Guidelines on community local flood warning and response systems

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

GUIDELINES

COMMUNITY LOCAL FLOOD WARNING

AND RESPONSE SYSTEMS

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BAN

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HYDROLOGY SUBCOMMITTEE

OF THE

FEDERAL INTERAGENCY ADVISORY COMMITTEE

GB ON WATER DATA
1399.2
G85
1985 COASTAL ZONE
INFORMATION CENTER

AUGUST, 1985

Additional copies may be obtained via the United States Geological

Survey, Office of Water Data Coordination, Reston, Virginia or through the

National Technical Information Service, Springfield, Virginia 22161.

COASTAL ZONE
INFORMATION CENTER
Foreward

Floods are the number one natural disaster in the nation. Every state is

affected. Thousands of communities are affected by flooding, which disrupts

businesses and causes evacuation of more than 300,000 people annually. During

the past decade, an average of 200 people died in floods each year inthe

United States, and annual flood damages now average nearly $5 billion. About

10 percent of the population is affected by flooding. These guidelines are

offered to promote better understanding of the types and applications of flood

warning systems.

We are indebted to the members of the Hydrology Subcommittee of the

Interagency Advisory Committee on Water Data whose efforts directed the work

of the task group. Special recognition is due the members of the task group

who were responsible for preparation of the guidelines:

Curtis B. Barrett, Chairman - National Weather Service

Joseph S. Haugh Soil Conservation Service
Property of CSC &ibraryl

Bruce F. Hearn Department of Community Affairs, State of Pennsylvania

Rebecca Hughes Flood Management Division, State of Maryland

41)
William S. Judkins - Federal Emergency Management Agency
66 -

/N (rx- Fad Charles E. Karpowicz - National Park Servi6 S. DEPARTMENT OF COMMERCE NOAA
cm Z) I AL SERVICES CENTER
Cos UVA
C= 2234 SOUTH HOBSON AVENUE
CHARLESTON , SC 29405-2413

Alan M. Lumb - United States Geological Survey

Ewell H. Mohler Bureau of Reclamation, Office of Research and

Technology

Donald W. Newton Tennessee Valley Authority

Lewis A. Smith - Army Corps of Engineers

Special thanks is also due our secretary, Kathleen O'Leary, for her

patience and excellent typing support.

Allen F. Flanders

Chairman, Hydrology Subcommittee

Preface

Local flood warning systems have become an increasingly important means to

mitigate losses from floods. In October 1982 the Hydrology Subcommittee of

the Interagency Advisory Committee on Water Data decided that there was an

urgent need for a document describing the basic principles of local flood

warning systems. An interagency work group was established in November 1982

to prepare a report that would describe (1) under what conditions a local

flood warning system would be effective; (2) the various types of systems that

can be used to identify flood problems and issue warnings; (3) the basic

elements of a community response system; and (4) sources of assistance from

Federal, State, and local agencies in evaluating and establishing a local

flood warning system. The work group was composed of representatives of the

Army Corps of Engineers, the Department of Agriculture Soil Conservation

Service, the Bureau of Reclamation, the United States Geological Survey, the

Department of Commerce, the National Oceanic and Atmospheric Administration,

the National Weather Service, the Tennessee Valley Authority, the Federal

Emergency Management Agency, and the National Park Service. Invaluable

assistance was provided to the work group by flood plain managers from the

States of Maryland and Pennsylvania, representing the Association of State

Flood Plain Managers.

It is the Hydrology Subcommittee's hope that this report will provide Federal,

State, and especially county and local government officials with a basic

understanding of local flood warning systems and the kind of help that is

available.

Guidelines

on
Local Flood Warning and Response Systems

Table of Contents
Page

Forevard. . . . . . . . . . . . . . . . . .

Preface o o o . . . 0 . . . . . . . . 0 0 . 0 0 0 0 0 0

1. Introduction. . . . o o . 0 0 0 0 . . . . . 0 0 0 0 0 0 0 a 0

11. Should Your Commnity Have a Local Flood Warning and Response System?
Ao Introduction o 0 0 . 0 . 0 . 0 0 0 * 0 * 0 0 a 0 0 0 0 0 0 0 0 9
B. Evaluation of the Need for a Warning System. o . . o a . . o * o o 10
lo Hydrologic Characteristics of the Watershed . . o o . . o o . 10
2. Frequency of Flooding . o o . . . o o o o & . . a o o * o o . o 13
3o Flood Loss Potential . . . . . . o o . . . 0 . . * . 0 . . . . 0 16
4. Warning Time as Related to Benefits . . o 0 . . 0 . 0 . . 6 0 & 18
5. Expansion of Hydrologic Capabilitieso o o - - o o - o . o o o o 19
C. Selection of a Local Flood Warning System* o - . o o o o . o * o o # 20
Do Need for a Response System o . . o . o o . o . . o o . o . . o * o e 21
1. Emergency Action Plans. # . . v o o o o o a o o 4 o o o o o o . 22
2. Training of Personnel o * . o o o . * o & . . o . o o o . * 22
3. Maintenance of the Response Systemo o o o a * o . * . o . . . . 22
4. Community Interest and Awareness* o . o . . . & . # . . o o 23
E. Selection of a Response System o . 0 0 0 . . . 0 . . 0 0 . 23

III. Local Flood Warning System
Ao Introduction o . o o . o . . . . . . . 0 . 0 0 0 a 0 0 0 0 0 0 25
B. Types of Local Flood Warning Systems . . o . . o o . o # o o . 25
Co Step I - Collect Datao . o . o . o . . o . o o . a o o o o o o'o o 28
1. Manual Systems . . . . . o . o . o . . . 0 . 0 . 0 * . 0 6 0 . 0 29
2. Automated Systems . o - o . . o o . . o o . o o o . o * a * & o 29
Do Step 2 - Transmit Data . . o - o . . . o . o o . o . . . . . o . . o 32
E. Step 3 - Forecast the Flood. o . . o o o o o 9 . o . o . o o . . o . 32
1. Manual Data Collection. o . o . . . . o o . o o o o . . o o o . 32
2. Automated Data Collection and Processing Equipmento . . o . . . 34
3. Flood Forecast Software o . o . . . . o . 0 0 a 0 0 . . . . . . 35
F. Step 4 - Inform Local Officialso . . . . . o . 0 . 0 0 . . . 0 0 . . 36
Go Current Usageo o . . o . . o o . o . . . . . o 0 . 0 . . . 0 0 . 0 . 36
1. Manual Systems . . . . . o . . . . . 0 . . 0 . * 0 0 . 0 0 0 37
2. Automated Systems . . . . o 0 . . . . 0 . . . 0 . . 0 0 . . . 37
3. ALERT . a # o o o o o o o o . o . . . . . o o . o . . . o . 39
4. IFLOWSo . o . o o o . . o . o . o 0 . . 0 . 0 0 0 0 0 0 0 . 40
5. Flash Flood Alarm Cages . o . . . . o . . . . . o o o . . o o . 40

IV. Community Response System
A. Introduction . . o . . o . o . . . 0 . 0 0 . 0 0 0 a 0 a & 0 0 . 43
Bo Responsibility o o o . . . . o o . o . . o . . . . * o . . o . . 43
Co Step 5 - Warn Local Residents. o . . o o o o . . . . . 0 0 . 0 0 0 0 44
Do Step 6 - Evacuate. . . . o . . . o . . . . . . . * 0 . . . . 0 . . 0 45
1. Saving Liveso o o o o . o o . . o - o o o . o o o o o . . o o . 45

2. Mitigation Measures - - * - - * - a . * 0 . . 0 . . . % 0 . 46
3. Other Emergency Operations . . . . . . . * * . . . . . . 4 . . 46
E. Step 7 - Re-Enter. . . . . . . . . . 6 47

V. The Integrated Local Flood Warning and Response System
A. Introduction . . . . . . * . . . . . . . * . . 0 . . . . . . . . . 0 48
B. Community interest and Awareness . . . . . . . . . 0 . . 6 90 0 0 . 48
C. Integrated System Maintenance. - . 0 . . . . . . . . . 0. . . . 50
D. Trained Community Officials . . . . . 0 . . . . . . . . . 52

VI. The Role of Government Agencies
A. Introduction . . . . . . . . . . 0 . . 0 53
B. Army Corps of Engineers . . . . . * . . . . . . 53
C. Bureau of Reclamation . . . . . . . . . ... . . . 59
D. Soil Conservation Service . . . . . . . . . . . . . . . . . . . . . . 60
E. United States Geological Survey . . . . . . . . . . . 0. . . . . 63
F. Nati@nal Weather Service . . . . . . . . . . . . . . *- - . . . 66
G. Tennessee Valley Authority . . . . . . . . . . . . 68
H. Federal Emergency Management Agency . . . . . . . . . . . . 69
1. National Park Service . . . . . . . . . . . . . . . . . . . . . . . . 72
J. State Assistance . . . . . . . . . . . . . . . . . 74

VII. Other Related Activities
A. Dam Safety Activities. . . . . . . . . . . . . 75
B. Principles and Guidelines . . . . 0.. 0 . . . . . . . . . . 76
C. The Unified National Program for Flood Plain Management . . . . . . . 77
D. Association of State Flood Plain Managers. . . * . . . . . . . 79

VIII. Selected References . . . . . . . . . . . . . . . . . 81

IX. Glossary, Acronyms and Abbreviations . . . . . . . . . . . 0 86

X. Appendix
A. Justification and Priority Setting . . . . . . . . . . . . . . . 94
B. Lycoming County, Pennsylvania - An Example of an Integrated System . 99
1. Hydrology of the Area . . . * . . . . . . . . . . . . ... . . . 99
2. Background . . . . . . . . . 0 . * . . . . . . . . . . . . . 99
3. :The Local Flood Warning System . . . 0 . . . . . . 100
4. The Response System . . . . . . . . * . . . . . . 102
5. Additional Flood Mitigation Efforts . . . . . . ... . . . . . . 103

LOCAL FLOOD WARNING AND RESPONSE SYSTEMS

FIGMS

Figure Page

I ANNUAL FLOOD DEATHS . . . . . . . . . . . . . . . . . . . . . 2

2 ANNUAL FLOOD DAMAGES . . . . . . . . . . . . . . . . . . . . 2

3 WATER RESOURCES COUNCIL REGIONS . . . . . . . . . . . . . . . 5

4 TYPICAL HYDROGRAPH . . . . . . . . . . . . . . . . . . . . . 12

5 STAGE - DAMAGE CHART . . . . . . . . . . . . . . . . . . . . 17

6 DAMAGE REDUCTION VS. WARNING TIME . . . . . . . . . . . . . . 18

7 SCHEMATIC ILLUSTRATION OF A TYPICAL FLOOD WARNING SYSTEM . . 27

8 DIAGRAM OF AN AUTOMATED PRECIPITATION GAGE . . . . . . . . . 31

9 SAMPLE FORECAST PROCEDURE FOR MANUAL

LOCAL FLOOD WARNING SYSTEMS . . . . . . . . . . . . . . . . . 33

10 MANUAL AND AUTOMATED LOCAL FLOOD WARNING SYSTEMS . . . . . . 38

11 SCHEMATIC ILLUSTRATION OF A TYPICAL FLASH FLOOD ALARM

INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . 42

12 THE INTEGRATED SYSTEM . . . . . . . . . . . . . . . . . . . . 49

TABLES

1. Communities With a Flood Problem . . . . . . . . . . . . . . 6

2. Relationship Between Recurrence Interval .. . . . . . . . . . 15
Frequency, and Risk (in percent)

Chapter I - Introduction

Throughout history, people have settled near rivers, lakes, bays and oceans

because of the many economic advantages of living in such areas. Fertile

flood plains, developed through erosion and sedimentation, have been used

extensively by man for growing food both for himself and his livestock. With

the intensification of agriculture, nearby water sources were available for

irrigation. As economic activity diversified, water sources became useful for

processing raw materials into other products; transporting raw materials,

crops and manufactured goods; and the development of water supply and waste

disposal projects for growing communities. In more recent times, recreational

interests have lead to intense land development along the shorelines of rivers

and lakes and in the ocean front and bay front areas of coastal zones.

A price was to be paid for the economic and recreational benefits of occupying

land adjacent to water sources. Heavy losses of both property and life have

resulted from the recurrent flooding of occupied flood-prone areas. Loss of

life due to floods varies greatly from year to year (as shown on Figure 1).

The annual average was 102 fatalities in the period 1940-1982; since 1970, the

average has increased to 200. The average annual property damage in 1940-1982

was $1.5 billion.

In 1983, there were more than 200 flood-related deaths, primarily from flash

floods. Flood damages (in 1983 dollars), as shown on Figure 2, continue an

upward trend; in 1983 they were almost $5 billion. Floods are the number one

natural disaster in the United States in terms of loss of life and property.

ANNUAL FLOOD-RELATED DEATHS

4W-

No-

900-

no-

200-

so-

100

0
wo
Yew

FIGURE I ANNUAL FLOOD DEATHS

ANNUAL FLOOD DAMAGE,, 1903-1983
w $ IN MILLIONS9 1983 DOLLARS

100@000

0
0 1

z
0

69
Li

U- 1900 1910 1020 1930 1940 1950 low 1970 lliIKI
FIGURE 2 ANNUAL FLOOD DAMAGESYFAAR

Two categories of floods account for most flood losses: those affecting land

areas adjacent to streams or rivers (riverine flooding), and those affecting

the shorelines of lakes, bays, and oceans. The main concern of this report is

riverine flooding and, in particular, locations in which flash floods are

likely to occur. In riverine situations, flooding results from rainfall

and/or snowmelt runoff that exceeds the capacity of the main channel of the

river or stream (bank full capacity). Flooding can also result from such

causative events as the@ breach of a dam or levee, or an ice jam. The source

of the threat can vary from a small creek or drainage to a large river such as

the Mississippi or the Ohio. A community can be vulnerable to many-sources of

riverine flooding.

Both structural and nonstructural.methods have been used to try to limit flood

damages. The structural methods include channel enlargement and the

construction of levees, reservoirs, and bypasses. While such structural

measures can greatly reduce the threat of flooding and consequent losses, they

may create a false sense of security and encourage development in partially

protectedareas. Thus, when a rare flood occurs, even greater flood losses

may be sustained. This may contribute to the rising trend in flood damages

shown in Figure 2. Nonstructural strategies for reducing flood losses include

the regulation of flood plain use, floodproofing of buildings, temporary or

permanent evacuation of threatened areas, and the development of flood

forecasting and flood warning systems. The goal of a local flood warning and,

response system is to reduce losses by increasing the length of warning time

in which a community can react to a potentially damaging event and, given the

extra warning time, improve its response. The time between the causative

rainfall and actual flooding will vary depending upon a variety of factors but

usually increases with the size of the upstream watershed.

About 20,000 communities in the United States are vulnerable to all categories

of floods (see Figure 3 and Table 1). River and flood forecast service is

provided to 3,100 of these. At the majority of locations with forecast

service, the rivers crest in 12 hours or more. Approximately 1,000 other

communities either have or are establishing local flood warning systems or are

receiving additional warning services from the National Weather Service

(NWS). This leaves thousands of communities without site-specific flood

warning services.

All counties receive generalized flash flood watches and warnings. A flash

flood is defined as one that occurs in a short time interval (minutes to

hours) following the causative event. A flash flood watch is issued by the

NWS if conditions indicate that flash floods are likely to occur in a

designated area. If flash flooding is imminent or reported, a flash flood

warning is issued on a county basis. Flash flood watches and warnings are

only a limited alerting and do not provide the specific forecast information

communities often need.

What can a community do to reduce the threat of floods, thus saving lives and

reducing property damage? One cost-effective strategy is to establish a local

flood warning and response system.

0900

1700

1000 0700 0"4000

0500
1600
1400
06M

low 1100
un IS00 ONO 0300
1300

1200

Water Resources Council Regions Of the Continental Unil
FIGURE 3 om, D.C.
Sourcez Water Resource, Council, Washingt

Table 1 -- Communities With a Flood Problem

Geographic Water Resources Communities With
Area Council Region a Flood Problem
(see Figure 3)

All Places With Population
Places 2,500 or More

- - - - - - - Number - - - - - - -

New England 0100 1,158 498
Middle Atlantic 0200 3,194 870
South Atlantic Gulf 0300 2$156 721
Great Lakes 0400 1$294 747
Ohio 0500 2,593 658
Tennessee 0600 441 117
Upper Mississippi 0700 1,823 536
Lower Mississippi 0800 809 192
Souris-Red-Rainy 0900 188 19
Missouri 1000 1$221 228
Arkansas-White-Red 1100 734 237
Texas-Gulf 1200 1,099 309
Rio Grande 1300 412 60
Upper Colorado 1400 144 19
Lower Colorado 1500 311 52
Great Basin 1600 213 52
Columbia-North Pacific 1700 1,270 212
California 1800 1,027 487
Alaska 1900 325 20
Hawaii 2000 271 34
Caribbean 2100 130 70

United States 20,813 6,148

Source: Water Resources Council, Washington, D.C., 1977.

It is important to note that a local flood warning and response system should

be only one part of a comprehensive effort to mitigate the hazards of

flooding. A warning and response system is effective primarily in reducing

loss of life and providing limited protection to existing flood-prone

property, but it does not necessarily promote significant long-term

mitigation. The most cost-effective and significant mitigation opportunities

occur eith er before development or before reconstruction after a flood and

require a strong local flood plain management program.

This report focuses on the reduction of flood losses through the use of local

flood warning and response systems. The topics covered are the need for local

flood warning systems; the types of systems; the need for community response;

the institutional action required to implement and sustain the systems; and

sources of information, assistance, and coordination.

Chapter II lists the factors community officials should consider when

evaluating the feasibility of establishing a local flood warning system.

These factors are: the hydrologic characteristics of the watershed; the

frequency of flooding; the flood loss potential; the warning time in

relationship to the benefits; community interest and awareness; and the need

for other hydrologic-related capabilities. The need for a response system is

also discussed, with information on community interest and awareness,

emergency action plans, and selection and maintenance of a response system.

Chapter III presents detailed technical information on the methods and

equipment available to forecast a flood and issue a warning. To be effective,

a local flood warning system must be coupled with a community response system;

this is the subject of Chapter IV.

Chapter V deals with total integration of the local flood warning and response

systems and presents an example of an existing integrated system. The kinds

of assistance that Federal and State agencies can provide are discussed in

Chapter VI; these include information on the flood hydrology of specific

areas, planning for local flood warning systems, and technical and financial

assistance. Additional chapters deal with other activities related to the

development of a local flood warning and response system.

Chapter 11 - Should Your Community Have a Local Flood Warning and Response

System?

A. Introduction

Flooding is a natural hazard that can occur at any time. The frequency and

magnitude of flooding can vary from minor flooding causing only inconvenience,

to major flooding resulting in loss of life and extensive damage to

agriculture, industry, transportation, and commercial and residential segments

of society. If the threat from flooding is persistent or the potential losses

significant, community officials should take steps to reduce flood losses. A

local flood warning and response system is one possible step that can be taken

to mitigate flood losses.

A local flood warning system is defined as a community or locally based system

consisting of volunteers; rainfall, river and other hydrologic gages;

hydrologic models or procedures; a communications network; and a community or

local flood coordinator responsible for issuing a flood warning. The purpose

of a local flood warning system, whether the most sophisticated automated

system or a simple manual system, is to provide responsible officials with

advance information that can be translated into response actions.

According to recent studies (Carter, 1980) of human behavior during flood

disasters, the public does not respond directly to warnings. An appropriate

.. response" refers to protective actions (i.e., evacuation, seeking shelter,

protecting property, etc.). The public typically responds to a warning

message by attempting to confirm the existence of a personal threat or risk:

tuning in broadcast media, comparing different stations to see if similar

warnings are being issued, looking for environmental clues such as heavy

rainfall or flooded roads, or seeking additional information from neighbors,

friends, relatives, or local authorities. Warning messages are most effective

when they confirm other sources of alerts or warnings. A warning should

advise people about the actions they should take and what they can expect

officials and emergency responders to do. It should also encourage people to

pass the word to others, especially those least likely to hear the warning. and

those who might need help. Obviously, a local warning system that provides

timely and accurate flood forecasts is of little value unless individuals take

protective actions to reduce losses. The response system defines these

critical actions.

B. Evaluation of the Need for a Warning System

While a local flood warning system can provide early recognition that flooding

will occur, it may not be effective in reducing flood losses in all

communities. Whether or not a local flood warning system is appropriate

depends on: (1) the hydrologic characteristics of the watershed; (2) the

frequency of flooding; (3) the flood loss potential; (4) the warning time in

relation to the benefits; and (5) the need for other hydrologic

capabilities. These factors should be evaluated when deciding whether a local

flood warning system is a practical means for reducing flood losses in a given

community.

B.I. Hydrologic Characteristics of the Watershed

The first step in evaluating the potential benefits of establishing a local

flood warning system is to identify the various sources of flood threat.

Sources can var)r from large, sluggish rivers that take days or weeks to crest

to small creeks that crest in minutes. Each watershed has a unique set of

hydrologic characteristics that describe the watershed's response to

rainfall. This response is typically represented by a hydrograph, which is a

graph of streamflow and/or stage in relation to time at a given location.

Figure 4 illustrates a hydrograph.

As rainfall or snowmelt occurs over the watershed, runoff begins and the

stream rises. The streamflow continues to increase as the rainfall continues

(see rising limb of the hydrograph).

Even after the rainfall or snowmelt ends, the stream will continue to rise in

response to runoff. Eventually the runoff will reach a peak and the stream

will crest. The stream will then begin falling and eventually recede to a

level below flood stage. The potential warning time (Twp) is the maximum lead

time available for warning communities of flooding. An effective local flood

warning system should identify the specific areas that,will flood, the time at

which flooding is first expected, when the flood is expected to crest, and the

flood crest elevation.

Areas subject to damage and evacuation must be identified in the warning

statement. Specific identification will lessen the possibility that the

National Weather Service (NWS) flood warning messages -- which give projected

flood levels -- may be misunderstood. Both local officials and the general

public need to understand how the projected flood levels relate to their

particular areas of concern. It is vitally important that the NWS forecast

Rainfall C
0
E 7

CZ
.S@
CZ

T
0 r
Pb F
L 0-Tw --le Crest
0 Twp
a)

as
.0-W
CD U) Falling
CD - - --- Major Fl Rising Limb----, L i m b
x C: - Flooding
%< ch
r Occurs
I M
a)
U
Flood Stage ------------------ Ts 0
Bankfull Stage ---------------- -- ----------- Toss Se

Hydro
Low
Stage

Willi

Passing of Time

The relation between a flood hydrograph and land development along a stream is shown. The hydrograp
rainfall amounts is shown in the darker tones with adjacent scales. A distorted cross section of land dev
is in lighter tones. The vertical scale is the same as the stage for the hydrograph. No horizontal scale is
for cross section.

tie in closely with the local flood response plan.

The potential warning time -- the time between the first measurement of

rainfall and the first occurrence of flooding -- may vary from minutes to

weeks, depending on the watershed. The actual warning time is less than the

potential warning time because of the time required to recognize that a flood

threat exists and to issue a warning. The potential warning time (Twp) is

equal to the sum of the time required for rainfall to accumulate in rain gages

before the system will recognize that a flood will occur (Tr) and the actual

warning time (Tw). The primary objective of a local flood warning system is

to increase the actual warning time until it is as close as possible to the

potential warning time.

other hydrologic characteristics that help define the nature of the flood

threat are the rate-of-rise and the length of time the flood waters remain

above flood stage (Ts).

B.2. FrequenSy of Flooding

An important factor in evaluating the potential benefits of a local warning

system is the likelihood or frequency of a damaging flood. The key questions

are: What are the potential damages, including loss of life, at various flood

levels? What is the likelihood that such a flood will occur? The benefits of

a flood warning system increase as the likelihood of damaging floods

increases. Also, the likelihood that a system's effectiveness will be

maintained increases with the frequency of its use. The rarer a flood event

with damaging potential, the more difficult it is to maintain community

awareness and an operationally ready warning system.

The probability per year of flooding at a particular location varies with

flood magnitude. The larger the flood the less likely its occurrence. Since

flooding depends upon storm-events that occur randomly in nature, there is no

way to predict when a flood will occur. It is possible by studying past

records to estimate the chances or likelihood that a flood of a given

magnitude will occur in a particular year or over a longer period of time.

The likelihood of experiencing a flood of a specified magnitude is expressed

by the percent chance of exceeding that magnitude in any one-year period.

Thus, a 1-percent-chance flood is a flood of a such magnitude that the

probability is one in 100 it will be exceeded in a given year. The recurrence

interval is often used to describe flood magnitude. Using the recurrence-

interval terminology, the 1-percent-chance flood is called a 100-year flood.

This terminology is misleading in that it suggests that one such event can be

expected in any given 100-year period. Actually, a 100-year flood can occur

at any time, and none or several can occur in a given 100-year period.

The risk of experiencing a flood of a given magnitude increases with the

length of the time period. For example, there is a 26-percent chance (the

odds are about one in four) that the 1-percent-chance flood will occur during

the 30-year period of a normal mortgage. This increases to a 39-percent

chance (the odds are about two in five) in a 50-year period. Table 2 shows

the relationship between recurrence interval in years, probability per year in

percent, and probability per 50-year period in percent.

Table 2 Relationship Between Recurrence Interval,

Frequency, and Risk (in percent)

Recurrence Probability in percent that a given flood

will occur

Probability

Interval Per Year "N or more times" during a 50-year period

In In

Years Percent N=1 N=2 N=3 :N=4 @N=5--

500 0.2 Nil Nil Nil- Nil

200 0.5 22 3 Nil Nil Nil

100 1.0 39 9 1 Nil @7MI

50 2.0 64 26 .8 2 Nil

25 4.0 87 60 32 14 5

10 10.0. 99 97 89 75 57

5 20.0 100, 100 100 99 98,

Note: Nil less than 1% chance

Historical records of floods are an important source of information, but they

can be misleading.. In most cases, the period of record is relatively short

(less than.100 years) and. may or may not include a severe flood. This limited

period may-not accurately reflect the flooding potential. for a community.

Floods that have occurred within the limited period of record.provide A means.

of communicating the relationship of flood magnitude and probability to the

community.

B.3. Flood Loss Potential

Evaluating flood loss potential is an important step in determining the need

for a local flood warning system. Flood loss potential, as used here, is the

potential for loss of life and property damage from the occurrence of various

magnitudes of floods. Evaluating flood loss potential consists of assessing

the resident population and damageable property located on the flood plain

that would be directly affected by flooding. Many communities have

established stage-damage charts that show the relationship between river stage

and flood damages (see Figure 5). These charts must be kept up to date to

reflect changes in urban development. The relationship of river stage to

inundation area is important in determining flood loss potential. Community

flood studies, such as those developed for flood insurance, provide profiles

and maps that reveal the magnitude of flooding expected and permit the

identification of critical public services that are vulnerable to flooding.

A number of questions must be answered when evaluating flood loss potential.

Is there a potential for loss of life associated with floods? What structures

are located within the flood plain? What are the annual flood damages? What

Is the potential flood damage for a particularly severe flood such as the I-

percent-chance flood? Where are the evacuation routes in relation to the area

of inundation?

In many instances, data are not available to answer all of these questions,

but the more questions that can be answered, the more certainty there will be

determining both the need for a local warning system and the cost effective-

ness of a particular warning system. Cost effectiveness is calculated by

0)
ID as
CD 0)
q - @- Major Flood
Cu Stage Damage

Flood-Sta e-=----
Bankfull Stage oss Section 01
(D
u

Low Stage ---------

-T-1 -VT i I FJ-T I I F-rp T]-FTT I I ]-T-TJ
Tr TTTJ
9

Increasing Damages

These graphs show the relation of flood damages and land develop along a stream. The darker tone is
damage with vertic'al and horizontal scales provided. The lighter tone is a compressed cross section o
development with the same vertical scale.

comparing the benefits (reduction of damages and loss of life) to the costs

associated with purchasing and maintaining a system. Such analysis is also

helpful in selecting the type of local flood warning system appropriate for a

given community. Appendix A contains a detailed description of the benefit-

to-cost analysis that can be conducted by a community. It is important for

community officials to review all possible sources of funding before making

decisions on a local system.

B.4. Warning Time as Related to Benefits

Warning time is a critical factor in mitigating flood losses. The more lead

time available for appropriate action, the greater the reduction in flood

damages that can be achieved. Figure 6 depicts the relationship between

warning time and the percent reduction of damages, often expressed as warning

time vs. benefits.

40-
MAXIMUM PRACTICAL EVACUATION (MPE)

30-

z 23 ............................... . ....

20-

z
W If ...........
10.

0 2 4 6 12 14 Is 24 30 36 42 48
FORECAST WARNING TIME(ERROR FREE)HOURS
..........

DAMAGE REDUCTION VS WARNING TIME

FIGURE 6

The curve represents a hypothetical suburban community with an active

emergency flood response system; it is presented here to illustrate the

potential benefits of an improved warning system. The hypothetical analysis

shows that even a few hours lead time can result in some reduction in flood

losses. In order to compute the economic benefits of implementing a local

flood warning system, a unique curve must be derived for each community. (In

many cases, data may not be available to conduct such an analysis.) To use

the curve, the present lead time must be computed. If the present lead time

is four hours and the installation of an automated flood warning system would

increase the lead time to 14 hours, the percent reduction in flood damages

would increase from 11 percent to 23 percent. The net reduction in flood

damages would be 12 percent by increasing lead time by 10 hours.

This reduction in annual flood damages can he significant to the economic

health of a community. In Ventura County, California, for example, flood

control district officials and Fillmore City officials credit an automated

flood warning system and response system purchased for 50,000 with preventing

$5 million in flood damages from the February 1980 flood (Bartfield & Taylor,

1982).

B.5. Expansion of Hydrologic Capabilities

Some communities use-automated local flood warning systems for other purposes,

such as managing reservoirs and allocating water for municipal and irrigation

use. In the future, these systems may be capable of providing information for

agriculture and forecasts-for water management and water quality.

C. Selection of a Local Flood Warning System (LFWS)

Selection of the type of local flood warning system most appropriate for a

particular community should be based on an evaluation of the hydrologic

characteristics of the watershed, the frequency of damaging floods, the

warning time vs. benefits, the need for other hydrologic capabilities, and the

cost of the system. Automated flood warning systems cost more but can provide

greater benefits, including the ability to meet other hydrologic forecast

needs. Manual systems are inexpensive but limited in their capabilities.

In the selection process, the accuracy, warning lead time, and reliability

requirements should be determined. Accuracy and reliability affect the

credibility of warnings and the extent of actions that can be taken in

response to them. The costs of flood response actions must be balanced

against the accuracy of the warnings and confidence in the local flood warning

performance.

Accuracy varies,according to the type of warning system selected, the quantity

and quality of the data input to the warning system, the hydrologic procedure

or hydrologic model used and the hydrologic characteristics of the watershed.

The reliability of the local flood warning system is another important

factor. Electrical and telephone service is disrupted during moderate or

severe floods. Power disruption or the failure of gages or other elements may

limit the usefulness of a system, So care must be exercised in selecting the

components. The planning must also include consideration of a backup

operation.

To maximize benefits from a local flood warning system, warnings must be given

as far in advance of actual flooding as possible. This inevitably leads to

some percentage of false warnings, a percentage thatwill increase as an

individual property's frequency of exposure to flooding increases.. Since

false warnings are inevitable, the costs they will generate should be

considered as a warning system cost when evaluating benefits and costs.

D. Need for a Response System

A flood warning system by itself.is useless. If it is to be effective, the

community must have procedures to ensure that people leave the flooding areas

and that actions are taken to reduce property damages. These procedures,

which consist of a planned set of responses to the threat, are known as a

communityresponse system. This.system is the mechanism.community. emergency

response officials can use to respond to any type of warning, whether

generated from a local warning system or another source.

A community response system consists of: (1) an emergency action plan (EAP);

(2) trained individuals to carry out the planned actions; (3) maintenance of

the system; and (4) means to foster community interest and awareness. The

roles of the various community infrastructure services must be clearly

defined, and key personnel such as the police chief, fire chief, the director

of emergency services, and staff must be trained and knowledgeable about how

to react,to various flood events. The following questions must.be answered:

Who will monitor flood events? Who will make decisions on the flood-fighting

actions to be taken? What support resources are available? Who will

21,

supervise volunteer labor if it is needed for such labor-intensive tasks as

sandbagging? Who will provide overall coordination? Defining the

organizational structure. and the key individuals and their respective roles is

extremely important in establishing an effective, response system. Chapter IV

outlines the steps necessary to implement a community response system.

D.I,. Emergency Action Plans

Each community should have an emergency action plan (EAP) that directs the

community to act in rapid response to a flood warning. The EAP includes

instructions. for emergency services personnel to reduce flood losses.

D.2. Training of Personnel

A continual training program is. essential sothat the technical staff is aware

of what to do in.specific. circumstances. Competent professional. support is

necessary to ensure that established procedures and training are current so

that, in an emergency, people will react efficiently,and effectively.

D.3. Maintenance of the Response System

Maintenance of the response system is critical to operational readiness.

Maintenance includes the training of individuals, updating the EAP, conducting

practice drills, maintaining inventories of equipmentand trained personnel

available for flood emergencies, and periodic testing of equipment, including

computerhardware and software.

D.4. Community Interest and Awareness

A vital factor in assessing the usefulness of a local flood warning system is

the interest and awareness of the local population* If a local system is to

function properly, community interest must be active and sustained. All types

of local flood warning systems require a network of knowledgeable and trained

individuals dedicated to the well-being of the community. 'Operation of these

systems requires extensive coordination and preparation of key personnel at

the community, county, State, Federal, and private-sector levels. Failure to

maintain a high level of community awareness and interest in flood problems

not only limits the effectiveness of a local flood warning 'System but usually

leads to its failure.

An information program should be started and maintained to acquaint flood

plain residents with actions to take when a warning is given@.@ The information

should be site-specific for each resident. Some flood plain residents would

have to evacuate immediately,,*while others may have time to take''steps to

protect their personal property. All residents must be continually reminded

of evacuation routes and centers where they can seek aid.

E. Selection of a Res2onse System

The type of response system and the level of involvement will vary greatly

from community to community, depending on local conditions. A community

response system designed for other hazards may require major adjustment to

accomodate flood warnings. These adjustments may consist of redefining the

organizational structure, redefining the roles of response officials, adding

personnel, and increasing the awareness and interest of the entire

community. There are many examples of successful response systems.

Interested community individuals may obtain information about model response

systems from various Federal agencies such as Federal Emergency Management

Agency, Soil Conservation Service, Tennessee Valley Authority, the Army Corps

of Engineers, and the National Weather Service. In communities with an

integrated emergency management system, a flood warning and,response system

may be one element of that system.

Chapter III - Local Flood Warning System

A. Introduction

e local flood warning system consists of four steps leading up to the

determination that an imminent flood threat exists, and the dissemination of

this information to local officials. The local flood warning system can be

classified into the following four steps:

1. Collect Data

2. Transmit Data

3. Forecast the Flood

4. Inform Local Officials

Each step is critical in the process of recognizing that a flood threat exists

and in determining the magnitude of flooding. This chapter discusses these

steps in relation to the basic types of local flood warning systems now in

use*

B. Types of Local Flood Warning Systems

There are two basic classifications of local flood warning systems available

for community use: manual systems, which are relatively simple and

inexpensive, and automated systems, which use state-of-the-art automated data

collection and warning transmission systems and computers to provide flood

forecasts. There are many variations within these two basic types.

The basic concept of a local flood warning system is simple. River and

rainfall data are collected upstream from a community. Data are then

transmitted to a central collection point. This information is used to

predict the magnitude of expected flooding, where flooding will occur, when

flooding will begin, when the crest will arrive, and when the stream will

recede below flood stage. This provides potential threat information and the

warning time that is critical for Federal, State, county, and local

0 organizations to take action to preserve life and property.

Within both manual and automated systems there are many approaches,

techniques, and.variations that can be applied to meet a particular

community is ne6ds,. The generic classifications of manual and automated are

presented here for ease of description. Many installations contain a mix of

automated and manual components. Since each watershed is unique and community

needs vary, a simple classification of automated or manual systems is not

strictly possible.

Manual local flood forecast systems consist of: (1) a data collection system;

(2) a community flash flood coordinator; (3) a simple-to-use flood forecast

procedure; and (4) a communication network to distribute warnings to

appropriate emergency response officials, including the mass media and the

National Weather Service (NWS). The forecast system should be linked to a

community response system. Figure 7 illustrates the concept of a manual self-

help local flood forecasting system. Although these systems are simple to

operate, their continuous operation over long periods of time may be

difficult, especially in areas where flooding is infrequent. They can be

surprisingly accurate when adequate data are available.

IRAINFALL AND STREAMFLOW'OMRVERSI

NWS PILOCAL COOMNATOR@- FORECAST
PROCEDURE

IPU13LIC OFMALS. ADIO AND TELE-VI-S-I-0-Nj

UBLIC NOT

SCHEMATI
OF TY
WARNI

Automated local flood warning systems consist.of,the following components:

(1) automated precipitation and river gages; (2) a communications system;

automated data collection and processing equipment; (4) data collection and

system forecasting software; and.(5),a warning distribution system.

Automated stream forecasting has developedin. the past decade as a result of.

rapid growth in the application of hydrologic models to computer technology,

coupled with decreases in the cost,of computers. The evolutionary development.

of automated systems continues to improve the accuracy, timeliness, and

reliability of flood warning capability. Automated-,,flood warning systems are

gaining in popularity around the nation; about 150 communities in 20 states

are now operating or planning to install automated systems.

Automated local flood warning systems vary in design, capability, and

operation. An assessment of needs must be conducted by the community to

determine the level of sophistication.required. System operation may vary

from a simple flash flood alarm thatlaudibly'announces imminent flooding, to

the continuous computerized analysis of precipitation and streamflow and a

hydrologic model to forecast flood levels. Since community needs and

resources vary greatly, the factors discussed in Chapter,2 mustbe fully

evaluated before the type of automated system required can be determined.

C. Step I Collect Data

For most local flood warning systems, hydrologic data c.onsists of river and@

rainfall data collected at manual or automated gages. Rainfall or.,

precipitation gages measure the amount and rate of precipitation falling at a

given location. Precipitation may be rain, snow, sleet, drizzle, freezing

rain, or all of them. River gages measure the height of the water surface

elevation in rivers or streams. Many types of river and rainfall gages are

available, depending on the degree of accuracy and sophistication required.

Although satellite and radar data are expensive, they can often be. integrated

into a local flood warning system by using information available at the local

NWS office. In most instances, it is desirable to use some automated gages

with manual systems and some manual gages with automated systems.

C.I. Manual Systems

The simplest and least expensive approach to data collection is to use

volunteer observers and inexpensive equipment to collect rainfall and river

level data. Inexpensive plastic rain gages can be used by volunteer observers

who report rainfall amounts by tele phone to a community coordinator. Rainfall

reporting criteria can vary from reporting three times a day once a .5 inch

rainfall has been measured, to hourly if flood conditions are severe. River

stages are usually obtained by an observer who reads a simple staff gage or

wire weight gage and telephones the observations to a coordinator.

C.2. Automated Systems

A tipping bucket precipitation gage is used in most automated systems. The

tipping bucket, or event, gage is simple. Every time one millimeter of

rainfall fills the bucketP the bucket tips and causes a signal to be

transmitted to a radio-transmitter unit. One tip of the bucket is frequently

called an event. The radio transmitter then instantaneously transmits a

unique station identifier and an accumulated precipitation value to a receiver

station located nearby. The receiver station keeps track of the accumulated

precipitation for each gage. (For areas in which precipitation can occur as

snow, a special type of displacement gage may be required; further information

on procedures for cold regions is contained in Rechard and Wei). Figure 8

shows a schematic diagram of a typical (non-snow area) automated o-r,event-

reporting precipitation gage.

An automated stream gage is a simple event-reporting unit that tran'smits

preselected incremental changes in stream elevation. Every time the stream

rises or falls to a predefined elevation (for example 0.5 ft.), a signal is

sent to a radio transmitter, which instantly sends a signal to a receiver

station identifying the station and describing the change in elevation. As in

the automated precipitation gage unit, the receiver station keeps track of the

stream height for each gage. Rante (1982) provides further information on

standard stream gaging techniques.

In remote locations for which a stream gage is not available, a bubbler gage

can be used. Bubbler gages, which measure water pressure, can be located a

considerable distance from the stream and still provide accurate information

on stream elevation.

Automated precipitation and stream gages are reliable in operation. Since

they can be operated by battery without AC power, they can transmit critical

data in the harshest environmental conditions.

Antenna

Antenna Mast

Stainless Steel Screen

Funnel Assembly

Humidity Vent

Tippinq Mechanism
L-L"LS Qj@ External Drain Holes

Nylon Lifting Rope

0 Signal Wire

Antenna Wire

Ground Surface

Rock and Concrete Fill

0'. Electronic Package

Battery Carrpartmcnt

Condensation Chamber

FIGURE 8 A DIAGRAM OF AUTOMATED PRECIPITATION GAGE

D. Step 2 - Transinit Data.

Various types of communications systems are used to transmit data. In manual

local flood warning,systems, information is generally transmitted by telephone

land lines, CB radio, or ham operators. Automated systems use UHF, VHF, or

microwave radio transmission, meteor burst telemetry, or satellites.

Data from automated precipitation and streamflow gages are transmitted via

line-of-sight radio transmission. The brief transmission time required by

self-reporting gages (less than 250 milliseconds) allows for large data bases

to be acquired in substantial detail while eliminating radio interference from

other gages in the network. Where direct radio transmission to a base station

is not feasible, radio relays are used.

19. Step 3 Forecast the Flood

9.1. Manual Data Collection

A flood forecast procedure provides a means to translate rainfall that occurs

over the watershed to a stream elevation at a stream gage. Manual procedures

normally use tables, graphs, or charts that use average rainfall and a flood

index (input) to provide a flood prediction (output). Flood predictions vary

from a categorical forecast (i.e., minor, moderate, or severe flooding) to a

crest value. Figure 9 shows a typical flood forecasting procedure used in the

operation of a local flood warning system.

In a typical forecast procedure, the NWS gives the flash flood coordinator a

weekly flood index. This flood index is a measure of soil moisture. In

Figure 9, the flood index is the amount of rainfall in six hours required to

produce flood stage. The local coordinator uses the flood index to set the

Yellow Creek at U.S. 25E Bridge Flood Advisory Table

Forecast is for the USGS gage near 25E bridge over Yellow Creek below Middlesboro
Flood,of Record was 23.4 ft. on April 4, 1977
Warning Stage is 16 ft. drainage area 61 sq. mi. Gage Datum 1097.99 ft. MSL

Flood *Stage is 12.0 feet

Crest occurs about 6 hours after heavy rain ends.

Stage Disch. Average Basin Rainfall (inches)
Ft. 1000 CFS For Time Duration of Guidance used

4.01 O@. 1 0.1 0. ' 2 0.2 0.3 0.4 0.5 0.7 1.0 1.2 1.4 1.7 21.0 2. 3@
5.0 0.3 0.1 0.2 0.3 0.4 0.6 0.8 1.1 1.4 1.6 1.9 2.4 2.9 3.3,
6.0 0.6 0.2 0. *3 0.4 0.5 0.8 ''1.1 1.4 1.8 2.1 2.5 3.0 3A 4.1
0.9 0.4 0-0,5 0.6 0.7 1.1 1.3 1.7 2.2 2.6 3.1 3.6 4.1 4.6
8.0 1.2 0.5 0.6 -0.8 1.0 1.4 1.6 2.1 2.5 3.0 3.5 4.0 4.5 5.1'
9.0 1.6 0.7 0A 1.0 1.2 1.7 2.0 2.5 3.0 3.5 3.9 4.4 4.9 5.5
10.0 2.1 0.9 1.2 1.3 1.5 2.0 2.5 2.9 3.4 3.9 4.4 4.9 5.3 5.9
11.Q 2-.6 1.1 1.3 1.5 1.7 2.2 2.7 3.2 3.7 4.-2 4.7 5.2 5. 7 6. Z
LO
LO 7 7
Flood@ 3.2 1.4 1.6
Index :1.8 2.0 2.5 - 3.0 3.5 4.0. 4.5 5.0 5.5 6.0 6.5
----------------------------------------------------------------------------------------------
13.0 3.8 1.7 1.0 2.1 2.3 2.8 3.3 3.8 4.3 4.8 5.3 5.8 6.3 6.8
7.2
,14.0 4.5 1.9 , 2.2 2.4 2.6 3.1 3.7 4.2 4.7 5.2 5.7 6.2 6.7
15.0 5.2 2.3 2.5 2.7 2.0 3.5 4.0 4.5 5.1 5.6 6.1 6.6 7.0 7.5
16.0 6.0 2.6 M 3.1 3.3 3.9 4.4 4.9 5.5 5.9 6.4 6.9 T.4 7.7'
17.0 6.9 2.9 3o2 3.4 3.7 4.3 4.8 5.4 5.9 6.3 6.8 7.3 7.7 8.0
18.0 7.7 3.3 3.6 3.8 4.1 4o7 5.2 5". 8 6.3 6o8 7.2 7.7 8.1 8o4- 1
-19.0 8.4 3.6 3.9 4.1 4.4 5.0 5.6 6.1 6.6 7o.1 7o5 8.0 8.4 8o7*
20.0 9 1 3.9 4.2 4.5 4.7 5.3 5.0 6;5 7.0 7.4 lo9 8.4 8.8 9.0
21.0 9:9 4.3 4.5 4.8 5.0 5.6 6,2 6.8 7.3 7.8 8.2 8.7 9.1 9.3
22.0' lOo6 4.6 4.9 5ol 5.4 6.0 6.6 7.1 7.6' 8.1 8.5 9.0 9.4 9.6
23oO ll.o4 4.9- 5.2 :5.5 5.7 6.3 6A 7.4 8.0 8.4 8.9 9.4 9.8 10.0
24.0' 12.2 5.3 M 5o8 6.1 6.7 7.3, 7.8 8.3 8.18 9.2 9.7 10.1 10.3

6 Hro Unitgraph Peak Ordinate 2320 CFS Flood Stage R.O. 1.38 in.

FIGURE 9 SAMPLE FORECAST PROCEDURE FOR
MANUAL LOCAL' FLOOD WARNING SYSTEMS

column to be used to provide a forecast.' He then calculates the average

rainfall over the watershed for a one-hour' period by collecting the individual

rainfall observations of the volunteer observers. Using the flood index-and

an average watershed rainfall, the coordinator can,produce a forecast. For

illustration pu rposes (Figure 9), assume that the current flood index is 3.5

inches, and that, average of 6.1 inches of rain has occurred in six hours over

Yellow Creek. Enter the raw marked FI (flood index) to 3.5 inches. Follow

down the column of rainfall values under 3.5 and find 6.1. Now proceed left

along the row and find a stage of 19 ft. The forecast is that 19ft. will

occur at the gage (7 ft. above flood stage) six hours after the heavy rain

ends.

9.2. Automated Data Collection and Processing Equipment

.In an automated system, data are gathered at strategically located remote

sites and transmitted to a centralized location for automated processing and

analysis. The processing hardware is under the control of the local agency

that has responsibility for the flood warning program. Similar equipment may

be located at the state emergency operations center (EOC) and/or at the

nearest NWS office responsible for flood forecast and warning. The components

of the system are a radio receiver for receipt of event-teported radio signals

and a dedicated microcomputer system. The data collection system operates

continuously in a fully automatic mode, constantly receiving data and

processing information for display to the user.

Because automated systems collect a great quantity of.incoming data, the

computer located at the base or receiver'station must have a data processing

system. Incoming data must be screened for errors and posted properly in a

data base for later retrieval. Since automated systems vary greatly in their

ability to screen incoming data and diagnose problems, s,ophisticated data

processing software is needed to provide an accurate representation of the

current hydrologic conditions,of a watershed. Poor data will obviously result

in poor forecasts.

E.3. Flood Forecast Software

The flood forecast software consists of various techniques and procedures that

can be used to post, process, and display data, warn community officials of

critical increases in rainfall and river gages, provide flood forecasts and

warnings, and provide advisory forecasts based on rainfall forecasts or other

predictions. Various levels of sophistication are available in computer

software. A community's choice of software will depend on its needs and its

computer resources. The following flood forecast software capabilities can be

obtained from private vendors:

� Precipitation and river gage data collection

� Quality control of input data

� Store and forward data

� Display of input precipitation data in tabular or map form

� Display of river gage data

� Visual or audible alarm based on excessive precipitation rate or

predetermined rise in river (rate of rise)

� Hydrologic models

� Advisory forecast information in which forecast rainfall.can be input

to determine resulting river forecast

� Linkup to the closest NWS forecast office

F. Step 4 - Inform Local Officials

Normally, a local flood warning system should specify precise, predefined

conditions that will determine the seriousness of the flood threat. When

these predefined conditions exist, the technical people responsible for

predicting the flood threat disseminate this information to appropriate local

officials. In the case of dam failure at a hydropower project or reservoir

licensed by the Federal Energy Regulatory Commission, the person responsible

for predicting the flood threat is often a consultant hired by the licensee.

[The consultant must collect all available data or make certain assumptions

about missing data, such as the time the dam failed, volume of water behind

the dam, etc. This data is required as input to a mathematical dam break

model, which will forecast the area of inundation caused by the dambreak.] It

is important to note that the consultant is not responsible for disseminating

this information to appropriate local officials; the licensee has that

responsibility.

Although disseminating a flood warning to the community is the responsibility

of the local warning coordinator, it is essential that dissemination

activities be coordinated with the closest NWS office and other need-to-know

agencies to assure that the warning messages are consistent. If the public

receives conflicting flood forecasts, it is unlikely to take action on any

forecast.

G. Current Usage

Approximately 1000 local flood warning systems are currently in operation

(Figure 10). Only 100 or so of these systems are now automated, but recent

developments in automated systems have led to their increasing popularity. It

is estimated that 500 automated systems will be in operation within this

decade.

G.I. Manual Systems

The most common flood warning systems are manual or self-help systems that

typically use volunteer observers and inexpensive equipment to collect data.

Data transmission is normally by phone. The flood forecast uses a manual

system such as the one shown in Figure.9. The following table lists the

advantages and disadvantages of a manual system.

Manual System

Advantages Disadvantages

� Simple to operate o Costly delays in data collection/

warning dissemination for short-fused

flood events with short lead times

� Inexpensive

� Encourages high level o High turnover rate of community volunteers,

of community involvement leading to reduced effectiveness

o Not as timely or accurate as

automated systems

o Volunteers requires training and

retraining

G.2. Automated Systems

Communities are increasingly turning to automated systems as their costs

decline and their reliability increases. Systems vary as to which and how

LOCAL R.OOD WARNING SYSTEMS

we 0%
00 Me
00
"so 0

00
00

46
4v
0
0 Jv:

FIGURE 10
811 MANUAL AND AUTOMA7ED SYSTIEMS

many components are automated. A fully automated system consists of automated

precipitation and river gages, a radio data transmission system, and a

computer to process the data and provide a flood forecast. Two examples of

modern automated flood warning system (ALERT and IFLOWS) are described below.

The following table lists the advantages and disadvantages of an automated

system.

Automated System

Advantages Disadvantages

0 Provides timely, accurate o High.'initial cost
reliable data and warnings

o Requires high level of expertise
to install and in some cases to

use

� Provides stable data o Maintenance costs of hardware
network and software' may@be substantial

� Provides comprehensive o Software'support may be limited
historical data base

� Continuously updates infor- o May require costly periodic
mation to provide current replacement
(real-time) data as it occurs

G. 3. ALERT

The Automated Local Evaluation in Real Time (ALERT) system,,a typical

automated local flood warning system, was developed by the NWS.California-

Nevada River Forecast Center in Sacramento, California Available from

private vendors, the ALERT system is being adopted at a growing number of

sites for flood warnings, reservoir management control, flood fighting and

data acquisition. The system consists of automatic self-reporting river and

rainfall gages, a communications system based on line-of-sight radio

transmission of data, and a base' station. The base station consists of radio-

receiving electronic equipment and a microprocessor'. Data Analysis software

is ava ilable to collect quality control and display data. A hydrologic model

to provide simulation of streamflow is also available as part of the ALERT

system. Many of the general capabilities of automated systems discussed above

are available in the ALERT system.

G04. IMWS

The Integrated Flood Observing and Warning System (IFLOWS) is an example of a

network of automated local flood warning systems. Each of the 100 counties in

IFLOWS has or is developing an automated -local flood warning system. The

county systems'consist of automatic radio reporting rain gages, radio rel ays

or repeaters (if required), a radio receiver, and system software. Each

county is usually capable of collecting and displaying real-time precipitation

data. All of the counties are linked to a designated State Emergency

Operation Center And NWS offices, so data can be retrieved by any county,

State or NWS office in the TFLOWS system. Some states also have a subsystem

that allows for voice communication between the States, counties, and NWS

offices.

G.5. Flasli Flood Alarm Gages

Flash flood alarm gages consist of water level sensor(s) connected to an alarm

or light located at a community agency that operates 24 hours a day. Stages

exceeding a preset level trigger the alarm. The distance between the upstream

alarm gage and the community determines the amount of warning time. Sixty

five flash flood alarm systems are now in operation. Specifications for the

construction of a cost-effective flash flood alarm gage system are available

from the NWS. Most of the required elements can be purchased "off the

shelf." The NWS has installed a few flash flood alarm gage systems in

connection with IFLOWS to test their performance and effectiveness. Figure 11

is a schematic illustration of a typical flash flood alarm system.

A more sophisticated gage, consisting of a radio/electronics signaling package

and antenna in a self-contained enclosure, has been developed by a private

firm. A water-level sensor pipe uses a pressure sensor to provide a single-

level alerting. When an alarm is triggered.at the remote station, an

identifier signal is sent to the control station.

The following table lists the advantages.and disadvantages of flash flood

alarm gages.

Flash Flood Alarm Gages

Advantages Disadvantages

o Relatively inexpensive o Warn of flood condition

o Simple operation only, no indication of

o Provide instant audio/ magnitude

visual alarm

o Lead time usually short

o Beeper-activated warning o Usually require,community

reaches key people expertise in electronics

p
DI

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Chapter IV Community Response System

A. Introduction

The community response system consists of the steps taken by a local community

in response to information that a flood is imminent. The community response

system can be generally defined as three steps that follow the four steps in a

local flood warning system (Chapter III):

5. Warn local residents

6. Evacuate

7. Re-enter

B. Responsibility

The best flood warning system is useless without effective dissemination of

the information to residents of the flood plain. Effective notification of an

impending flood is necessary to reduce loss of life and property damage.

Timely warning of citizens is especially important in communities where

flooding has not occurred recently. Local community responsibilities and

actions required to warn residents effectively of immediate or possible flood

hazards include:

0 Establishment of an emergency action plan (EAP) that describes actions

necessary to mitigate flood damages and provides for the dissemination

of information on immediate and potential flood hazards.

o Maintenance of the warning system and the EAP;

� Maintenance of public awareness of and interest in the system and the

plan;

� Anticipation of problems associated with establishing and maintaining

public awareness and interest.

C. Step 5 - Warn Local Residents

A community response system presumes the existence of a flood recognition

system such as the local flood warning system described in Chapter III. Using

related information such as flood watches, flood warnings, and other

information received from Federal, State, or local agencies, local emergency

services personnel must make decisions on the actions necessary to save life

and property.

A physical location should be established to receive all flood-related

information, prepare local forecasts, and issue warnings. This control center

should be located outside the flood plain and supplied with an emergency power

source. The center may be an emergency operations center (EOC), police

station, fire station, or other facility.

Operating procedures at the central control center should be thoroughy planned

and spelled out within the emergency action plan. The flood operations

section of the EAP should cover the elements of warning, evacuation and

rescue, damage mitigation, recovery, other emergency operations, public

information, plan implementation, and plan maintenance.

Once local emergency services personnel have made a judgment as to the

severity of flooding expected, the impact the event will have on the

community, and the actions necessary to save life and property, a public

warning should be disseminated.

A community should have established procedures for issuing a warning to the

pub.lic. These procedures will provide warnings to residents directly

threatened by the flood (those residing within the flood plain) and to the

general public. Warnings can be disseminated by telephone, state police

emergency microwave networks, radio and TV, in person, by helicopter, sirens,

or truck-mounted loudspeakers.

Warnings should be coordinated with the NWS and other agencies responsible for

warning and response actions. This action is important since misinformation

and false rumors develop quickly during severe flood events.

D. Step 6 - Evacuate

D.l. Saving Lives

To prevent loss of life from flooding, a community must plan evacuation and'

rescue operations. As part of the EAP, the community needs to identify: (1)

areas subject to coastal and riverine flooding at various elevations; (2)

areas that will be inundated because of poor drainage; and (3) areas that may

require evacuation for reasons other than inundation, such as loss of access

or escape routes, loss of emergency services, or other site-specific problems.

Local officials need to determine evacuation procedures and should select an

appropriate destination for each area to be evacuated. The evacuation

procedures should identify the best available evacuation routes and establish

evacuation priority areas on the basis of the warning time available.

Facilities such as hospitals and elderly housing located in the flood plain

may need special evacuation assistance.

D.2. Mitigation Measures

To reduce public and private damages from flooding or flood-related causes,

planned flood fighting, property relocation, and floodproofing tasks should be

discussed in the EAP. Comaunities may wish to include, as appendices to the

EAP, plans and guidance documents on long-rAnge, permanent mitigation measures

or programs. The appendices could include discussions of programs for public

acquisition and open-space use of the most severely affected areas; capital

improvement programs to correct infrastructure deficiencies; and the placement

of warning signs and flood crest elevation signs in strategic public locations

to enhance public awareness. Inclusion of such guidance in the EAP may

encourage local officials to investigate and recognize the need for a

comprehensive flood plain management program.

D.3. Other Emergency Operations

Other emergency operations such as utility management (established procedures

for curtailing services to flooded areas), traffic control, and maintenance of

vital services (establishing operational procedures for police, fire, and

medical services, utility repair, rescue services, etc.) should be included in

the EAP. Special attention should be given to water, power, and sewer

problems due to flooding. Lack of potable water is often a serious problem

after a flood. Also, since flooding may divide a community and limit the

service available to each section, emergency operations should be planned to

allocate emergency services to all parts of the community.

E. Step 7 - Re-Enter

The objective of the re-enter step is to initiate and carry out post-flood

actions that will maintain public health, return community services to normal

at the earliest possible time, and provide aid and assistance in the re-entry

process*

In the re-entry step, public health must be maintained by following

established procedures for handling the dead and injured. To assure smooth

return to normal services, the EAP should specify procedures for resuming

utility services and returning traffic to normal patterns.

Procedures for mobilizing volunteer organizations such as the Red Cross, the

Salvation Army, etc., using State and Federal assistance, and activating

mutual aid programs should also be identified in the EAP.

Chapter V - The Integrated Local Flood Warning and Response System

A. Introduction

The integrated local flood warning and response system combines the local

flood warning system (Chapter III) with the community response system (Chapter

IV). Figure 12 illustrates the seven-step process of the integrated system.

These seven steps are applicable to the simplest manual system or the most

sophisticated automated system.

The integrated system is the entire process of collecting data, transmitting

it to a centralized collection center, analyzing and processing the data,

preparing a flood forecast, informing local officials, issuing a warning,

taking actions to save life and property, and re-entry. The critical links

between a local flood warning system and a community response system are

community awareness and interest, a high degree of system maintenance, trained

individuals to carry out planned actions, and a master emergency action plan

(EAP) to follow. An integrated system in Lycoming, Pennsylvania, is described

in Appendix B.

Systems that involve numerous local communities along small streams and rivers

should be coordinated on a multi-county or multi-community basis. Downstream

communities may benefit from warnings given to upstream communities.

B. Community Interest and Awareness

Consistent with every community's responsibility to protect its citizens from

harm and to promote public safety, each community with flood plain areas must

w STEP 1. COLLECT DATA

cl)

z STEP 21. TRANSMIT DATA
z

0 STEP 3. FORECAST THE FLOOD
-i
U-

STEP 4. INFORM LOCAL OFFICIALS

- - - - - - - - - - - - - - - - - - - - - - - -

STEP 5. WARN LOCAL RESIDENTS

STEP 6. EVACUATE
w
U)
z
0
CL
w STEP 7. RE-ENTER

FIGURE 12 THE INTEGRATED SYSTEM

keep its residents informed of the potential for flooding, promote the

mitigation of hazards and losses in the flood plain, and sustain citizen

interest in the operation and maintenance of the integrated system. The chief

executive officer of the community needs to designate a government official

such as the director of emergency operations, the director of public works,

the fire chief, or the police chief to be the official responsible for

establishing and maintaining the local flood warning system and the community

response system. This official should be responsible for ensuring that all

residents of structures located in the flood plain are aware of the flood

hazard, the existence of the local flood warning system and the community

response system, and the actions that should be taken in response to flood

watch and warning notifications. Both the chief executive officer and the

person with principal responsibility,for the flooding warning and response

systems should promote the mitigation of existing and potential flood

hazards. Various Federal and State agencies are available to assist community

officials in establishing and maintaining the integrated system and hazard

mitigation programs.

In areas where flooding is frequent and visible to community residents, some

level of community interest and awareness is sustained. In areas where

flooding is infrequent or rare, the maintenance of community interest and

awareness is difficult.

C. Integrated System Maintenance

Every community must establish procedures to update, improve and ensure the

efficient operation of the integrated system. The tasks involved in

maintenance of the system range from maintaining and upgrading equipment and

software (if an automated system is involved) to updating and improving the

emergency action plan. To maintain an integrated system properly, the

community must:

� Yearly, or shortly after a flooding event, update and improve the

emergency action plan.

� Maintain and replace equipment, including hydrologic gages, electronic

equipment, computer, hardware, radio transmitter and receiver

equipment, flood fighting equipment, and communications equipment.

� Test equipment periodically to assure that it is functioning properly.

� Establish procedures for evaluating the performance of the system

during actual or simulated flood conditions.

� Establish procedures and schedules by conducting drills (at least

annually) that simulate floods.

� Include funding for personnel and equipment operation, maintenance.

purchase and replacement in the annual community budget.

� Provide special personnel training to ensure capabilities when floods

occur*

o Develop backup systems and substitution procedures for equipment,

people, and processes to assure a rapid response to any breakdown in

the system.

D. Trained Community Officials

Maintaining a high degree of operational readiness for the integrated system

requires on-going training of key personnel. All assigned personnel must be

knowledgeable enough to execute the established procedures. On-going training

is especially critical in communities that have a high turnover rate of people

involved in emergency services.

Maintaining a training program for volunteer observers, the local flood

warning system coordinator, emergency services personnel, maintenance

personnel and central control center personnel is vital to the successful

operation of the entire system.

Chapter VI The Role of Government Agencies

A. Intro&ction

A number of State and Federal agencies have instituted programs for helping

communities identify and solve local flood problems. The programs and

responsibilities vary, but the objectives are the same -- wise use of the

flood plain and a reduction in the loss of life attributable to flooding. A

local flood warning and response system is often an integral part of a

community's flood damage abatement and public safety strategy.

The National Weather Service is responsible for forecasting the weather and

for warning the public about life-threatening weather conditions, including

floods. Other Federal agencies have flood damage abatement programs as 'Well

as response and recovery roles. The roles of the various Federal and State

agencies in developing flood warning and response systems are broadly

described in the following pages to provide a guide to local communities

seeking assistance in evaluating the need for local flood warning and response

systems and developing appropriate local programs.

B. Army Corps of Engineers

The Army Corps of Engineers provides a broad range of water resource

development projects to the Nation. The Corps has constructed and operates

major dams, hydroelectric power plants, levees, harbors, waterways, locks, and

recreation areas throughout the United States.

The Corps may undertake investigations of water and related land resources

plans under specific authorizations by the Congress or, for smaller studies,

under general continuing authorities. Special authorizations are either

legislative actions by the Congress or resolutions by either the House Public

Works and Transportation Committee or the Senate Environment and Public Works

Committee. Continuing authorities permit the Corps to undertake

investigations and construction of small projects for flood control,

navigation, beach erosion control, clearing, and emergency bank protection.

Other legislation empowers the Corps to undertake investigations for modifying

completed projects or their operation; for modifying or adding to structures

and the operation of structures; or for cooperative assistance to States in

the preparation of comprehensive plans for water resources development,

utilization, and conservation.

These authorities require the Corps to consider all alternatives in

controlling flood waters, reducing the susceptibility of property to flood

damage, and,mitigating human and financial losses. The Corps considers both

structural and nonstructural measures in planning for flood damage prevention

or reduction. The Corps also considers all practicable and relevant

alternatives applicable to sound flood plain management, including modifying

the ways in which people would otherwise occupy and use flood plain lands and

waters.

Nonstructural solutions include local floodwarning and response systems;

temporary or permanent evacuation and relocation; emergency flood fighting and

financial relief; land-use regulations and building codes; floodproofing with

or without land-use regulations; and area renewal and conversion to open

spaces. Structural solutions include dams and reservoirs, levees, dikes,

walls, diversion channels, bridge modifications, channel alterations, pumping,

and land treatment. Structural and nonstructural solutions are considered

individually or in combination.

Under another authority, the Corps can provide information, technical planning

assistance, and guidance on request to both Federal and non-Federal entities

in identifying the magnitude and extent of the flood hazard and in planning

wise use of flood plains. Direct response and assistance of this kind are

provided through the Flood Plain Management Services Program. The Corps also

administers studies that provide basic hydrologic and hydraulic information to

the Federal Emergency Management Agency.

For help, guidance, or technical assistance, contact the local Corps of

Engineers office listed below.

Office, Chief of Engineers
Department of the Army
Washington, D.C. 20314

DIVISIONS AND DISTRICTS

U.S. Army Engineer Division, U.S. Army Engineer Division,
Lower Mississippi Valley North Atlantic
P.O. Box 80 90 Church Street
Vicksburg, Mississippi 39180 New York, New York 10007

U.S. Army Engineer District, Memphis U.S. Army Engineer District, Baltimore
668 Federal Office Building P.O. Box 1715
Memphis, Tennessee 38103 Baltimore, Maryland 21203

U.S. Army Engineer District, New Orleans U.S. Army Engineer District, New York
P.O. Box 60267 26 Federal Plaza
New Orleans, Louisiana 70160 New York, New York 10007

U.S. Army Engineer District, St. Louis U.S. Army Engineer District, Norfolk
210 North 12th Street 803 Front Street
St. Louis, Missouri 63101 Norfolk, Virginia 23510

U.S. Army Engineer District, Vicksburg U.S. Army Engineer District, Philadelphia
P.O. Box 60 U.S. Custom House
Vicksburg, Mississippi 39180 2nd and Chestnut Streets
Philadelphia Pennsylvania 19106

U.S. Army Engineer Division,
Missouri River U.S. Army Engineer Division,
P.O. Box 103 North Central
Downtown Station 536 South Clark Street Illinois 60605
Omaha, Nebraska 68101 Chicago, Illinois 60605

U.S. Army Engineer District, Kansas City U.S. Army Engineer District, Buffalo
500 Federal Building 1776 Niagara Street
East 12th Street Buffalo, New York 14207
Kansas City, Missouri 64106
U.S. Army Engineer District, Chicago
U.S. Army Engineer District, Omaha 219 South Dearborn Street
6014 U.S. Post Office and Court House Chicago, Illinois 60604
215 North 17th Street
Omaha, Nebraska 68102 U.S. Army Engineer District, Detroit
P.O. Box 1027
Detroit, Michigan 48231
U.S. Army Engineer Division,
New England U.S. Army Engineer District, Rock Island
424 Trapelo Road Clock Tower Building
Waltham, Massachusetts 02154 Rock Island, Illinois 61201

U.S. Army Engineer District, St. Paul U.S. Army Engineer Division,
1125 U.S. Post Office & Customhouse Pacific Ocean
St. Paul, Minnesota 55101 Building 230 Fort Shafter
Honolulu, Hawaii 96813
(Write APO San Francisco 96558)
U.S. Army Engineer Division,
North Pacific
P.O. Box 2870 U.S. Army Engineer Division,
Portland, Oregon 97208 South Atlantic
510 Title Building
U.S. Army Engineer District, Alaska 30 Pryor Street, S.W.
P.O. Box 7002 Atlanta, Georgia 30303
Anchorage, Alaska 99510
U.S. Army Engineer District, Charleston
U.S. Army Engineer District, Portland P.O. Box 919
P.O. Box 2946 Charleston, South Carolina 29402
Portland, Oregon 97208
U.S. Army Engineer District, Jacksonville
U.S. Army Engineer District, Seattle P.O. Box 4970
P.O. Box C-3755 Jacksonville, Florida 32201
4735 East Marginal Way, South
Seattle, Washington 98124 U.S. Army Engineer District, Mobile
P.O. Box 2288
U.S. Army Engineer District, Walla Walla Mobile, Alabama 36628
Building 602
City-County Airport U.S. Army Engineer District, Savannah
,,Walla Walla, Washington 99362 P.O. Box 889
Savannah, Georgia 31402

U.S. Army Engineer Division, U.S. Army Engineer District, Wilmington
Ohio River P.O. Box 1890
P.O. Box 1159 Wilmington, North Carolina 28401
Cincinnati, Ohio 45201

U.S. Army Engineer District, Huntington U.S. Army Engineer Division,
P.O. Box 2127 South Pacific
Huntington, West Virginia 25721 630 Sansome Street
Room 1216
U.S. Army Engineer District, Louisville San Francisco, California 94111
P.O. Box 59
Louisville, Kentucky 40201 U.S. Army Engineer District, Los Angeles
P.O. Box 2711
U.S. Army Engineer District, Nashville Los Angeles, California 90053
P.O. Box 1070
Nashville, Tennessee 37202 U.S. Army Engineer District, Sacramento
650 Capitol Mall
U.S. Army Engineer District, Pittsburgh Sacramento, California 95814
Federal Building
1000 Liberty Avenue U.S. Army Engineer District, San Francisco
Pittsburgh, Pennsylvania 15222 211 Main Street
San Francisco, California 94105

U.S. Army Engineer Division, Southwestern
1114 Commerce Street
Dallas, Texas 75242

U.S. Army Engineer District, Albuquerque
P.O. Box 1580
Albuquerque, New Mexico 87103

U.S. Army Engineer District, Fort Worth
P.O. Box 17300
Fort Worth, Texas 76102

U.S. Army Engineer District, Galveston
P.O. Box 1229
Galveston, Texas 77553

U.S. Army Engineer District, Little Rock
P.O. Box 867
Little Rock, Arkansas 72203

U.S. Army Engineer District, Tulsa
P.O. Box 61
Tulsa, Oklahoma 74102

C. Bureau of Reclamation

The Bureau of Reclamation,, an agency of the U.S. Department of the Interior,

plans, builds, and operates water development projects in the Nation's 17

western states. Dams, reservoirs, and canals have been built to provide water

for agricultural, municipal, industrial, and other purposes. The Bureau can

furnish information on the potential for flooding at locations affected by

water development projects. Technical assistance can be obtained from a flood

hydrologist at each of the Bureau's seven regional offices. For more

information, contact the nearest office at the address shown below.

Regional Offices of the Bureau of Reclamation:

Upper Missouri Region Pacific Northwest Region
P.O. Box 2553 P.O. Box 043
Billings, MT 59103 550 West Fort Street
Boise, ID 83742

Lower Missouri Region
Building 20 Mid-Pacific Region
Denver Federal Center Federal Office Building
Denver, CO 80225 2800 Cottage Way
Sacramento, CA 95825
Upper Colorado Region
P.O. Box 11568 Southwest Region
Salt Lake City, UT 84147 Commerce Building
714 S. Tyler, Suite 201
Lower Colorado Region Amarillo, TX 79101
P.O. Box 427
Boulder City, CO 89005

D. Soil Conservation Service (SCS)

The Soil Conservation Service (SCS) recognizes the use of flood warning

systems along with other nonstructural and structural measures as means of

reducing flood damages. SCS can provide both financial and technical

assistance to develop and install local flood warning systems.

In watersheds that are less than 250,000 acres in size (Public Law 566

watersheds), SCS can pay up to 80 percent of the installation costs forflood

warning system. Similar funding authorities are available under the Resource

Conservation and Development Program. Because the principles and,.guidelines,

of this program (U.S. Water Resources Council, 1973) are applicable to the

watershed program, flood warning systems must be economically justified to be

eligible for cost-share assistance. Normally, SCS cooperates with NOAA-NWS to

develop and install the systems. Cogr-sharing may be provided for the.

installation of rain and/or stream gages, radio relay equipment, a computeror

analysis system, and a warning system. After the system is operational,%the

local sponsors must operate and maintain it. SCS makes a major effort to

interview flood plain residents to help them understand how a flood warning

can reduce their specific flood losses. The major reasons that SCS is not

extensively involved in flood warning systems are the short time between a

.flood warning and the necessary community response, and the large commitment

required of local sponsors to operate and maintain the system after it is

installed. SCS may participate in pilot projects to demonstrate new

technology or to gain acceptance of innovative approaches using special funds

available under the Resource Conservation Act. These funds are limited, and

only one application has been made to date.

STATE CONSERVATIONISTS

ALABAMA FLORIDA KENTUCKY
665 Opelika Road Federal Bldg., Rm. 248 333 Waller Avenue, Rm. 305
Auburn, Alabama 36380 401 S.E., Ist Avenue Lexington, Kentucky 40504
Gainesville, Florida 32601
ALASKA LOUISIANA
Suite 129,-Professional Bldg. GEORGIA 3737 Government Street
2221 E. Northern Lights Blvd. Federal Bldg., Box 13 Alexandria, Louisiana 71301
Anchorage, Alaska 99508 355 East Hancock Avenue
Athens, Georgia 30601 MAINE
ARIZONA USDA Building
Suite 200 HAWAII University of Maine
201 E. Indianola Avenue 300 Ala Moana Blvd. Orono, Maine.04473
Phoenix, Arizona 85012 Honolulu, Hawaii 96850 MARYLAND . .
ARKANSAS IDAHO, Hartwick Building, Rm. 522
Federal Office Building 304 North 8th St., Rm. 345 4321 Hartwick Road
700 West Capitol Street Boise, Idaho 83702 College Park, Marylahd 20740
Little Rock, Arkansas 72201
ILLINOIS 14ASSACHUSETTS
CALIFORNIA Springer Federal Building 451 West Street
2828 Chiles Road 301 North Randolph Street Amherst, Massachusetts 01002
Davis, California 95616 Champaign, Illinois 61820 MICHIGAN
COLORADO INDIANA Room 101
Diamond Hill, Bldg. A, 3rd Fl. Corporate Square-West 1405 South Harrison Road
2490,West@26th Avenue Suite 2200 East Lansing, Michigan 48823
Denver, Colorado 80211 5610 Crawfordsville Road
Indianapolis, Indiana 46224 MINNESOTA
CONNECTICUT 200 Federal Bldg. & U.S.
Mansfield Professional Park IOWA Courthouse
Route 44A* 693 Federal Building 316 North Robert Street
Storrs, Connecticut 06268 210 Walnut Street St. Paul, Minnesota 55101
Des Moines, Iowa 50309
DELAWARE MISSISSIPPI
Treadway Towers, Ste. 210 KANSAS Federal Bldg., Ste. 1321
9 East Loockerman Street 760 South Broadway 100 West Capitol Street
Dover, Delaware 19901 Salina, Kansas 67401 Jackson, Mississippi 39269

MISSOURI OKLAHOMA VERMONT
555 Vandiver Drive Agriculture Center Bldg. 69 Union Street
Columbia, Missouri 65202 Farm Road & Brumley Street Winooski,..Vermont 05404
Stillwater, Oklahoma 14074
MONTANA VIRGINIA
Federal Bldg., Rm. 443 OREGON Federal Bldg., Rm. 9201
10 East Babcock Federal Bldg. 16th Floor 400 North 8th Street
Bozeman, Montana 59715 1220 S.W. 3rd Avenue P.O.-Box 10026
Portland, Oregon 97204 Richmond, Virginia 23240
NEBRASKA
Federal Building, Rm. 345 PENNSYLVANIA WASHINGTON
100 Centennial Mail, N. Federal Bldg. & Courthouse- 360 U.S.:Courthouse,
Lincoln, Nebraska Box 985, Federal Sq. Station West 920 Riverside Ave.
Harrisburg, Pennsylvania 17108 Spokane, Washington.99201
NEVADA
U.S. Post Office Building PUERTO RICO WEST VIRGINIA,
50 S. Virginia Street Director, Caribbean Area 75 High Street, Mii. 316
Reno, Nevada 89505 Federal Bldg., Rm. 639 Morgantown, WV 26505
Chardon Avenue, GPO Box 4868
NEW HAMPSHIRE Harrisburg, Pennsylvania 17108 WISCONSIN
Federal Building 4601 Hammersley Road
P.O. Box G RHODE ISLAND Madison, Wisconsin 53711
Durham, New Hampshire 03824 46 Quaker Lane
West Warwick, Rhode Island 02893 WYOMI14G
NEW JERSEY Federal Office Bldg.
1370 Hamilton Street SOUTH CAROLINA 100-East "B" St., Rm. 3124
Somerset, New Jersey 08873 1835 Assembly St., Rm. 950 Casper, Wyoming 82601
Strom Thurmond Federal Bldg.
NEW MEXICO Columbia, South Carolina 29201
517 Gold Ave., S.W., Rm. 3301
Albuquerque, New Mexico 87102 SOUTH DAKOTA
Federal Building
NEW YORK 200 4th Street, S.W.
100 S. Clinton Street Huron, South Dakota 57350
Syracuse, New York 13260
TENNESSEE
NORTH CAROLINA* U.S. Courthouse, Rm. 675
Federal Office Bldg, Rm. 535 801 Broadway Street
310 New Bern Avenue Nashville, Tennessee 37203
Raleigh, North Carolina 27601
TEXAS
NORTH DAKOTA W.R. Poage Federal Building
Federal Building, Rm. 522 101 S. Main Street
Rosser Avenue & Third St. P.O. Box 648
P.O. Box 1458 Temple, Texas 76501
Bismarck, North Dakota 58502
UTAH
OHIO 4012 Federal Building
200 North High St., Rm. 522 125 South State Street
Columbus, Ohio 43215 Salt Lake City, Utah 84147

E. United States Geological Survey

The mission of the United States Geological Survey's Water Resources Division

(WRD) is to providethe hydrologic information and understanding needed to

best use and manage the-Nationts watiar resources for the benefit of*the people

of the Uni,.ted.States.. to accomplish this, the Division assesses the Na.tion's

water resources in.terms of the quality, quantity, And use of water,.and

develops the knowledge and hydrologic understanding necessary to predict the

consequences,ofalternative plans and policies for developing and using water

resources.- Much of this work is done through cooperation with and funding

from Federal, State, an d local agencies. Most of the cooperative work .is

based on a shared 50'-50 funding with State or local.agencies. During the 1983

fiscal year, the 50-50.matching program was carried out in working partnership

with more than 800 State, regional, and local agencies. The data-collection

component of the coopera Ctive program provides the basic data needed for

hydrologic investigations such as the establishment of a flood warning system.

The United States Geological Survey's Office of Water Data Coordination

coordinates the acquisition, storage, and dissemination of water data.,

National Water Data Exchange (NAWDEX) assists users in the identification,

location, and acquisition of water data. NAWDEX services are available

through a nationwide network of 60 Assistance Centers, located in 45 States and

Puerto Rico. The Centers provide direct access to NAWDEX and make local"area

expertise available to aid in identifying and locating needed data. NAWDEX

provides a nationwide indexing of more than 375,000 sites for which water data

are available from more than 400 organizations. A current directory

containing the names, addresses, and telephone numbers of all Assistance

Centers is available free from the NAWDEX Program Office, United States

Geological Survey, 421 National Center, Reston, Virginia 22092; telephone

(703) 860-6031.

DISTRICT CHIEF OFFICES

Northeastern Region

ILLINOIS PENNSYLVANIA LOUISIANA
Champaign County Bank Plaza Post Office Box 1107 P.O. Box 66492
102 E. Main Street, 4th Fl. 4th Floor, Federal Bldg. Baton Rouge, Louisia Ina 70896
Urbana, Illinois 61801 228 Walnut Street
Harrisburg, Pennsylvania 17108 MISSISSIPPI
INDIANA Suite 710, Federal Bldg.
6023 Guion Road, Ste. 201 WEST VIRGINIA 100 West Capitol Street
Indianapolis, Indiana 46254 Rm. 3416, Federal Bldg. & Jackson, Mississippi 39269
U.S. Courthouse
MID-ATLANTIC DISTRICT 500 Quarrier Street, East NORTH CAROLINA
208 Carroll Building Charleston, West Virginia 25301. P.O. Box 3857
8600 La Salle Road Room 436, Century Station,
Towson, Maryland 21204 WISCONSIN 300 Fayetteville St. Mall
1815 University Avenue Raleigh, NC 276b2
NEW ENGLAND DISTRICT Madison, Wisconsin 53705
150 Causeway Street PUERTO RICO
Suite 1309 Southeastern Region G.P.O. Box 4424
Boston, Massachusetts 02114 San Juan, Puerto Rico 00936
ALABAMA
MICHIGAN 520 19th Avenue SOUTH CAROLINA
6520 Mercantile Way, Suite 5 Tuscaloosa, Alabama 35401 Strom Thurmond Federal Bldg.
Lansing, Michigan 48910 Suite 658
ARKANSAS 1835 Assembly Street
MINNESOTA Room 2301 Federal Office Bldg. Columbia, SC 29201
702 Post Office Building 700 West Capitol Avenue
St; Paul Minnesota 55101 Little Rock, Arkansas 72201 TENNESSEE
A413 Federal Building
NEW JERSEY FLORIDA U.S. Courthouse
Room 430, Federal Building 325 John Knox Road Nashville,.Tennessee 37203
402 E. State Street Suite F-240
Trenton. New Jersey 08608 Tallahassee, Florida 32303 Central Region

NEW YORK GEORGIA COLORADO
P.O. Box 1350 6481 Peachtree Industrial Blvd. Building 53, Denver Federal
343 U.S. Post Office Suite B Center, MS 415, Box 25046
& Courthouse Doraville, Georgia 30360 Lakewood, Colorado 80225
Albany, New York 12201
KENTUCKY
OHIO Room 572, Federal Bldg.
975 West Third Avenue 600 Federal Place
Columbus, Ohio 43212 Louisville, Kentucky 40202

Central Region (Cont.)

IOWA UTAH
P.O. Box 1230 1016 Administration Building
Room 269, Federal Bldg. 1745 West 1700 South
400 So. Clinton Street Salt Lake City, Utah 84104
Iowa City, Iowa
WYOMING
KANSAS P.O. Box 1125
1950 Avenue A Campus West J.C. O'Mahoney Federal Center
University of Kansas Room 4007
Lawrence, Kansas 66044 2120 Capitol Avenue
Cheyenne, Wyoming 82003
MISSOURI
1400 Independence Road Western Region
MS 200
Rolla. Missouri 65401 ALASKA
1515 E. 13th Avenue
MONTANA Anchorage, Alaska 99501
Federal Bldg., Drawer 10076
Helena, Montana 59626 ARIZONA
Federal Building
NEBRASKA 301 W. Congress, FB-44
Room 406, Federal Bldg. Tucson,, Arizona 85701
& U.S. Courthouse
100 Centennial Mall North CALIFORNIA
Lincoln, Nebraska 68508 Room W-2235 Federal Bldg.
2800 Cottage Way
NEW MEXICO Sacramento, California 95825
Western Bank
505 Marquette N.W., Rm 720 HAWAII
Albuquerque, New Mexico 87102 300 Ala Moana Blvd., Rm. 6110
Honolulu, Hawaii 96850
NORTH DAKOTA
821 E. Interstate Avenue IDAHO-NEVADA
Bismarck, North Dakota 58501 230 Collins Road
Boise, Idaho 83702
OKLAHOMA
Room 621 OREGON
215 Dean A. McGeen St. 847 NE 19th Ave., Suite 300
Oklahoma City, Oklahoma 73102 Portland, Oregon 97232

SOUTH DAKOTA WASHINGTON
Room 317, Federal Bldg. 1201 Pacific Avenue, Ste. 600
200 4th St., Southwest Tacoma, Washington 98402
Huron, South Dakota 57350

TEXAS
649 Federal Building
300 East 8th Street
Austin, Texas 78701

F. National Weather Service

The National Weather Service (NWS), Hydrologic Service program has two basic

goals: 1) to warn the public about weather and floods in order to savelives

and property; and 2) to report on the Nation's rivers in order to support

water resources management for the benefit of all sectors of the economy.

These goals are in accordance with the Congressional Organic Act of 1890,

which designates the NWS as responsible for "...the forecasting of weather and

flood signals for the benefit of agriculture, commerce, and navigation, the

gaging and reporting of rivers...".

To meet the first goal, the NWS has established a flood forecast and warning

service. This service consists of Weather Service Forecast offices, which

collect hydrologic data and relay it to NWS River Forecast Centers. The River

Forecast Centers (RFCs) are staffed with professional hydrologists who are

responsible for the quality control of data, the input of data into

computerized hydrologic models, the analysis of the model output, and the

relay of flood forecasts back to the local Weather Service Forecast office for

dissemination to the public, other agencies, and the media. These forecasts

can usually be achieved only for the larger river basins with crest times

greater than 12 hours. For communities located on small flashy streams with

crest times of less than 12 hours, the NWS provides generalized flash flood

watches and warnings and works with communities to establish local flood

warning and response systems.

The NWS recognizes the importance of local flood warning and response systems

in improving flood warning service to communities, and provides technical

assistance to communities with flood problems. Technical support involves

recommending alternative flood warning systems appropriate to the econom'ic

capabilities of the community; helping communities in the design,

installation, and,implementati6n of warning afid"respoft6e systems-and-the

training of personnel;'and providing operational support to responsible

community officials. In the case of automated systems, the NWS provides site

selection of the hydrologic observation network-, radio path analysis, generic

standards f6r,automated local flood warning systems, consulting service on the

calibration of hydrologic models, and when the system is operational,

additional weather information.

Any individual desiring information on local flood warning systems should

contact the local Weather Service Office.'

G. Tennessee Valley Authority

As part of its local flood damage abatement program, the Tennessee Valley

Authority (TVA) provides flood plain management assistance to flood-prone

communities within the Tennessee River watershed. This assistance includes

working with community officials or their designated representatives to

determine the feasibility of local flood warning and response systems, and

providing the technical information needed to implement local flood warning

and response systems.

TVA is cooperating with the National Weather Service (NWS) in the development

of local flood warning and response systems and in the past has provided

financial assistance in support of NWS efforts to implement a computer-based

flood warning system known as IFLOWS in the Tennessee Valley. TVA has also

participated directly in the development and construction of local flood

warning and response systems at several locations in the Tennessee River

watershed. These systems include both flash flood alarm gages and an

automated real-time forecast of flood elevations based on a continuous

computer analysis of recorded rain and streamflow.

Communities in the Tennessee River watershed may contact TVA for information

and assistance by writing to:

Tennessee Valley Authority
Flood Protection Branch
Liberty Building
Knoxville, Tennessee 37902

R. Federal Emergency Management Agency (FIKKA)

Planning for emergencies, responding to them, and recovering from them are

responsibilities shared by Federal, State, and local.,governments, and the

private sector. The capability of meeting an emergency must be based

essentially at the local level, with State and local governments,providing

guidance and support in all aspects of the emergency management-process*

Through coordination of planning and preparedness activities and the provision

of financial and technical support. the Federal Emergency Management Agency

(FEMA) encourages the development of predisaster and postdisaster emergency

preparedness and response plans.

Among FEMA's activities are:

0 Supporting State and local governments in a wide range of disaster

planning, preparedness, mitigation, response, and recover efforts.

As necessary, the agency provides funding, technical assistance,

services, supplies, equipment. and direct Federal support for

fulfilling state and local government emergency management.

responsibilities. Various-States, including Illinois and Minnesota,

have included detailed planning for local flood warning systems in

their State emergency preparedness plan.

Additional services and products that FEMA may fund include:

1. An inventory of properties and structures inflood-prone areas.

2. A statewide flood hazard mitigation plan developed in a

predisaster context.

3. Public awareness media presentations on flood hazards.

4. Handbooks or other technical assistance on a variety of flood

hazard topics, which may include flood warning systems.

Administering the National Flood Insurance Program (NFIP). The NFIP

provides insurance coverage to property owners in commu nities with

flood hazards in exchange for community agreement to adopt flood

plain management measures to protect lives and reduce property

losses. Technical assistance is provided to communities in both

flood plain management and postdisaster hazard mitigation activities,

such as encouragement of new construction away from flood-prone

areas,. At present, there are approximately 17,000 communities

participating in the NFIP and nearly 2 million insurance policies in

effect. FEMA has published detailed flood plain mapping for about 50

percent of the communities and approximate flood plain delineations

for most of the remainder. A detailed Flood Insurance study and

backu
.p materials are also available.

Developing community awareness programs for weather emergencies and

home safety.

Regional Offices

There are 10 FEMA Regional Offices. Each office is he aded by a Regional

Director who reports to the FEMA Director and is responsible for all FEMA

programs in the region.

Region I (Boston) Region VI (Dallas)
442 J.W. McCormack, POCH Federal Regional Center
Boston, Massachusetts 02109 Denton, Texas 76201

Region II (New York) Region VII (Kansas City)
26 Federal Plaza Old Federal Office Bldg., Rm. 300
Mew York, New York 10,278 Kansas City, Missouri 64106

Region III (Philadelphia) Region VIII (Denver)
Curtis Building, 7th Floor Federal Regional Center, Bldg. 710
6th & Walnut Streets Denver, Colorado 80225
Philadelphia, Pennsylvania 19106

Region IX (San Francisco)
Region IV (Atlanta) Building 105
Seventh Floor Presidio of San Francisco
1371 Peachtree Street, N.E. San Francisco, California 94129
Atlanta, Georgia 30309

Region X (Seattle)
Region V (Chicago) Federal Regional Center
300 South Wacker Drive (24th Floor) Bothell, Washington 98021
Chicago, Illinois 60606

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1. National. Park Service (NPS)

The National Park System is made up of 334 units covering some 79 million

acres. These park units are of such historic or natural significance as to

justify special recognition and protection by the Congress. New park units

are continually being added to the system by the Congress. Many of these

units are subject to flooding from rivers, lakes, oceans, and tsunamis.

Flooding problems are sometimes aggravated by improper development within

flood plains, by dam failures, and by unanticipated rises at reservoirs.

Every year, millions of dollars are spent to repair flood-damaged areas within

the National Park System. Occasionally, loss of life occurs because of park

flooding. To minimize losses. the National Park Service (NPS) has implemented

policies on flood plains and dam safety in accordance with Executive Orders.

As part of these policies, both manual and automatic local flood warning and

response systems are being installed.

The Engineering and Safety Services Division of the NPS has responsibility for

the Safety of Dams Program. With technical review assistance from the Bureau

of Reclamation, parks are installing flood warning systems on their high dams

and dams with significant hazard potential as part of required emergency

action plans.

The Air and Water Quality Division promulgates NPS guidelines for implementing

the Flood Plain Management and Wetland Protection Executive Orders. Several

of these warning systems have been installed with the assistance of the

National Weather Service and the Army Corps of Engineers.

For additional information about the use of local flood warning and response

systems on flood plains or at dam locations, contact the appropriate NPS

Division.

J. State Assistance

Generally, two types of assistance are available from a State agency:

technical and financial. The availability of either or both varies, however.@

according.to the individual State and its particular resourcese,

A local municipality seeking financial assistance from a State may have to

contact several State agencies. Funding may be available from the State

emergency management agency, or from another agency such as a the.,natural

resources or community affairs department. Funding may have to be packaged

from.several State sources to make a project viable. It is also possible that.

financial assistance is not available.

Technical assistance in various forms is available from most States. The

agency responsible for the State's flood plain management, National Flood.

Insurance Program activities, and/or state emergency management will usually

be able to provide information on local flood warning and response systems and

to advise aJocal municipality interested in developing such asystem. The

type and extent of.assistance will vary with the capabilities and resources of

each State.

Chapter VII. Other Related Activities

A. Dam Safety Activities

Local'flood warning and response systems are an essential part of emergency

action plans prepared for dams. Federal involvement in emergency action plans

as well as other dam safety issues are coordinated among the various Federal

agencies by the Interagency Comndttee on Dam Safety (ICODS). MODS has

developed'guidelines for emergency action plans that address emergencies at

dams and downstream of dams.

Flood emergencies at dams are very different from flood emergenci es that do

not involve a dam. The most notable difference is the size and speed of a

flood wave associated with the failure of a dam.

Local flood warning and response systems in areas that could experience dam

failure must be based on consideration of both floods that could occur without

dam failure and those associated with dam failure. Failure is unlikely at

dams designed according to current hydrologic and structural standards, but

should it occur, the failure is often sudden as well as unexpected.

B. Principles and Guidelines

The Economic and Environmental Principles and Guidelines for Water and Related

Land Resources Implementation Studies (P&G) (U.S. Water Resources Council,

1973) is applicable to water resource plans of the Corps of Engineers, the

Bureau of Reclamation, the Soil Conservation Service, and the Tennessee Valley

Authority.

The P&G require specifically that, in the planning of projects, consideration

be given to nonstructural measures as a means to address the problems and

opportunities of each project. Nonstructural measures are interpreted to

include, among other things, a local flood warning and response system.

The P&G also require that, unless an exception is granted by the Secretary of

the Department involved in the project, the plan selected for implementation

must be the one that provides the maximum net economic benefits.

C. The Unified National Program for Flood Plain Management

In 1968, when the Congress enacted the National Flood Insurance Act, it,

recognized that a reduction in the Nation's escalating flood losses could be

achieved only if all floodloss reduction programs structural and

nonstructural; local, State, and Federal -- were brought to bear in a

concerted effort focused on wise use of the Nation's flood plains. In the

Act, the Congress directed the President to prepare a Unified National Program

for Flood Plain Management. The Unified Program provides for establishment of

a Federal Interagency Flood Plain Management Task Force to carry out

recommendations set forth in the Program. Initially under the auspices of the

United States Water Resources Council, the Unified Program and the Task Force

is now assigned to the Federal Emergency Management Agency, which is also

responsible for the National Flood Insurance Program.

The Task Force agencies are:

Department of Agriculture Department of Transportation

Department of the Army Environmental Protection Agency.

Department of Commerce Federal Emergency Management Agency

Department of Energy Tennessee Valley Authority

Department of the Interior

Department of Housing and Urban

Development

The Task Force has been responsible for the preparation of the various

technical flood plain management documents published by the United States

Water Resources Council and available through the National Technical

Information Service. Each year, the Task Force holds several seminars on

flood plain management issues.

The Task Force recognizes.the importance and utility of'local flood-warning

systems. In order to implement more effective strate@gie-s to reducel6ss of

life and property, the Task Force believes that greater attention mu.st be:

given to local flood warning and response systems, and that, where

practicable, these systems should be linked to regional and national warning

systems.

D. Association of State Flood Plain Managers

The.Association of.State Flood Plain.Managers.is a national association,of

persons involved with flood plain management and related concerns such as

flood hazard mitigation, flood preparedness, flood warning, and flood

recovery*

One of the functions of the association is to facilitate cooperation and the,

exchange of information among State, local and Federal units of government and

the private sector on innovative ideas and trends in flood plain management.

The association also provides a forum for the education of those involved in

flood plain management.

A municipality interested in or planning the establishment of a local flood

warning and response system should contact the association for advice on

resource persons and helpful materials. Financial assistance is not available

from the association.

Regions

Region I Region VI
Dept. Environmental Mgmt. Soil & Water Conservation
100 Cambridge Street One Capitol Mall, Suite 2D
Boston, MA 02002 Little Rock, AR 72201
(617) 727-5804 (501) 371-1611

Region 11 Region VII
Dept. Environmental Protection Dept. Water, Air & Water Mngmt.
P.O. Box CN 029 Wallace State Office Building
Trenton, NJ 08625 Des Moines, IA 50319
(609) 292-2373 (515) 292-2373

Region III Region VIII
Flood Plain Mgmt. Division Disaster & Civil Defense
551 Forum Building P.O. Box' 1709
Harrisburg, PA 17120 Cheyenne, WY 82003
(717) 787-7403 (307) 777-7566

Region IV Region 1K
Miss. Research & Dev. Cntr. Dept. of Water Resources
3825 Ridgewood Road 99 E. Virginia Avenue
Jackson, .MS 39211 Phoenix, AZ 85004
(601) 982-6376 (602) 255-1566

Region V Region X
Div. of.Waters, Land Use Management Idaho Dept. of Water Resources
444 Lafayette Rd., 3rd Floor Statehouse
St. Paul, MN 55101 Boise, ID 83720
(612) 296-9226 (208) 334-4470

AsSOCIATION OF STATE FLOODPLAIN MANAGERS, INC.
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Chapter VIII Selected References

Automated Local Evaluation in Real Time--A Cooperative Flood Warning System

for Your Community. National Weather Service, Western Region, October 1982.

Barrett, Curtis B. The NWS Flash Flood Program. Paper presented to the 5th

Conference on Hydrometeorology, October 17-19, 1983, Tulsa, OK. Boston, MA:

American Meteorological Society.

Barrett, Curtis B. National Prototype Flash Flood Warning System Paper,

presented to the 4th Conference on Hydrometeorology, October 7-9, 1981,

Reno, NV. Boston, MA: American Meteorological Society.

Bartfeld, Ira, and Taylor, Delores. A Case Study of a Real-Time Flood Warning

System on Sespe Creek.. Ventura County, California., Proceedings from

Symposium Storms Floods and Debris Flows in,Southern California and,

..Arizona 1978 and 1980. Washington, D.C: National Acaddy Press, 1982.

Benefit Model NWS Gaging Network.. A report to the National Weather Service

prepared by GKY &Associatesl Inc.,, Springfield, Virginia, March 31, 1981.

Carter, Mike. Natural Hazards Warning Systems. NHS Report Series No.

Minneapolis, MN: University of Minnesota, 1980.

Disaster Relief Act of 1974 Public Law 93-288, 88 Stat. 143 (1974), as

.amended.

Federal Assistance Handbook: Emergency Management, Direction and Control

Program. CPG 1,-3, revised October 1983.

Federal Civil Defense Act of 1950, Public Law 81-920, 64 Stat.:1245 (1951), as

amended.

Federal Coordinating Council for Science, Engineering, and Technology. Federal

Guidelines for Dam Safety Ad hoc Interagency Committee.on Dam Safety, June

252 1979.

Federal Emergency Management Agency. Disaster Response and Recovery, Digest of

Federal Disaster Assistance Programs October 1979.

------- Directory of Governors and State Officials Responsible for Disaster

Operations and Emergency Planning., March 1982.

------- Disaster Operations - A Handbook for Local Governments. CPG 1-6V July

1981.

------- Financial Assistance Guidelines.. CPG-32, February 1984.

------- Flood Hazard Mitigation Handbook of Common Procedures, Interagency

Regional Hazard Mitigation Plans.

------- Guide to the Disaster Preparedness Improvement Grant Program. CPG 1-

31, April 1982.

------- Interagency Agreement for Nonstructural Damage Reduction Measures as

Ap2lied to Common.Flood Disaster Planning and Post-Flood Recovery Practices.

December 15, 1980.

------ Interagency Task Force for Nonstructural Flood Damage Reduction

Measures and Flood Disaster Recovery Status Report and Recommendations.

November 12, 1982.

------- local Government Emergency Planning. GPG 108, April 1982.

-------- Standards for Local Civil Preparedness. GPG 1-5, November 1980.

Industrial Flood Preparedness. Proceedings of the Flood Warning and Flood

Proofing Seminar for Industry, Williamsport, PA, April 16-17, 1979.

Little, Jeanne L..Flood Plain Management in Lycoming County, April 1982.

Lycoming CountyPlanning Commission.-Lycoming Creek Watershed -- Flood

Mitigation Pilot Project, Phases 1, 2, and 3 Lycoming County, PA, September

1983.

National Advisory Committee on Ocean and Atmosphere. The Nation's River and

Flood Forecasting and Warning Service. Special Report to the President and

Congress, March 1983.

National Flood-Insurance Act of 1968, Public Law 90-448,82 Stat. 572 (1968),

as amended.

National Governors Association. Federal Emergency Authorities Abstracts.

Emergency Preparedness Project, Center for Policy Research. Printed for

Defense Civil Preparedness Agency, May 1979.

National Weather Service. Guide for Flood and Flash Flood Preparedness

Planning. Prepared for Disaster Preparedness Service by H. James Owen,

Owen, H. James. Flood Warning System,Does Your Community Need One?. Prepared

for the National Weather Servicet October 1982.

-------- Information for Local Officials on Flood Warning Systems Prepared for

the National Weather Service, May 1979.

Peterson, Jack J. IFLOWS System Description Prepared for Flash Flood Program

Office, National Weather Service, July 15, 1980.

Rante, S.F. 1982 Measurement and Computation of Streamflow. Volume 1,

Measurement of Stage and Discharge; Volume 2. Computation of Discharge.

Geological Survey Water Supply Paper 2175.

Rechard, P.A., and Wei, T.C. Performing Assessments of Precipitation Gages for

Snow Measurement. Water Resources Series no. 76, Water Resources Research

Institute, University of Wyoming, Laramie,

U.S. Water Resources Council. Economic and Environmental Principles and

Guidelines for Water and Related Land Resources Implementation Studies.

February 3, 1983.

Title 44.CFR, Emergency Management and, Assistance.

Chapter IX Glossary, Acronyms and,Abbreviations

Glossary

Backwater flooding.is the backup of water into a stream from a river, lake, or

ocean with a higher water elevation.

Bank full stage is the water elevation that reaches the top of the banks along

a stream.

Base station is the central location for receiving flood data from,sensors

in the ALERT system.

Bubbler gage is an automated device that measures,water pressure near the

bottom of the stream; this pressure equates with water depth above the gage.

Cost effectiveness.is the relationship between the benefits derived from a

system and the cost of purchasing, operating, and-maintaining.it.

Crest is the maximum elevation of a flood at a specific location.

Critical public services typically consists of police and fire assistance,

emergency medical services, communications, utilities, transportation, and

public works.

Dambreak analysis is the use of a model to calculate the effects of a flood

caused by the actual or hypothetical failure of a dam.

Emergency action plan is a detailed description of the actions that mast be

taken to reduce flood losses and to disseminate information about an actual or

expected flood hazard.

Emergency operation center is the center of decisionmaking, information-

gathering and dissemination, initiating of emergency actions, and coordinating

responses to emergencies. The center may be part of a public service or

safety unit in a local government or may be activated only when emergencies

arise.

Event as used in da ta collection represents a point at which a gage reaches a

preset value and records the occurrence or transmits it to a receiver.

Falling limb refers to the declining portion of a hydrograph following a

cres't.

Flash flood watch is the public notification issued by the National Weather

Service when climatic, ground, and topographic conditions indicate that flash

floods are likely to occur in a given area.

Flash flood is a flood that occurs a short time (minutes to hours) after the

causative event.

Flash flood warning is the public notification issued by the National Weather

Service on a county basis when flash flooding is imminent or has been

reported.

Flood index is the amount of rainfall that will produce flood stage in 6

hours; it is calculated by measuring soil moisture.

Flood loss potential is the potential loss of life and property from flooding.

Gage datum is the elevation level that corresponds to stage 0.0 at a stream

gage; it is often set at the stream bottom or the elevation of a very low

flow.

Hydrograph is a chart that shows the relationship between streamflow or water

elevation to time at a certain location.

Hydrologic characteristics of watershed are the parameters that control the

runoff in a watershed. These include the basin size, ground cover conditions,

slope of the land, stream lengths (and slopes), topographic and geologic

features, and physical features constructed by man that alter runoff.

Hydrologic models are mathematical equations, algorithms, and/or logic that

represent the rainfall runoff process in.a watershed.

Hydrologist is a person who studies.,water on or through the earth's surface.

Land line.for communications is typically telephone service but includes any

communication lines.

Line"of-sight is an unobstructed straight line from a radio transmitter to a

receiver site.

Mean sea level is the mean of all hourly ocean elevations over a 19-year

period.

Meteor burst radio transmission uses the phenomenon of meteors entering the

upper atmosphere to bounce signals back to earth.

Meteorological sensor data is collected weather data such as rainfall)

humidity, temperature, and wind.

MicroRrocessor is a small computer that is usually more powerful in processi ng

ability and more flexible in using other equipment than a typical home,

computer.

Microwave radio transmission is a frequency of transmission that requires

line-of-sight. The frequency has high resistance to atmospheric interruption

(telephone tower relay stations are an example).

Nonstructural methods of reducing damage from floods include local flood

warning and response systems, temporary or permanent evacuation and relocation

of people or property, emergency flood fighting and financial relief, land use

regulations and building codes, floodproofing, area renewal and conversion to

open space, and flood insurance.

Percent chance is a probability multiplied by 100.

Probability is the ratio of observed or expected events to all possible

events; it is expressed as a decimal less than or equal to one.

Radio rej2ys_, or repeaters, are repeating or relaying devices that transfer

data from a self-reporting gage to a base station.

Rain gages are instruments that collect and meas ure rainfall.

Rate of rise indicates how quickly &stream is rising, typically expressed in

feet per hour or feet per day.

Recurrence interval is the average interval of time within which a given

hydrological event is expected to be equaled or exceeded once.

Response system is the planned protective reaction to flooding or the threat

of flooding.

Rising limb is the rising portion of a hydrograph preceding a crest.

River forecast centers are the organizational units within the National

Weather Service that forecast floods.

Stream gages are instruments that measure the depth of the water in a stream.

Self-reporting gages are instruments that automatically transmit rainfall or

stream stage data from a remote gage to a base station.

Staff gage is a vertical board or structure with a graduated scale for

measuring the depth of a river in feet.

Stage is the depth of water in a river or stream above the gage datum, or 0.0

level..

Stage-damage graphs or charts show the relation between flood depth or

elevation and damages in the area.

Station identifier is info.rmation transmittedwith data to identify,the

sending station.

Structural:methods of reducing,-damage from-floods,include dams and reservo Iirs,

levees, dikes, floodwalls, diversion channels, bridge modifications,@,channel

alterations, pumping stations, and land treatment.

Tipping bucket Rrecipitation gage is an electrical-mechanical device that

accumulates a small, precise amount of rainfall before tipping to spill the

water. The spill triggers an electrical signal that is counted and/or

transmitted to a base station. Each count represents a preset rainfall

accumulation amount 0 millimeter) and.is tagged with.the time of, occurrence,*

Twp, or potential warning time, is the maximum time available for warning

local.,communities prior to impending flooding.

Tw, or actual warning time,.is something less, than potential warning time.

Unitgraph or unit hydrograph is a typical streamflow hydrograph of a river

basin produced by 1 inch of surface runoff uniformly distributed over the

watershed during a specified period of time.

UHF, or ultra high frequency, is a range for the transmission of signals;

television channels above 13 are in this frequency.

@LHF, or very high frequency, is a range for the transmission of signals;

television channels 13 and below are in this frequency.

Acronyms and Abbreviations

ALERT Automated Local Evaluation in Real Time

B/C benefits divided by costs

cfs cubic feet per secon6

Corps U.S. Army Corps of Engineers

BAP emergency action plan

EOC emergency operations center

FEMA - Federal Emergency Management Agency

ICODS - Interagency Committee on Dam Safety

IEMS - Integrated Emergency Management System

IFLOWS - Integrated Flood Observing and Warning System

LFWS - local flood warning system

MSL - mean sea level

NAWDEX - National Water Data Exchange

NOAA - National Oceanic and Atmospheric Administration

NPS - National Park Service

NWS - National Weather Service

P&G - Principles and Guidelines

RFC - River Forecast Center

SCS - Soil Conservation Service

TWP - maximum potential warning time

Tr - time to recognize that rainfall is going to cause flooding

Ts - amount of time flooding occurs

TVA - Tennessee Valley Authority

Tw - actual warning time

USGS - U.S. Geological Survey

Chapter X. Appendix

A. Justification and Priority Setting

Flood warning systems require resources of money or manpower to design,

install, operate and maintain. Since resources are limited in many

organizations, priorities must be set and justification developed for adopting

a system. A rational approach is to weigh the cost of a flood warning system

against its potential benefits. This approach requires quantifying the

benefits in dollars. When the ratio of the economic benefits (B) to the cost

(C), or B/C, is greater than one, benefits exceed costs, and the system may be

described as beneficial. A flood warning system with a B/C ratio of less than

one (that is, costs exceed benefits) may still be beneficial, especially since

some benefits (for example, reducing potential loss of life) may not be

readily quantifiable in economic terms. To assign dollar values to an

intangible such as loss of life is very difficult and may never be realistic,

but a methodology is available for incorporating such intangibles into he

calculation of benefits.

The analysis methodology for justification, or priority setting, is based on

three classifications of the length of warning time:

1. Long warning times, when damageable property can be moved and a cost

savings calculated. Immediate flood dangers are not present and

there is ample time for egress*

2. Short warning times, when safety and security of egress is the

dominant concern. Damageable property cannot be readily moved and a

B/C analysis is not usable.

3. length of time between these-extremes, when justification for both

property damage and safety is needed.

For long warning times, the existing river and flood forecast services allow

enough time to move belongings, and the potential flooding is not an immediate

threat to life and community safety. The time available is typically adequate

to bring motor vehicles in to aid in the transfer of portable belongings -

industrial, commercial, and residential belongings to safer locations. Egress

from the flood area is relatively slow, permitting the occupants to remove

more belongings than would be possible with less warning times. It is

possible that lengthening the warning time from 18 hours to 24 hours, for

example, may accrue enough benefits.to justify a warning system.

The B/C analysis begins to falter when short warning times are involved

because they require quick egress of people with no time to move belongings.

When little time is available, safety and social well-being become the

dominant evaluation factors. The cost savings from moving damageable property

is nil, and a typical B/C analysis is not usable. Saving lives becomes the

dominant justification. Lengthening the warning time by 30 minutes may save

lives in a flash flood area, and this benefit will dominate the concern of the

residents.

A period of warning time somewhere between long and short may allow the

movement of damageable property, but the risk of lingering too long may in

itself present dangers. Although a warning system might extend the usable

time in which to prepare for a flood, a community plan would be needed to

ensure appropriate response time. In addition, the cost saving.from

relocating damageable property might be marginal compared to.the saving of

lives.

Classification of an area according to the lenth of warning time is site-

specific and highly dependent on the following discriminators:

1. rate of rise

2. extent in area of flooding

3. depth and velocity of water

4. access to and egress from flooded area

5. public services available

6. time available to move property

7. implementation of a community flood disaster plan

These discriminators must focus on the safety of the residents and the

prevention of damage to their belongings.

For short warning times, the rate of rise and the velocity and depth of the

flooding will be the dominant discriminators. Consideration.will also be

given to the extent of flooding, egress, and the development of a flood

emergency action plan. The justification will be a significant increase, in

warning time that will save lives and lessen the dangers associated with

egress. As an example, a life-threatening situation could occur when the rate

of rise is 10 feet per hour, depths exceed 3 feet, and velocities exceed 3

feet per second. People who recognize the danger and react quickly may get to

safe places. People who react slowly may be swept off their feet if they try

to wa lk, be trapped by pockets of deeper water, or swept downstream into

hazardous situations if they attempt to paddle a boat, drive a car, or swim.

People who do not react to@the short warning will'be trapped where they are.

If high ground or structures are not immediately available, or if the occupied

structures cannot withstand the velocity of the water, these residents are at

risk of losing their lives.

A flood warning system for short warning times should alleviate some or all of

the dangers noted in the example. To calculate the benefits of such a system,

quantify the rate of rise of flood waters in the developed areas, the velocity

of flows through these areas, and the potential depths for various floods.

Next, quantify, from this, any dangerous scenarios. Then determine critical

warning, reaction, and egress times for the various floods. Improvements in

the set times will be dependent on quick notification of residents.. To assure

this, the local community must immediately develop an emergency action plan

that provides for notifying residents and obtaining their compliance for quick

evacuation. When significant lessening of'danger's can be quantified, the

implementation of a warning system and emergency action plan can be justified.

For long warning times, justification will be based largely on the cost

savings that will result from increasing the warning time. The primary

discriminators will be access to and egress'from the threatened areas, public

services'-available before and during'the flood, the time available to move

property, and"the timely implementation of a flood disaster plan. The rate of

rise@ofthe flood waters and the extent of flooding may be significant

discriminators when flooding approaches a critical egress time. These

parameters will be used to evaluate the benefits of increasing the time to

evacuate'br remove property. The savings to be accrued from the increased
time, plus other savings, should be calculated according to appropriate State,

local, or agency guidelines. Next-,,`-ihe @cost of-instai'lation, operat on, 'and
maintenance (including periodic replacement of hardt-7are) f'or-t'he' life of-the

system is determined. The benefits and costs are annualized, and the ratio of

benefits to costs is determined. It the B/C is greate r than 1.0, the system

is usually justified.

For warning times between the two des@cribed Above, a mix of justifications is

undertaken. The relative importance of one type 'of justification over another

will become apparent upon analysis of all the discriminators. Calculating the
benefits for this classification of warning time will be more complex, since

the life-threatening situations may materialize as belongings are being

moved.. Safeguards against a false sense of security are paramount, and a

flood disaster plan is a must for this scenario.

To assure both economic justification and quick egress from dangerous floods,

all warning systems require two essential components. If these components are

not part of the overall plan, the system may create problems, dangers, and a

false sense of security. Therefore, for a flood warning system to achieve its

claims of costsavings and safe, t imely egress, the following components are

essential;

1. An emergency action plan designed to be implemented by local

residents to aid in the timely, orderly movement of belongings and people.

2. The monitoring of available evacuation time to assure that people

leave the threatened areas while critical time remains.

B. Lycoming County,-Pennsylvania - AnExample of an Integrated System

B.I. Hydrology of the Area

Lycoming County, Pen nsylvania, is one of the.most completely studied and

thoroughly managed watersheds in the country. Lycoming County is

predominantly rural, encompassing 1200 square miles in north central

Pennsylvania. According to the 1980 census, a total of 118,416 people reside

in the county, the majority in or near the Susquehanna River Valley, in the

Williamsport urban area, and in the valley areas of the Susquehanna's

tributary streams that flow to the river within the county.

Average rainfall varies throughout the watershed; the range is 35-40 inches

per year. Flooding usually occurs when there is heavy rainfall in short time

periods or when snowmelt combines with rain in the early spring. Ice Jams may

also cause flooding.

B.2. Background

A major effort was conducted to mitigate flood losses.for the residents,

businesses, and industries located in the flood plain of Lycoming Creek in the

county through the development of an integrated local flood warning and

response system. The system was developed because the area involved is

considered critical to the county's future economic development and because it

experiences costly annual flooding and threats of flooding that limit the

achievement of its full potential. The goals of the integrated system

development were to: (1) reduce yearly flood damages along the stream; and

(2) improve emergency preparedness in the five most heavily populated

political subdivisions involved.

The system has proved to be quite effective since its inception in 1976.

During a flood event in March 1979, for example, the system was credited with

reducing flood damages along the creek.by $750.,000. Residents, businesses,

and industries received adequate warning of impending inundation and, as a

result, had time to evacuate and relocate property that would otherwise have

been damaged.

B.3. The Local Flood Warning System

Early flood warning has been provided to residents and property owners of the

stream valley through a manual local flood warning system since 1976. A well

established network of volunteer stream and gage observers provides the data

necessary to make accurate flood forecasts. The county's manual system

consists of more than 100 volunteer observers, a county flash flood

coordinator and a flood prediction procedure developed by the National Weather

Service. Data collected by the observers is compiled, interpreted, and used

in the flood prediction procedure to determine whether a flood will occur, the

time of its occurrence, and the-magnitude expected. Appropriate notice

(including projected water heights, areas of inundation, and warning and

evacuation times) is given to the public,and responsible officials so that

protective actions can be initiated. The Lycoming Creek manual network, which

is a subset of the county network, provides data from a system of four rain

gages and three stream gages.

Late in 1982, the manual system was augmented by several automatic stream and

precipitation gages provided by the National'Weather Service to give warning

of particularly heavy precipitation accumulations in remote areas or of sudden

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stream rises at night. Two flash flood alarm gages and four automatic

precipitation gages were installed as part of the Integrated Flood Observing

and Warning System. The alarm .gages@are located'upstream of a location with

high potential for flash flooding,and are programmed to ring automatically in

a home about 100 feet from their location and simultaneously in the"couinty's

communication center (EOC).

The county system can be activated in at least three ways. First, the system

is activated if an observer or network coordinator notifies the county's

Emergency Management Agency that a particular location has received I inch of

rain in 12 hours in the winter or 2 inches in rain in 12 hours at any other

time of the year. Second, the system is activated if the National Weather

Service or a private weather forecasting service predicts conditions that

could lead to flooding. Third, the system is activated if the flash flood

alarm gages record critical stream levels.

The overall effectiveness of the system is enhanced by built-in backup

systems. Because of possible errors in measuring watershed rainfall and

computing runoff and stream height, and the vulnerability of any data

collection and transmittal system, it is undesirable to depend heavily on a

single aspect of the system. Thus, a series of backup commanication devices,

personnel, and additional data collection methods were included to provide the

most accurate information possible.

Using hydrologic data, streamflow history, and United States Geological Survey

(USGS) gage records, the Baltimore district of the Corps of Engineers, in

conjunction with personnel from the County Planning Commission's Emergency

Services staff, compiled detailed flood stage mapping for five densely

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and is using land-use controls aimed at discouraging inappropriate development

in flood-prone areas.

*U.S. GOVERNMENT PRINTING OFFICE- 1985-461-135:36642

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