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;;oastal Zone COASTAL 1@ information v Center TER, Sep L A N D - U S E P A T T E R N S I N T H E T E X A S COASTAL ZUY Prepared by BUREAU OF ECONOMIC GEOLOGY THE UNIVERSITY OF TEXAS AT AUSTIN Dr. BiZZ Fischer, Project Leader Dr. Peter T. Flazon, Director October 1970 for COASTAL RESOURCES MANAGEMENT PROGRAM INTERAGENCY NATURAL RESOURCES COUNCIL DIVISION OF PLANNING COORDINATION Cl OFFICE OF THE GOVERNOR HD 211 .T4 F47 1970 CONTENTS I. Introduction II. Specific Use Patterns A. Agriculture B. Range-ranchland C. Woodland-timber D. Marshlands E. Urban-industrial-residential F. Recreation G. Formal Wildlife Refuges H. Barren Lands I. Made Land and Spoil J. Water K. Hurricane Flood L. Shoreline M. Canals III. Physical Processes A. Barriers B. Tidal Channels C. Bays and Lagoons D. Bayhead and Estuarine Deltas E. Marshes F. Fluvial Systems G. Folian Systems IV. Effects of Man's Activity on Coastal Environments A. Channelization and Dredging B. Devegetation C. Land Reclamation D. Coastal Construction E. Waste Disposal F. Mineral Extraction LAND-USE PATTERNS, TEXAS COASTAL ZONE I. INTRODUCTION The interface of the sea and the land, inherent in a coastal zone, prescribes a variety of land-use patterns. Variations in re lief (from low coastal marshes and river swamps to upland prair- ies), in climate (from temperate-humid along the upper coast to semi-arid-subtropical in the lower coastal zone), in soil fertility (from fertile organic clays to barren sand), and in original vegetation (woodlands, prairies, and marshes) are natural features superimposed on the variety of land-use patterns attendant on population and industrial concentration. Further, in the dynamic and diverse environments of the Coastal Zone, the effects of man's use of land and water on natural systems is drawn sharply into focus. The result of these several factors is a complex pattern of land, water, and submerged-land use. Detailed analyses of the several land uses of the Texas Coastal Zone are beyond the scope of this report. Data have been derived from a series of extensive Coastal Zone maps currently in preparation by the Bureau of Economic Geology; at present, these are only partially completed.- The categories shown on the accompanying map (Plate 1) and the statistical delineation in Table I have been geneplized and derived from several of these more detailed maps. Principal general-use categories shown on Plate I include Agriculture (crops), Range-Ranchland (cattle grazing), Woodland-Timber, Marsh (chiefly range and wildlife), Swamp (primarily wildlife), Recreation, Spoil, Made Land, Formal Wildlife Refuges, and No Principal Use Pattern. Industrial, urban, and other cultural features are shown on the Army Map Service topographic base (scale 1:250,000). These features were adapted for use in Table I from detailed maps of the Bureau's Environmental Geologic Atlas Series. Several ]Anticipated completion date is the late spring of 1971. 2Component maps of the Bureau of Economic Geology Environ- mental Geologic Atlas of the Texas Coastal Zone, currently in preparation, include (1) geologic-landform map, (2) engineering- properties map, (3) topographic map, (4) active physical-properties map, (5) land-use map, (6) mineral and energy resource map, (7) vege- tation and animal distribution map, (8) man-made features map, (9) climatic map, and (10) major depositional systems map. An index and map are provided in Attachment A. 1 categories pertinent to land use and land-use patterns, partially shown on Plate I, are given in the statistical summary of Table I. These include 1. total area: includes both land and water; data for five counties are partial, covering only that portion of the the county shown on the accompanying map: 2. agricultural lands; 3. range-ranchland; 4. woodland-timber areas; 5. marshland-swam p (wetlands) areas; 6. bays (surface-water area); 7. urban-industrial-residential areas; 8. natural fresh-water bodies (surface-water area); 9, artificial reservoirs (surface-water area); 10. recreational lands (primarily public beaches); 11. made lands (reclaimed); 12. formal wildlife refuges; 13. no existing use (principally wildlife); 14. subaerial spoil mounds and spoil wash; 15. hurricane flood areas (areas of inundation by Hurricanes Beulah and Carla); 16. bay-shore line; 17. open ocean-gulf shoreline; 18. total maNne shoreline; 19. major drainage and irrigation canals; 20. major transpbrtation canals. 2 II. SPECIFIC USE PATTERNS Following are brief notes on the patterns and distribution of principal land and water uses of the Coastal Zone. These cover the 18-county area of the Coastal Zone with the exception of Harris, Jackson, Nueces, San Patirico, and Victoria Counties, which have not been completely surveyed. AGRICULTURE - Agricultural use of land is extensive within the 18-county area of the Texas Coastal Zone, with approximately 41% of the total land available in the area used for this purpose: approximately 5,Z20 square miles are presently under cultivation. Concentration is on the original prairie grasslands of the central and upper Coastal Zone: agricultural use becomes less extensive in the South Texas Coastal Zone with the progressive decrease in rainfall. Total income from agricultural crops amounted to $164 million in Z969, with an additional value of $25 million in U. 5. Government payments, combined to represent about 10% of the total State income for these items. Land is used principally for the cultivation of rice, with 60% of the total production of Texas coming from the Coastal Zone. Main producing counties, north of the San Antonio River, include Brazoria, Chambers, Harris, Jackson, Jefferson, and Matagorda. Relatively high rainfall and extensive irrigation are main contributing factors. A second important agricultural crop in the Coastal Zone is grain sorghums, accounting for about 12% of the total State production. Principal yields are centered in the Corpus Christi area (Nueces and San Patricio Counties) and in the southernmost part of the Coastal Zone (Willacy and Cameron Counties). Use of Coastal Zone land in the production of cotton is significant only in the Coastal Bend (Calhoun, Nueces, and San Patricio Counties) and in the lower Rio Grande Valley (Willacy County). Approximately 8% of the total State production comes from the Coastal Zone. Use of Coastal Zone land for production of corn and hay is relatively minor, resulting in less than 3% of the total State production. Concentration of these crops is in the central Coastal Zone (Matagorda, Brazoria, and Harris Counties), co-extensive with the area of principal beef production in the Coastal Zone. Grains such as oats and wheat are grown locally, but not in signi- ficant quantities. With the exception of the subtropical lower Rio Grande Valley (Willacy and Cameron Counties), little land of the Coastal Zone is used in the production of fruits and vegetables. Other areas with at least limited production of these crops usually surround principal population centers. 3 RANGE-RANCHLAND - Approximately 42% (4,425 square miles) of the total area of the Coastal Zone is devoted to range and ranch sites; marshlands also used as range sites include an additional 760 square miles. Principal sites include the more arid region of South Texas, the low-lying coastal marshes, and the nonwooded barrier islands and levees of the central and upper Coastal Zone. The grazing of beef, the production of which accounts for nearly 10% of the State total, is the principal use of the range land and is most significant in Brazoria, Harris, Jackson, Matagorda, and Victoria Counties. Cash receipts for livestock, mainly beef, from the Coastal Zone amounted to about $83.5 million in 1969. WOODLAND-T-TMBER - Woodlands occur throughout the Coastal Zone of Texas but are most extensive in Orange County (a southern exten- sion of the East Texas Piney Woodlands), in Brazoria and Matagorda Counties (along existing and ancestral drainage of the Colorado and Brazos Rivers), and in Kenedy County (including vegetated dunes of the South Texas sancrsheet). Smaller areas of woodlands elsewhere in the Coastal Zone occur along streams, including low- swamp areas with water-tolerant vegetation, and on certain of the abandoned Pleistocene barrier island sands. Total woodland area in the Coastal Zone is approximately 1,600 square miles (Table I and Plate I). Principal vegetation in the upper Coastal Zone woodlands includes pine and mixed hardwoods@ in the central Coastal Zone, a variety of water-toterant hardwoods@ and in the southern Coastal Zone, chiefly oak. Commercial timbering is not significant in the Coastal Zone and is restricted primarily to Orange County. Some natural woodlands have been cleared for agricultural use in the Coastal Zone, but the total acreage for this purpose is small. MARSHLANDS - Approximately 760 square miZes of the Texas Coastal Zone exist as marshlands or wetlands. These include dominantly low-lying coastal lands, the back sides of barrier islands, and low areas at the terminus of major river valleys and associated bayhead deltas. Salt marshes, brackish marshes, and fresh-water marshes (mapped separately in the Bureau of Economic Geology Environmental Geologic Atlas Series) are restricted to areas below the 4-feet above mean sea level. Grasses of varying tolerance to fresh and salt water are the sole vegetation. Most of the marsh- lands are used as ranch and range sites for the grazing of beef cattle, although the lowest parts of the marshlands, commonly with salt vegetation, are not overly suited for this prupose. Portions of some of the coastal marshes have been reclaimed, some by filling and others by draining. Conflicting and detrimental uses of marsh- lands are considered in another section of this report. URBAN-INDUSTRIAL-RESIDENTIAL - General distribution of lands used in this category and their relationship with other uses of the land in the Coastal Zone are shown as a part of the Army Map Service base on the accompanying map (Plate 1). Data given in Table I were derived from more detailed base maps. Specific breakdowns in this category are not given at the scale of the accompanying map but have been mapped in the Bureau of Economic Geology Environ- mental Geologic Atlas Series. 4 The principal urban and industrial concentration is in the upper part of the Coastal Zone. Highest concentrations are in .Brazoria (Freeport area), Jefferson (Galveston area), Harris (Houston area), and Nueces (Corpus Christi area) Counties. Nearly 1,000 square miles are included in this use category, based on the area covered in the accompanying map. This does not include all such land use in the 18-county Coastal Zone area; for example, only about 20% of the urbanTindustrial area of Harris County is included in Table 1. RECREATION - The area designated as recreational use, shown on the accompanying map (Plate I) and on Table I, includes primarily public beaches of the Coastal Zone. This amounts to a total area of about 23 square miles. Not included are a variety of public parks and other recreational areas, surface waters, and the National Seashore of Padre Island. FORMAL WILDLIFE REFUGES - Five major National Wildlife Refuges have been designated in the Texas Coastal Zone: Anahuac Refuge in Chambers County (69 square miles); two refuges in Brazoria County (a total of 43 square miles); Aransas Refuge in Aransas County, with a small area extending into Refugio and Calhoun Counties (approximately 83 square miles); and Laguna Atascosa Refuge in Cameron County, with a small part extending into Willacy County (approximately 70 square miles). Total area formally designated as wildlife refuge is about 213 square miles. In addition, wild- life use is coestensive with many of the other use categories. BARREN LANDS - Barren lands, or land for which there is no existing use other than a limited use for wildlife, comprise nearly 580 square miles in the Coastal Zone. Principal distribution of these lands is in the semiarid southern part of the Coastal Zone from Klp-berg County south. Principally, these include extensive wind-tidal flats landward of Padre Island, as well as some of the active dune fields on the South Texas sand sheet. Smaller areas of wind- tidal flats exist on the back side of barriers in Calhoun and Aransas Counties. A small area of barren land exists in the coastal mudflats of Jefferson County, just south of Sabine Pass. MADE LAND AND SPOIL - Made land, or land built up to higher levels by grading, represents about 34 square miles in the Coastal Zone. These occur principally in metropolitan areas along the coast: for example, the city of Galveston and most of Pelican Island are both on made land. The areas indicated as subaerial spoil on the accompanying table include only dredged sediment presently above sea level: the category does not include the extensive areas of subaqueous spoil within the bays. Subaqueous spoil generally flanks dredged canals either as submarine mounds or as reworked spoil flats; subaerial spoil is most extensive in areas where the Intercoastal Canal is cut into land. Some of the spoil areas have re-established vegetation; other areas are barren. 5 WATER - The extensive bays of the Coastal Zone comprise the principal surface-water bodies, covering approximately 2,100 square miles and making up about 13% of the total surveyed area of the Coastal Zone (Table I and Plate I). Principal bays and estuaries include Sabine Lake; Trinity-Galveston Bay, including East and West Bays; Matagorda Bay, including East Matagorda Bay; Espiritu Santo Bay; Lavaca Bay; San Antonio Bay; Aransas Bay, Copano Bay; Corpus Christi Bay; Baffin Bay; and Laguna Madre. The bays of the Coastal Zone have extensive uses, many of which are conflicting - commercial and sport fishing and oystering, recreation, shell dredging, and oil and gas production with their accompanying pipeline systems. Some of the conflicting uses of the bays are considered in another section of this report. Specific features of the mineral industry's uses of the bays are considered in the Task Area on Minerals and Mining. Fresh-water bodies existing either as natural-water bodies or as artificial reservoirs comprise the other water areas of the Coastal Zone. The surface area of natural-water bodies in the Coastal Zone is about 1,700 square miZesl artificial reservoirs cover about 65 square miles (Table I and Plate I). HURRICANE FLOOD - Approximately 3,208 square miles of the lower parts of the Texas Coastal Zone have been inundated by salt water from surges of Hurricanes Carla and Beulah during the past decade; particularly prone to flooding are the low coastal marshes and the lower reaches of the main river valleys. Coastal flood areas are not specified on the accompanying map (Plate 1); statistical data reported in Table I are based on detailed maps of hurricane flooding prepared as a part of the Bureau of Economic Geology Environmental Geologic Atlas Series (available in the spring of 1971). SHORELINE - Total shoreline in the Texas Coastal Zone amounts to slightly over 1,890 miles. Of this total, 1,419 miles are bay shoreline and 373 miles are open-ocean or gulf shoreline. These figures are computed from detailed 715-minute topographic maps of the Coastal Zone, most of which were constructed during the past decade. The shoreline is a dynamic zone subject to constant change in the form of erosion or accretion: it is thus subject to change in total length. The main physical processes of the shoreline are considered in another section of this report. CANALS - An extensive canal system has developed in the Texas Coastal Zone, including both transportation canals and irriga- tion-drainage canals. Major transportation canals amount to a total of 668 miles within the surveyed part of the Coastal Zone (Plate I and Table I); this figure includes the portions of the transportation canals dredged within bays, as well as the land- cut parts of the canals. Approximately 3,120 miles of irrigation and drainage canals have been cut in the Coastal Zone, mostly coestensive with agricultural lands. 6 III. PHYSICAL PROCESSES Determining factors in land use are the degree, variety, and nature of physical processes. In the dynamic environments of the Coastal Zone, these factors assume prime importance. A distinct suite of processes affect the barrier islands, the bays, lagoons, and estuaries, and the mainland.. Among the more important processes are those that determine rates of erosion or accretion by either water or wind, extent and kind of flooding, and transportation and dispersal of sediments. Following is a brief outline of the main physical processes existing in the Texas Coastal Zone, listed in terms of natural systems and their component environments. A. BARRIERS 1. Shoreface (offshore, 0 to approximately 30 feet) a. Normal sea conditions - Onshore and lateral trans- port of sand by bottom currents (tidal and wind- generated waves). Some suspension material deposited on the lower shoreface and mixed with sand through organic activity. b. Storm conditions - Sand and shell are transported onshore as large sand waves. Sand and mud are carried offshore in suspension by turbidity currents and are deposited on parts of the shoreface. 2. Foreshore and backshore a. Normal sea conditions - Sand is spread in thin sheets on the foreshore by swash and backwash; some of this sand is transported by wind across the berm onto the backshore where it may accumu- late as coppus mounds. Some areas of the back- shore are deflated of sand, leaving a pavement of shell and shell debris. b. Storm conditions - Under storm conditions the foreshore is eroded and sand is deposited as a storm beach above normal high-tide mark. The beach is reworked by eolian processes. 3. Foredune ridges These ridges accvete under prevailing southeast-wind conditions; sand is derived from the backbeach area. Hurricane tracks passing over the barrier severely erode the foredunes. Vegetation is the main agent of dune stabilization; this may be severely affected by overgrazing. Salt-tolerant plants are the main stabilizers; therefore, exceptionally heavy rainfall may reduce the plant cover, resulting in dune activation. 4. Beach-accretion ridges These are affected by the same processes that operate on foredunes. 7 5. Storm channels and washover fans Channels are scoured during storms; sand is transported by unidirectional currents toward the bay during storm- surge flood. Sand deposition occurs within the channels as bars and sheets that spread radially away from the distal parts of the channel. These bars form a coalescing sand body called a "washover fan." Some sediment returns seaward through storm channels during the ebb surge. Under normal sea conditions, the seaward part of the channel is sealed with sand that is swept along shore and into the channel mouth by longshore drift; this sediment is then transported bayward with the next storTn. Once established, storm channels are avenues of high-velocity storm currents. 6. Blowouts and dunes Foredune ridges and beach accretion ridges, when barren of vegetation, are eroded by the wind. Sections of foredunes or beach-accretion ridges may be breached when vegetation is removed by fires, overgrazing, etc.. Intense local scour by the wind is termed a "blowout." Downwind from blowouts sand migrates as dunes; dunes will continue to migrate downwind until stabilized by vegetation or until they meet with a body of water. Likewise, blowouts will remain active until the breach is vegetated. 7. Vegetated barrier flats Sediment accumulation here is chiefly fine sand blown into the area from beach and foredune areas by the prevailing southeast wind. Biologic activity here consists of root-mottling and burrowing by rodents and crustaceans. B.- wind-tidal flats Wide, barren areas lying between the vegetated barrier flats and the coastal bays receive much of their sediment from the bay. Generally during periods of strong north wind, these flats are inundated and fine sand is moved across the flats by wind-generated currents. Suspension material settles across the flats as the water recedes-following cessation of ihe wind. These flats also receive some sand and mud brought into the area at time of storms; at other times, under normal bay-level conditions, wind-transported sand derived from barriers accumulates here. These are areas of great variation in intensity of physical conditions: temperature fluctuation is extreme, and chemical properties of surface and interstitial water is quite variable. 8 B. TIDAL CHANNELS 1. Main channet Main channels are the primary lines of communication between the Gulf and the bays. Tidal range along the Gulf of Mexico is low (1.5-2.0 feet), and tidal currents are of relatively low velocity. Strong, persistent winds either offshore or onshore sometimes increase flow through tidal channels. During flood tide, the highest velocity is attained on the seaward side of the channel; during ebb tide, on the bayward side. Direction of flow through channels reverses itself twice daily with the tides. Deposition occurs at the bayward and seaward ends of channels by vertical accretion and along the channel banks. On the Texas Coast, lateral accretion is along the east bank. Holes are scoured in the channel at points of current conver- gence on the Gulf side and the bay side during flood and ebb tides, respectively. 2. FZood deZta Flood deltas, on the bay side of tidal channels, are constructed of sediment largely derived offshore. Jet flow develops at the distal end of the main channel; here, as the flow spreads radially, distributary channels form, and sediment accumulates as sand and mud shoals. Shoals may become emergent, creating new land, with the subaerial part of the delta developing into marshes, beach ridges, etc., that are affected by the same processes that act on similar features on the barriers. This type of land creation is especially significant at the mouth of the Brazos River. 3. Ebb deZta Sediment from which the ebb delta is constructed is also derived offshore. The process of deposition is the same as on the flood delta - by a decrease in velocity as the jet moves downcurrent from the channel mouth. Higher physical energy (wind-generated currents, primarily) in the Gulf waters than in the bays redistrib- utes much of the ebb-del.ta sediment and prevents emergence of these features. C. BAYS AND LAGOONS Bay perimeter - areas not permanently inundated. Marsh, beach, and tidal-flat environments comprise the bay area above sea level. Processes on marshes and beaches are generally the same everywhere; how- ever, beaches along bay margins are less well developed than those on the seaward side of barriers because of a lower physical-energy expenditure along bay margins. 9 Beaches within bays are not affected by astronomical tides; beach construction is by wind-generated waves. Material from which beaches are constructed consists of shell derived from barriers along the seaward-bay margin and of either river-borne sand or sand derived locally by undercutting of the Pleistocene. 2. Shoal, marginal deposits In the larger bays, sand shoals occur along both the mainland and barrier shoreline. Sand source is fluvial (along mainland shore), from Pleistocene barrier islands, and from the back side of modern barriers. Distribu- tion is by longshore drift; breaker bars are associated with unvegetated sandflats, particularly in either areas that front the prevailing southeast winds or areas that face into the tract of polar-air masses. Processes here are analogous to those operating on the upper shoreface of barrier islands;'however, physical energy is less intense and biological activity relatively greater than along the barrier shoreface. Where bottom drift of sand is less vigorous, marine grasses become established; these plants retard the movement of the traction load and provide an energy baffle that allows deposition 'of suspension load (muds). 3. mud-settling basin Suspension-load material is derived from rivers, from the Gulf, and from undercutting of Pleistocene deposits along the mainland shore. Mud is supplied to bays from the Gulf through storm channels and tidal channels during storm-surge flood. Mud is the dominant sediment in most bays where water depth is 6 feet or more. Under normal bay conditions, transport of sand along the bay floor occurs in water less than 6 feet deep. 4. oyster reef Sedimentation within bays is affected by the larger, laterally extensive oyster reefs. Reefs cause an increase in current velocity by decreasing water depth immediately upcurrent and across the reef crest. As flow passes beyond the reef crest, velocity again decreases and pseudo-feces and suspension sediment are deposited. Oysters themselves build up the bay floor by shell accumulation. D. BAYHEAD AND ESTUARINE DELTAS These depositional features are the product of the inter- play between fluvial and marine processes. Traction and suspension load travel together through the fluvial system to the mouth of distributaries. Beyond the mouth, traction and suspension load'are segregated; traction load (sand) is dropped near the distributary mouth as current velocity 10 decreases abruptly, Suspension load (mud) is carried out into the bay, where it accumulates as prodelta muds. Rost baybead deltas front the prevailing onshore wind, which drifts fine sediment Into interdistributary and marsh areas. Coarser material, sand, from the delta front Is spread laterally and onshore by wind-qenerated waves to form relatively widespread sand sheets and beaches@ Delta surfaces are built up from fine grained sediment (predominantly silt and mud) transported to the area through crevasse splays, from overhanking from distribu- taries, and from mud brought in from b4ys and deposited by wind tides. Much of 6e traction load accumulates in distributaries at about the point where the fluvial system begins to become shallow and to break up into numer- ous channels. Marshes, lakes, and swamps are integral parts of deltas; these receive mostly fine sediment from suspension. Water in the lakes and marshes ranges from fresh to normally saline, Areas permanently inundated by a few inches of water or freqaently flooded by astronomical tides are the habitat of salt-tolerant plants. Marshes occur on barriers and along mainland shorelines. Vegetation of these coastal marshes displays zonation with elevation, and the salt marshes are divided into low and high marsh@ The low marsh is dominated by S artina alterniflora, which grows in a few to several , te, -and can be seen forming a narrow vegetated band along the bays and tidal creeks, Where marginal areas are very shallow, �RLrtina alterni- flora forms extensive marshlands. Landward, tFe--low marsh grades into succulent plants @e,j_ Batis, Salicornia. and Suaedi) and finally into _Borri@_hia @rd _@Maf"Ea iRE@ Physical processes range from the minimal to the intense, Marsh sediment is disturbed by plant roots and burrowing animals (crustaceans and worms). Sediment deposited in marsh areas is transported into the area by a veriety of processes and is derived from several sources. On mainland sides of bays, sediment deposited in marshes is fluvially derived and is deposited by means of crevasse splays, overbanking, and wind tides. Sediments of marshes associated with barriers are deposited by wind tides, eolian processes, and hurricane washovers. Coastal marshes are areas of intense biological activity and extreimas in physical processes. Fluctuations exist in temperature, in aridity, and in soil salinity, Because of their vegetation, marshes are very resistant to erosion, even when subjected to storm-generated currents and breaking waves. F. FLUVIAL SYSTEMS Most fluvial systems along the Texas Coastal Plain are of the fine-grained meander-belt type, e.2., Trinity, Brazos, and Nueces. The Colorado is a coarse-grained meander-belt type, and the San Bernard is locally braided. These stream types result from their particular types of discharge. Braided streams have very short-duration peak discharge, and fine-grained meander-belt streams have relatively long-duration peak discharge. Most of the coarser grained sediment of meandering streams is deposited as lateral accretionary features - point bars adjacent to the convex bank. Levees are constructed of both traction- and suspension-7oad material that is deposited along the channel banks at times when the stream overflows the channel; relatively coarse material is carried beyond the levee when crevasses are scoured through them. These deposits are the fan-shaped "crevasse splays." Beyond the levees, suspension load accumulates in the flood basin; flood waters move very sluggishly and finally stagnate. The flood plain is underlain by point-bar, levee, and flood-basin deposits. The flood plain is characterized by abandoned channel segments and meander cut-offs that are later filled with overbank sediment. These inactive channel segments show varying degrees of sediment fill and occur as linear or oxbow lakes, swamps, marshes, or depressions filled with mud. Swamps and marshes are best developed on flood plains near channel mouths. G. FOLIAN SYSTEMS Sand transport is generally toward the northwest under the driving force of the prevailing southeast winds. Dunes commonly develop downwind from devegetated older dunes. Blowouts result from devegetation of older dunes; this vegetation is killed or physically removed by over- grazing, fires, or storms. In this area, the wind is able to remove sand down to the water table. This sand moves downwind from the blowouts as parabolic or sief dunes. Sief dunes have crests modified by northers, but these north winds are not of sufficient duration to alter dune shape significantly or.to transport a large volume of sand to the southeast. Dunes are ultimately stabilized by a vegetal cover of grass, mesquite, chaparral, some cacti, and, in some instances, live oaks. Conditions which favor construction of an eolian plain such as that in South Texas are (1) a local.sand source and (2) arid to semiarid climate. Sand here is derived from underlying abandoned deltaic-plain and.meander belts. Winds blow from the southeast 9 months each year; average annual rainfall is generally fewer than 20 inches. 12 IV. EFFECTS OF MAN'S ACTIVITY ON COASTAL ENVIRONMENTS The numerous uses of Coastal Zone lands and waters by man result in some use patterns essentially in harmony with natural processes and in others that severely jeopardize the natural balance: certain uses are in sharp conflict with other uses, especially within the Coastal Zone bays. Proper land and.water uses will come only from a greater understanding of the natural processes at work in the area and of their relation to man's activity. The purpose of this section is to outline some of man's activity and its relation to the natural environments and processes of the Coastal Zone. CHANNELIZATION AND DREDGING - To date, the Coastal Zone bays have been the site of extensive dredging and channelization, involving the construction of transportation canals, access canals for specific bay operations, and sheZZ dredging. All these activities are deemed a necessary part of the existing Coastal Zone industries, yet they affect the natural bay system significantly. Spoil dredged from canals and piled along the margins of the canals tends to compartmentalize the shallow bays and restrict circulation. Reworking of dredged spoil by waves and currents provides the principal supply of sediment to the bays. In many areas, marginal grass flats - vital components in the bay ecosystem - are being blanketed by reworked spoil, converting grass flats to barren sand areas. Another type of channelization, construction of artificial passes between bays and the Gulf, affects the natural bay systems. Every pass cut through the barrier islands decreases the tidal surge through the existing passes. Most of the bays of the Texas Coastal Zone can naturally maintain only one pass per bay; artifi- cial channels have tobe maintained by continual dredging. In addition, passes, whether natural or artificial, receive the main tidal surges during storms. Additional passes make the barriers and the protected bay more vulnerable to storm destruction. DEVEGETATION - The importance of vegetation in land stabilization is obvious when considering the changes in natural landforms along the present Texas Coast. The upper Coastal Zone is in a humid climate with mostly,vegetated landforms; the southern part of the Coastal Zone is subtropical, with relatively low rainfall and fewer vegetated landforms. This dryness in large measure accounts for the extensive inland dune fields and the active dunes on the barrier islands of South Texas, as well as the extensive wind- tidal flats of Laguna Madre. The devegetation of natural land- forms, whether a consequence of development, overgrazing, waste disposal, or marsh burning, exposes bare sediment to erosion by storm and by normal waves and currents and significantly reduces the stability of the land. Vegetated barrier islands afford the 13 best natural protection from hurricanes and storms. Devegetation in Zandaide-drainage systems greatly increases the sediment load of streams, resulting in increased infilling of the bays into which the streams discharge. For example, the natural and artificial drainage system of Gum Hollow, a small stream emptying into Nueces Bay, delivered 270,000 cubic yards of sediment into the bay during the heavy rainfall accompanying Hurricane Beulah. This resulted chiefly because stabilizing vegetation in the stream was killed by brine discharge from petroleum production operations. LAND RECLAMATION - Artificial filling of bays and-marshlands pro- vides valuable shorefront development land or room for industrial expansion, but it also provides sediment for hurricane erosion and redistribution, impedes effective bay circulation, and locally reduces bay area, causing additional flooding elsewhere during high water. COASTAL CONSTRUCT-TON - Construction of numerous groins, piers, jetties, and platforms has modified circulation patterns within many bays and estuaries. Erosion and deposition within the natural system is upset, and entire baylines may become unbalanced, resulting in choking deposition in some areas and damaging erosion in other shoreline stretches. Necessary coastal construction should be planned to minimize alteration of natural circulation, thus preventing unmanaged shoreline changes. Several factors should be considered when planning coastal structures designed to prevent destruction of property by hurricanes. Barrier islands are natural barriers to much of the surge effect of storms. :Some of the storm's energy passes through natural passes in the barriers to flush bays and naturally dredge tidal channels. Because some hurricanes are of such great magnitude, breaching in the form of washover channels permits additional amounts of the storm surge to reach bays. Isolating back-bay areas by man-made structures may adversely affect flushing of these water bodies, a very critical process, since man has already restricted the volume of streams entering the bays by construction of upstream dams. Reduction of naturalflushing processes would increase and emphasize the effects of pollution of the bay waters. WASTE DISPOSAL - Most of the problems of waste disposal associated with large industrial and metropolitan areas have been well publi- cized. An area usually not emphasized is the disposal of waste through subsurface media. Areas of permeable substrates should be avoided as sites of disposal, since these perTneable materials directly connect with the ground-water system. Construction of septic tanks in loose and permeable spoil should also be avoided. Abandoned sand pits may make readily available sites for waste disposal,from an immediate economic point of view, but they are the worst possible sites form the standpoint of protecting ground- water supplies. Extensive areas of the Coastal Zone are underlain by tight impermeable clays which are ideal waste-disposal sites. Unfortunately, these clays support the more fertile soils of the coastal area. 14 MINERAL EXTRACTION -The bays and.estuaries of the Texas Coastal Zone are the sites of numerous oil and gas fieZds; they are also sites for the dredging of sheU. Both of these operations are potential.sources,of pollution if production operations are not carefully managed. 15 T A B L E I ARANSAS BRAZORIA CALHOUN CAMERON CHAMBERS GALVESTON USE Total 7Fre-al 464.0 1520.0 960.0 1200.0 896.0 696.0 Total Land Area2 281.0 - 61.0 1443.0 - 95.0 536.0 - 56.0 1082.0 - 90.0 625.0- 70.o 431.0 - 62.0 Total H20 Area2 183.0 - 39.0 77.0 - 5.0 424.0 - 44.0 118.0 - 10.0 271.0- 30.0 265.0 - 38.0 LAND AREAS A g -ri -cu-Ft u-r-e T 21.0 - 7.s 620.0 - 43.0 717.0 - 21.8 704.0 - 65.1 345.0- 55.2 246.0 - 57.1 Range-RanCh3 132.0 - 47.0 84,0 - 5.8 262.0 - 48.9 132.0 - 12.9 51.0 - 8.2 40.0 - 9.3 Woodland-Timber3 --- --- 502.0 - 34.8 42.0 - 7.8 --- --- 70.0 - 11.2 16.0 - 3.? Marsh-SwaMp3 22.0 - 7.8 56.0 - 3.9 75.0 - 14.0 0.1 - 0.0 101.0- 16.2 55.0 - 12.8 Urban Industrial-Residential3 10.0 - 3.6 128.0 - 8.9 18.0 - 3.4 7.1 - 6.6 37.0 - 5.9 58.0 - 13.5 RecreationaI3 1.2 - 0.4 1.8 - 0.1 2.3 - 0.4 1.7 - 0.2 10.1 - 0.0 3.2 - 0.7 Subaeria' Spoi13 1.6 - 0.6 4.8 - 0.3 8.0 - 1.5 8.2 - 0.8 2.5 - 0.4 8.3 - 1.9 Made Land3 --- --- 3.2 - 0.2 --- --- --- - - --- --- 3.9 - 0.9 Wildlife Refuge3 77.0 - 27.4 43.0 - 3.0 4.0 - 0.7 69.0 - 6.4 18.0 - 2.9 Barren Land3 16.0 - 5.6 --- --- 8.0 - 1.5 96.0 - 8.9 --- --- 1.0 - 0.2 WATER AREAS BaTs2'--- 179.0 - 38.6 42.0 - 2.8 404.8 - 42.2 92.0 - 7.7 243.0 - 27.1 257.0 - 36.9 Artificial Reservoirsi --- 16.0 --- 10.0 4.4 1.2 Natural Fresh Water Bodiesi 4.2 19.2 18.9 T6.0 24.0 6.4 OTHER FEATURES Bay Shoreline' 140.0 54.0 286.0 96.0 63.0 120.0 Open ocean Shoreline4 20.0 30.0 38.0 32.0 1.0 50.0 Total Shoreline4 160.0 84.0 324.0 128.0 64.0 170.0 Drainage ChanneIS4 3.0 372.0 100.0 430.0 280.0 85.0 Transportation Canals4 29.0 68.0 52.0 32.0 44,0 76.0 Hurricane Flood Areas2 135.0 - 48.4 422.0 - 29.2 371.0 - 69.2 120.0 - 11.1 283.0 - 45.3 257.0 - 59.6 Imeasured in square miles 2measured in both square miles (gothic print) and % of total area (italics) 3measured in both square miles (gothic print) and % of total land area (italics) 4measured in linear miles T A B L E I (Continued) USE HARRIS JACKSON JEFFERSON KENEDY KLEBERG MATAGORDA. Total Area' 544.0 576.0 1024.0 1824.0 960.0 1408.0 Total Land Area 2 522.0 - 96.0 572.0 - 99.o 946.0 - 92.0 1757.0 -96.0 812.0 - 85.0 1157.0 -82.0 Total H20 Area 2 22.0 - 4.0 4.0 - 1.0 78.0 - 8.0 67.0 - 4.0 148.0 - 15.0 251.0 -18.0 LAND AREAS Agriculture 3 285.0 - 54.6 250.0 - 43.7 442.0 - 46.7 --- 32.0 - 3.9 593.0 -51.3 Range-Ranch 3 --- --- 257.0 - 44.9 24.0 - 2.5 1186.0 67.5 704.0 - 86.7 180.0 -15.6 Woodland-Timber 3 56.0 - 10.7 42.0 - 7.3 81.0 - 8.6 245.0 13.9 24.0 - 3.0 245.0 -21.1 Marsh-Swamp 3 16.0 - 3.1 13.0 - 2.3 220.0 - 23.3 --- --- 2.4 - 0.3 87.0 - 7.5 Urban Industrial-Residentia 13 160.0 - 30.6 10.0 - 1.7 168.0 - 17.8 0.5 0.0 12.0 - 1.5 37.0 - 3.2 Recreationa 13 ___ --- --- --- 2.0 - 0.2 3.3 0.2 1.4 - o.2 36- 0.3 Subaerial SPOW 4.8 - o.9 --- --- 1.3 - o.1 18.0 - 1.0 4.8 - 0.6 11 0 - 1.0 Made Land3 --- --- --- --- 6.1 - 0.6 --- --- --- --- --- --- Wildlife Refuge 3 --- --- --- --- --- --- --- --- --- --- --- --- Barren Land 3 --- --- --- --- 1.6 - 0.2 304.0 -17.3 31.0 - 3.8 0.8-o.1 WATER AREAS Bays' 15.2 - 2.8 --- --- 32.0 - 3.1 64.0 - 3.5 128.0 - 13.3 242.2 - 17.2 Artificial Reservoirsi 3.0 --- 24.0 --- --- --- Natural Fresh Water Bodies 1 4.0 4.0 22.0 3.2 20.4 8.4 OTHER FEATURES gay Shoreline4 40 0 --- 17.0 126.0 144.0 129.0 Open Ocean Shoreline' --- 33.5 50.0 23.0 62.0 Total Shoreline 4 40.0 --- 50.5 176.0 167.0 191.0 Drainage Channels4 115.0 154.0 320.0 --- 1.0- 340.0 Transportation Canal S4 26.0 --- 80.0 54.0 23.0 58.0 Hurricane Flood Areas 2 54.0 - 10.3 78.0 - 13.6 468.0 - 49.5 160.0 - 9.1 90.0 - 11.1 464.0 - 40.1 imeasured in square miles 2measured in both square miles (gothic print) and % of total area (italics) 3measured in both square miles (gothic print) and % of total land area (italics) 4measured in linear miles T A B L E I (Continued) NUECES ORANGE REFUGIO SAN PATRICIO VICTORIA WILLACY USE Total 7Fre-al 1024.0 392.0 832.0 600.0 440.0 768.0 Total Land Area2 739.0 - 72.0 378.0 - 96.0 792.0 - 95.0 590.0 - 98.0 438.0 - 100.0 717.0 - 93.0 Total H 0 Area2 285.0 - 28.0 14.0 - 4.0 40.0 - 5.0 10.0 - 2.0 2.0 - o.o 51.0 - 7.0 2 LAND AREAS A cu'tu re 450.0 - 60.9 77.0 - 20.4 117.0 - 14.8 363.0 - 61.5 119.0 - 27.1 336.0 - 46.9 'r' c 3 --- R.nge-Ran h 86.0 - 11.6 640.0 - 80.8 166.0 - 28.1 240.0 - 54.8 241.0 - 33.6 Woodland-Timber3 22.0 - 3.0 159.0 - 42.1 11.2 - 1.4 12.8 - 2.2 73.0 - 16.7 8.0 - 1.1 Marsh-Swamp3 14.4 - 1.9 71.0 - 18.8 68 .0- o.9 19.0 - 3.2 3.2 - 0.7 0.8 - 0.1 Urban Industrial-Residential3 138.0 - 18.7 69.0 - 18.3 15.0 - 1.9 28.0 - 4.7 3.2 - 0.7 7.0 - 2.0 RecreationaJ3 1.9 - 0.3 --- --- --- --- --- --- --- --- 0.8 - 0.1 Subaerial Spoi13 8.0 - 1.1 16.0 - 0.4 --- --- --- --- --- --- 1.8 - 0.3 Made Land3 19.0 - 2.6 --- --- --- --- 1.6 - 0.3 --- --- --- --- Wildlife Refuge3 --- --- --- --- 1.6 0.2 --- --- --- --- 0.8 - o.1 Barren Land3 --- --- --- --- --- --- --- --- --- --- 121.0 - 16.9 WATER AREAS BaYs-- 282.0 - V.5 12.5 - 3.2 33.6 4.0 6.0 - 1.o --- --- 42.0 - 5.5 Artificial Reservoirsi 1.3 1.9 --- 1.5 1.0 0.4 Natural Fresh Water Bodiesi 1.4 --- 6.8 2.1 0.6 8.4 OTHER FEATURES 36.0 Bay Shore ine7- 80.0 9.3 32.0 47.0 --- Open Ocean Shoreline4 21.0 --- --- --- --- 12.6 Total Shoreline4 101.0 9.3 32.0 47.0 --- 48.6 Drainage Channels4 133.0 154.0 70.0 83.0 80.0 100.0 Transportation Canals4 72.0 39.0 --- --- --- 15.0 Hurricane Flood Areas2 88.0 - 11.9 94.0 - 24.8 42.0 - 5.3 40.0 - 6.7 24.0 5.4 18.0 - 2.5 ileasured in square miles 2measured in both square miles (gothic print) and % of total area (italics) 3measured in both square miles (gothic print) and % of total land area (italics) 4measured in linear miles T A B L E I (Continued) TOTALS USE Total Wreal 16128.0 Total Land Area2 13818.0 - 86.0 Total H 20 Area2 2310.0 - 14.0 LAND AREAS Ag r -1c-u 555-r-e 7 5117.0 - 37.0 Range-Ranch3 4425.0 - 32.0 Woodland-Timber3 1609.0 - 11.6 Marsh-Swamp3 762.7 - 5.5 Urban Industrial-ResidentiaJ3 969.7 - 7.0 RecreationaJ3 23.3 - 0.2 Subaerial SpoiJ3 84.7 - 0.6 Made Land3 33.8 - 0.2 Wildlife Refuge3 213.4 - 1.5 Barren Land3 579.4 - 4.2 WATER AREAS BaTs-r- 2075.3 - 12.9 Artificial Reservoirsi Natural Fresh Water Bodies' .OTHER FEATURES Bay ShorelineT- Open Ocean Shoreline4 Total Shoreline4 Drainage ChanneIS4 Transportation CanalS4 Hurricane Flood Areas2 3208.0 23.3 imeasured in square miles 2measured in both square miles (gothic print) and % of total area (italics) 3measured in both square miles (gothic print) and % of total land area (italics) 4measured in linear miles LOCATION MAP ----------- PLATE AGRICULTURE: CULTIVATED LANDS IN THE- ''COASTAL ZONE 20 LOCATION MAP T. PLATE I-B. RANGE- RANCHLAND IN THE COASTAL ZONE 21 LOCATION MAP PLATE I-C. T I M B E R W 0 0 D L A N D S I N T H E C 0 A S T A L Z 0 N E 22 LOCATION MAP r lo - ---------- PLATE I-D. M A R S H L A N D S I N T H E C 0 A S T A L Z 0 N E 23 LOCADON MAP -------- ir ob PLATE I-E. S W A M P L A N.D S I N T H E C 0 A S T A L Z 0 N E 24 LOCAT*N MAP N ---------- L 30 --------- ---- - r PLATE I-F. R E C R E A T 10 N A L B E A C H E S I N T H E C 0 A S T A L Z 0 N E 25 p- LOCATION MAP I. A Al ------ ------ NOTE: Those areas shown here are largely spoil islands and acretions along the Gulf Intracoastal Waterway. Many lesser acretions exist but cannot be shown at such a scale. - ------------ - PLATE I-G. S P 0 1 L I S L A N D S A N D 0 T H E R B U I L T U P L A N D S I N T H E C 0 A S T A L Z 0 @ E 26 LOCATI@ MAP PLATE I-H. F 0 R M A L W I L D L I F E R E F U G E S I N T H E C 0 A S T A L Z 0 N E 27 LocArim MAP A % PLATE 1-1. BARREN LANDS IN THE COASTAL ZONE 28 ATTACHMENT A Purpose @The Environmental Geologic Atlas is designed to provide critical infornation for planning and land use in the populous and industrial coastal zone of Texas and for a better under- standing of physical, biological, and chemical environments of the coastal zone in order to assess and judge properly the status of these resources. Approach Detailed mapping and study in the field and by light air- craft; geologic environments, sediments, landforms were mapped on 1:24,000-scale aerial photographs. Approximately 20,000 square miles of coastal zone from shoreface to about 50 miles inland (see index). Status Four geologists and several technicians and cartographers have worked for 18 months on the project. All mapping is now complete and the maps and report are in preparation for publica- tion. Contents The Environmental Geologic Atlas of the Texas Coastal Zone will consist of a folio of 63 geologic and multi-colored environ- mental maps accompanied by text explaining use and interpretation. The coastal zone was divided into seven map areas: Brownsville- Harlingen, Kingsville, Corpus Christi, Port Lavaca, Bay City- Freeport, Galveston-Houston, and Beaumont-Port Arthur. For each of the areas, the following maps were prepared: Environmental Geologic Maps: scale 1:125,000; total of 125 map units including landforms, sediments, bedrock, and certain plant communities; Bureau-constructed base map includes 5-foot contours, 3-foot bathymetric lines, paved roads, cities, pipelines, and other physical and cultural information. Emphasis has been on mapping basic units from which a variety of data can be derived. Land-Use maps: Inventory (25 map units) of present use including agriculture, range, woodland-timber, wildlife, spoil and made land, recreation, residential-urban, indus- trial, and sewage disposal. 29 Water Systems - Man-made Features: Inventory (15 map units) of made land, types of spoil land, jetties, piers, sea walls, rivers, lakes, sloughs, estuaries, reservoirs, canals and ditches, channels, and tidal inlets. Engineering Properties: Distribution (15 map units) of properties such as water-holding capacity, compressibility, shrink-swell, drainage, relief, shear strength, plasticity, flooding, permeability, mineral content, faults, and other features. BioZogic-Assembtage Map: Approximately 45 subaerial plant and subaqueous animal communities. Physical Processes Map: Hurricane surge and flood areas, shoreline erosion, equilibrium and deposition, circulation patterns, sediment dispersal, tidal data. Salinity-Ctimat'''maps: Contoured salinity in bays and estu- aries during droughts and rainy seasons, average salinity; graphs of salinity for each bay and estaury; rainfall data; water and sediment discharge for rivers entering coastal zone. Mineral and Energy Resources map: Approximately 15 units including source of sand and clay, oyster reefs, utility lines, pipelines, quarries, oil-gas fields, sulfur fields, salt domes, cement plants, power plants, brine wells and other data. Depositional Systems map: Display of active or ancient genetic units such as fluvial, deltaic, marsh, swamp, barrier-cheniers, bay-lagoon-estuary, eolian and off-shore systems. Publication Date The folio will be available during the first half of 1971. 30 SE+ONT PORT 'E@T F.. ' '@T @T '@T tIOUSTON IE I -IE'R__ BEAUMONT- PORT ARTHUR AREA INDEX FORT GALVESTON GALVESTON-HOUSTON A 1. AREA 'BAY elii&, BAY CITY-FREEPORT AREA iCTORII T-.@_, PORT LAVACA BEEN RE 10- PORT LAVACA AREA E' CORPUS CHRISTI AREA FIGURE I KLE INDEX TO AN ENVIRONMENTAL KINGSVILLE GEOLOGIC ATLAS, TEXAS COASTAL AREA ZONE - ------ 1 0 20 40 60 Y BROWNSVILLE- Scale in Miles HARLINGEN AREA BUREAU OF ECONOMIC GEOLOGY t@WALLEN QHARLINGE THE UNIVERSITY OF TEXAS AT AUSTIN BROWNSVILLE 31 COASTAL ZONE INFORMATION CENTER I @ @ 3 6668 14109 8113 @