

Freshwater Input

-50
Artificial Phosphorus Input

LJ Natural Phosphorus Input 0
4- -40
D 40-
a
C

=r
0 0
30- -30
7/z =T
0

20 20

10 -10
7/71

.... ........

rim
0 0
Pass Tangipahoa Net Tchefuncta Bayous City of jefferson
Manchac River Precipitation River Liberty New Orleans Parish
On Lake and (N.O. Suburbs)
Lacombe

Fig. 12. Major freshwater and phosphorus sources of Lake Pontchartrain.
71

91*00 9013or

30*00

AREA I

29'30 AREA 11

0 5 to is 20 Mi

0 6 10 15 20 29 30 Km

Fig. 13. Terrebonne Basin: Area I and Area II.

El Area Closed to Oyster Culture, April 1976

Fig. 14. Current closure of oyster grounds in Terrebonne Basin.

30'00'

Point Chevreuil f
Rabbit Island
29o3O'

0 5 10 15 20 Mi.
0
m
0 5 10 15 20 25 30 Krn

Fig. 15. Atchafalaya Basin.

93*30-

Calcasieu Lake

L a.

2 7

..Phos*o-a.te ('onceni-atlon a- 0-017COO
L' 0
3.0 o Total P@-,os-,Ihoruzs at OBC17090
To`al Phosn-@-_us at 3014-.'209".1135-00
Total -P-'los7h,or'@s at 295 '00932CLOOO
Sz Total Phcs-.:@horus at 00015900
0
-4 2.0-

0
S::
0

J1
0.0. -------T
1O/-_'q 1C/70 1C/71 1P72 1C/73 10/74 10/75 Time
Fig. 17. The variation in phosphate concentration at one station (Burton Landing) on the
Calcasieu River and the variation in total phosphorus concentration at this and three
additional stations along the river. Data is graphed for the water years 1970-1975.
Note that total phosphorus is measured on a phosphorus basis, whereas the phosphate
concentration is graphed on a phosphate basis. There appear to be relatively high
values of P during late summer, perhaps largely due to the low river-flow rates at
that time (Johnson 1977).

030-

20 -

15 -

10-
0

:2
.s 5-
.0@
40 60 80 100 120 140 160 180 200

Total Nitrogen and Phosphorus, Ibs/acre
Fig. 18. Yield of sugarcane (lbs/acre) compared to amount of
total nitrogen and phosphorus added (lbs/acre).

125--12.5
0 Dry Matter 50-
0 Nitrogen
8 P205
V K20
100-10.0 40- _150

(D
I
U (D-

75--75
30-

CL
CIL
50-5.0 1 D
20- C1
OCI4

-50

25--2,5 10-

0' 0
March April May June July Aug Sept Oct Noy

Fig. 19. Uptake rates over time for nitrogen and P 20 5 in sugarcane.

I
I
I
I
I Part Il 0 Land Loss
by N. J. Craig, R. E. Turner
I and J. W. Day Jr.
I
I
I
I
I
I
I
I
I
I
I
I
I

CONTENTS
Part 11

List of figures 96

List of tables 97

Abstract 98

Introduction 99
Documentation of Land Loss lot
Adams et al. (1976) inventory lot
Barrett's inventory 104
Chabreck's inventory 105
Land loss by vegetative type and management unit 106
Summary 106
Causes of Land Loss Ito
Natural land loss Ito
Man-induced alterations ZZ3
Man-induced vs. natural land loss Z25
Summary of land loss L26
Cumulative Impacts of Land Loss 129
Salinity changes and eutrophication L29
Waste buffer Z30
Storm buffer Z30
Fisheries Z31
Management Concepts and Guideline Recommendations Z33
Management Data Needs 135
References Z38
Figures after page Z40
Acknowledgments 157

LIST OF FIGURES

la. Land loss and gain in the coastal zone. Z4Z

lb. Vegetative types in the coastal zone. Z42

2. Rate of shoreline change. Z43

3. Rockefeller Refuge on the Chenier Plain. 144

4. Golden Mi@adow oil field, 1940. Z45

5. Golden M@adow oil field, 1953. 146

6. Golden A!adow oil field, 1969. Z47

7. Relationship between size and increase in width of canals. Z48

8. The relationship between density of canals and the average annual
land losses in coastal Louisiana from 1930-1969. L49

9. The areas in south Louisiana which were investigated to determine the
absolute area of canals and marshlands from 1960-1974. Aerial photomosaics
were used! (Adams et al.). Z50

10. The relationship between canal density and the land losses from 1960-1974
for each area shown in Fig. 2. Land areas were determined from aerial
photographs. Z5Z

11. Relationship between shrimp yields and wetland area on world-wide basis. 2'.52

12. Relationship between fisheries yield and intertidal areas for the Gulf -
of Mexico. Z53

13. Relationship between average inshore shrimp yields and marsh acreage in
several hydrological units of Louisiana. Z54

14. Recent landings for Louisiana and the Gulf of Mexico (U.S. only). Z55

15. Recent value of fisheries landings in Louisiana and for the Gulf of
Mexico (ex-vessel). Z56

LIST OF TABLES

1. Areas of man-made features in the Barataria Basin Management Unit.
(from Adams et al. 1976). Z03

2. Summary of inventory results. Z07

3. Land loss (acres/year) per vegetative type and % of total land loss
for management units of Louisiana coastal zone calculated from Fig. 1.
(1890-1960). ZZ9

4. Deltaic units of Mississippi River and Carbon-14 age (Morgan and
Larimore 1957). ZZ9

5. Change in width of major passes in Barataria area (ft.) (Van Sickle
et al. 1976). 119

6. Canal area over time (acres). Z19

7. Annual increase of canal width W and the time necessary to double
the canal area (dt). The dav, a- extrapolated from the previous six
tables. 120

8A & B. Deltaic units vs. shoreline retreat and land loss rates. 127

ABSTRACT

The causes and consequences of wetland losses in coastal Louisiana

are examined, in this paper. The coastal zone area, particularly the

Barataria Basin, has been inventoried by several different mapping tech-

niques. Some of these methods appear to underestimate actual land loss,

perhaps by as much as 50 percent. It appears the use of photomosaics

most accurately delineates land loss and the true density of canals.

Total wetland loss in the Barataria Basin, calculated from Gagliano and

van Beek (1970) for the interval 1890-1960, is 1,908 acres per year.

The data of Adams et al. (for the interval 1960-1974) indicates total

marsh area losses between 3,135 to 6,510 acres per year for the basin.

The rate of 'Land loss in the Barataria Basin appears to be accelerating.

Of all land 'Loss occurring in the coastal zone, 75 percent is in the

brackish and saline marshes.

Land loss is a cumulative impact, the synergistic result of many

impacts both natural and man-induced. Natural land losses are due to

land subsidence, natural decay of abandoned river deltas, and

erosion due to wave energy and storms. Man-induced land losses result

from flood control practices, impoundments, and dredging of canals and

channels with their subsequent widening. Wetland loss also results from

the placement of spoil upon the marsh and impounded areas which are

drained for land reclamation.

In the Barataria Basin 2.6 percent of wetland area has been con-

verted to canals. The total wetland area lost due to canals may be close

to 10 percent if spoil area is included. The interrelationship between

hydrology, laad, vegetative type, substrate, subsidence, and sediment

supply are complicated, however hydrologic units with high canal density

are generally associated with higher rates of land loss. Natural land

losses are magnified by man-induced losses and the activities of man are

becoming the principle determinant of the rate and nature of land loss.

Some of the cumulative impacts of land loss are: increased saltwater

intrusions, a loss of a capacity to buffer the impact of large additions

of nutrients, and a reduction in storm buffering capacities. One measure
of the impact is that approximately 8-17 x 106 dollars of fisheries

products and services are annually lost as a consequence of present land

loss.

Land loss, when viewed at a basin level, transcends the differences

in local vegetation, substrate, geology, and hydrology. Management con-

cerning land loss should, therefore, focus at the basin level. Manage-

ment concepts and guideline recommendations revolve around the need to

appreciate the long-term interrelations of the wetland estuarine system.

I. Introduction

Land loss in Louisiana's coastal zone is a problem which has broad

cnvi7--onmental and economic ramifications. The cumulative impacts

resulting from land loss include (1) changes in hydrology which contribute

to an increase in saltwater intrusion and eutrophication; (2) losses in

storm buffer capacity; (3) a decrease in waste assimilation by wetlands;

and (4) diminishing nursery grounds for Louisiana's coastal finfish and

shellfish resources. Land loss is the consequence of many interacting

factors, including flood control, navigation improvement, impoundments,

canalization, and channelization as well as natural biological and

geological processes. Land loss, when viewed at a basin level, tran-

scends differences in local vegetation, substrate, geology, and hydrology.

The coastal area of southern Louisiana is the result of' sediment

deposition by the Mississippi River over the past 5,000-10,000 years

since the last rise in sea level. The broad nature of the deltaic

plain results from the frequent channel changes by the Mississippi River,

creating extensive areas of near-sea level marshes and swamps (Frazier

1967).

In an active delta complex, deposition of sediments will exceed

erosion and there is a net land gain. In an abandoned delta, the reverse

holds true. Historically in Louisiana, the loss of land in an old delta

was compensated for by the building of new land in the active delta.

This is no longer the case. Due to the extensive man-made levee system

along the.Mississippi, overbank flooding has been virtually eliminated

and much of the sediment is deposited along the continental shelf in deep

Gulf of Mexico waters. Although the Atchafalaya is creating new sub-

deltas, it is not keeping up with the rate of land lost throughout the

coastal zone.

The coastal land that is lost is generally wetlands (marsh and

swamp). This occurs in three basic ways: (1) Wetland can be converted

to open water due to natural or man-made processes. Land loss of this

type can be caused by erosion, or by dredging to form canals, channels,

harbors, etc. (2) Wetland can be covered with fill material and con-

verted to terrestial habitat. This type most often results from the

placement of spoil from dredging. Examples of this type are spoil

levees formed. along channels and canals and also along "fingerfill"

type impoundments. (3) Wetlands can be partially or completely isolated

by levees. Some impoundment areas are permanently flooded to enhance

waterfowl populations and/or maintain freshwater conditions. Examples

of this type of impoundment are on the Sabine and Lacassine National

zoo

Wildlife Refuges. Other diked areas are often drained, most frequently

by pumping, for agricultural or urban purposes. Most of metropolitan

New Orleans is drained wetlands.

We will define land loss as the substantial removal of land from

the ecological role it played under natural conditions. This definition

includes all three types of wetland alteration mentioned above.

Objectives

We have four objectives in this paper:

(1) To review the existing information and make a qualitative and

quantitative documentation of land loss in coastal Louisiana.

(2) To determine the relative importance of various processes in

causing land loss.

(3) To investigate the cumulative impacts of land loss.

(4) To present management guidelines, recommendations, and data

needs.

II. Documentation of Land Loss

Several inventories have been made of water bodies (including canals

an@. impoundments) in Louisiana's coastal zone. These surveys were under-

by Adams et al. (1976), Barrett (1970), Chabreck (1972), and

Gagliano and van Beek (1970). The results of these studies are not

completely consistent, therefore, we feel that an analysis of the methods

and results is necessary.

A. Adams et al. (1976) Inventory

Adams et al. measured the man-made features within the Barataria Basin

Management Unit from the 1969 New Orleans District Corps of Engineer's uncon-

trolled photomosaics. Different areas were computed automatically using a

Calmagraphic T.1 Digitizing System. Where coverage by the photomosaics was

not complete, the latest editions and largest scale USGS quadrangle charts

were used. The resolution included all canals and impoundments that show areal

extent ona standard 7 1/2 minute quadrangle chart.

The use of uncontrolled photomosaics results in some loss in accuracy,

but the interpretation is not difficult and boundaries can be easily determined.

The use of one scale (1:20,000) and one date for the inventory of the entire

area yielded reproducible data (Adams et al. 1976). Twelve types of man-made

features were recorded: rig access canals, pipeline canals, oil field naviga-

tion canals, navigation canals, transportation embankments, agricultural

drainage canal:3, agricultural impoundments, industrial impoundments, urban

drainage canalS, agricultural commodity-transportation canals, oil field

embankments, and mineral extraction navigation canals. These were all computed

by environmental unit (saline, brackish, fresh marsh and swamp). Of these man-

made features, rig-access canals are the most important components of land loss

in saline and brackish marshes while agricultural impoundments, are most important

in fresh marshes and swamps. Areas of these man-made features, are presented in

Table 1.

Canals in the Barataria Basin are 1.5 percent of the total area
(including marsh, swamp, and topographic high land and water) and 2.6

percent of the total wetland area (saline, brackish, fresh marsh and
swamp f ores t) .. I
Barataria Basin - Percentage of Wetland Area

Saline Brackish Fresh Swamp Total

Canals only 3.8% 3.7% 2.1% .94% 2.6%

All man-made
features 3.8% 4.6% 8.4% 7.7 % 4.9%

102

TABLE 1. AREAS OF MAN-MADE FEATURES IN THE BARATARIA BASIN
MANAGEMENT UNIT (From Adam et al. 1976).

Environmental Units (sq. miles)

Man-made features Saline Brackish Fresh Swamp Total

Rig Access Canals 5.29 11.68 5.21 1.09 23.27

Pipeline Canals - 2.23 1.65 .48 .20 4.56
61 ft width

Pipeline Canals - .29 .05 -.16 0 .50
130 ft width

Oil Field Navigation Canals .02 .19 .19 0 .40

Navigation Canals .87 1.98 .5 1.18 4.53

Transportation Embankments 0 .43 .51 .48 1.42

Agricultural Drainage Canals 0 .91 .82 .98 2.71

Agricultural Impoundments 0 3.55 21.39 6.06 31.00

Industrial Impoundments .05 0 0 .07 .12

Urban Drainage Canals 0 .40 .10 .07 .57

&gricultural Commodity - 0 .03 0 .02 .05
Transportation Canals

Field Embankment 0 0 0 .22 .22

Extraction .61 0 0 0 .61
i@@avigation Canals

@her .05 0 0 0 .05

9.41 20.87 29.36 10.37 70.01

Summary:
Total area of all Total area of
Environmental Unit man-made features canals (sq. miles)

Saline 9.41 9.36
Brackish 20.87 16.89
Fresh 29.36 7.46
Swamp 10.37 -3.54
Total 70.01 31.25

L03

Land loss rates were determined for different environmental units

salt, brackish (including intermediate) and fresh marsh -- within Lafourche,
Jefferson, and Plaquemines parishes in the Barataria Basin. Fourteen sampled

areas were selected to measure land loss throughout the years 1960, 1971, and

1974. USGS quadrangle sheets (7 1/2 and 15 minute scale) were: used for the

1960 base information. For 1971, USGS orthophoto quadrangles were utilized

and where possible, NASA infrared color photographs were used. Infrared color
photographs (NASA Mission 293) were used to obtain 19.74 data (Adams et al. 1976).

The figures showed considerable variation for test sites within the same

environmental unit. A high and low annual value were presented as below:

Salt Marsh -- loss 1,262 to 959.3 acres/year
Brackish Marsh -- loss 3,872 to 1,299 acres/year
Fresh Marsh -- loss 1,376 to 876.8 acres/year
Total. combined marshes -- loss 6,510.4 to 3,135.3 acres/year

B. Barrett's Inventory

Barrett ('1970) measured the area of canals, natural channels, and

water bodies south of the Intracoastal Waterway and surrounding Lakes

Pontchartrain and Maurepas. The total area studied comprised 11,055

square miles. The surface area of large water bodies was measured by

planimeter; the area of canals and streams was determined by multiplying

the measured length by the average width. Maps scales used ranged from

1:250,000 to 1:24,000. The dates of individual maps also varied con-

siderably ranging from 1948 to 1969. Although mapping in coastal

Louisiana has been generally very complete, in some instances the most

recent maps were 21 years old (Gagliano 1973). It is probably that

because of the age of some maps used, a large percentage of the more

recently developed canals were not included in this inventory. There-

fore, the estimates should be conservative.

Z04

Barrett reported that there were 4,572 miles of canals and 7,227

miles of natural channels (Bayou and Passes) in the coastal zone. The

total area of canals and channels was 42,004 acres (65.8 sq. miles), or

0.6 percent of the total study area.

C. Chabreck's Inventory

Another study which generated information on the areas of canals was

clone by Chabreck (1971). The measurements were a product of a helicopter

survey of marsh vegetation and soils. Sampling was at 0.25 mile intervals

along north-south traverse lines spaced at 7.5 minutes of longitude along

the coast. The total study included 12,224 square miles. Surface fea-

tures were recorded at 7,127 different points, from which surface areas

of various water body classes were determined.

Canals were recorded as a point and the total points representing

canals were taken as a percentage of the total acreage. Chabreck esti-

mated that the total acreage of canals was 5,198 or 1.1 percent of the

area sampled in Barataria Basin, and 47,475 acres or 0.7 percent of the

entire coastal zone.

D. GaEliano's Inventory

Gagliano and van Beek (1970) determined net land loss in the Louisiana

coastal zone from 1890 through 1960 (See Fig. 1), U.S. Geological Survey

maps at scales of 1:24,000 and 1:62,500 were used, and 80,580 sample grid

points were evaluated in a study area of 20,400 sq. miles. These data

were used to establish rates of change of land/water ratio. Results of

the study indicated that land is being lost in the Louisiana coastal zone
at a rate of 16.5 miles 2 per year.

Gagliano's estimate of canal acreage of 0.9 percent of the coastal

zone seems conservative compared to Adams et al. It appears that linear

Z05

features such as navigation and pipeline canals may be underestimated by

the point-counting method.
A comparison of the size of the study area, percentage canal area/

marsh area, and methodology of each inventory is provided in summary form

in Table 2.

E. Land Loss; by Vegetative Type and Management Unit

To obtain a general idea of land loss by environmental units and manage-

ment units, a composite map was created by superimposing Gagliano (1970) map

of land loss and gain in the coastal zone over Chabreck et al.'s (1968) map of

vegetative types (environmental units) (see Fig. 1@. This composite map was

digitized to determine land loss in acres per year per vegetative type for

the seven management units of the Louisiana coastal zone (see Table 3).

These results indicate that the brackish marsh is deteriorating at a

higher net rate than any other wetland type (Table 3). The total rate of land

loss for brackish marsh across the state is 3,320.2 acres per year, @704.2

acres per year for saline marsh, 1,212.5 acres per year for fresh

marsh, and 54.1.7 acres per year for the swamp forest.

F. Summary

The Barataria Basin has been inventoried by several mapping methods. It

appears that photomosaics most accurately delineate the true density of canals

and total marsh area in the Barataria Basin. The accuracy lies in the fact

that it gives complete coverage of the coastal zone during a single year period,

in contrast to, maps whose dates may vary as much as 20 years. The scale for

the photomosaics is 1:20,000. The photomosaics are all recent and are a direct:

picture of the area. Their use is much preferred over the use of maps,

106

TABLE 2. SUNHARY OF INVENTORY RESULTS

% Canal/
Area -Marsh Methodology Reference

Barataria Basin 2.6% photomosaic Adams et al.
(2,427 sq miles) (1976)

Barataria Basin 1.1% Points counted by Chabreck
(2,015 sq miles) helicopter from (1972)
preselected tran-
sects

Barataria Basin 1.0% map measurementwith Barrett
(to Intracoastal Water- various dates and (1970)
way, 1,370.5 sq miles) scales

% Canal/Total Area Marsh and Water

Louisiana Coastal Zone .9% Point count samples Gagliano
(20,480 sq miles) of 2 series of maps, et al.
80,560 pts per (1970)
series

Louisiana Coastal Zone .7% points counted from Chabreck
(12,224 sq miles) Preselected tran- (1972)
sects

Louisiana Coastal Zone .6% map inventory Barrett
(11,055 sq miles) (1970)

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TABLE 3. LAND LOSS (ACRES/YE,AR) PER VEGETATIVE TYPE AND %
OF TOTAL LAND LOSS FOR MANAGEMENT UNITS OF LOUISIANA
COASTAL ZONE CALCULATED FROM FIG. 1 (1890-1960).

Saline Brackish Fresh Swamp
Managenent Unit Marsh Marsh Marsh Forest

Pontchartrain - St. Bernard 399 1060.6 7.4 178.3
24% 64% 1% 11%

Mississippi ]R-iver 3.7 232.8 286.2
1% 37% 62%

Barataria BaSin 818 901.9 188.2 142.7
40% 44% 9% 7%

Terrebonne Basin 441 454.1 411 167.2
30% 31% 28% 11%

Atchafalaya River* 1.7 11.6 105.6q 16.2
1% 9% 78% 12%

Vermilion Basin 12.9 397.8 27.3 37.3
3% 84% 6% 7%

Chenier Plain 27.9 261.4 186.9
6% 55% 39%

TOTAL 1704.2 3320.2 1212.5 541.7

25% 49% 18% 8%

*This does not include the current delta building in the At&Aafalaya Bay.

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especially older maps, of the 1930s, when surveying techniques were not

accurate, and in which canals and other features appear to be stylized.

Within the entire coastal zone, canals alone are equal to at least

0.9 percent of the total present area of marsh and water. If we assume

a marsh:water ratio of 1:1.52 (Chabreck 1971), this equivalent to at

least 1.37 percent of the present marsh area. This latter estimate is

low because of the techniques used and does not include significant

amounts of other man-made features. The greatest rate of land loss is

occurring in the brackish and saline marshes (74 percent of all land

losses). The land loss data calculated from Gagliano and van Beek (1970)

are for intervals 1890-1960. The data of Adam et al. is for the inter-

val 1960-1974. A comparison of the two data sets for the Barataria Basin

is presented below:

CALCULATED FROM

Gagliano and Van Beek Adam et al.

Salt Marsh loss 818 acres/yr loss 1,262.4 to 959.3 acres/yr
Brackish Marsh loss 902 acres/yr loss 3,872.0--1,299.2
Fresh Marsh loss 188 acres/yr loss 1,376 to 876.6
lotal Marsh Area loss 1,908 acres/yr loss 6,510.4--3,135.3

The rate of land loss determined by Adams et al. is significantly

hipher than that calculated from Gagliano and van Beek. This may be

because of the methods involved. Tests comparing digitized areas and

point-counted results yielded similar findings (Adams et al.). The

only difference between the two methods, then, could be due to the

sources of information. Gagliano employed maps dating back to 1890.

Adams et al. used 1960 quadrangle maps and 1971, 1974 aerial photography.

It is not likely that these methods can account for the large dif-

ferences in land loss rate. Therefore it seems that the rate of land

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loss in the Barataria Basin is accelerating.

III. Causes of Land Loss

Land loss is a cumulative impact, the synergistic result of many

individual and multiple impacts. These impacts are b oth natural and man-

induced. Natural land loss is caused by subsidence and net erosion in

abandoned ri,mr deltas, while land loss caused by man results from such

activities as reclamation and dredging. In this section of the paper

we will discuss the various causes of land loss and their relative

importance.

A. Natural Land Loss

1. Land Subsidence

Land subsidence, the lowering of land surface relative to sea level,

plays an active role in the coastal zone. The causes of subsidence are (1)

eustatic sea level changes, (2) regional subsidence caused by base downwarping

isostatic adjustment) from sedimentary loading (3) compaction of sediments

(discussed below) and 4) tectonic activities including faulting, folding,

fracturing, and flowing within the thick sedimentary section (Adams et al.

1976).

Compaction of sediment is a result of several factor s, some of which

are caused by man.

a) Differential consolidation owing to textural variability in the

sediments. (natural)

b) Consolidation of underlying sediments from weight of features

such as natural levees, beaches, artificial levees -- particu-

larly when the features have been deposited over week

compressible foundations. (both natural and man-made)

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losses of the sediment are high as are resulting subsidence rates. As

connate fluids are lost, the rate of compaction and subsidence gradually

diminishes (Morgan and Larimore 1957).

3. Loss of Barrier Islands and Inlet Widening

Barrier islands, such as Timbalier Island, Grand Isle, and Grand

Terre are a strong defense against marine processes and hurricanes. The

tidal passes associated with barrier islands can be viewed in part as

control valves of the estuaries (Gagliano 1973) because they regulate the

amount of salinity intrusion, storm energy, etc. that enters the

estuaries.

The barrier islands along the coast are undergoing erosion. In the

Barataria Basin, the barrier islands Grand Isle and Grand Terre were

listed as areas of "critical erosion" by U.S. Army Corps of Engineers,

National Shoreline Study. Between 1960-1972, 172 acres (18 percent) of

the principal Grand Terre island was eroded away. Between 1932 and 1969

the average rate of barrier island erosion in the Barataria Basin was

119 acres per year. The width of the tidal passes in the Barataria Bay

area is increasing as is the rate of increase of width (Table 5).

The coastal erosion of the barrier islands is due to lack of sedi-

mentation from the Mississippi River regional subsidence, hurricane

damage and man-induced changes such as dredging of canals on the bay-

side of a number of islands (Gagliano 1973).

4. Type of Substrate

Land loss will be locally affected by the substrate type, i.e.,

clay, silt, peaty areas, natural levees, beaches, etc. Across the

coastal zone, particularly in the deltaic plain, the substrate is highly

diverse and in many cases unstable, resulting in a complex, variable

c) Local subsidence of compressible materials through consolidation

or displacement by objects such as buildings, pile structures,

fills, bench marks, and tide gages. (man-induced)

d) Lowering of water table through extraction of groUrLdwater,

salt, or sulfur; also "reclamation" practices that employ

diking, construction of water control structures, and drainage

of lands for agriculture or flood protection. (man-induced)

e) Extraction of oil, gas, sulfur, and water-from salt: domes is

known to have resulted in subsidence. (man-induced)

The direct supply of sediment from the Mississippi River which could

balance the affect of subsidence has been eliminated due to levee construction.

Some compensatory sedimentation comes from the organic matter deposited on the

floor of the marsh and estuary by marsh plants, but it is not enough to

counteract the subsidence rate.

2. Delta, Growth and Decay

Coastal Louisiana is the result of deposition of the Mississippi

River sediments in different delta lobes during the past 5,000-10,000

years since the last rise in sea level. The modern Birdfoot delta is the

latest of seven major lobes of the Mississippi (see Fig. 2). For the

past several thousand years, the Mississippi River has followed a pattern

of extending a delta seaward into the Gulf in one area, and after a few

hundred years, abandoning it gradually in favor of a shorter adjacent

route of steeper gradient (Morgan and Larimore 1957). The abandoned

deltas are in. various stages of decay. Table 4 lists the approximate

ages of several deltaic units.

Rates of' subsidence and erosion of an abandoned subdelta follow a

decelerating pattern. Immediately upon abandonment, interstitial water

ZZ2

surface (Adams et al. 1976). A three-dimensional knowledge of an area

can help explain local variations in land-loss rates. For example, a

network of natural levees, at the surface or submerged, provide a more

solid, stable substrate than the surrounding marsh. These areas are

capable of withstanding erosional forces such as wave attack for longer

periods of time. St. Mary's Point, a remnant of a natural levee in

Barataria Bay, is such an example. In Lake Salvador, Little Lake areas,

there are several examples of old channels which are eroding more slowly

than surrounding marshes. Organic soils, such as muck (20 percent-

10 percent organic content) and peat (50 percent or greater organic

content) are more unstable and more susceptible to the natural and man-

made forces influencing land loss.

B. Man-induced Alterations

1. Flood Control

The Mississippi River deltas historically have been areas of dynamic

change as a result of fluvial processes advancing the delta seaward and

marine erosion coupled with subsidence encouraging delta retreat. As a

result of many years of levee construction, the Mississippi River has

been effectively "walled in." The levee line on the west bank begins

just south of Cape Girardeau, Mo., and with its incorporated structures

(except where the St. Francis and Arkansas-White Rivers join the

Mississippi) extends unbroken to the Gulf of Mexico. The east bank is

protectedby levees alternating with high bluffs. When major floods occur

and the carrying capacity of the channel is exceeded, relief outlets

through Birds Point-New Madrid, Atchafalaya Basin, and Bonnet Carre

floodways are opened and the flat lowlands at the junctions of tributaries

with the Mississippi are flooded (Mississippi River Commission 1964).

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These flood control measures have interrupted the balance between

riverine and marine processes causing sediment transport, deposition,

and valuable fresh water nutrients which built and stabilized the marsh

and swamp areas to be virtually eliminated in coastal Louisiana. Most

of the sediment and nutrients of the river are now being depOSited in the

deep Gulf of Mexico and do not contribute to the construction or main-

tenance Of the coastal wetlands. The development of the Atchafalaya

Delta is an exception.

2. Canals

Canals built for oil recovery, navigation, and other activities

densely Interlace the coastal zone. The construction of these canals

has led to direct land loss by dredging and spoil deposition and to

changes in hydrology. In section II the areal extent of canals was

documented. In this section, canal widening and spoil banks will be

discussed.

a. Canal widening

"Many channels began as small significant pirogue ditchE@S, which

allowed the trapper to successfully work in the alluvial wetlands.

However, through repeated use, storms, and current flow, they enlarged

so sailboats and an occasional lugger could take advantage of' the

channel and have become major landscape features. They are now permanent.

The only indications of human origin lie in their straightness and rela-

tionship to the natural waterway. The work of the canal builders con-

tinues to have a decisive and cumulative impact on wetlands environment.

Some trails (trainasse) are over 100 years old and have become a vital

part of the total transportation network; they are a visible segment on

the landscape and have affected drainage patterns, influenced salinities,

Z14

and are a reminder of Man's abilities to unknowingly change the delicate

balance in the natural system" (Davis 1973).

There are numerous example that demonstrate the widening of various

canals over extended periods of time. Canals widen through usage, gener-

ally as a result of wave action, and altered hydrological pattern. Another

important factor is the condition of the marsh substrate;the softer or

more fluid and organic the marsh, the more susceptible it will be to

erosion,(Table 3).

i. Example of pirogue canal widening

one extreme example of canal widening is in the Barataria Basin.

Fifty years ago Matthew Creppel used a pirogue paddle to cut a 40-inch wide,

12-inch deep ditch (trainasse) between two bayous in the vicinity of

Bayou St. Denis in Barataria Bay. Today this trainasse has eroded into

a bayou 200-feet-wide and 8 to 10 feet deep. There is no evidence this

canal has ever been dredged. The widening has probably resulted in a

change in circulation patterns. Other settlers recall when large parts

of the basin were trapped using trainasses. Many of these trapping

regions are gone, eroded away, the ditches having enlarged into major

channels or coalesced to form larger water bodies (Davis 1973).

ii. Rockefeller Wild Life Refuge

Lewis Nichols conducted several studies concerning the erosion of some

of the numerous canal banks on the Rockefeller Wild Life Refuge (Nichols

1958, 1959). He presents examples of canals, relating to oil field

activities on the Chenier Plain of Louisiana, and their widening over

extended periods of time (See Fig. 3).

Humble Canal, extending from East End Headquarters on the Grand

Chenier Ridge Complex to Joseph Harbor Bayou (5.26 miles), was originally

IZ5

dredged as 65 feet in width in 1940. In 1953, it was redredged to a width

of 65 feet. Since 1954 the canal has widened at a rate of 1.16 feet per

month (as of 1958). The canal is used by:

1. Union Producing field development (6 wells) and production.
2. Shell Oil Company offshore field development standby usage,
since the fall of 1954.
3. Rockefeller Refuge management usage.
4. Royalite Lease exploration (3 wells, nonproductive).

Each of these four sections of the Humble Canal widened at different rates over

the five-year period:

1. East End Headquarters to Union Producing Junction,

Average width . . . . . . 135 feet
'Increase . . . . . . . . . 70 feet
Usage . . . . . . . . . . 1,2,3, and 4 (refer to units
itemized above)

2. Union Producing Junction to Joseph Harbor Bayou,

Average width . . . . . . 121 feet
Increase . . . . . . . . . 56 feet
Usage . . . . . . . . . . 2,3, and 4.

3. Union Producing Junction to Field,

Average width . . . . . . 110 feet
Increase . . . . . . . . . 45 feet
Usage . . . . . . . . . . 1 and 3.
4. Joseph Harbor Bayou to Royalite Lease exploration,
Average width . . . . . . 105 feet (approximate one section)
Increase . . . . . . . . 40 feet
Usage . . . . . . . . . . 3 and 4.

ZZ6

On Humble Canal the average canal and levee width is 239 feet.equivalent

to a land loss of 24 acres per mile of canal. Union Producing Canal averages

37 acres of land lost per mile of canal,and the Royalite lease canal approxi-

mately 37 acres per mile. By 1958, the entire Humble system contained 504

acres of wetland lost as a result of canal construction (Nichols 1958).

Another example is the Superior canal system. Construction began in the

winter of 1951-52, and when finished had a total of 15.3 miles of canals and

well locations. The canal system is a freshwater system and all canals and

well locations are lined with levees. All canals were constructed 65

feet in width and the spoil placed to make continuous levees on both sides.

The Superior Canal system is used for field development and production. The

total area of wetland lost to re.fuge management from canal and well construc-

tion was 648 acres as of 1958 (Nichols 1958).

Width of the Superior Canal (1952-1958).

Constance Bayou Field

1. Main Canal - Center of Section 4, T15S, R3W

Initial width . . . . . . 65 feet
Present width . . . . . . 158 feet
Increase . . . . . . . . . 93 feet
Present Canal is 243% wider than initially.

2. Main Canal - NW Corner of NE 1/4 of Sec. 15, T15

Initial width . . . . . . 65 feet
Present width . . . . . . 137 feet
Increase . . . . . . . . . 72 feet
Present Canal is 210% wider than initially.

L17

Deep Lake Field

3. Main Canal - Center of SW 1/4 of Sec. 14, T15S, R

Initial width 65 feet
Present width . . . . . . 150 feet
Increase . . . . . . . . . 85 feet
Present Canal is.231% wider than initially.

4. Main Canal - Center of NE 1/4 of Sec. 23, T15S, R3W

Initial width . . . . . . 65 feet
'Present width . . . . . . 137 feet
Increase . . . . . . . . . 72 feet
Present Canal is 210% wider than initially.

iii. Golden Meadow oil field

A study done by James H. Blackmon (personal communication) on the

Golden Meadow oil field represents canal widening over time. Blackmon

looked at Department of Agriculture 1:20,000 black and white photographs

of the Golden. Meadow oil field taken in 1940 and 1953. For -the year 1969,

he used U.S. Corps of Engineers 1:20,000 black and white uncontrolled

mosaics (See Figures 4, 5, and 6). Tracings of these maps were digitized

by Craig to determine canal widening over time. A summary of the

increase of canal area over time is given in Table 6.

iv. Summary of canal widening

From these examples it is evident that canal widening is occurring

throughout the entire coastal zone, influencing the geologically more

stable Chenier Plain as well as the Deltaic Plain. Its influence also

transcends the various marsh types; affecting fresh, brackish, and saline

marsh. The annual increase in canal width ranges from about 2 to 14

TABLE 4. DELTAIC UNITS OF MISSISSIPPI RIVER AND
CARBON-14 AGE (MORGAN AND LARIMORE 1957)

Deltaic unit . . . . . . . . . . . . . . Carbon-14 age of Deltaic
Units: years ago before
present

Late Lafourche Subdelta . . . . . . . . . About 200 to 300

Early Lafourche Subdelta . . . . . . . . 800 to 1500

Barataria Area (Barataria-
St. Bernard Subdelta) . . . . . . . . 2200 to 2700

St. Bernard Area (Barataria-
St. Bernard Subdelta) 2200 to 2700

Teche Subdelta . . . . . . . . . . . . . 3000 to 3500

Maringouin Subdelta . . . . . . . . . . . 4800

TABLE 5. CHANGE IN WIDTH OF MAJOR PASSES
IN BARATARIA AREA (FT.)
(VAN SICKLE ET AL. 1976).

% Year % Year
Pass .1932 1954 Change 1969 Change

Barataria 2,149 2,373 .45 3,500 2.59

Abel 212 499 3.89 1,233 6.03

Quatre Bayou 2,181 2,921 1.32 3,700 1.57

TABLE 6. CANAL AREA OVER TIME (ACRES)

Canal

Year AE BF GC BH Total

1940 28.1 5.1 8.3 16.6 58.2

1953 36.4 8.3 14.0 21.7 80.6

1969 58.8 10.8 24.3 25.6 119.6

TABLE 7. ANNUAL INCREASE OF CANAL WIDTH (K) AND THE TIME
NECESSARY TO DOUBLE THE CANAL AREA (dt). THE
DATA ARE EXTRAPOLATED FROM THE PREVIOUS SIX TABLES.

Annual Increase
Example Of Canal Width Doubling Time
(years )f survey) K (% per year) (years)

A. Bayou St. Denis 8.2 8.4
1926-19 76

B. Humble Canal 1) 8.3 8.3
1953-1-958 2) 7.5 9.3
3) 6.9 .10.1
4) 6.5 10.7

C. Superior Canal 1) 14.8 4.7
1952-1.958 2) 12.4 5.6
3) 13.9 5.0
4) 12.4 5.6

D. Golden Meadow 1) 2.0 :34.8
1940-1953 2) 3.7 18.5
1953-1969 3) 4.0 17.2
1940-1,953 4) 2.0 :33.6
1953-1969 5) 3.0 33.1
6) 4.6 42.1
7) 3.0 120.1
8) 2.0 6 7. 1

120

percent per year for a doubling time of 5-60 years (Table 7). There is

an apparent relationship between the size of the canal and the increase

in width (Figure 7). The larger the canal the faster it widens. This

may reflect the amount of boat traffic but certainly could reflect the

impact on the hydrologic flows since the larger the canal the larger the

water mass is that can move through it. To put this in perspective, as
previously stated, Gagliano estimated that 16.5 mi 2/yr or <.3 percent of

coastal Louisiana's land is being lost each year due to all factors --

natural and man-made. Canals, which represent 2-4 percent of the laud,

are widening at a rate an order of magnitude greater and may eventually

be the dominant factor in causing land loss in Louisiana - simply by

widening at this current rate. For example, assume an enlargement rate

of 5 percent/year. This is equivalent to a doubling rate of 14 years.

Thus in 14 years the present 2.6 percent canal density in Barataria Bay

(Table 1) may become 5.2 percent of the total area or -10.0 percent by

the year 2001.

These figures are preliminary estimates but the analysis indicates

that further work is warranted on this subject. It seems likely that

either boat traffic or increased water flow in the canals may contribute

to canal widening. Plugging canals, wherever possible, at both ends and

at intervals between should reduce the water flow and eliminate the boat

traffic, thus decreasing the annual rate of widening.

3. Spoil Banks

The discussion to this point has determined only the surface area

of wetland loss due to dredging. This, however, ignores the area of

spoil banks created in the process. Spoil, the material excavated by

dredging, is deposited alongside the dredged area and results in the loss

Z2Z

of wetland. Revegetation of the spoil area eventually does occur but

the change in elevation causes a change in species composition. At

elevations above high water, a full canopy of shrubs and small trees

may develop (Monte 1975). It is also possible that marshes in the vicinity

of the spoil. banks deteriorate due to impact of the bank on the sur-

rounding marsh. A specific example is the Mississippi River Gulf Outlet

(MRGO). Construction of the MRGO resulted in the destruction of 23,606

acres of marsh comprising 6548 acres for the channel and 17,,058 acres by

spoil deposition (Rounsefell 1964). For this example the ratio of canal

area to spoil area is 1:2.6.

McGinnis et al. (1972) noted that a 50-ft-wide pipeline floatation

canal the direct conversion of marsh area to canal area was 6 acres per

mile. The conversion of marsh to spoil levee was 12 to 18 acres per mile.

For this case the canal:spoil ratio ranges from 1:2 to 1:3. They r@oted

that the total marsh area with altered character would be in the range

of 30-36 acres per mile. Nichols (1958) suggests that the area of land

whose productivity is altered is 5 to 6 times that of the canal itself.

The inclusion of spoil bank area in the total figures for wetland

loss indicates that canals may be much more important in land loss than

previously indicated. For example, as previously mentioned, Gagliano

and.van Beek (1970) estimated the rate of land loss in coastal Louisiana
to be 16.5 mi2/yr. Of this, 6.53 mi 2/yr (39%) was due to canals. The

following table indicates changes in the ratios of wet land loss and

the percentage due to canals with different canal area:spoil area

assumptions. Even the 1:2 ratio is probably an underestimate because

the examples above suggest that spoil area is 2 to 3 times greater than

canal area.
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Canal area:spoil area Total Wetland Loss ' Amount due to
mi2/yr Canals mi2/yr

1:0 16.5 6.5 (39%)
1:1 23.0 13.0 (56%)
1:2 29.6 19.6 (66%)

Thus during the period covered by Gagliano and van Beek's study,

(1931 to 1967), wet land losses may have been much higher than he

estimated. Adams et al. (1976) estimated that 2.6 percent of the wetland

area in the Barataria Basin has been converted to canals. Using the same

ratios as above, the total wetland area lost due to canals may be around

10 percent,if spoil area is included. The area of wetland affected by

canals in the Barataria Basin may approach 20 percent of the total wetland

area if the area of wetland affected by canals is 5 to 6 times the area of

the canal, as previously mentioned. This suggests that the effects of

canals may be much greater than formerly thought. We believe that more

data are needed on both the ratio of canal area to spoil area and the

indirect effects of canals.

4. Land Reclamation

Land reclamation programs have been attempted in Louisiana since the early

18th century. These drainage projects, mainly for agricultural purposes,

reached a peak between 1915 and 1920. The majority of these failed due to

poor drainage, deterioration of levees, seepage, and the shrinkage and

oxidation of the organic soils--all resulting in land loss. The marshes

of the coastal zone have numerous rectangular lakes which document the

failures of these projects (Gagliano 1973).

In the early part of this century land reclamation of the wetlands for

urban and industrial developments began. New Orleans is the most extreme

example of this expansion. By the late 19th century New Orleans had used

all the available high grounds and began expanding into the marshes and

swamps. This expansion continues today. There are numerous, reclamation

projects in the planning today. "Active and proposed schemes related to

industrial sites, nuclear power plant locations, planned cormnunities, recrea-

tion complexes (harbor towns and fishing resorts), airports, and Florida-type

waterfront communities are appearing at an alarming rate." (Gagliano 1973).

Although this is not direct land loss, it is direct marsh loss and results

in loss of habitat, waste buffer, storm barrier, and nursery grounds. The

information in Table 1 shows that land reclamation is a major cause of land

loss.

5. Other Causes of Land Loss

In much of the coastal zone, there is a trend towards increasing salinity

(Lindall et al. 1972, Pollard 1973), which is due to several factors: (1) land

loss and inlE@t Widening, (2) changes in the flow of the Mississippi River

resulting in loss of freshwater input to the upper basins, and (3) specific

projects such as the Mississippi River Gulf Outlet (MRGO) and the

Barataria Waterway.

Canals which extend through various marsh types allow salt water,

which previously had no means of reaching fresh marsh, to have swift

and direct ingress into fresh areas. Small tidal channels and canals

connect MRGO with adjacent marsh areas, and the dieback of oak trees

along old natural levee ridge, dieback of marsh grass and enlargement

of marsh ponds is probably due to the increased salinities. In some

areas marginal to the channel, marsh deterioration is severe (Gagliano

1973). Changes in salinity due to the MRGO are well documented; the

recording stations in the vicinity of the channel show significant

changes after the channel was opened (1959) and completed (1962)

Z24

(Gagliano 1973). Similar situations exist for the Barataria Waterway,

the Houma Navigation Canal, and the Calcasieu Ship Channel. There is a

pressing need for more detail studies of this phenomenon.

Marsh deterioration also occurs as a result of severe storms such

as hurricanes, marsh fires, and muskrat eat-outs. Occasionally during

storm tides, waters with salinities above 50 percent sea water are carried into

fresh and brackish marsh. If this fails to run off rapidly, the vegetation

rots and results in areas denuded of vegetation (Treadwell 1955). If this

occurs in fresh floating marsh, the vegetation may be completely destroyed

and permanent ponds and lakes open up (Gagliano 1973). Deleterious effects

of high salinity flooding caused by hurricanes are mostly felt in altered areas

such as impoundments. The effects in natural marsh areas are often insignificant

or transient (Chabreck and Palmisano 1973, Ensminger and Nichols 1957,

Morgan 1959, O'Neil 1949, Webert 1956, Wright et al. 1970). The extent of

marsh deterioration which results from muskrat eat-outs and marsh fires is

not known.

C. Man-induced vs. Natural Land Loss

Land loss, as stated previously, is due to factors both natural and

man-induced. Natural land loss is magnified by loss attributed to man's

activities. According to Gagliano (1973) "the rate of land loss increase

directly attributed to man's activities is greater than the rate of

increase due to natural causes."

If land loss in the coastal zone were due solely to natural pro-

cesses, it is expected that the oldest deltas would be losing land at the

slowest rate, while the youngest would be losing land at the fastest.

Although this is true for shoreline retreat (Morgan and Larimore 1957),

Z25

it does not seem true for land loss in the four comparable areas with

available data (See Table 8A and 8B).

Figure ;B shows the direct relationship between the density of canals

(1969) and the land loss (1930-1969) for each hydrologic unit in Louisiana

(numbered 1 through 9, east to west). For 9 specific sites in Barataria

Basin (Figure 9) there is a tendency for land losses (1960-1974) to be

directly related to the density of canals (Figure 10). For these sites,

the average land loss is 0.21 percent per year or a'2.19 per@cent per

decade. For a thirty-year-period this is a 6 percent decline in wetland

area. Both of these examples suggest that the cumulative impact of canals

is to increase natural rates of land loss.

Summarizing, canals result in direct loss of habitat through

dredging and spoil disposal, and an indirect land loss effect due to

changes in hydrology, eutrophication, saltwater intrusion, and accelera-

tion of marsh deterioration. The increase of man-made water bodies has

had a secondary effect of increasing the rate of loss attributed to

natural causes.

D. Summary of Land Loss

The coastal zone is the result of a balance between marine and

riverine influences. Landing building is due to sediment deposition

from delta progradation and overbarik flooding, and to a minimal extent

compensatory sedimentation from organic matter deposited by marsh plants.

The rate of this land building is modified by water flow type o f

sediment, watE!r depth, and vegetation.

Flood control measures and navigation projects have interrupted the

natural balance between riverine and marine processes which built and

stabilized the. marsh areas.
Z26

TABLE 8A

Deltaic Units Shoreline Retreat Age of Unit
(feet/year-average) (years ago)

1) Late Lafourche 62.0 200 to 300

2) Early Lafourche 27.0 800 to 1500

3) Barataria Area 16.0 2200 to 2700

4) St. Bernard Area 13.7 2200 to 2700

5) Teche Subdelta 9.2 3000 to 3500

6) Maringouin Subdelta 7.5 4800

TABLE 8B

Deltaic Units Land loss rate (acres/yr) Age of Unit

1) Barataria Area 2050.8 2200 to 2700

2) St. Bernard Area 1645.3 2200 to 2700

3&4)Late and Early 1473.3 200 to 1500
Lafourche

A. Morgan and Larimore
B. Land loss map-Table 3

Z27

The other synergistic factors influencing land loss are the

following:

1. Subsidence

2. LoSS of barrier islands and inlet widening

3. Type of substrate

4. Loss of sediment input

5. Shoreline retreat

6. Salinity changes

7. CanELls and spoil areas

8. Land reclamation projects, impoundments

9. Hurricanes, marsh fires, ani-ini.1 eat-outs

10. Erosive forces-currents, wave energy, etc.

These factors, both natural and man-made, interact in a complex

manner. For example, the loss of sediment input increases the rate of

loss of barrier islands and inlet widening. This in turn increases the

rate of salinity intrusions and erosion.

There is an apparent direct relationship between the size of the

canal and its rate of widening. An altered hydrological pattern seems

to be the principal cause for this relationship. The implication is

that canal canstruction has long-term impact beyond the actual loss of

land used for canal itself. In addition, the area of spoil and levees

created in the building process and maintenance is at least 1-:2 for

canal to spoil, and often higher. An estimated 10 percent of' the

wetlands in Barataria Basin (the only basin with a strong data base)

have been lost due to canal construction activities.

Z28

IV. Cumulative Impacts of Land Loss

The cumulative impacts of land loss are deleterious to the environ-

mental and economic quality of the coastal zone. The impacts are

changes in the hydrology of the various systems resulting in saltwater

intrusion and eutrophication, loss of an important storm buffer, loss

of the waste treatment afforded by healthy marsh, direct loss of

habitat, and loss of nursery grounds of commercially important fish and

shellfish.

A. Salinity Changes and Eutrophication

As previously mentioned, there are trends of increasing salinity in

much of the coastal, zone. Increasing salinity is a cause of land loss, and

land loss in turn may result in increasing salinity. As the saline marsh

deteriorates, the hydrology of the system changes and salt water may

extend into the brackish marsh causing more land loss, creating a posi-

tive feedback loop with no control. In the Barataria Basin this is

coupled with a reduction of fresh water input from the upper basins

(flushing of fresh water) which could reduce the effect of saltwater

intrusion.

Canals short circuit the natural flow of nutrient-laden water into

lakes an d bays rather than allowing it to trickle through the wetlands.

This flow of water from urban run-off, agriculture, and sewage goes

directly into water bodies via canals causing hypereutrophic conditions

in the lakes and bays. A study done by Craig and Day in Barataria Basin

indicates that if present rates of development which lead to increased

eutrophication, and salinity intrusions continue, there is the potential

for the degradation of the nursery grounds of the commercial fisheries

as sociated with Barataria Basin.

Z29

B. Waste Buffer

The eutrophic conditions created by shunting nutrient-laden water

into lakes andbays can be mitigated by allowing the water to trickle

through the basin where the nutrients are taken up by wetland vegetation.

Marshes have evolved adaptations to high nutrient levels and can remove

and recycle inorganic nutrients (tertiary treatment) at a much cheaper

cost than'if done artificially by man. In Barataria Basin, this "free

work"of nature would be equivalent to 5.6-23.6 million dollars per year

if using overland flow waste treatment were used rather than tertiary

treatment. This would also serve to increase marsh productivity (Craig

and Day 1976).. Loss of marsh is loss of this important waste buffer.

An acre of marsh-estuary (calculated from mid-Atlantic estuaries which

are overtaxed) is capable of doing about $14,000 worth of tertiary

treatment (inorganic nutrient removal) per year at a daily loading of

nutrients equivalent to 19.4 lb BOD, assuming the cost of artificial

treatment is $2 per lb BOD. In other words, this is what it would cost

to artificially treat this waste, if the land were not available to do

this work (Gosselink et al. 1974).

C. Storm Buffer

The salt marsh acts as important storm buffer, absorbing the energy

from the waves created by the storm and providing a water reservoir for

storm waters. "Some idea of the protective value of a wide band of

energy-absorbing marshes and barrier islands is seen in the increasing

national cost for 'disaster relief' in coastal areas which either lack

these natural protective 'breakwaters' or where they have been filled in

or bulkheaded for housing or other development." Marsh and island-

130

protected coasts suffer comparatively little damage even in fierce

hurricanes (Gosselink et al. 1974).

D,. Fisheries

The impactcE canal construction on commercial fisheries yields is

directly related to the area of coastal wetlands affected. The result of

this coupling between wetlands and fisheries yields in the coastal zone

is illustrated in Figure 11, 12, and 13. Figure 11 shows the empirical

relationship between shrimp yields and wetland area on a worldwide basis.

The yield of shrimp per acre of wetland area is higher toward the equator

but the relationship follows a consistent pattern in spite of the

inaccuracies inherent in the data. Ihe relationship between intertidal

areas and fisheries yields for the Gulf of Mexico, and for inshore yields

of shrimp in Louisiana as shown in Figure 12 and 13, respectively. Higher

yields are associated with larger areas of wetlands and only incidently

associated with larger areas of wetlands and only incidently associated

with water surface area of volume. Neither of these data sets include

any adjustments to compensate for movements of the fishing craft or the

organisms from nursery grounds to where they are harvested or landed.

2hus the official data may not record that Alabama vessels might harvest

T
L,ouis--.ana's menhaden in Mississippi waters.

In light of these relationships and in the absence of conflicting

data, we can thus directly proportion wetland losses with fisheries

losses. To do this we need to estimate the yields and value of Louisiana's

iisheries. The recent landings for Louisiana and the Gulf of Mexico

(U.S. only) are shown in Figure 14. The recent rise in Louisiana

landings is due to the opening of several menhaden processing plants in

Z3Z

south Louisiana. The reported shrimp landings have remained essentially

constant since the 1950s in spite of a much larger fishing fleet, changes

in techniques, and a rise in prices. There are very large variations in

annual yields (100 percent of the average for 30 years) which may mask

the impact of land losses (6-10 percent for 10 years). We will use here
the average yield for 1969-1973 of 1,222 x 10 6 lbs. In the future other

species may be exploited, but presently the catch-per-unit effort for both

shrimp and menhaden has peaked or begun to decrease.- These two species

represent a major portion of the landings weight and value to fisheries

industry. Shrimp generally represent 60-70 percent of the total dockside

or ex-vessel value (the-ex-vessel value is generally 60 percent of the

processed value). The price per pound of product has almost doubled in

the last ten years (Figure 15), so the latest data (1973) were used to

compute the ex-vessel value to Louisiana (6.7-^, per lb). This price does

not include the social asthetic, recreational, or other values of

marshes (see for example, Gosselink et al. 1974). The total average

annual value of Louisiana fisheries based on 1973 prices and 1969-1973

landings is thus $75.4 million, ex-vessel ($109.9 million, processed).

The direct loss of marshlands from spoil banks and canals is at least

2.6-5.2 percent (Table 1 and in the previous discussion) of the total

area. This percentage would be higher of course if land erosion were

assumed to be partially a result of canal construction, as suggested in

the previous figures and discussion. Using this wetland loss, a minimum

estimate is $2.9-$5.7 million annually "lost" as cumulative consequence

of previous canal construction (or $4.8-$9.5 million based on the

processed value). This value will change as more canals are built,

previously built canals widen and/or cause further erosion, and the

132

economic structure of the industry changes or other geological factors

predominate. A proportional assessment can also be made for the impact

of canals on employment. Additionally, for each dollar spent on

fisheries directly, approximately $3 are spent indirectly (Jones et al.

1974). In general economic terms, this multiplier effect means that

the present cumulative economic impact of land loss is a minimum of

$8.7-$17.1 million annually.

V. Management Concepts and Guideline Recommendations

Land loss is an extensive problem in the coastal zone. The factors

which control land loss are highly interconnected and include such things

as altered hydrology, salinity changes, vegetation changes, man's

activities, as well as land loss itself. At the basin level land loss

transcends differences in local vegetation, substrate, geology, and

hydrology. Management concerning land loss should focus at the basin

level. (Knowledge of the local hydrology, geology, and ecology is necessary

to understand the causes of land loss in a specific area.)

There are two means of minimizing land losses: (1) additional

land can be built to offset the loss of land in other areas, and (2)

reduce, where possible, the impact of those natural and man-made factors

which are most important in increasing land losses.

Land building could be accomplished in several different ways.

Gagliano et al. (1972) outlined a program to create man-made diversions

of the Mississippi River in order to initiate new subdelta lobes,

increase upper deltaic plain aggradation, and control salinity patterns.

According to Gagliano, the most efficient way to build land is simply to

create diversions into broad, shallow lakes and sheltered bays. To

133

increase biclogical productivity, however, it may be more useful if

additional subdelta lobes extended beyond the existing Gulf shoreline.

At present, there are many legal problems associated with this, but

if land losses in the coastal zone become critical, innovative techniques

such as this will need to be employed.

Another method of land building is to develop creative means for

spoil disposal in efforts to convert the spoil into viable marsh areas.

Land building, currently, is in progress in the Atchafalaya delta

and could be optimized by proper management techniques.

To preVE!nt or minimize the amount and rate of land loss due to man's

activities (and to insure the continuation of Louisiana's productive

wetland resources), we have formulated the following guidelines based

on this study, and the work of Lindall and Trent (1975). These center

on avoiding the disruption of wetlands as much as possible.

1) Construct no new canals that connect

a) the edge and center of a hydrological basin and

b) fresh and saltwater areas.

2) Plug pipeline canals wherever possible at both ends and at

intervals between in order to reduce water flow and eliminate

boat traffic and to decrease the annual rate of widening. If

a canal crosses a natural creek bank, plugs should be placed

where the canal intersects the natural tributary.

3) Build no new swamp or marsh impoundments.

4) Miniii-Lize new canal construction by multiple use of existing

canals, integrated planning, common use of pipeline canals,*

directional drilling, etc. The alignment of canals should take

advantage of the existing natural or man-made channels.

134

5) Reserve adequate spoil disposal sites and easements on high,

dry land (non-wetland areas) for future dredging; or use the

spoil to build "new" marsh.

6) Avoid "fingerfill" development in wetlands by restricting

residential development and canals to non-wetland areas.

7) Canal depths should not exceed that of the euphotic zone (1.8-

2.0 m at mean low water) except where normal turbidity results

in extremely shallow euphotic zones.

8) a) Canal depths should never exceed the depth of water body

where canal terminates.

b) Access canals should be of uniform depth or become

gradually shallower proceeding inland from a central

water body. This is to prevent formation of stagnant

pockets of water.

9) Canals should not be cut into an aquifer.

10) Avoid constructing canals which shunt nutrients from urban

areas directly into water bodies.

11) Natural levees should be allowed to remain between constructed

spoil levees, so that the natural "sheet flow" hydrology is

intact. A 1:1 ratio seems desirable.

VI. Management Data Needs

On the basis of the information reviewed in this paper, our

experiences with the biology of Louisiana's marshes and our understanding

of coastal zone management needs, we feel that the following data should

be developed in order to more fully comprehend the magnitude and impli-

cation of land loss:
Z35

A. Canals apparently are an important factor in land loss (e. g.

Figures 8 and 10). This needs to be investigated more thoroughly.

Especially important is the further documentation of:

1) Canal density and land loss in relationship to different

substrate, vegetation and hydrologic regimes.

2) Canal widening vs. width over long periods of time.

3) Wetland losses as a consequence of different spoil

disposal practices.

B. The couplings of sediment sources, sinks, and hydrology need

to be further explored in order to develop a clearer perspective of the

consequences of man-made changes in hydrology, especially the cumulative
impacts. 1) 'What is the impact of "channel" widening and deepening

,at barrier island inlets on the hydrology of an entire

hydrological unit? Obvious case studies are the

Calcasieu ship channel, the Mississippi River Gulf Outlet

near New Orleans; and the Barataria Bay Waterway.

2) How will different schemes for "controlled diversions" of

sediment-rich water affect the entire basin?

C. Planning for management of the newly emerging Atchafalaya Delta

should begin "in toto" now. This is new land owned entirely by the

people of the state of Louisiana. A piecemeal management approach for

the temporary benefit of a few interest groups is in the long-run

unsatisfactory. A long-term planning perspective is necessary to optimize

its potential benefits -- economic, social, environmental, recreational,

cultural and others.

136

D. The couplings within wetlands need to be more fully appreciated.

@@,o project should be approved without considering its impact on the

entire hydrological units. In particular:

1) Public agencies need a clear documentation of these

couplings.

2) The natural work services of wetland should be considered

in evaluating project impacts -- especially the long-term

impacts on biological productivity and-what is known as

11secondary impacts" which accompany successful project

development. An outline of these probable secondary

developments is needed for a more complete basis for

planning.

137

References Cited

Adams, R. D. B. B. Barrett, J. H. Blackmon, B. W. Gane, and W. G.
McIntire. 1976. Barataria Basin: Geologic Processes and Frame-
work. Louisiana State University, Center for Wetland Resources,
Baton Rouge, La. Sea Grant Publ. No. LSU-T-76-006.

Barrett, B. 1970. Water Measurements of Coastal Louisiana. Louisiana
Wildlife and Fisheries Commission, U.S. Dept. of the Interior Fish
and Wildlife Service, Bureau of Commercial Fisheries Project 2-22-
T of P.L. 88-309.

Chabreck, R. 1972. Vegetation,water, and soil characteristics of the
Louisiana coastal region. La. Agr. Exp. Sta. AEA Information
Series No. 25.

and A. W. Palmisano. 1973. The Effects of Hurricane Camille
on the Marshes of the Mississippi River Delta. Ecology, Vol. 54,
No. 5.

31 T. Joanen, and A. W. Palmisano. 1968. Vegetative type map of
the Louisiana coastal marshes. La. Wildl. and Fish. Comm., New
Orleans, La.

Craig, N. J. and J. W. Day, Jr. 1976. Barataria Basin: Cumulative
impacteutrophication. Louisiana State University Center for Wet-
land Resources, Baton Rouge, La. Duplicated MS.

Davis, D. W. 1973. Louisiana canals and their influence on wetland
development. Ph.D. diss., Louisiana State University, Baton Rouge,
La.

Ensminger, A. B. and L. G. Nichols, 1957. Hurricane damage to Rocke-
feller Refuge. Proc. Southeast. Assoc. Game Fish Comm. 11:52-56.

Frazier, D. E. 1967. Recent deltaic deposits of the Mississippi:
their development and chronology. Trans. Gulf Coast Assoc. Geol.
Soc., 17: 287-315.

Gagliano, S. M. 1973. Canals, Dredging, and Land Reclamation in the
Louisiana Coastal Zone. Hydrologic and Geologic Studies of
Coastal Louisiana, Report No. 14, Coastal Resources Unit, Center
for Wetland Resources, Louisiana State University, Baton Rouge, La.

J. L. van Beek. 1970. Geologic and Geomorphic Aspects of
Deltaic Processes, Mississippi Delta System. Hydrologic and
Geologic Studies of Coastal Louisiana, Report No. 1, Coastal Re-
sources Unit, Center for Wetland Resources, Louisiana State Univer-
sity, Baton Rouge, La.

138

Go88elink, J, G,, E* P. Odum, R. N. Pope, 1114, The value of the Tidal
Marsh. Center for Wetland Resources. Louisiana State University,
2aton Rouge, La. Sea Grant Publ. No. LSU-SG-74-03.

,,@)ne3, L. L., J. W. Adames, W. L. Griffin, and J. Allen. 1974. Impact
of Commercial Shrimp Landings on the Economy of Texas and Coastal
Regions. Dept. of Agricultural Economics. Texas Agricul. Exp.
Stat. TAMU-SG-75-204. Dec. 1974.

Kolb, C., and J. Van Lopik. 1958. Geology of the Mississippi River
deltaic plain, southeastern Louisiana. U.S. Army Corps of Engi--!
neers Waterways Exp. Sta., Vicksburg, Miss. Tech. Rept. 3:483.

Lindall, W. N. Jr., J. R. Hall, J. E. Sykes, and E. L. Arnold Jr.
1972. Louisian Coastal Zone: Analysis of resources and resource
development needs in connection with estuarine ecology. Secs. 10
and 13 - Fishery Resources and Their Need. Report of Commercial
Fishery Work Unit. Nat'l. Mar. Fish. Serv. Biol. Lab. St. Peters-
burg, Fla.

McGinnis, J. T., R. A. Ewing, C. A. Willingham, S. E. Rogers, D. H.
Douglass, and D. L. Morrison. 1972. Final report on environmental
aspects of gas pipeline operations in the Louisiana coastal marshes.
Battelle Columbus Labs.

Mississippi River Commission, Floods and U.S. Army Engineer Division.
Lower Mississippi Valley. 1964. Flood Control in the Lower
Mississippi River Valley. Corps. of Engineers, Vicksburg,
Mississippi.

Monte, J. A. 1975. Man-induced vegetation change,in the Bayou La-
Fourche basin, La.: Vegetational succession on spoil banks.
Ph.D. diss., Louisiana State University, Baton Rouge, La.

Horgan, J. P. 1959. Coastal morphological changes resulting from
hurricane Audrey. In R. A. Ragotzkie (ed.) Proc. Salt Marsh Conf.
Marine Inst. of the Univ. Ga., Sapelo Island, Ga. Pp. 32-36.
March 25-28, 1958.

and P. B. Larimore. 1957. Changes in the Louisiana Shoreline.
Trans. Gulf Coast Assoc. Geol. Soc., 7:303-310.

Nichols, L. G. 1958. Erosion of canal banks on the Rockefeller Wild-
life Refuge. Louisiana Wildlife and Fisheries Comm., Refuge Div.,
New Orleans, La.

. 1959. Rockefeller Refuge Levee Study. Tech. Rept., Louisi-
ana Wildlife and Fisheries Comm., Refuge Div., New Orleans, La.

O'Neil, Ted. 1949. The muskrat in the Louisiana coastal marshes. La.
Wildlife Fish. Comm., New Orleans. 159 pp.

Z39

Pollard, J. F. 1973. Experiment to re-establish historical, seed
grounds and to control the southern oyster drill. La. Wildlife
and Fish. Comm., Oysters, Water Bottoms and Seafoods Div., New
Orleans, La. Tech. Bull. No. 6.

Rounsefell, G. A. 1964. Preconstruction Study of the Fisheries of the
Estuarine Areas Traversed by the Miss. River - Gulf Outlet Project.
U. S. Fish and Wildlife Services Fisheries Bulletin, Vol. 63, No.
2P Pp. 373-393.

Treadwell, R. C. 1955. Sedimentology and ecology of Southeast
Coastal Louisiana. Coastal Studies Institute, Louisiana State
University, Tech. Report. No. 6.

Turner, R. E. 1977. Intertidal vegetation and commercial yields of
penacid shrimp. Trans. Am. Fish. Soc. (In press).

Turner, R. E. 1977. Wetland-water couplings: With an emphasis on
commercial fisheries. Center for Wetland Resources, Louisiana
State University, Baton Rouge, La. Sea Grant Publ. No. LSU-56-77.

Van Sickle, V. R., B. B. Barrett, T. B. Ford. 1976. Barataria Basin:
Salinity Changes and Oyster Distribution. Louisiana State Univer-
sity Center for Wetland Resources, Baton Rouge, La. Sea Grant
Publ. No. LSU-T-76-002.

Webert, F. J. 1956. Hurricane damage to fur industry. La. Conserv.
Nov. 1956. Pp. 10-13, and 20-21.

Wright, L. D., F. J. Swaye, and J. M. Coleman. 1970. The effects of
Hurricane Camille on the landscape of the Breton-Chandeleur
Island Chain and the eastern portion of the lower Miss. Delta.
Coastal Studies. Inst., La. State University Tech. Report No. 76,
34 pp.

140

mmm MMI OEM M M

L4ke
ftnichatirain

0
'Al

Lose Gain

0-50

so - 100

100-200

200 - 300

- above
300

10 AO
0 20 30 50

93* 92* 91, 900

Fig. la. Land loss and gain in.tthe coastal zone.

Ar
7,

-dr2

LOUISIANA COASTAL ZONE

SALINE MARSHES

FRESH MARSHES
12= BRACKISH MARSHES 0
F
INTERMEDIATE MARSHES W@--
FOREST SWAMPS Af E C 0
x

Fig. lb. Vegetative types in the coastal zone.

LJ@Jl 1"NA 184 12 X

ADVANCING SHOREUNE RETREATING SHORELINE
A-1 Modern Delta R-I More than 50 it/yr
(Major Accretion) R-2 25-50 ft/yr
A-2 Less than 15 ft/yr R-3 15 - 25 f t/yr' New
R-4 Less than 15 ft/yr rC 2 n s

STATIC SHORELINE

S No change 18T2-195A
m Rates affected 6y man
(jetties, etc.)

X>
v

CL
r %
e ch e t r
/L a T e

e t a Lofo@rche
.,of o ur ce/

D I t u e It 0

X/ 3 1 @,e
0 1

R
'? silt

u 0
0 f
e x c

Fig. 2. Rate of shoreline change.
FF7,

I@d- e

Lake

.7i

Rockefeller Refuge

0 10 20 30 AO 50

miles
913* 9`2* 91,

Fig. 3. Rockefeller Refuge on the Chenier Plain.

urbar.

Fig. 4. [email protected] Yi-sadou Gf--! 1-940.

Z45

... ... ....

Natural Water Bodies

Canals

Forested Levee or Swamp

Agricultural
0 1116111
urban

Fig. 5. Golden Meadow Oil Field, 1953.

Z46

Natural Water Bodies

Canals

-Westec! Levee oF Swamp

Iml
Urban

6. Golden Meadow Oil Field, 1969.

147

14-

12-

10- 0

C) 8-

6-
0
0

4- 0
0 0

0 T-
40 60 80 100 140
wld`@-@ of the canr;i At)

Fig. 7. Relationship between size and increase in width of canals.

Z48

0
K.2

5 10 15 20
9S of Canals/ Total Marsh Area

Fig. 8. The relationship between density of canals and the average
annual land loss in coastal Louisiana from 1930-1969.

149

3 U, 90o0o,
N

30'00'

Heavily influ

----------
Lightly /mo
study area
N
0.19 0.011 % Annual I

+0.01 % Annual la
r

M n-
1.01
K-4
r
L n A C
Q3
k

Fresh Marsh .....
K

Intermediate Marsh nC7
29'30 =Brackish Marsh
Saline Marsh

0.58
1%9 Ratio of total inlet change -Rn
1932 along parish coast line
1.0 ..
1.89
"2 -1
"169 --n Relative coastline retreat by parish

.72
1P

0 -5 to 15 20 W

0 5 10 15 20 25 30 Km.
VP

Fig. 9. Areas of south Louisiana investigated to determine absolute area of canals and.m
1974. Aerial photomosaics used "'Ad-sm et =1 4 1976).

0
.2

of Average Canal Area

Fig. 10. Relationship between canal density and land
loss from 1960-74 for each area.shown on Fig. 2.
Land areas determined from aerial photographs.

Z5Z

'1000

100

0 10 20 30 ..40
LATITUDE

Fig. 11. REIationship between shrimp yields and wetland area on a world-
wide basis (after Turner 1977).

Z52

4000- Total Fish only
I
v Total Landings

3000-

--------Louisiana

C
2000-

1000-

-Mississippi
0 -Alobarria
1000 2000 3000
10316 of Fisheries Product Landed

Fig. 12. Relationship between fisheries yields and intertidal areas for
the Gulf of Mexico.

v) tj
:) cd
0
4,
N 4j
E

LOUISIANA

< 0 INSHORE SHRIMP
C@

w YIELDS

0
C)

<
LD

1 O@)

10 100 1,000 mt

INSHORE S@iRimT YIELDc
Fig. 13. Relationship between average inshore shrimp yields and
marsh acreage in several hydrological units of Louisiana
(after Turner 1977).

Z54

2000-
Gulf Landings
Louisiana Landings

1500-

D
0 LIZ
1000- /*
A /* /*

500 1
1960 65 70 75

Fig. 14. Recent landings for Louisiana and the Gulf of Mexico (U.S. only).

300-
Gulf

Louisiana

200

0
loop
E-4

100-

0 1960 65 70 75
Y e a r

Fig. 15. Recent value of fisheries landings in Louisiana*arxd for the Gulf of Mexico
(ex. vessel).

ACKNOWLEDGMENTS

Efforts toward implementation of coastal zone management in Louisiana

have enlisted the interest and participation of many public agencies and

institutions. As a cornerstone for this program, scientific information

from every available source is being compiled and digested in a series

of Coastal Zone Management reports. The collection is ultimately in-

tended as an authoritative central reference source for persons involved

in administration of an operational CZM program.

The information presented in this report has been synthesized from

research studies @dministered by the Louisiana Sea Grant Program, a part

of the National Sea Grant Program maintained by the National Oceanic

and Atmospheric Administration of the U.S. Department of Commerce.

Additional support from Ford Foundation Grant No. 740-0595 is acknowledged.

Other acknowledgments:

Louisiana State University, Baton Rouge: Robert Chabreck, Associate
Professor, Forestry and Wildlife Management.
Louisiana Wildlife and Fisheries Commission: Alan B. Ensminger, Chief,
Refuge Division; Robert A. Beter, District VIII Supervisor, Game
Division; Barney Barrett, Geologist.
Editorial, manuscript., and publication services were provided by the
Louisiana Sea Grant Program,

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