I

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Design Guidelines for

Flood Damage Reduction
Acknowledgements

Many people contributed valuable assistance to the preparation of this

manual. We wish to acknowledge first the guidance provided by Melita

Rodeck, the Federal Emergency Management Agency's technical representative.

Also invaluable were the members of the project's advisory committee:

Armando C. Lardieri, Assistant Chief, Engineering Division, U.S. Army

Corps of Engineers, Pittsburgh District.

Larry A. Larson, Chief of Floodplain and Shoreland Management Section, Wisconsin Bureau of Water Regulation and Zoning, Madison.

Luna B. Leopold, Professor, University of California at Berkeley.

Rutherford Platt, Associate Professor, University of Massachusetts at

Amherst.

Gray Plosser, AIA, Kidd Wheeler and Plosser, Inc., Birmingham, Alabama.

Mark Riebau, Assistant Chief of Floodplain and Shoreland Management,

Wisconsin Bureau of Water Regulation and Zoning, Madison.

Robert B. Riley, AIA, Professor, University of Illinois, Urbana.

Conrad B. Wessell, AIA, Goldsboro, North Carolina.

Others who provided guidance and review included:

Christopher Arnold, Building Systems Development Inc., San Francisco; Raymond R Fox, Associate, Dames and Moore, Washington,

D.C.; Narendra N. Gunaji, Director, Engineering Experiment Station,

New Mexico State University, Las Cruces; George Phippen, Chief of

Flx)dplain Management, Office of the Chief of Engineers, U.S. Army

Corps of Engineers, Washington, D.C.; Gilbert F White, Natural Hazards Research and Applications Information Center, University of

Colorado, Boulder; and John Ziegler, AIA, Regional Director, Federal

Emergency Management Agency, New York.

Prepared by

ALA Research Corporation

1735 New York Avenue, Northwest

Washington, D.C. 200(Xi

Charles R. Ince,jr.-President

Donald E. Geis-Project Manager

Barry Steeves-Research Associate & Author

David A. Robillard-Research Assistant & Illustrator

Fred If. Greenberg-Design

Paul K. McClure-Editor

Consultants

EDAW Inc.

Environmental Planning, Urban Design, and Landscape Architecture

San Francisco and Alexandria, Virginia

Elliot Rhodeside, Principal

Sheila Brady, Project Manager

Sheaffer and Roland, Inc.

Environmental Planners and Engineers

Chicago and Washington, D.C.

H. Crane Miller, Vice President and General Counsel

James F. Goddard, Consulting Enginecer

October 1981

This manual was prepared under Contract Number EMC-C-0010 with

the Federal Emergency Management Agency.

Disclaimer

The statements and descriptions contained in this manual are those of

the ALA Research Corporation and do not necessarily reflect the views

of the U.S. Government in general or the Federal Emergency Management Agency in particular. The U.S. Government, and FEMA make

no warranty, expressed or implied, and assume no responsibility for

the accuracy or completeness of the information herein.
IAble of Contents

Acknowledgements

1 Preface

Section I: Background

3 Chapter 1: Introduction

Flood Damage

Response to Flooding

Purpose of the Manual

Organization of the Manual

9 Chapter 2: Flooding and the Built

Environment

The Natural System

The Hydrologic Cycle

Riverine Flooding

Coastal Flooding

The Built Environment

Riverine Development

Coastal Development

Urbanization

Effects of Ievelopment

Development Pressures

21 Chapter 3: Policies, Programs, and

Strategies for Flood Damage Reduction

Evolution of Flood Policy

Policy Results

New Focus of Federal Policy

Executive Orders

Strategies for Flood Damage Reduction

Land Use Planning and Management

Urban Redevelopment and Preservation

Acquisition and Relocation

Floodproofing

Forecasting, Warning, and Preparedness

Relief and Rehabilitation

Section II: Design for Flood Damage Reduction

31 Chapter 4: Design Analysis for Flood

Damage Reduction

Regulatory Information

National Flood Insurance Program

Local Planning and Floodplain Management

State Programs

Regional Jurisdictions

Federal Agency Regulations

Flood Hazard Data

I Hydrologic Data

Site Characteristics

Existing I)evelopment

53 Chapter 5: Design Techniques for Flood

Damage Reduction

Type of Project

Applicability of Design Techniques

Site Design Teclmiques

Control of Stormwater Runoff

Building Design Techniques

Section III: Resource Index

75 Glossary

77 Federal Emergency Management Agency,

Regional Offices

79 U.S. Army Corps of Engineers, District

Offices

81 U.S. Department of Agriculture, Soil

Conservation Service, State Offices by

Region

85 U.S. Department of the Interior, Water and

Power Resources Service, Regional

Offices

86 U.S. Geological Survey, State Offices

89 State Coordinating Offices for the National

Flood Insurance Program

93 Flood-Related Building Codes

Excerpts from the Building Officials and Code

Administrators (BOCA) Model Code

State Building Code Offices

97 National Flood Insurance Program, Rules,

Building and Insurance Rate Information

98 Bibliography
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Preface

The Federal Emergency Management Agency, is charged

with implementing the National Flood Insurance Act of

1968. Under this act FEMA is responsible for administering the National Flood Insurance Program and sponsoring other activities intended to reduce losses attributable

to flooding. In pursuit of the latter goal FEMA has sought

to:

* Encourage wise land-use and watershed management

practices.

* Encourage better integration of natural and social

systems.

* Encourage appropriate design and construction

practices in flood-prone areas.

This manual has been prepared by the AIA Research

Corporation as a special study for the FEMA to assist in

meeting these objectives. The manual focuses on the need

for improved building and site design in flood-prone

areas-not, however, in isolation from effective floodplain

management which must accompany improved design if

flood losses are to be reduced significantly

Reduction of flood losses depends on damage mitigation activities by a variety of those involved in the use of

our water and land resources. This responsibility falls to

a large extent on those who design the built environment,

since damage to buildings and their contents is the most

common source of monetary loss in a flood disaster For

these designers to effectively contribute to flood damage

reduction, they need specific information on the causes of

flood damage and on ways to decrease losses through the

design process. This manual has been prepared to provide that information

. .9 .

Chapter I

Introduction

The process of human development hats been linked to

oceans and rivers since the earliest phases of western

civilization Access to water has been essential for sanitation, transportation, energy, economic development, defense, recreation, and social amenity The preeminence of

these factors has fluctuated throughout history, but the

reliance on water has continued.

Parallel to cultural evolution and its need for access

to water has been the development of large segments of

the built environment along seacoasts and riverbanks,

with human settlement patterns having taken both social

and economic advantage of the natural environment 4!

However, this pattern has also led to a conflict between

natural systems and social systems: The need for direct ac- -E

cess to water has resulted in human occupation of lowlying areas that are subject to periodic inundation.

Flood Damage

Flooding occurs naturally as one part of the earths hydrologic system. It is when this natural event is combined

with the human tendency to live at the water's edge that

the interaction of natural and social environments produces the potential for disaster Unfortunately this poten- K

tial has been realized repeatedly throughout history, and0

the conflict is not yet resolved; losses due to flooding continue to increase.

Cultural evolution led to

ihe location of largesegments of the built enviLX: X f~f00f1V+V S N ronment adjacent to waler

This pattern can lead to

disaster when flooding

occurs.

v | E

1 g~~~~~~~~~~~~

[)vpartuen( *t H()sing and irhm.ui Developmentl
Area problem

Area in which flooding causes major damage to agricultural,

urban, and other developments

Unshaded area may not be j problem-free, but problem was not considered major

Reasons for intensified flood

damage

Urban, suburban, and industrial W development on flood plains

Accelerated runoff from urban 0 areas

A Inadequate upstream watershed A management

Loss of flood control from inadequate structural systems

Tidal effects along coasts during W storms and hurricanes

Flooding Problems in the

United States This map

shows the areas of the

country in which flood

damage i most prevalent

and identifies some of the

causses of flooding in the

respective areas.

In the United States, approximately 160 million acres

of land are in floodplains, with more than 6 million

dwellings and a large number of nonresidential buildings located there. Periodic inundation of these floodplains is

responsible for more damage to the built environment

than any other type of natural disaster The following figures indicate the seriousness of the problem

* In the six-year period between 1973 and 1979, there

occurred 193 major natural disasters and 77

Presidentially declared emergencies; of these approximately 80 percent involved flooding

* In 1978, the total flood damage-both economic and

social-has been estimated to have been $3.8 billion

* The estimated average property loss in the 1970's was

over $1.7 billion annually

* In 1978, 17 states suffered flood damage serious

enough to be declared disaster areas.

* In 1979, Hurricane Frederic alone caused $1.8 billion

in damages, much of it from flooding,

Response to Flooding

There have been many attempts to moderate the impact of flooding, with modern efforts dominated by structural

flood control measures devised to reduce or eliminate

flooding itself or to protect areas from the effects of

flooding However, the continuing damage due to flooding and current awareness of the nature of flooding have

led to a shift toward a more comprehensive range of

flood damage reduction methods. Attention has turned

from total reliance on dams, levees, etc., to include non4
structural measures such as land and water resource

management and techniques for floodproofing individual

buildings.

The reason for the expanded view of damage

mitigation strategies is twofold First is the realization that

floods cannot be totally eliminated Second is the realization that better integration of the built environment with

natural forces provides an environment that is both benign and rewarding

The need for a more comprehensive approach to

flood damage reduction is recognized and supported by

the various government agencies with a role in management of water resources and mitigation of natural disasters. Official policy of The American Institute of Architects

(AIA) reflects this same awareness, as the following excerpt from the AlAs policy statement on the subject indicates.

$1,719,324 (in thousands)

o e 0 f 0 ts X 0 o0 M C M o (0 

cN co V U V) (D (0 D o , C, C) 0 6, C,

Flood Losses. This table

shows the average annual

losses of property from

flood in the United States,

19261975. The US. Water

Resources Council, inpreparing the data, concluded

that the escalating flood

damages resultedfrom

continued development in

floodplains and increases

in the costs of making

needed repairs.

5

391,946

369,381

175,495

501,468

168,615

120,928

175,737

37,454

99,937 1
Flood damage is more

than dollars and cents. It S

affects thousands ofpeople,

causing loss of their homes,

personal property, and

often lives.

D)epartment of Housing and tUrban Development

The AIA calls upon its members to exert leadership

by alerting their clients to federal flood hazard

boundary maps and data as to the human and material hazards and the potential environmental impacts of building in riverine floodplains, and by assisting clients in seeking alternative locations for

building projects. However, when construction in

riverine floodplains is undertaken, AlA calls upon its

members to incorporate mitigating measures into

both site development and building designs.

The premise underlying this statement is hasic to this

manual as well: The best way to reduce hazards in floodprone areas is to eliminate buildings from them, thus

transforming what would be human disasters into unexceptional natural events. However, such total prohibition

_ENLNFEWV k is no more likely to be achieved than is complete control

Deparunent of Housing aid Urban D)evelopmient of flooding It is inevitable that some buildings will continue to be located in flood hazard areas. This being the

case, designers of the built environment are compelled to

give consideration to flood hazards and ways to reduce

them.

Purpose of the Manual

It is within this context that the present manual of dcsign guidelines for flood damage reduction has evolved.

The purpose of this manual is to assist designers in their

task-in effect to give them the basic information and the

tools necessary to reduce the losses that continue to result from flooding Specifically the manual tries to meet

this need by answering the following questions:

* What are flooding's inherent characteristics?

* How does flooding relate to the built environment?

* What steps have been taken to mitigate flood damage?

6
* What programs influence development in flood-prone

areas?I

* What essential information is needed to design in

floxd-prone areas?

* What design techniques are available to mitigate flood

damage to the built environment?

* Where can the designer obtain additional information

about flooding?

Organization of the Manual

In answering the above questions, the manual has been

organized into three sections.

The first section, Chapters 2 and 3, provides background information on flooding to assist the designer in

addressing the problems of designing in flood-prone

areas. Chapter 2, Flooding and the Built Environment, discusses the natural characteristics of flooding

and the interrelationships between flooding and the built

environment. Chapter 3, Policies, Programs, and Strategies for Flood Damage Reduction, deals with the

evolution and content of government flood-related programs and outlines general strategies for reducing flood

losses.

The second section deals specifically with design

issues. Chapter 4, Design Analysis for Flood Damage

Reduction, details the range of information that is

needed for pre-design analysis of projects in flood-prone

areas, including a discussion of relevant regulations,

hydrologic data, and physical site characteristics. The final

chaptert Design Techniques for Flood Damage

Reduction, outlines the various techniques that designers can use to mitigate the flood damage pIotelntials identified in pre-design analysis.

Finally, the third section of the manual is 

a

Resource Index, which provides additional sources of

information that can be investigated by the designer

when further detail is necessary Included here are literature references on a wide range of flooding aid development issues, as well as listings of key regional contact

points for the variety of government agencies with an interest in flooding and development.

It is hoped that this manual proves to be a frequently

used addition to the designers reference shelf It is intended to mark a beginning towards a more conscious inclusion of flooding issues in the routine procedures of

design practice. It beyond that, it helps the designer accept the challenge of finding creative and effective solutions to the problems of building in flood-prone areas,

then both clients and the community will benefit

7

Chapter 2

flooding & the Built Environment

Building design does not occur in a vacuum Rather, it is

one of the interrelated elements in the larger sphere of

the development process. Likewise, development is but

one component of the environment as a whole An

understanding of these relationships is requisite to

reducing flood damage through design of the built environment.

Of primary importance is the interdependence of

the respective systems, natural and social. Buildings, as

part of the social system, unavoidably affect and are

affected by flooding, which is part of the natural system.

Design in general, and design to reduce flood damage in

particular, should respect this relationship and seek to

achieve a balance among the various components.

The Natural System

Floods are natural-that fact must be stressed Floods

become a problem only when they coincide with human

9
c_

Evaporation Precipitatio

The hydrologic cycle constantly' circulates water

throughout the earth's environment.

habitation To better understand this problem we look

first at the natural system of which flooding is a part.

Mhe riverine watershed is

a hierarchical drainage The Hydrologic Cycle

system that conveys water Flooding is part of the earth's natural hydrologic cycle.

through the land-based The cycle circulates water through a process of evaporaportion of the hydrologic tion and transpiration, precipitation, water runoff and

cycle, stream flow This process maintains an overall global balance between atmospheric moisture and water on the

surface and in the ground Often, however, local imbalA Rills ances result in flooding.

C Rvers Flooding results when the flow of water is greater Rivers t ~\ than the normal carrying capacity of a stream, or where

coastal waters exceed the normal high tide. This raises an

important distinction between riverine and coastal flooding; though both are part of the global hydrologic system,

the respective causes are dissimilar Rivers flood when

water overflows the channel because of excessive water

runoff or blockage of the channel. Coastal flooding results

from high water produced by storm systems or tsunamis

(seismic sea waves).

Riverine Flooding

The magnitude, duration, and frequency of floods are

influenced by a region's natural characteristics. One pri10
Riverine systems evolv'e to

form distinct stream channels andfloodplains. The

drawings at left illustrate / ~~~this gradualformation,

while the photo at far leqft

shows a well-defined chain

nel andfloodplain.

mary variable is the watershed, which is the natural drainage basin that conlveys water runoff in the land-based

portion of the hydrologic cycle. Water that is not absorbed

by the soil and vegetation becomes surface water runoff

seeking the natural drainage lines according to local topography These lines merge to form a hierarchical systemn of streams that includes rills, creekcs, and rivers, each

of successively larger capacity.

Streams have specific physiographic characteristics.

The primary element is the stream channel, which carries

the normal flow of water through the watershed system.

The area of flat or gently sloping land adjacent to the

channel is the floodplain Flooding usually involves a

build-up of water in the channel, followed by overflow of E

excessive quantities of water that inundate the floodplain.

Generally this rise in water surface elevation is quite slow

in large streams and more rapid in smaller ones.

Flooding is part of the natural renewal of the earth' 

resources. Overflows play a positive role in the natural

system by replenishing soil moisture and depositing fertile silt from the river channel onto the floodplaine

Flas F flooding Flash flooding usually consists of a

quick rise in water surface elevation with abnormally 

high water velocity often creating a 'wall' of water moving down the channel and floodplain. Flash floods usually

1 1
Aerialphotographs

dramatize the potentialfor

flood damage. The picture

on the left shows the normalflow of a river through

an urbanized region. At

right is the same area during a flood.

Flash flooding can occur 

in small, usually shallow

or dry streams, sudh as arroyos in the southwestern

Part of the country.

result from some combination of intense precipitation,

steep slopes, a small drainage basin, and a high proportion of impervious ground surfaces. They are evident in

many parts of the country and often occur in small

streams; that are otherwise shallow or dry, such as arroyos.

Shallow Flooding Shallow flooding of several types

occurs commonly throughout the country. Included in

this category are unconfined flows over broad, relatively

low areas such as alluvial plains;, intermittent flows in arid

or semi-arid regions that have not developed a system of

well-defined channels; minor overbank flows that remain

unconfined; overland flow of runoff in dense urban areas;

and flows where heavy debris deposits cause constantly

shifting channels, such as in alluvial fans. These types of

flooding are also referred to as sheet flow, ponding, shallow overflow, and alluvial fan flow. it is very difficult to

determine shallow flooding depths, the extent of such

,, Fir T\+t :: ff'%;X"D Ut', , -t'

12
flooding or the direction of flow, because shallow flooding is not readily analyzed in relation to more serious

channel flooding

Flood Sewrity Flood severity is determined first by

the amount of water runoff to be conveyed through the

watershed Flooding is most likely to occur during times

of heavy rainfall or snowmelt, when the amount of runoff

is higher

Soil characteristics, ground and surface water storage, and vegetation also influence flood levels. Soil permeability determines how much surface water can be absorbed rather than adding to runoff Water runoff that collects in surface depressions will be released gradually

into the ground and atmosphere and not contribute to

flooding. Likewise, ground water that collects in cavities

beneath the earth's surface helps reduce runoff and flooding Finally, vegetation slows the rate of water runoff by

holding moisture on leaves and in roots, and then releasing it to the air through evaporation and transpiration.

Thus, if a specific site has little permeable soil, no

water storage capacity and sparse vegetation, water either

from a storm or from higher ground will flow directly

across the surface of the site, adding to a build-up of

water that may be in excess of the nearest stream's capacity Obviously the bigger this hypothetical site or region

the greater the flooding impact throughout the watershed

Coastal Flooding

Coastal flooding on the other hand, has little to do with

the movement of water through a watershed Rather, it is

due to the effects of severe ocean-based storm systems.

Hurricanes, tropical storms, and extratropical storms such

as 'northeasters" are the principal causes, with flooding

occurring when storm tides are higher than the normal

& Transpiration &

Top Sll

Variable soil porosity as

illustrated above, influences the degree of surface

water absorption and

runoff Vegetation, left,

bolds water in leaves and

roots, releasing it gradually through transpiration and infiltration.

Water absorbed by the soil,

below, is held as ground

water in cavities below the

water table.

Coastal storms cause damage through the combined

effects of wind, rain, wave

wash, storm surges, scour

and battering by debris.

LI

af

13

Ground Water $tora.
CD

Wetland areas are fre- high tide This is known as a storm surge

quentlv part of the coastal The velocity and range of coastal floods vary in part

ecosystem. They can pro- with the severity of the storm that induces them. The

vide a reservoir for storage damaging effects of coastal flooding are caused by a

of flood waters and protect combination of the higher water levels of the storm surge

against storm-induced and the rain, winds, waves, scour, and battering by debris.

erosion. The maximum intensity of a storm surge accompanies

high tide, so storms that persist through several tides are

the most severe

The extent and nature of coastal floxding is also related to physiographic features of the terrain and the

characteristics of the adjoining body of water Pacific

coastal areas are vulnerable principally to tsunamis,

R a-rip ~~~~~~~~~~~~Base Flood Elevation

A typical coastal ecosystem Bas Floo Eeai

consists of beach, dunes, _, __'__

and troughs between and

behind the dunes. The 77 

beach and dunes are the

more fragile components

of this environment and

.should not be disturbed b~y

development. Trough Secondary Dune Trough Primary Dune Beach Ocean

14
earthquakes, and other natural forces that can trigger excessive erosion, mud slides, and flash flooding Great

Lakes coastal areas are subject to erosion and severe winter storms. The Atlantic and Gulf Coasts are consistently

exposed to the forces of hurricanes, lesser tropical storms,

and northeasters. Each of these coastal areas suffers significant flooding, but it is the latter that has received the

greatest amount of damage.

Balance of Coastal *ystem. Most of the Atlantic and

Gulf Coasts are made up of a succession of low-lying harrier islands, beaches, sand dunes, and bluffs. This collection of physiographic elements constitutes a fragile ecosystem that serves an important function in maintaining

the natural environment

A dynamic balance of natural elements occurs as the

movement of sand by wind, waves, and ocean currents

maintains the beach and dune system. Dunes serve to

catch and hold sand, thus keeping a constant supply to

replenish the natural erosion of beach sand This coastal

system helps buffer the force of storm tides and surges.

Wetlands, which are often an added element in the coastal

system, provide flood water storage and protect against

storm-induced erosion.

Physiographic characteristics vary along the length of

the coast, and influence the type and extent of flooding.

Beaches may be wide and flat, with low dunes, or they

may be of medium-to-narrow width, with higher dunes

and bluffs back from the water. The coast may be terraced,

with height gradually increasing as the distance from the

water increases. Or there may be a barrier dune or sand

bar as a natural levee between water and land These configurations will influence flooding by providing variable

degrees of buffering.

The Built Environment

As noted in the previous chapter, development along

coasts and rivers is the result of a logical evolution, with

human settlements benefiting both socially and economically from the natural system. The majority of this development occurs in urban areas, but is also apparent at the

urban fringe, in small towns, and in rural areas. Development ranges from the single isolated building to the

multi-building complex, and includes residential, commercial, and industrial building types.

However, this pattern has also led to a conflict between natural and social systems. The need and desire for

direct access to water has resulted in human occupancy

of low-lying areas, and this has put a large proportion of

the built environment in flood-prone areas. The floodplain is transformed into a flood hazard area, and destruction of the human habitat becomes commonplace

Low Dunes and Flat Beach

Low Coastal Bluff and Narrow Beach

High Dune and Wide, Sloping Beach

Terraced Coast

Variations in coastal topography can influence

the extent offlooding because of their variable resistance to storm surges

and tidal waves.

15
Floodplain Channel Floodplain

Development occurs in

urban, suburban, small

town, and rural settings, and buildings in many of

these areas have been located on hazardous

flood-prone sites

Development in the watershed alters natural drainage characteristics and decreases the permeability of

soil, thus exacerbating the

effects offlooding.

Riverine Development

The introduction of built elements into flood-prone areas

adds a range of factors, other than physiographic, that affect the degree of flooding In riverine watersheds, development has consistently altered the natural topography,

thus modifying drainage patterns and increasing storm

water runoff Development also displaces much of the natural vegetation that would otherwise absorb water, and

decreases the permeability of soil by covering it with

buildings or with nonporous surfaces (eg., roads, sidewalks, and parking).

Ultimately these development characteristics, either

singly or in combination, cause a drastic increase in the

amount and velocity of water runoff Thus, during times

of severe storms or heavy snowmelt the river system is

quickly filled beyond its capacity and flooding results

The levels of flooding are increased not only by the

abnormal runoff but also because buildings located on

the floodplain displace a volume of flood water The more

buildings on the floodplain, the greater is the displacement and the greater the level of flooding,

0-20% Runoff

80-100% Infiltration

40-50% Runoff

50-60% Infiltration

90-100% Runoff

0-10% Infiltration

16
Coastal Development

In coastal areas development has similar effects because

the delicate balance of shoreline elements is easily upset l Before 

The removal of beach sand and the leveling of dunes,

along with the construction of seawalls, jetties, and piers,

have been common practices in coastal construction Yet,

these measures weaken the shoreline's natural protection o After 

system by introducing static elements into the dynamic

process that, left alone, is able to respond to constant

wind and wave action Such changes exacerbate the im- Construction of seawalbs

pacts of storm surges and high winds. Filling natural wet- alters the dynamic balance

lands to increase developable land also eliminates such of the coastal ecosystem

natural defenses against flooding and causes erosion of the

beach and seabed. The dotUrbanization ted line (A) represents the

The effects of development on flooding are most pro- original profile with gently

nounced in the urban environment. If a building and its sloping beach and seabed.

accessories, such as sidewalks, parking lots, and access The profile after construcroads, can increase water runoff, then the combined effect tion of the seawall (B)

of many buildings, streets, parking lots, and sidewalks can shows loss of beach area 

increase it far beyond the capacity of the watershed sys- and steep slope of seabed. 

tem. The same is true of ocean-side cities and their effect 

on delicate coastal ecosystems. 

With the rapid expansion of cities since the late

1940's, ever-larger concentrations of land have been covered with buildings and pavement. As a result, surface

drainage has been continually increased, and the capacity

of the natural system to accommodate it has been ex- Groins, constructed to

ceeded repeatedly And, the problem has not really been stabilize the beach at one

alleviated by flood control projects. On the contrary, flood point, can have a reverse

control structures have encouraged much of the expan- effect for adjacent areas.

sion onto floodplains, since these seemingly attractive Shoreline erosion increases 

building sites were thought to be protected the beach area updrift qf 

Energy restrictions, economic forces, land specula- the groin (A), but detion, increases in household formation, and the desire for / / / ,5 I creases it downamenities will bring continuing pressure for urban ex- 'A,,\ driti of the

pansion As this development occurs, people both in and /1 '1x groin (B).

out of the building process must be aware of the full \ \ 

costs and other effects arising from the necessary inter- \ \\

dependence of natural and social systems. I A/l,\\I) IS5S}? I llsM 

Effects of Development l \\

The dangers of development in floodplains take several I , forms. As discussed above, development can increase the L 

severity of flooding Also apparent is that buildings them- I, l /,,1\ \

selves, subject to the forces of flood waters, will be dam- I \\

aged. And, when damaged, parts of a building can break I / l \

loose and act as battering rams when carried by the cur- / N \

rent of the stream or storm surge. 

A less obvious danger can result from development

in areas that are not subject to direct flood hazard. Virtually every site is part of a riverine watershed or coastal

17 
Development at any place

in the watershed can reduce the permeabilit~y of

the soil, thus increasing

runoff and flood levels.

This increase in flood

levels can then endanger

properties that may have

previously been above the

base flood elevation.

U.S. Army Corp" of Engineers

system. Even if the site itself is not likely to he flooded,

development on it can have a major influence on flooding and flood damage at other locations. Any modification

that increases runoff or disrupts natural protective systems will increase flooding at other locations, whether it

be in the downstream portions of the watershed or inland portions of the coastal area.

Alteration of the natural balance on a single site may only have a small impact. But the cumulative impact of

many individual sites or of large-scale developments, as is

the rule more than the exception, can be massive. This is

amply illustrated by the flash flood in Kansas City in 1977

Due to an unusually heavy thunderstorm, the rapid

accumulation of runoff in a highly developed urban area

created a six-feet-high wall of water in an otherwise dry

creek bed. The result was over $30 million in damages

and 24 lives lost.

Development Pressures

Human occupation of flood-prone areas brings with it

inevitable losses of life and property and the disruption

of commerce and services. I)espite a long history of such

losses, we continue to build and rebuild in hazardous

locations. Ideally this should not happen; however, the

forces of development are as inevitable as the storms that

produce flooding in the first place. In many cases people

are unaware of the hazards of a given site or the effects of

development on flooding at other sites. In yet other cases

the risks are known, but locational advantages seem to

override the hazard. Or the existing infrastructure in 

a

flood-prone area is considered too enormous a capital

investment to abandon. Too often, the speculative pressures of development override common sense.

Flooding is a normal occurrence, with the degree of

18
inundation influenced first by precipitation or storms, and

then by such natural characteristics as topography soil porosity drainage, vegetation, and beach composition. Development in flood-prone areas often alters these natural

features and can increase flood levels, chiefly by increasing the rate of water runoff:

To minimize adverse impacts, development should

be prohibited or minimized in the most hazardous areas

and carefully monitored to avoid undesirable effects in

others. The design of the built environment should be

carried out with complete knowledge of flooding characteristics and with conscious concern for maintaining

the balance of environmental features.

Literature Resources

Coastal Ecosystems. John Clark. Washington, D.C.: The

Conservation Foundation, 1974.

Design With Nature. Ian L. McHarg. Garden City, New

York: Doubleday/Natural History Press, 1971.

Floods. William G. Hoyt and Walter B. Longbein.

Princeton, NewJersey: The Princeton University Press,

1955.

Flood-Prone Areas and land Use Planning. A. 0.

Waananen, et. al. Washington, D.C.: U.S. Geological

Survey, 1977.

How To Live With An Island. Orrin H. Pilkey, et. al.

Raleigh, North Carolina: Science & Technology Section, North Carolina Department of Natural and Economic Resources, 1975.

Water: A Primer. Luna B. Leopold. San Francisco: W H.

Freeman & Company, 1974.

Department of Housing and Urlran Development

Development in floodprone areasfrequently results in damage to buildings. The house atfar left

has been swept completely

off itsfoundations by the

force of a riverineflood.

The house above has suffered similarlyfrom coastal

flood water Shown at leftcenter is the inundation of

a small town's entire central butsiness district.

19

Chapter 3

Policies, Programs, & Strategies for

Flood Damage Reduction

Through time, the natural riverine and coastal systems

have experienced increasing pressures from a rising population, the shift from an agrarian to an industrial society,

and the limited amount of land close to water Growing

technological ability provided the means to translate

these pressures into expanded development in floodprone areas-even in the face of repeated disasters that

showed that flooding cannot be controlled The resultant

cycle of destruction and rebuilding has been made more

palatable for some due to the benefits of locating near the

water At the same time, there have been constant efforts

to reduce the risk of flooding with the federal government taking the initiative

Evolution of Flood Policy

Early measures to reduce flood hazards in this country-most commonly dikes and levees, seasonal evacuation, and buildings on stilts-were limited, and were

usually the result of private or local initiatives. Since the

1920's, however, there has been a surge in technological

advances and an active interest by the federal government

In 1928, after a devastating flood of the lower Mississippi Valley, Congress passed the Lower Mississippi River

Flood Control Act to provide federal funds for flood control in that region The subsequent Flood Control Act of

1936 enlarged the scope of Congressional interest by declaring that flood damage was a national problem and

should be addressed with federal funds. This legislation,

which shaped policy for 30 years and remains an important influence on it, directed federal efforts towards pre- 7F7m<

venting floods by controlling the flow of water in the nation's major river systems. This policy was implemented

by the construction of structural modifications such as

dams, levees and channel improvements.

Flood control projects such

as the dam and reservoir

above and the channelization project at left have

been constructed in an attempt to reduceflood

damage by controlling

streamflow

21

Levee construction in 1890, U.S. Army Corps of Engineers
ER 

Letvees are constructed to Between 1936 and 1965 the government constructed

protect developed areas 260 reservoirs, 6,000 miles of levees, and 8,000 miles of

from flooding. channel improvements, with an expenditure of over $7

billion. This massive effort did provide protection for

many previously vulnerable areas and had other positive

benefits, yet did not reduce the expenditure for flood

damages: In 1953 flood relief and rehabilitation required

a federal expenditure of $53 million; by 1965 this figure

had jumped to $237 million

Policy Results

Federal programs to provide structural flood control projects have had numerous benefits. Increased control of

river flow has often resulted in less inundation of major

floodplains during times of heavy runoff. In effect, this

has expanded the usable area of the floodplains, opening

the way for increased economic opportunities in those

areas. In addition, there have been significant increases in

recreation opportunities at the many reservoirs and, in

some cases, an increase in wildlife conservation habitats.

However, flood losses have climbed despite the structural program. It was found that preventive measures

were not synonymous with elimination of flooding and

that new development was frequently located in vulnerable locations. Thus when the limits of structural controls

were exceeded and flooding did occur, damage resulted

on a larger scale

This was exacerbated by a simultaneous trend of

rapid urban expansion The growth of cities, already located in flood-prone areas, created development pressures for all available land. This pressure extended onto

floodplains, which were perceived to be safe because of

the structural flood control programs. These combined

pressures caused insufficient attention to be directed at

22
Flood control projects can

have numerous benefits.

They often gene7erate hydroelectric power and create

recreation and conservation habitats.

maintaining equilibrium in the total watershed system.

The federal program for structural control of flooding also failed to provide an effective deterrent to coastal

flooding. The programs were aimed predominantly at the

riverine environment, largely because little hurricane activity occurred during the period in which early floodrelated legislation was passed Consequently little Congressional attention was focused on the unique problems

of the coastal environment

New Focus of Federal Policy

In the middle 1960's there was a reassessment of national

policy and the beginning of a shift to a more comprehensive approach to flooding. Paramount was the recognition that structural works needed to he complemented by

nonstructural measures Rather than trying solely to preU.S Army Cq)> or Engiiicers

23
vent floods, the new emphasis was on the need to correct

many of the imbalances that resulted from the conflicts

between the natural and the built environments and that

had precipitated escalating losses.

In 1965 Congress passed the first of a succession of

laws updating federal flood policy The effect of this policy

evolution was not to eliminate flood control as a strategy

but to shift much of the emphasis of federal programs to

nonstructural strategies. It also required greater involvement by local governments, put more attention on protecting the natural environment, increased the attention

given to coastal flooding and redistributed some of the

financial burden of flood losses from the general public

to the individual users of flood-prone property

Executive Orders

Presidential Executive Orders concerning flooding were

issued in 1967 and 1977 These interpret and reinforce the

intent of the legislative acts as they are implemented by

the appropriate executive agencies.

0 E.O. 11296, issued in 1967, required evaluation of flood

hazards in connection with any proposed action by 

a

federal agency The order was supplanted in 1977 by

E.O. 11988, Floodplain Management, which advocates

protection of floodplains as natural phenomena and

provides explicit support for nonstructural measures

wherever they are feasible

It is significant that the Executive Order 11988 applies

to all federally funded construction and development,

including that funded by Community Development

Block Grants. The Executive Order actually calls for

higher standards than the National Flood Insurance Act,

thus putting federal agencies in a leadership position

regarding floodplain management.

* E.O. 11990, Wetlands, also issued in 1977, requires all

agencies to act to minimize the destruction, loss, or

degradation of natural wetlands.

Strategies for Flood Damage Reduction

As mentioned above, the emphasis of federal flood policy

has shifted from almost exclusive use of structural control

measures to equal consideration of nonstructural strategies. Included in this new approach are a number of

methods, each supporting and supplementing the others.

It is now recognized that the various approaches

must be combined to fit the unique circumstances of any

given situation Flood control is effective under some conditions, but cannot succeed alone. Water and land resources should be regulated to complement structural

controls. Warning systems should be devised or refined.

Individual buildings should be protected as necessary

24
The coordinated use of the full range of strategies is

essential to achieving a significant reduction in flood

losses. Following is a brief review of the nonstructural

methods that have emerged in recent years.

Land-Use Planning and Management

The principal nonstructural strategy for reducing flood

damage is to effect better use of water and land resources.

This goal is achieved through comprehensive planning

for and management of these resources throughout riverine watersheds and coastal environs.

Planning and management as a strategy to reduce

flood damage, addresses the critical need to better integrate the natural and built environments. This approach

to the problems of flooding is based on the knowledge

that, while floods cannot and should not be totally eliminated, the built environment can nevertheless be successfully developed if it respects the natural system.

Planning and management, in practice, are based on

compiling technical data on topography drainage, soil

composition, climate, and other natural characteristics

and analyzing it in light of the physical, social, and economic aspects of the built environment This analysis is

then used to determine appropriate locations for both the

encouragement and prohibition of building Implementation then relies on regulations, such as zoning ordinances,

subdivision regulations, and health and building codes, or

on incentives that induce positive development practices.

Floodplain management objectives can also be realized in

conjunction with programs for urban revitalization and

preservation, or through land acquisition by public bodies

to control development

Urban Redevelopment and Preservation

Renewal of the nation's cities is by its nature a continuous

process It offers the opportunity to rectify many of the

earlier development practices that have contributed to

flood damage In some cases land that is particularly vulnerable to flooding can be cleared by "down-zoning" it to

open space uses. In many cases, however, economic constraints or the historical significance of a building or district can make this impossible

When renewal is to occur, design and development

can make use of site design and floodproofing strategies

to lessen the impact of flooding. Obviously, there is more

latitude when working with a cleared site, but these strategies can also be applied to existing buildings.

Historical preservation is often a high priority in rehabilitation. Schemes to preserve important cultural artifacts require careful and creative use of damage reduction

strategies to make a building safer from flood damage

while respecting the integrity of the original design.

Th.e floodplain planning

proce&s allows careful consideration of the various zssues related toflood., resulling in the regulation

and gWuice of design

and development.

25
Department 4f Housing and tirhan D )evelopnie

Urban redevelopment and

presentation inflood-prone

areas offer opportunities to

rectify many of the development practices that contributed toflood damage_

in the past. Such projects

can use site design and

floodproofing strategies to

lessen the impact offlooding.

Acquisition and Relocation

In many flood-prone areas existing development suffers

repeated damage Often such locations can be protected

only by removing development, but this can rarely be accomplished without public ownership of the land. Public

ownership is, likewise, the surest way to protect vacant

i land that is subject to development pressure.

A growing number of public bodies recognize the

desirability of both acquiring such hazardous sites, either _ through negotiation or eminent domain, and relocating

existing uses to safer sites. This strategy mitigates recurring losses, helps to restore natural processes in the

floodplain, and promotes open space uses such as agriculture or recreation

Federal authority to implement such policies exists

in several forms. Section 1362 of the National Flood Insur -

ance Act allows the Federal Emergency Management

e^, 0. y - ; Agency (FEMA)to acquire certain flood-prone sites.To qualify properties must meet several criteria-they must be inlit sured, they must be substantially damaged or repeatedly flooded, and the relevant local government must be willing to take the property under its controL Implementation of Section 1362 has been slow, partly because of the

constraints described above and partly because of a lack

of funding. Fiscal year 1980 was the first time that funds . lol t00were available specifically for Section 1362 acquisitions, with over $5 million used for that purpose in that year.

Earlier acquisition and relocation projects have been

carried out using a variety of other funding sources. A 3 1 project 01!11 to relocate the business district of Soldiers Grove, i; -X ;0 eM UWisconsin-, ^ out of a riverine floodway has been initiated

using discretionary funds available to the Departments of - ~~~Interior and Housing and Urban Development and a

grant from the Economic Development Administration

Section 73 of the 1974 Water Resources Development Act

an V;S.;: i 93-251) ?(PL provides for acquisition and relocation, and -P-,L-;-I-I 'I - - -J irinaji LCVCIC)ifment

26
Department of Housing and Urban Development

several programs are underway For example, in Prairie

du Chien, Wisconsin, the US. Army Corps of Engineers is

in the process of moving both residential and commercial

buildings out of a highly vulnerable floodplain.

The scope of acquisition can vary widely Following

the devastating flash flood of 1972 in Rapid City South

Dakota, the entire floodway of Rapid Creek was acquired

and cleared for open space A local effort in Baltimore

County Maryland, purchased more than 200 dwellings

that were located in the floodplain of several suburban

streams. In Littleton, Colorado, the Corps of Engineers

purchased 750 acres of land downstream from a reservoir

to protect it from urban expansion Other such projects

are gaining momentum as funding sources are identified.

Floodproofing

Despite floodplain management and related programs to

remove structures from hazardous locations, buildings

will inevitably continue to be located in such areas. It is

necessary that these buildings be protected from flood

damage Floodproofing working in conjunction with

floodplain management, provides this kind of protection.

Floodproofing encompasses any technique intended

to protect buildings from flooding and typically includes

elevating buildings above the flood hazard level, providing watertight closures for doors and windows, and using

floodwalls around ground level openings or, alternatively

eliminating such openings. Also included are the use of

water-resistant materials, structural reinforcement to withstand water pressures, and placement of mechanical elements in the upper parts of buildings.

Floodproofing is applicable to historic buildings, to

essential uses that are not suitable for alternative locations, and to areas in which the capital investment in the

existing urban infrastructure requires continued occupation of a hazardous location In these situations floodSome existing development

cannot be effectively protectedfrom flooding. Recently federalprograms

have been used to acquire

these properties and relocate them in safe areas.

Above is a portion of

Prairie du Chien, Wisconsin (within circle), that was

relocated by the Corps of

Engineers.

27
U.S. CicolIicau Survey

Small-scale dikes can be

constructed as part of an

emergency preparedness

plan. The sand-bag dike is

protecting the houses from

flood damage.

proofing can be indispensable Floodproofing is especially suitable where moderate flooding with low stage,

low velocity, and short duration is experienced

Forecasting, Warning, and Emergency

Preparedness

Forecasting, warning, and emergency preparedness measures are integral parts of a well-balanced floodplain management system For example, adequate warning allows

time for the preparation of temporary floodproofing closures and the evacuation of people and building contents

from hazardous locations. This is, in part, a technical issue

of concern to meteorologists and hydrologists and, in

part, an administrative issue requiring a system of emergency planning organization, communication, and public education

Relief and Rehabilitation

Relief and rehabilitation are, in the first instance, not

methods of reducing flood damage, but ways of dealing

with damage after other measures have been insufficient

Relief and rehabilitation assistance can include direct

clean-up operations as well as loans, grants, and tax reductions to facilitate rebuilding and relocating where necessary Federal agencies are the primary source of this aid,

with private support available from organizations such as

the Red Cross.

Rehabilitation can provide important damage mitigation opportunities. When rehabilitation is necessitated by

flood disaster, future flood losses can be reduced by

ameliorating many of the problems that contributed to

destruction There are often strong local pressures to rebuild as quickly as possible, particularly where economic

livelihood is involved. And such pressures are justified.

Yet, just as often there are long-term economic and social

reasons for breaking the cycle of repeated destruction

and ensuring that earlier development mistakes are not

duplicated.

Post-disaster rehabilitation is most effective if it responds quickly to the needs of local residents but minimizes future destruction. This requires that redevelopment proceed according to sound principles of floodplain

management, taking advantage of the various methods for

reducing flood damage that apply to new development.

Experience has shown that any needed improvements in structural flood control devices should be seen

as supplementary to the nonstructural measures now

available Changes in land use, acquisition and relocation

of flood-prone properties, and appropriate floodproofing

protection for buildings should all be used in the rebuilding effort This comprehensive approach requires

planning and coordination, which is properly the role of

28
Wben flooding occurs, reliefprograms include the

_ oft1_ r reinevitable clean-up as well

as assistance to victims of

IXIRI 1 : Or -I ~~~~~~~~the disaster.

government agencies, but also needs the cooperation and

support of all participants in the redevelopment process.

The issues and methods discussed in this and the

preceding chapter must be integrated into the process of

development. The remaining chapters will tie flood problems more specifically to one of the crucial components

of development, design of the built environment

literature Resources Department of Holming and Urban Develo

Coastal Flood Hazards and the National Flood Insurance Program. H. Crane Miller. Washington, D.C.:

Federal Insurance Administration, 1978.

Evaluation of the Economic, Social, and Environmental

Effects of Floodplain Regulations. Sheaffer and Roland, Inc. Washington, D.C.: Federal Insurance Administration, 1979.

Flood-Prone Areas and Land Use Planning. A. 0.

Waananen, et. al. Washington, D.C.: U.S. Geological

Survey, 1977.

Options to Improve Federal Nonstructural Response to

Floods. Rutherford H. Platt. Washington, D.C.: U.S.

Water Resources Council, 1979.

Regulations for Flood Plains. Jon A. Kusler. Chicago:

American Society of Planning Officials, 1972.

Regulation of Flood Hazard Areas to Reduce Flood

Losses. Washington, D.C.: U.S. Water Resources Council, 1972.

Unified National Program for Flood Plain Management. Washington, D.C.: U.S. Water Resources Council, 1979.

pment

mIepanrment of Housing and Urban lkvelopmcnt

29

-6t

1:

Chapter 4

Design Analysis for Flood Damage Reduction

Achieving a significant reduction in current levels of

flood damage requires attention to all aspects of the development process, from structural flood control to

floodplain management to design of the built environment. Designers are principally involved in the latter,

with their necessary response being the explicit inclusion of damage reduction strategies in the design process. Such action requires that they first be aware of

regulatory restrictions and guidelines, site-specific flooding characteristics, and appropriate techniques for

mitigating flood damage through project design.

Previous chapters discuss the general relationship

between flooding and the built environment. This chapter examines the specific information the designer

needs for projects in flood-prone areas. This information is used in pre-design project analysis, both to ascertain basic flood hazards and to ensure that the project

meets relevant regulatory requirements. The concluding

chapter explores the associated techniques that are

applied during development of the actual design.

E

I

31

ALAjournal
The development process involves a wide range of

decisions that directly influence the subsequent design

of any project. The designer's role in making these decisions varies according to the nature of any given project,

but generally centers on project analysis and evaluation.

This phase culminates in the design program, which

identifies problems and issues and sets out the requirements and criteria that will guide the generation of appropriate design responses. It is essential that analysis of

flooding issues be part of this pre-design phase.

As with any aspect of a design problem, the starting

point in analyzing the potential effects of flooding on 

a

project is the collection and analysis of pertinent data.

This research adds the necessary technical information

to the client's initial program of needs and resources,

thus making the connection between the individual site

and the larger context of natural systems and the existing built environment.

Project analysis first requires knowledge of what

data to collect, why it is important, and where it can be

obtained. Analysis should identify the interaction of

components in the natural and built environments and

the relationship of these components to design of the

proposed project.

The following sections identify the data relevant to

flood damage reduction, outline the importance of the

data, and review potential data sources. Pertinent data is

categorized first according to the variety of flood-related

regulatory programs and then according to specific

flood hazard data.

Regulatory Information

A number of local, state, and federal requirements apply

to development in flood-prone areas, foremost of which

are a variety of programs for floodplain management.

Part of the pre-design collection and analysis of information should include identification of these regulatory

requirements and assessment of their constraints and

opportunities.

National Flood Insurance Program

A primary impetus for mitigating flood damage comes

from the National Flood Insurance Program (NFIP),

which was established by Congress in 1968 to reduce the

losses associated with flood damage. Administered by the

Federal Emergency Management Agency (FEMA), this program's primary component is a stipulation that flood insurance is available only in communities that have satisfied federal requirements for floodplain management.

This stipulation serves as an incentive to local governments to undertake appropriate planning measures to

The design process must include analysis offloodplain regulatory information and flood hazard

data.

32
reduce flood losses by regulating development in hazardous areas. In addition to the planning incentive, the

intent of the NFIP is expressed through insurance rate

differentials and financial restrictions on federally

guaranteed loans.

Emergency Program. Insurance regulations governing the NFIP vary according to the status of an individual community's floodplain regulatory process.

When the available data on local flood hazards is insufficient to support final regulations, the community enters

the "emergency phase," which provides limited insurance coverage with a large subsidy A community may

enter this emergency phase prior to completion of a detailed flood hazard survey The local government, relying on an initial Flood Hazard Boundary Map, must

adopt preliminary regulations to encourage proper development practices in flood-prone areas.

Regular Program. After the completion of detailed

surveys (which are funded by FEMA), the resulting technical studies allow more comprehensive regulations.

These technical reports identify pertinent information

such as base flood elevations, areas inundated by various

magnitudes of flooding, floodway boundaries, and

coastal high hazard areas. This information is provided

in the form of Flood Insurance Rate Maps, Flood Boundary Maps, and Floodway Maps.

Flood Hazard Boundary Map FHBM

City of Floodville, Pennsylvania Flood County

-- --Flood Hazard Boundary

Creek, Maps like this one are used

| 'Zo1 Wrr----tns s t I / I as R the basis ofpreliminary ,h cane A floodplain regulations in

=cf | AdPacific R.R the emergency phase of the National Flood Insurance

Program.

0.

,.Route 3 & Route 17 ZDZFT 7- 77i ______

Corporate Limits 

Zone A Areas of Special Flood Hazard

Note: These maps may not include all Areas of Special Flood Hazard in the

community Afer a more detailed study, the areas shown on this map may

be modified and other areas added.

33
ELEVATION REFERENCE MARKS

_ g sesaw I_ A wclNdl T:. 0 Sd P_ d I- *_ _ SI 

KEY TO MAP

2.,... r A.Ag~~~~~l~~lgAI 

'EXPLANATION OFAZNKDE11IGNATIONS

Al-A Al... .g ISf 10l0 A- 5 CI- I,,AI s~ AIVsOgi M50

I U -.- A f h A_ PiWh

gVggAV gAd,*.,gg.. ....... .. S,.g.S5 Id Vg~~. .

A A- .g I---ggA41, I .... l dtggt lA 

R11- _U c _ _W~~~~~~~~~~~T.v h__os _ wfvlb c

ELEVATION REFERENCE MARKS

nioli in,, sayp SCSAIPIS F CA~r LOAIo~oS

555 a X VAAff-AgfugA..Iggg.I OgIg.IS IV-I . VV r s-e g..g~ghu~ r. .gg.I ... g s B w

T IfR1~ s~ adBta t

r*---. nfl V~pogg.ggg.a..gS.A..op,.. T-sAA ub I

L . _ KEV TO MAP

_S- -I fd Soone.

...... = L -AA~ , i 1 *obmlarA A Yoof Fbod M

IllB t.. Fb~~~dI Adn..-

RP~o.mAOO A . A S _

V.0,45'xse~e *hO ASW Iods F14. 

*1g olo dAWVI, SIbw clVVVtI ow Tl_ M,* .015.4 _llonI Vuoda 

Flood Insurance

Rate Map

Flood Boundary and

Floodway Map

34

. __

I.. d II.. T. ... -n w._. 

I., _ .. n=RY11:_zn .. P.nz^ b .... ".. h ¢rz I..... ---~ss IT.hl
Upon completion of technical floodplain studies,

designation of appropriate flood boundaries, and adoption of floodplain regulations that meet NFIP minimum

standards, a community is eligible for the NFIP "regular

phase." Regulatory standards for the regular phase are

more specific and more stringent than for the

emergency program (see accompanying box for details

of NFIP regulations). Entry into the regular program

qualifies local property owners for full flood insurance

coverage at actuarial rates that vary according to the degree of risk.

Insurance Rate Differentials. The variable rate

structure for flood insurance premiums is another important component of the regular program of the NFIP

Flood hazard areas are divided into different zones,

based on the degree of hazard. The rate for insurance

then varies according to the zone and to the elevation of

the building in relation to the base flood elevation.

This variable rate structure adds a dimension to the

restrictive element of the program by providing an incentive in fringe areas to increase safety beyond the

regulatory minimum. Designers should be cognizant not

only of the minimum standards, but also of the immediate and longterm economic benefits to the client

that are provided by the rate differentials.

Local Planning and floodplain Management

With the NFIP as incentive, nearly 17,000 communities

around the country have begun to implement floodplain

management through their local planning process. The

principal tool for achieving this objective is the traditional zoning ordinance, which is used to prohibit and

regulate development in designated flood hazard areas.

Zoning is supplemented by subdivision regulations,

which provide an administrative review to ensure that a

project meets specified development standards. Of particular interest in this regard is the provision of public

facilities, roads, and utilities in a manner that will not

contribute to flood problems.

Innovative Planning 7bols. In addition to traditional zoning and subdivision regulations, some communities use innovative planning techniques to address

the specific problems of flooding. Notable here is the

After completion of detailed survevs, floodplain

management regulations

are implemented using

Flood Insurance Rate Maps

(opposite page, above) and

Flood Boundary and Flooduway Maps (opposite, below).

Department of HK umg and Urban Developmllenlt

35
use of performance standards, where development limits are based on measurable impacts. In a project in a

flood fringe area where certain kinds of development

are acceptable, development densities might be tied to

maintaining minimum elevations, to a minimum impervious surface ratio to control water runoff, or to providing stormwater detention systems on the site.

Another technique that can be useful for a floodprone area is Planned Unit Development (PUD). This

method of cluster development is used predominantly

for large-scale residential and/or commercial projects,

and requires a special planning ordinance. With PUD,

part of a given site is built on at a higher density than

would otherwise be permitted, thus leaving the remainder of the site as open space. In a flood-prone area, the

development could be clustered on the part of the site

36
that is safe, leaving the flood-prone part free of buildings but still usable as recreation space or parking.

Any of various local planning techniques can be

used to control development to reduce flood damage.

The designer should refer to these regulations to identify both restrictions that will apply to proposed buildings and opportunities that may be presented by planning regulations such as the PUD ordinance. The local

planning agency is also a primary information resource

for the designer. In addition to zoning maps, it will often

provide access to other data that is useful in identifying

flood hazards, such as is contained in the variety of

technical floodplain studies.

Building Codes. Building codes are used infrequently to address the specific problems of flood

damage. However, there are elements of design that

L I _f i 

Cluster development allows

part of a site to be developed at higher density than

would be permitted with

traditional zoning, thus

leaving flood-prone parts

of the site as open space

37

III __ ::F
Though this house remained intact, the force of

a coastalflood knocked it

off its foundation, causing

extensive damage

conceivably can be included in building codes in regard

to flooding. For example:

* Codes may prohibit basements in certain areas or

can require that basements be floodproofed to protect against damage.

* Structural reinforcements, waterproofing, or other

protective measures may be required for structures

with the first floor or basement below the base

flood elevation.

* Buildings may be required to be anchored to prevent flotation during flooding.

* Building materials for use in flood-prone areas may

be specified.

One of the national model codes does make general references to flood-related standards. The Building

Officals and Code Administrators (BOCA) model code

includes sections requiring structural integrity of foundations, walls, floor slabs, and retaining walls that might

be subjected to water pressure. This model code (see

the Resource Index for specific sections of the BOCA

model code) is used in many parts of the country, often

being adopted by reference. Other communities may

have similar or more stringent requirements, and the

designer should consult with local or state building officials to ascertain what codes are in effect.

State Programs

Some states have regulations applying to development

in floodplains, along river channels, or in coastal zones.

These regulations may be parallel to local requirements

or in addition to them. The appropriate state government departments responsible for floodplain management, water resources, building codes or coastal zone

management should be consulted prior to design of any

project in a flood hazard area (state agencies are listed

in the Resource Index).

Each state has designated a State Coordinating

38
Agency to assist in the implementation of the NFIP This

agency is a focal point for information on flood insurance, floodplain management, and coordination of the

diverse state agencies with responsibilities for riverine

and coastal floodplains. The authority of each state's

coordinating agency varies, and can best be determined |

through direct contact. These agencies can be impor -l .L .,I .. ~ tant sources of physical data, information on community

eligibility for flood insurance, state regulations, references to other agencies, and, in some instances, techni- . cal assistance (State Coordinating Agencies are listed in

the Resource Index).

Regionaljursdictions ... %.... ...4 

Several regional jurisdictions, both governmental and

quasi-governmental, have taken an interest in floodplain

management. Foremost of these is the Tennessee Valley

Authority (TVA), the federally owned corporation established in 1933 to conduct a unified program of resource 

development for the economic growth of the Tennessee valle Y Autot iwdblotiot

River Valley It has played a leading role in both structural and nonstructural aspects of floodplain management, and is a particularly valuable source of physical

data and technical assistance to professionals and communities in the region.

Within the thirteen-state Appalachian region, the

Appalachian Regional Commission has been established

as a cooperative federal-state entity to analyze regional

problems and coordinate federal and state initiatives in

Appalachia. It has addressed flooding and other natural .. .. ............ hazards problems, and is a valuable source of economic,

physical, and social data for its region.

Nine federal and state River Basin Commissions l

conduct a similar range of policy, planning, research,

and coordinating activities in their respective regions, working closely with the U.S. Water Resources Council.* ... i

Federal Agency Requirements

A variety of federal programs other than the NFIP deal

with flooding issues. For example, the U.S. Army Corps -

of Engineers requires permits for development adjacent

to major river channels or flood control projects. For

many projects it is necessary to submit an Environmen-

*Delaware River Basin Commission, Great Lakes Basin Appaelahin Regional Comnission judsdlcon

Commission, Mississippi River Commission, Missouri

River Basin Commission, New England River Basin

Commission, Ohio River Basin Commission, Pacific

Northwest River Basin's Commission, Susquehanna River

Basin Commission, and Upper Mississippi River Basin

Commission

39
Federal, state, and local

sources of information on

flooding and floodplain

management (see Resource

Indexfor detailed listings

of information sources).

40

tal Impact Statement prior to project approval by a governing body or agency. And, on all projects funded directly by the federal government, Presidential Executive

Orders require special consideration of flooding issues

(E.O. 11988) and protection of wetlands (E.O. 11990).

Such requirements should be checked by referring to

the appropriate federal agency (see Resource Index for

list of agencies and their regional offices).

Flood Hazard Data

Flood hazard data identifies essential flood-related factors for both the general region and the specific site.

This basic data helps determine the degree of hazard

that is likely at any proposed site, identifies the expected

impacts of proposed development on future flooding

severity, and provides the necessary information for

evaluating and choosing mitigation strategies.

Hydrologic Data

Much of the data relevant to damage mitigation concerns the flow of water associated with the various

stages in the hydrologic cycle. A variety of components

of the natural system-both riverine and coastal-combine to cause flooding. The designer must analyze these

components to understand the threat from flooding that

is to be mitigated in design.

Hydrologic data is available from numerous sources.

Various governmental agencies carry out floodplain

technical studies, the scope and content of which varies

according to the needs of each agency. General information on flooding characteristics, as well as detailed analysis of flood boundaries, levels, velocities, etc. are availLocal goecrmulilll p000mglsl{__^^

agency of munrc pal errgutrecr|__ 

Stdte floodtoamroatilrwgerrmrrr| _^

cotgnaramtmg agency ow _w _ _ _ Stlat of e oQ-f ta_ l

Zolle management ___

Fedora. oorotgeoocy m~anagomoot * ** 

National lOceanmc aod_ _a 

Afmesftfietac Attrrmttilllatroo 

(ftopaltltmooo of Commlrce)

Sort Corisetoafrort Sutvlce___

ft5 SKept of Agrlcr~ItturO) O w S U S. Army t2Atpc of Logrrootfs_____

(Oopettmenl(t cf tofnno)_ 0 _ __

USG~oorogmCd Sorv.y 

_ __'A) _ _ w _ *@ * _ _ 0 _

_ _ __-100--O Id og - tAw h , ......
* . - . ' .:

. . ~ ~ .~ .~ ~ ~ ~~~. 4.

- * . . '~~~~~~~~. R*..;X 

* ~ ~~~~ * , LI, JB

0'' ' .'f .""""'

Flood fringe Floodway Flood fringe

.0 =Floodplain

able for all areas of the country and for many specific

sites. The accompanying matrix identifies relevant agencies and notes the flood-related data that each agency is

usually able to provide.

In cases where agencies cannot provide the information or where existing reports do not include a particular site, hydrologic specialists can develop the required information through site-specific surveys. Some

large design firms have staff engineers capable of completing hydrologic studies, or such specialists can be retained as consultants for specific projects as required.

Data concerning hydrologic conditions at the proposed site should include the following elements.

Flood Hazard Boundaries. Boundaries for the different degrees and types of flooding, including floodways, floodway fringe, coastal high hazard areas, coastal

fringe, and shallow flooding areas, must be identified.

Flood hazard boundaries are most significant because

they determine the specific flood hazard zones that are

part of a proposed development site or that will influence development on the site. In addition, boundaries

indicate where floodplain management regulations and

flood insurance requirements apply to the site. Flood

hazard boundary data can be obtained from floodplain

maps or be developed from topographic maps, zoning

.

Coastal high

Coastal fringe hazard area Ocean 

4 Floodlain -40 ~~~~~~Floodplain 0

The regulatory floodplain

consists of two components. The riverinefloodplain (left) consists of the

floodway and the flood

fringe. Corresponding designations for the coastal

floodplain (right) are the

coastal high hazard area

and the coastalfringe.

41
A flood profile (or water

surface profile) such as this

one identifies the elevation

of various levels offloodingfor a specific stream

channel.

maps, aerial photographs, and related hydrologic data.

Flood Depths. Flood depths are determined by the

difference between water surface elevation at times of

flooding and normal ground surface elevations. This information is important both in determining the elevations at which flood damage is likely to occur and in

defining the appropriate building elevations for flood

insurance and floodplain management regulations.

Flood depths also influence the hydrostatic forces that

are in effect during flooding, including the horizontal

loads that can cause lateral displacement or overturning,

and the vertical loads that can cause uplift, flotation, or

downward pressure on roofs. Flood depth data is available from various technical studies that include flood

elevations, water surface profiles, or stream and coast

cross-sections. In the absence of official reports, information on flood depths can be obtained from site survey and historical records.

Flood proflles-Sowahe Crook

_LQVA~~~~~~~~

Stream distance In miles above confluence with Okatibbes Crookc

Flood Water Velocity The average and maximum

velocity of flood water is important in determining bydrodynamic forces, which influence horizontal loads in

excess of hydrostatic loads. Velocity also affects the

magnitude of debris impact loads (i.e., force of floating

objects carried by flood waters), and can increase ero42
Flood water v'elocitv pro- duces lateral forces that

can cause scour and resuilt

in collapse offoundations,. o ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~~~~~~7w(abov e lkft), increase the .- ~ magnitude o dEbris impact

lod~(below left), and dislocate buildings from their

foundations (below).

sion and affect soil stability on slopes. Data on water

velocity is available from the various floodplain technical

studies or can be determined by special hydrologic

studies.

Advance Warning. The amount of advance warning prior to flooding is determined largely by the speed with which flood waters rise, which depends on the rate

at which water enters the system and the topography of

the watershed. The topography of the watershed influences warning time by affecting the rate of storm water

runoff. A watershed with flash flooding characteristics will allow very little warning, while a larger and flatter

drainage basin will usually result in slower rise and

more warning time. Warning time is important in plan- ning for emergency evacuation, as well as in determining the feasibility of incorporating waterproofing techDepartment ot I IJuning land Urban Development

43
lTptoI flood stao hydrograph

28

26

24

22

S

20

1a

16

14

8 12 16 20 24 28 2

Apwil May

A hydrograph charts water

depth in relation to time,

indicating the rate at which

flood water will rise and

fall. This information is

useful in determining the

amount of advance warning likely and the duration

offlooding.

Water pressure, both above

and below the ground, is

increased by the rise of

flood water This pressure

causes increased stress on

buildings'foundations,

footings, andfloor slabs.

niques that require time to install. It is also a factor in

designing systems for wet floodproofing and influences

the design of drainage systems.

710 Data on rates of rise and fall of water is typically presented in the form of a hydrograph, which charts

water depth over time, and is part of many of the techro8 nical reports. In addition to the usual sources, data on

warning time may be available from local civil defense

706 3 offices or the historical records of local police or fire

departments.

Duration of Flooding. The duration of flood inun- 704 dation, which is a function of the rate of rise and fall of

j water, has several important influences on design. Dura702 S tion influences the saturation of soils and building mate- I rials, the amount of seepage, and the length of time that

facilities might be inaccessable or inoperable, which

700 might have major economic impacts. These factors can

affect design decisions on building orientation, config696 uration, and use of the various floodproofing techniques. The various floodplain technical studies and historical records are the sources for this information. 696 Frequency of Flooding. The frequency with which

flooding occurs is of course a major factor in determining building locations. It can also be important in considering techniques for floodproofing, particularly those

that require installation prior to each flood event. For

44
example, frequent use of temporary protective coverings over vulnerable doors and windows requires that

such coverings e easy to put in place and remove. Fre

quency of flooding also indicates the need for special

access to or from the site if flooding is anticipated to be

a common occurrence.

Climate and Weather. Climate and weather are fac8

tors in predicting the frequency and type of precipitation that might be common to a particular area, which,

in turn, influences flooding severity. For example, a

propensity for cloudbursts or heavy snowfall will indicate a need for dealing with quick water build-up in the 

:

design of a given project. Seasonal variations might also

be a consideration in this respect. Data on climate and 

0

weather is obtainable from the records of the local office of the National Weather Service, as well as from 

local newspapers, police, and civil defense officials.

Ground Water Levels. Groundwater levels interact

with the effects of precipitation and storm water runoff These examples of structo help determine the water pressure on footings, foun- tural damage illustrate the

dation walls, and floor slabs during flooding. With high possible effects of u'ater

ground water levels, the uplift forces associated with pressure associated with

flooding will occur more quickly and more frequently, flooding.

and should be accommodated in the design of all structures on the proposed site.

Flood Control Measures. Existing flood control

works will have been accounted for in the basic flood

hazard data such as flood boundaries and flood depths.

However, the designer still needs to be aware of the limits of the control works and of the effects on the

proposed site if water does exceed the design limits.

Beyond these issues, the designer should know of any

proposed flood control structures that will alter local

flooding characteristics. If such devices are proposed,

45
Physiographic features

must be analyzed to determine which areas of the

site should be avoided or

protected during development. In both riverine (left)

and coastal (right) environments attention should

focus on stream channels,

drainage patterns wetlands,

and existing vegetation.

information from the relevant implementing agency

or from the Federal Emergency Management Agency

(FEMA) can help determine the probability of the control project being implemented and can give an estimate

of its expected effects and completion date.

Site Characteristics

In addition to hydrologic data, a number of specific site

characteristics affect flooding and the choice of strategies for flood damage reduction. As with hydrologic

data, local planning offices and various federal agencies

are primary sources of information on site characteristics. In addition to these resources, much of the site

analysis depends on site surveys, both visual and technical, by design staff and professional consultants. Relevant

site characteristics include the following.

Physiographic Features. Physiographic features on

the site, such as the location of stream channels or

meandering channels, drainage patterns, wetlands, sinkholes, and erosion patterns affect flooding. These natural features should be identified to indicate which areas

of the site should be avoided or protected during development. Such features will affect orientation, distribution, and density of built elements on the site, and will

help identify advantages and constraints to be considered in site development. Physiographic features can be

~'-Z - -/N / I __ ( 0 - '_ __ I~~~~~~ \\\ V-1 -- 

46

i i I I I 
Soil To"

Division5Soil0Description Value As ADt Material Foundation | ainage

Well graded gravel, or qravel/qand mirtre, little or no fines Ercollent Encellent

Poorly graded gravel, or gravel/sand mirturvs. little or no fines Good Excellent

Gravel and Gravelly Soils

Silty graves gravel/sand/slt mixtures Good Poor

Ciayey sands, sand/clay mvtumrs Good Poor

Well graded sands or gravelly sands Olte or no ines Good Eacellent

Poorly graded sands. or gravelly sands: little or no tines Fair Eocellent Sand and Sandy Soils ___

Silly sands sand/silt mixtures Fair Fair

Clayey sands. sand/c ay mixtures Fair Poor

Inorganic sills and very fine sands rock flour silly or clayey Fair Poor I ne sands, or clayey slits with slight plasticity

Inorganic sits of low to medium plasticity gravelly sands. sty Imperorous

clays, ean clays Fair

Organic silt/clays of low plasticity Poor Impervious

Silts and Clays lrorganic silts. micaceous or diatomaceous fIne sandy or silty soils Poor Poor

elastic silts

Inorganic clays of high plasticity, tat clays Very Poor Impervious

Organic clays of medium to high plasticity organic silts Very Poor Impervious

Highly Organic Solis Pvat and other highly organic soils Not Suitable Poor

Soil characteristics must be

analyzed to determine the

soil's drainage characteristics and its value asfoundation material.

identified by referring to topographic maps and floodplain technical studies, as well as by conducting detailed

site surveys.

Site Toplography Identification of topographic elements such as slopes and ground elevations is most important in determining the buildable portion of a site.

Topographic data also indicates erosion potential and

the need for, and feasibility of, using fill material to enhance the site for construction.

Soil Characteristics. Soil characteristics affect flood

damage reduction in several ways. The permeability of

soil determines the degree of water absorption, which

influences the rate of storm water run-off, erosion, and

ground water storage. Soil characteristics also determine

the feasibility and design specifications for the use of

land fill to elevate buildings, the use of backfill around

foundations, and the construction of earth berm levees

on the site. Finally, soil analysis will indicate the necessary depths for footings and pilings, as well as piers and

columns used to elevate buildings.

Soil data can often be obtained from the U.S. Department of Agriculture's Soil Conservation Service in

the form of maps, elevations, tables, and reports, or can

be collected by design staff and consultants as part of

site-specific surveys.

Stability of Slopes. The combination of topography

and soil characteristics determines the stability of slopes

on the site and affects design decisions in several ways.

Slope stability affects the choice of the actual building

site, the use of fill material, and the design of founda47
tions, footings, and pilings. Slope stability also influences

, t >erosion, which determines the need to use protective

techniques such as terracing, planting, or other forms of

ground cover.

Vegetation. Both existing and potential vegetation

on a proposed site affect the choice of flood damage

reduction strategies. Vegetation aids in the control of

storm water runoff and helps discourage erosion. Site

surveys carried out by design staff or consultants should

identify how existing vegetation is related to flooding

and how vegetation can be used in site development to

minimize flood-related losses.

Water Storage. Water storage, either temporary or

permanent, is another factor in controlling storm water

runoff. Storage devices can be used to hold excess

runoff until it can be released gradually into the

watershed system, thereby avoiding the rapid accumulations that cause flooding. Additionally, stored water can

aid in recharging ground water levels and, in some instances, provide environmental amenity. Site analysis

should identify where water collects on the site prior to

development, such as in natural surface depressions,

and should indicate how water can be detained after

development. This information can be obtained from

topographic maps, surface profiles, and site surveys.

Existing Development 7 Existing development at the site and in the surrounding l11I! region t n also influences design in flood-prone areas. The

intensity and type of development adjacent to the proposed site will influence the movement of water

through the hydrologic cycle, and thus influence flooding at the site. With a high level of development intensity

in the region there is likely to be more surface runoff of

Vegetation is an important

part of controlling water

runoff It helps prevent erosion and reduces the flow

of surface water on slopes

(top). It also stabilizes dune

composition in coastal

areas (center) and protects

wetland areas (bottom).

Water storage can be an

important aid in control- wri

ling water runoff.±

48
storm water, which will increase the volume of water

entering the site from upstream.

Likewise, the designer must gauge the impact of

the proposed project on the existing built environment

and the cumulative impact of existing and new development on the natural environment. Analysis of these

elements in relation to flood potential can increase the

designer's sensitivity to the importance of maintaining a

balance with the natural system, and can help minimize

flood losses, both on-site and downstream.

Existing Infrastructure. In addition to general consideration of the existing development, specific attention

should be given to the location and design of existing

streets and utilities. The location of utilities is one aspect

to consider in making buildings waterproof and affects

maintenance of essential services during floods. Streets

and utilities are important in determining site use layouts, and should be analyzed in reference to building

locations and access to and from the site during floods.

After all information regarding flooding, regulatory

requirements, and related design requirements is collected, it is synthesized in the design program: floodrelated constraints are identified, building requirements

are outlined, and the buildable portions of the site are

determined. The next step is to develop design alternatives, drawing on the full range of available techniques

for reducing flood damage, within the context of the

overall design program.

Literature Resources

Design With Nature. Ian L. McHarg. Garden City, New

York: Doubleday/Natural History Press, 1971.

Earthscape: AManual of Environmental Planning. John

0. Simmonds. New York: McGraw-Hill Book Company, 1978.

Ecology In Design. Graduate School of Fine Arts.

Philadelphia: University of Pennsylvania, 1968.

Environmental Analysis For Land Use and Site Planning. William M. Marsh. New York: McGraw-Hill Book

Company, 1978.

Michigan Soil Erosion and Sedimentation Control

Guidebook. Lansing, Michigan: Bureau of Water Management, Michigan Department of Natural Resources,

n.d.

The Role of Vegetation in Shoreline Management. Great

Lakes Basin Commission. Chicago: U.S. Army Corps of

Engineers, North Central Division, 1977.

Shore Protection, Planning and Design. U.S. Army

Coastal Engineering Research Center. Washington,

Permeability influences

water runoff An undeveloped site (top) is highly

porous and allows water to

percolate into the soil. Developed sites with most of

their surfaces covered with

nonporous materials (bottom) do not allow this percolation, resulting in

greater runoff

D.C.: U.S. Army, Office of the Chief of Engineers, 1966.

Water in Environmental Planning. Thomas Dunne and

Luna Leopold. San Francisco: W H. Freeman and

Company, 1978.

49

11___11

___ 4-
Summary Ibble:

Design Analysis for Flood Damage Reduction

Information Required Purpose or Implications of Date Possible Forms of Det Potential Sources of Date

* National Flood Insurance Pro- * Requires local communities to * Program regulations * Federal Insurance Administration

gram (NFIP) implement floodplain regulations. * Insurance rate information and * Federal Emergency Management * Sets minimum standards for tables Agency

floodplain regulations * Flood Insurance Studies * State Floodplain Management * Prohibits federal funding for * Flood Maps Coordinating Agency projects in violation of floodplain Section 1362 Guidelines * Local Government Planning regulations Agency * Prohibits federal loan guarantees for projects in violation of

floodplain regulations.

* Establishes flood insurance rate differentials for properties in

flood-prone areas

* Local Government Planning * Implements floodplain regulations * Planning and Zoning Ordinances * Local Government Planning

Programs * Determines local floodplain * Zoning Maps Agency

regulations based on NFIP * Building Codes * Local Government Engineer guidelines (includes zoning and * Building Code Officials

subdivision regulations per- formance standards, Planned

Unit Development ordinances.

building codes etc.)

Note Local regulations can be set at a higher standard than

NFIP minimum standards. depending on local needs and

circumstances

* State Floodplain and Coastal * Provides statewide floodplain * State program regulations * State Floodplain Management

Zone Programs development regulations and * Slate development guidelines Coordinating Agency guidelines * State Office of Coastal Zone

* Regulates development in Management coastal zones a State Office of Natural or Water

* Coordinates implementation of Resources

NFIP in local jurisdictions and in

areas where multiple stale

agencies have an interest in

flooding

* Clearinghouse for Floodplain

Management Information

* Regional Planning Restrictions * Can provide additional regula- 0 Program regulations * Regional Authorities (e.g. Tenor Guidelines tions and guidelines for regional * Development guidelines nessee Valley Authority, Appajurisdictions lachian Regional Commission.etrc. * Coordinates activities of differ- *Regional Planning Commissions

ent agencies within the region * River Basin Commissions

* Source of information and, in

some cases. technical assistance

* Federal Agency Requirements * May include regulations relating * Program regulations * U.S Army Corps of Engineers

and Guidelines (other than NFIP) to development in flood-prone * Environmental Protection Agency

areas (e g. Corps of Engineers * Federal Emergency Managepermits for development on ment Agency

navigable rivers) * State Floodplain Management * May involve federal funding. the Coordinating Agency use of which is restricted in * Local Planning Agency

flood-prone areas

* Projects may require federal

approval for development in

flood-prone areas (e.g., Environmerntal Impact Statements)

Information Required Purpose or Implications of Data Possible Forms of Data Potential Sources of Information

r m . . . ..,_* Flood Hazard Boundaries * Determines where floodplain

regulations, insurance, and federal financing restrictions apply

* Determines specific flood hazard zones.

* Determines variable flood insurance rate zones

* Flood Hazard Boundary Maps

* Flood Insurance Rate Maps

* Flood Boundary and Floodway

Maps

* Hydrologic Atlases

* Local Zoning Maps

* Flood Insurance Studies

* Flood Depths * Indicates elevations at which * Flood Elevations

flood damage is likely to occur. * Water Surface Profiles

* Determines appropriate build- * Stream and Coast Cross-sections

ing elevations for meeting * Flood Insurance Studies

floodplain regulations and flood

insurance restrictions and rates.

* Indicates hydrostatic loads in

flood-prone areas

* Flood Water Velocity * Determines hydrodynamic * Floodplain Technical Studies loads in flood-prone areas a Hydrologic Studies

* Determines debris-impact loads * Flood Insurance Studies in flood-prone areas

* Indicates potential for erosion

and slope deterioration.

* Warning Time * Indicates importance of a Hydrographs

emergency evacuation as part * Floodplain Technical Studies

of the design program * Historical Records

* Influences design of floodproofing * Flood Insurance Studies

techniques such as flood shields

* Influences design of drainage

systems

* Influences design of wet floodproofing techniques.

* Local Government Planning Agency

* Local Government Municipal

Engineer

* State Floodplain Coordinating Agency

* State Office of Natural Resources

* Federal Insurance Administra- tion

* Federal Emergency Management Agency

* U S. Army Corps of Engineers

* U.S. Geologic Survey

a Regional Authorities

-Tennessee Valley Authority

-Appalachian Regional Commission

-River Basin Commissions

* Hydrologic Engineering Consultants

* Surveys by Professional Staff

0r

IC

It

a

50
Purpose or Implications of Dafta Poaaible Forms of Data

* Duration of Flooding * Affects seepage into buildings * Floodplain Technical Studies

and saturation of soils and * Historical Records

buiidirng materials * Flood Ir surance Studies

* Affects the length of time facilities might bte inaccessible or

inoperable

* Affects building design relative

t0 orientation configuratlion and

choice of floodproofing techniques

* Frequency of Flooding * Influencesite choice * Floodplain Technical Studies

* Affects choice oi lloodproofing * Historical Records

techniques especially those tha require installation betoie

every flood

* Indicates need for special access

* Climate and Weather * Indicates frequency and type of * Weather Service Records

precipitation and. in turn. the * Historical Records

type and magnitude of flooding

that is likely

* Ground Water Level * Influencess potential watni * Geologic Surveys

pressure on footings. founda- * Soil Analysis Reports

tions. and floors

* Affects site design teclniques for controlling water runoff

* Structural Flood Control Measures (e g.. dams, levees, channel improvements)

* Existing measures can affect

site it the limnrit ci the flood ccnc

Irol device are exceeded

* Proposed measures can, when

implemented, alter basic flood dati

* Feasibility Studies

* Design Specificationns

* Probability Reports

Poteotl Sources of Information

* U S Department of the Interior

Water and Power Resources

Service (operates west of the

Mississippi River)

A

I

I

Information Required Purpose or Implications of Data Possible Forms of Data Potential Sources of Information

* Physiographic Features * Affects location and magnitude * Toprxgraphic Maps * Local Government Planning of flooding on the site, * Floodplain Technical Studies Agency

* Identifies areas of the site that * Site Surveys

should be avoided or protected * Local Government Municipal * Affects orientation. distribution Engineer

and density of built elements on

the site * State Floodplain Coordinating

* Identifies physicar constraints Agency

and advantages for site devel

opment * State Off ir e for Natural Resources * Topography * Influencesiting of buildings. * Topographic Maps

* Indicates erosiorn potential. * Floodplain fechnical Studies * Soil Conservation Service U S

* Indicates need for, and feasiltil * Site Surveys Department of Agriculture

ny of using, fill material on the site

* Indicates appropriate site de- * U S. Geologic Survey

sign techniques for cortolling water runoff * Regional Authorities

* Soil Characteristics * Soil porosity influences the rate * Soil Maps * Hydrologic and Civil Engineer of water runoff and flooding po- * Soil Analysis Reports ing Consultants

tential * Site Surveys

* Determines the feasibility and * Surveys by Professional Staff

design specifications for use of till material to elevate buildings * U S Departmenl of the Interior

the use of backfill around foun- Water and Power Resources

dations. and crnstruction of Service(operates west of the

carth berms Mississippi River

* Indicates required depth for

footings pilings, or columns

* Slope Stability * Affects choice of building sites. * Analysis of combined effects of the use ofl fill material, and the topography and soil charac

design of fccundations. foolinds lerislics

and pilings * Site Surveys * Influences erosion

* Indicates the need for lerracing or ground cover to protect slorpes

* Vegetation * Aids in crintrol of water runoff * Site Surveys

and thus can be a factor in reducing flooding levels

* Water Storage * Aids in control of water runoff * Gerclogic. soil, and hydrologic

and thus c an be a factor ci re- surveys

duying flooding levels * Site Surveys * Recharges ground water supplies

51

Information Required

Chapter 5

Design Techniques for

Flood Damage Reduction

The pre-design analysis outlined in the previous chapter

enables the designer to incorporate data on flood-related

restrictions and opportunities into the clients basic program of the needs and requirements that the design must

meet At this point the focus shifts to generating design alternatives and, ultimately, to detailed design decisions.

Ibpe of Project

The type of design project has a direct bearing on flood

damage mitigation strategies. The variations most relevant

to flooding include multiple versus single buildings, new

versus existing buildings, and building use

Multiple Buildings The complexity of siting decisions

is affected by whether a project involves a single building

or multiple buildings. With a single building it is a matter

of siting the building on that part of the site least likely to

suffer flooding. With multiple buildings, site use can vary

from clustering all buildings on one part of the site to

dispersing the buildings throughout the site but locating

each of them above base flood elevations.

New or Existing Buildings New construction offers

wide latitude in making site decisions and in deciding on

the use of flood-related design techniques. Conversely

projects involving expansion, improvement, preservation

or rehabilitation of existing buildings require special consideration of design alternatives. Site choice is predeterFlooding can affect all

types of development. It

'._11_ la id, f \ ,can damage either new or

existing buildings, and is a

relevant design factorfor

industrial, commercial,

1__|_ r :'; , and residential uses. In

some projectsflooding

must be considered in relation to multiple buildings,

while others may involve

only a single building.

VAKNG Photo

53

Gordon H. Schenck, Jr
54
mined unless relocation is feasible. Older buildings often

have structural limitations and seldom prove to be feasible candidates for elevation above the base flood leveL

Additional constraints arise if the project involves a historical building that cannot be altered to the extent of reducing its historical integrity All such issues affecting existing

buildings must be analyzed in relation to strategies for

flood damage reduction.

ape of Use Residential, commercial, industrial and

public building projects have different factors influencing

the choice of techniques for flood damage reduction

First, in meeting National Flood Insurance Program

(NFIP) regulations, residential structures are required to

be above the base flood elevations, while other uses have

the option of being either elevated or floodproofed to the

same level. Second, the type of use also influences site decisions. For example, the use of clustering techniques will

be different for residential buildings than for commercial

or industrial uses. Third, the type of use can affect the site

layout in terms of required access to buildings during

flooding, and will influence the methods for controlling

water runoff

Finally, different uses influence floodproofing techniques. Waterproofing is generally more relevant for commercial buildings that have easily damaged materials and

finishes, valuable records, and vulnerable contents. Wet

floodproofing might be more appropriate for an industrial building that is easier to clean and has more easily

protected contents.

Applicability of Design Techniques

As previous chapters have made clear, buildings ideally

will be located so that they are not subject to flooding Yet

there are still a variety of situations where this ideal is impractical or unnecessary and that call for special measures

to reduce flood damage- For example, when:

* The project site is not itself in a flood hazard area,

but is where development might increase flood levels

elsewhere.

* Buildings are located in a fringe area that is subject

to only mild flooding

* Buildings can be cost-effectively floodproofed to

achieve an acceptable level of safety

* The project includes existing buildings that; due to

historical or economic significance or an existing

urban infrastructure, must remain in a flood-prone

area

* Existing buildings are to be removed from a flood

hazard area, but the period of amortization will require temporary protection

t JS. Army Corps of Enginmer,

55
Buildings must be located

on the part of the site that

analysis of basi flood data

has indicated is above the

Base Flood Elevation

(BEE).

Where some construction is

allowed in thefloodfringe,

buildings should be

oriented to minimize

obstruction offloodflows

Buildings in coastal areas

must be sited in areas that

are tolerant to development in order to minimize

damage to both the buildings and the natural balance of the coastal

ecosystem.

K

Site Design Techniques

Site design techniques for flood damage reduction fall

BFE into two categories-distribution and density of built elements on the site and control of storm water runoff

These categories represent different types of problems to

be addressed in site design in relation to mitigating flood

damage both on the site and throughout the region The

range of available techniques should be used in varying

combinations to fit the unique circumstances of each site

and the associated design program

Distribution and density is, foremost, a question of how

to locate and orient buildings on the site Related concerns are the determination of circulation and access

routes and the alteration of site topography through excavation and use of fill materiaL

Siting Individual Buildings The primary objective in

siting individual buildings is to locate structures so that

they will be safe (or can be made safe) from flooding In

practice this means locating on that part of the site that

analysis of basic flood data has indicated is above the base

flood elevation. However there are other factors to be

considered

Nonresidential structures can use a combination of

elevation and waterproofing to achieve the required degree of safety, as long as they are not located in the floodway or coastal high hazard area For all structures, the designer should consider the potential for going beyond

regulatory minimums, thus providing greater protection

wherever possible Some sites, for instance, allow buildings to be located completely outside the flood fringe,

and this should be done wherever possible

Buildings should also be oriented so that foundations and floodproofed walls minimize obstruction of

flood flows. Natural drainage lines and other natural features that help control storm water runoff should be preserved These measures avoid raising the level of flood

waters and minimize negative impacts on downstream

property

Coastal areas require additional safeguards in locating buildings. There must be no construction on beaches

or dunes; buildings should be sited behind the secondary

dune or elevated in the troughs between dunes, since

56

F FF__
i LiLoi¶

I ;

U I..~.. W L .J 

II - J - I

these areas are generally more tolerant to alteration It is

also important that the stabilizing composition and vegetation of dune systems not be disrupted Access to

beaches should be carefully controlled, using elevated

walkways to avoid damaging the dunes. And, buildings

should not be located, nor should any fill material be

used, in wetland areas.

Siting Multiple Buildings Where multiple buildings

are to be placed on the site, the objective when locating

structures is the same as with an individual building The

approach to achieving this objective, however, can vary

with project circumstances. One approach is to disperse

buildings throughout the site, applying the criteria

discussed above to each building

An alternative to dispersal, where local zoning ordinances allow, is grouping buildings in clusters on the higher

57

X , ". -,j.E m.. , _ a,,,,~~ -I!I I, , . ! 

, ' 3

..... V. L-.
Alteration of site topograpby should include

measures to control water

runoff Slopes can be pro

tected by using ground

cover, retaining walls, terraces, and channels to direct the flow of water

Even when buildings are

aboverflood levels, the improper location of streets

can result in blocked access routes and damage to

vehicles.

parts of the site, leaving the more vulnerable areas open.

(See box) This approach not only reduces direct flood

damage but also allows greater flexibility in protecting the

natural features on the site and controlling water runoff

Large open areas can be used in a number of ways,

depending on the nature of the project They can be

retained as agricultural or conservation preserves or

developed as low-intensity recreation areas. Smaller

parcels also have conservation and recreation potential

and can be effective buffers between conflicting land

uses. With any of these uses, open space can serve as an

amenity that enhances the value of developed property

Another alternative is to develop open areas as parking or

temporary storage for transportable goods.

Restructuring Topognrapy On some sites it may be

possible to use fill material-from either on-site or offsite-to create locations for buildings that are above the

base flood elevation and meet other development criteria

This method would be aimed at the same objectives as

described above, only being used where it will not increase flood levels due to displacement Site restructuring

also can be used to improve drainage and control runoff

Special consideration should be given to soil conditions and slope stability as well as flood water velocities

and duration, to ensure that erosion does not add to

flooding problems and endanger the structural integrity

Philip Schmidt, Department of Housing and Urban Development

58
of the building When restructuring topography, exposed

cut and fill slopes, as well as borrow and stockpile areas

areas, should be protected Runoff should be diverted

from the face of slopes, and slopes should be stabilized

with ground cover or retaining walls.

Circulation and Acces Every site must connect with a

road system for access to the surrounding infrastructure,

and larger development projects require circulation

within the site The objective in site design is to meet the

program needs for circulation and access while maintaining safe access during flooding and avoiding damage

to natural features that aid in the control of runoff and

flooding

Roads should be minimized to reduce the amount of

surface paving Site layout should locate roads to approach buildings from the direction away from the floodplain so that access routes will be less likely to be

blocked by the flow of flood waters and debris. This approach will protect natural features in the floodplain and

will minimize obstruction of the floodway To reduce

potential erosion, siltation, and runoff problems, roads

should not disrupt drainage patterns, and road crossings

should be perpendicular to streams, with adequate

bridge openings and culverts to permit the unimpeded

flow of water. If roads are to be raised, the slope of embankments should be minimized and open faces stabilized with ground cover or terracing

Control of Storm Water Runoff

Water enters a given site either from precipitation or

as runoff from upstream portions of the watershed What

happens to this water is a major determinant of both the

degree of flooding and the potential of damage from flooding It through development of a site, there is an increase in

the volume or velocity of storm water runoff there will be

an increase in flooding levels. Thus, as an ideal, runoff rates

after development should not exceed the rates before development This ideal may not always be possible or practical

and may not be required by regulations, but should remain

the objective of good site planning and design

Site design techniques should work to protect the individual site, as well as minimizing increased flood levels

elsewhere There are a number of key factors that influence storm water runoff and the combination of these

must be considered in the site design process.

Soils Soil porosity is one component in controlling

water runoff. Soil composition needs to be firm enough

to adequately support buildings but at the same time permeable enough to allow percolation of water to recharge

the water table and to allow water to drain away from

buildings. Balanced soil composition slows water runoff

increases infiltration, and helps prevent the build-up of

Streets should be located to

approach buildinrgsfrom

the direction aw ay from the

floodplain so that acce~ss is

leas likely to be blocked

and vehicles are not damaged hyflood water Road

crossings should he perpendicular to streams, with

adequate culverts or bridge

openings to permit unimpeded flou of water

Section AA

Section BB

59
Water runoff should be

routed away from the

building'sfoundation before being allowed to percolate into the subsoil and

water table.

extreme water pressure on foundation walls, footings, and

floors.

The type of soil on the site dictates the appropriate

response for site development Soils that remain saturated

with water tend to corrode foundations. Heavy clay soils

require the addition of sand to improve their drainage,

the provision of good surface drainage, or a bed of gravel

between soil and foundation to prevent foundation corrosion Sand and silt, though porous, are unsuitable for

stable foundations. They necessitate pilings to anchor the

structure to deeper bearing soil

Vegetation. Vegetation aids in slowing the rate of

storm water runoff by holding water, both internally and

externally thus allowing it to filter into the ground or

evaporate gradually In addition, vegetation makes an important contribution by helping to prevent erosion and

sedimentation that exacerbate flooding.

Attention should focus on retaining natural vegetation wherever practicable, and on introducing planting in

locations that will be most affected by runoff The selection of plants should emphasize compatibility with natural conditions and the ability to hold the maximum

amount of water. Leaf type, branching characteristics, and

the texture of bark all affect water-holding capacity A

fibrous root structure can help control erosion

Dune Stabilization. Protection of the dune structure

is a vital part of flood damage reduction in coastal areas.

Dunes should be preserved in order to fulfill their role

in maintaining the balance of the coastal ecosystem In

addition to keeping all buildings off dunes, natural vegetation should be retained to stabilize the dunes' sandy

composition Dunes should not be cut or breached by site

development features such as walkways, The construction

of jetties, groins, and similar structures should likewise

be carefully controlled to prevent disturbance of the

Vegetation is useful in controlling runoff and stabilizing slopes Foliage and

roots bold water and prevent erosion. Plant leaves

vary in their ability to hold

water Horizontal branching is most effective in preventing water runoff down

the tree truck and erosion

at the base of the tree.

Rough bark holds and

slows water running down

the tree trunk and prevents

erosion at the base of the

tree.

60

t '. 0 /

Lo 

'.Zt
natural balance of the beach and dune system.

Irpervious Surfaces Nonporous surfaces contribute

to the volume and velocity of water runoff adding to the

level of flood waters and increasing the chance of flash

flooding This is especially important on steep slopes and

in the urban environment, where a large proportion of

the surface has already been covered by buildings, streets,

and parking areas.

Site design should maximize the preservation of

open space and vegetation and avoid large continuous expanses of impervious surfaces. Large parking areas should

be punctuated with planting Streets, walkways, and park- ing areas should be constructed of porous paving materials wherever possible. Gravel, for instance, is highly

porous, and bricks and flagstones can allow infiltration

between joints. When soil conditions vary on the site,

buildings should be located on the less porous soils, leaving areas with better filtration as open space

Water Storage. Water storage can be either temporary

or permanent, depending on local ground water supplies,

geology, and climate. Temporary storage can take a variety

of forms, including the preservation of natural surface depressions in the landscape Such 'dry pond' storage helps

to detain water after a storm, with gradual drainage, percolation, and evaporation to reduce the volume and velocity of runoff This technique also helps replenish ground

water supplies and can boost property values by increasing the site amenity and providing recreation space.

Temporary water storage can also be designed into

parking areas by creating depressions in paved surfaces

that, in combination with drainage channels, allow grad- ual runoff In some situations large expanses of flat roof

L _ _ - __ 

F- - -- -

I~~~~~'

I .*,I - /S H X <

I $

I II I~~~~~~~~~~'V~

I "~~ FDunes should not be cut by

site-development structures

Access to beaches can be

provided by catwalks,

stairs, and ramps that protect the fragile composition

of the dune system.

Large expanses of nonporous surfaces, such as those

usedfor parking lots, increase runoff Parking

areas should be designed to

minimize impervious surfaces, using vegetation to

maintain or improve natural drainage characteristics.

61

- - -- - - - - - __J
Rlpra Channel.

Open channels can be used

to divert runoff around the

face of vulnerable slopes

and to direct the flow to

larger drainage courses

Various linings can be

used depending on the

steepness of the channel.

Porous linings offer the advantage of allowing gradual infiltration while water

is being transported

-

Grass-Uned Channel.

Concrete C el

Concrete Channel.

can be used to detain water, but this requires special attention to the roof's structural ability to support the

weight of collected water and reliable waterproofing

measures. Both of these methods can be helpful in offsetting the effects of existing impervious surfaces in urban

areas where there is little open space to absorb runoff

Permanent water storage in the form of ponds or

lakes can be used in circumstances where a consistent

supply of water and sufficient space exist Ponds and lakes

can add to site amenity and offer added potential for recreation and conservation habitats, though they do require

regular maintenance.

Open Channels Open channels can serve as both

small-scale storage devices and a means of directing runoff away from vulnerable areas. Their primary purposes

are to divert water away from areas likely to erode, such

as large, gently sloping areas and shorter steep slopes, and

to collect and transport water runoff to larger drainage

courses. Channels with grass cover are appropriate where

the channel gradient is low; they can serve as percolation

trenchs by allowing gradual infiltration while water is

being transported Linings are necessary in channels

where vegetation cannot be established because flow is of

long duration, runoff velocities are high, erodable soils

exist, or slopes are steep. Concrete and asphalt paving or

riprap are the most commonly used channel linings.

However, such linings can increase the velocity of runoff

and thus should be designed with velocity checks to control the rate of water flow.

Streets and Curbs Streets and curbs are frequently

added during development and the layout and gradient

should be designed to complement runoff control systems. Streets, by decreasing the area of permeable surface,

can create excessive runoff and contribute to localized

flash flooding Their design should avoid these problems,

and should work to collect and convey water runoff at

controlled velocities and to safe outlet points.

Storm .eu Srystem. Installation of a storm sewer system is often part of site development in large projects,

usually parallel to the street and curb system. Storm sewers should interconnect with other drainage devices to

Channel running across the slope to divert water.

62
63
Sediment traps, installed at

storm sewer inlets, help

prevent sediment deposits

and maintain the steady

drainage of storm water

Flooding causes the buildup of exterior water

pressure, which must be

equalized to avoid major

structural damage to

buildings located in

flood-prone areas.

-~~~1 

-

I

decrease the velocity of storm water runoff and to release

water at controlled points and rates of flow. Lines and access points need to be sized and distributed to accommodate the runoff likely to be associated with the site and

not cause backup of water and the resulting overspill of

flash flooding The capacity of the storm sewer system can

be impaired by sediment deposits within the systems; to

avert this problem, drain inlets should be designed with

sediment traps and filters

Building Design Techniques

In the design of buildings that must be located in a flood

hazard area, several problems should be addressed in reducing the threat of flood damage. These include:

* Entrance of water through building openings

* Damage to building finishes and contents

* Seepage through walls, floors, and foundations

* Water pressure on foundations, walls, and floor slabs

* Back-up of water through sewer systems

* Access to and from buildings during floods.

To deal with these problems adequately the designer

can incorporate a variety of flood damage reduction techniques in building design These techniques interact with

site design features and, as with site design, the techniques used for any given project will vary with individual circumstances, needs, and resources

Floodpmofing. The term floodproofing is used here

to describe any method of making buildings resistant to

flood damage. Floodproofing strategies are particularly

appropriate where moderate flooding (ie., low flood

stage, low velocities and short duration) is likely or where

buildings' uses require riverine or coastal locations. The

principal approach to achieving this objective is to protect

buildings from water by keeping their interiors dry during flooding This can involve raising buildings above

flood levels or waterproofing the portions of the building

that are below flood levels.

Keeping flood water out of buildings requires special

structural support During flooding, water entering the

building serves to equalize water pressure that builds up

on the exterior. If this equalization is eliminated by waterproofing, then the building is likely to collapse. If a strategy is adopted that keeps water out, then the building

must also be made structurally capable of withstanding

these exterior water pressures.

The "dry" floodproofing approach, as described

above, is the most common and widely applicable way to

protect buildings and their contents from flood damage.

An alternative that can be used in some situations is "wet"

floodproofing, which involves purposely allowing water

to flow into a building when flood levels rise, thereby

equalizing water pressures and avoiding major structural

64
65
damage. This technique also focuses on minimizing damage to the interior of the building when water does enter

The following discussion of specific techniques assumes adoption of the dry floodproofing approach to

mitigating flood damage Wet floodproofing is discussed

after the other methods as a separate technique

Fleiating Buildings Elevating buildings above the

base flood level is a common technique for reducing

flood damage. Flood insurance requirements mandate

that residential buildings in flood-prone areas be elevated

and that other types of buildings be elevated and/or

floodproofed It is a particularly useful technique where

site elevations are consistently below the base flood elevation, and offers the greatest assurance of keeping a building dry during flooding

One method of raising buildings is to use fill material to achieve the desired elevations. This technique interacts with the various site design issues, and requires

consideration of the type of fill, compaction and settlement of fill, protection against erosion, and the effect of

- ,FE

Buildings can be raised

above the BFE b y the use of

fill material.

66

z~_ ==mmg 1 

1

A, ~

! ,,V-sm
Buildings can be raised

above the BFE on posts,

piers, or columns. They

must be securely anchored

to the stilts, which in turn

must be anchored to footings. Stilts should be secured in the ground by

backfilling.

altered land forms on the flooding levels elsewhere in the

watershed system.

Another approach to elevating buildings is to raise

them on some form of stilts, such aS piers, posts, or columns. This method puts the building above the base

flood level and leaves the ground level predominantly

open. The open ground offers the advantage of not impeding the flow of flood water or displacing a significant

volume of water, thus being less likely to increase downstream or upstream flood levels.

In using stilts, the designer must consider the size

and spacing of stilts to ensure adequate support with

minimum obstruction Stilts should penetrate to bearing

soil and be firmly anchored to ensure that they will be

able to resist vertical and horizontal water pressure and

debris impact loads.

Extended foundation walls can also be used to elevate buildings above flood levels. However, the vertical

surfaces of walls can obstruct the flow of water and are

This beach house has been

elevated on concrete piers

to minimize flood damage.

i)epartment of Hmusing fund Urban Development

67

Detail 1 Detail 3

77

-J,

 .4 r

. I; :$ $ i: -

I ,'
Raymond R. Fox, Dames and Moore

Above, left, are examples of

how the forces offlood

water can damage a building if it is not securely anchored to piers, foundations, and footings. Above,

right, are examples of anchoring systems designed to

resist the forces offlooding.

Buildings can be elevated

on extendedfoundation

walls. Vertical walls should

be sited to minimize

obstruction of waterflow

during flooding.

L

tZ.

4 _?

- "'r "I

Y _11_'__'_"TE: I OFE

40 &WRAM,

subject to greater lateral water pressure Longer walls

should be located parallel to the flow of flood water to

minimize these dangers. All foundation walls that might

be subjected to flooding should be anchored to prevent

displacement or flotation

In some cases it can be advantageous to use a combination of methods. For example, a building can be raised

on fill at one end and on stilts at the other. This would be

beneficial in providing ground floor access at the end of

the building that is away from the floodplain while minimizing obstruction of water at the end nearer the stream

channel. Techniques for elevating buildings can also be

combined with waterproofing techniques in some circumstances.

In using any of the methods for elevating a structure,

the designer must consider access to and from the building during flooding and the protection of utility lines and

points of entry

Spatial Organization. The internal spaces of buildings located in or partially in a floodplain should be organized to minimize damage in the event of inundation

The most vulnerable elements of the building should be

located above flooding levels. This would typically include placing all mechanical equipment on the upper

floors or roof of the building Depending on the respec68
tive elevations, machinery and similar equipment should

be raised off the floor or anchored to prevent flotation

Particularly valuable and vulnerable contents, such as

computer equipment, should be located in areas above

flood levels or otherwise securely protected from inundation (eg., raised on stilts or surrounded by a waterproof

enclosure). Spatial configuration should also allow for access to, from, and within the building during flooding

Elimination or Protection of Openings The most vulnerable components of the basic building fabric are the

points where walls below flood levels are penetrated

These points include doors and windows, as well as utility

inlets and in some cases, underground tunnels to adjacent buildings Such points should be either located

above flood levels or thoroughly waterproofed

Ideally all doors and windows should be above the

base flood elevation, with access provided via ramps,

stairs, or fill Rubber gaskets can sometimes be used to

seal openings below the base flood elevation, and waterproof conduits can be used to protect utility lines.

Openings for doors and windows unavoidably located below flood levels can be protected by flood shields

that would be put in place upon receipt of flood warnings. These shields can cover openings ranging from

small areas to large display windows. They can sometimes

be incorporated in the building's structure, out of the way

when not needed and, using hinges and rollers, put in

place when necessary They can also be separate from the

structure and stored when not in use Adequate warning

time is a prerequisite to the effectiveness of shields.

Openings below the base flood elevation in existing

buildings can often be eliminated, with alternative entry

points provided at higher levels. Windows below flood

level can sometimes be replaced by glass bricks, which alThe internal configuration should be located on upper

of buildings in flood-prone floors or on the roof Maareas must be organized to cbinery or other contents

minimize damage to con- that must be in vulnerable

tents in the event offlood- locations (3) should be proing. Computersfinancial tected, either by surroundrecords, and other vulner- ing it with a watertight enable contents (1) should be closure (3A) or raising it

placed on upperfloors. aboveflooding levels (3B).

Mechanical equipment (2)

i IJ

Detall 3A DetaI 3B

69
13FE-iff

- P4FI}l \

Doors and windows below

the BEE can be protected by

flood shields that can he

put into place on receipt of

flood warnings The examples below use rollers

and/or hinges.

2) 

On-siteflood control

measures, such as earth

berms, can be used to protect buildingsfromflooding. They can be free standing (1) or direct/y against

the building (2) When

berms or other types of

flood ualls are used it is

important to install sump

pumps (3) to enasure that

dry conditions are maintained within the enclosure.

Water pressure caused by

flooding affects both vertical and horizontal structural members. This

pressure must be countered, either by structural

reinforcing or by allowing

an equivalent amount of

water into the structure, to

avoid major structural

damage.

low light but can withstand moderate amounts of water

pressure during flooding.

On-Site Fkood Gontol. Levees and retaining walls can

be used as on-site flood control measures to keep water

away from all or part of a building These can be in the

form of earth berms-either free-standing or directly

against the building-which can also provide access

routes. Retaining walls can be incorporated into buildings as fences or patio enclosures to protect openings that

are below the base flood level, and provide privacy and

amenity as well

Such control measures should be designed to resist

lateral and vertical water pressures, protect against erosion, and not obstruct the flow of water.

Enclosures designed to protect openings should be

combined with sump pumps to ensure that dry conditions are maintained within the protected area Emergency power supplies should always be available for operating the pump during storms, when normal power is

likely to be disrupted Levees and walls can be combined

with flood shields to maximize their effectiveness, and can

be appropriate for any size or type of building Their use

should be carefully coordinated with site design issues

Building MateriaRs Even when using "dry" floodproofing approaches to reducing flood damage, some

parts of a building may be exposed to water If so, waterresistant building materials should be used This could include the use of water-resistant lumber, floor coverings,

adhesives, and paints, as well as masonry construction and

finishes, and waterproof mechanical and electrical fittings.

The use of water-absorbent materials such as gypsum

board paneling should be avoided below flood levels.

Structural WalLs All structural walls should be designed to accommodate hydrostatic, hydrodynamic, and

debris impact loads. The walls should be able to withstand

the lateral forces from the predicted depth and velocity of

flood waters, as well as the vertical forces from flood waters

and rising ground water levels, which require secure anchoring to footings and foundations. Potential seepage re-

(luires the use of sealants, external wall coatings, and the

secure joining of walls, floors, and foundations

B*D < a~~~~~~

HeW a~~~~~~~~

70

onC1
Fkxvrs Flooxrshould be designed to withstand the vertical pressures associated with flooding This requires consideration of soil composition and ground water levels, as

well as the likely floxo levels in relation to building elevations. Floor design should provide adequate thickness and

reinforcing to resist water pressure and can include the provision of extra weight (e.g, concrete pads) to prevent flotatio)n. Flooxrs should be securely anchored to foundations

and joints between walls and floors should be securely tied

and sealed to prevent displacement or seepage

kxotings and Ibundations Footings and foundations

require special consideration in flood-prone areas. They

should be at a sufficient depth and on bearing soil in order to provide the necessary lateral resistance to water

pressure, and should also be able to resist vertical pressures. In some cases this may require additional anchorage with pilings or extra weighting with concrete pads.

Also necessary is the protection of footings and foundations from erosion and scour, which is especially important where they will be subjected to extreme velocities,

such as with coastal tides and storm surges.

Utilities All utility lines should either enter the building above the base flood elevation or be waterproofed

and secured to prevent displacement due to water pressure. When a utility line enters the building below the

base flood level, it should be routed so that the interior

outlet point is above the flood level. Internal and external

fittings that are below flood levels should be thoroughly

waterproofed and control panels should be above the

base flood elevation to allow access during flooding. Controls for lower floors and basements can often be isolated

to allow them to be disconnected independently during

flooding.

Mc-hanical .Svsters All mechanical equipment and

controls should be located above the base flood elevation

to prevent damage and to allow access to the equipment

during flooding. The duct work associated with the mechanical system should be elevated or otherwise protected from water damage.

Plumbing. Floor drains and other plumbing will

often be unavoidably located below the base flood level.

They should be fitted with valves to prevent the backflow

of water that would damage the interior of the building.

Sump pumps should be installed to remove small quantities of water, with the drain outlet of the pump located

above the base flood level and an emergency power

source available.

Wet Fkx)dpmx)Jing. As mentioned earlier, wet floodproofing is a special technique that can be used under

certain circumstances to reduce flood damage. The distinguishing characteristic of wet floodproofing is that rather

than trying to keep water out, water is purposely introSecure connections between different parts of the

building are necessary to

prevent flood damage. The

building must be firmlv

anchored to foundations

Detail 2

(1) andfoundations must

be anchored to footings

(2). The house below was

not adequately anchored

to its foundation.

Departientt ,f I lousing and Urban Development

71
nor ustilg an1- un euvelopment

All potentially damaging elements must be firmly

anchored. Storage tanks

can be damaged when

torn from their mountings and can increase hazards

if their contents are spilled

or if they are carried away

as debris.

Plumbing drainage lines (1

and 2) should befitted with

valves to prevent the backflow offlood water into the

building. Sump pumps

should be installed to remove small quantities of

water that might build up,

even infloodproofed

buildings

duced into a building at times of flooding. This is done so

that the water level inside will counteract the pressure of

rising flood water on the outside, thus reducing the possibility of major structural damage This technique is potentially useful where damage from exposure to water will

be minimal and post-flood clean-up relatively easy

Wet floodproofing requires that all parts of the

building below the base flood level be constructed and

fitted with water-resistant materials and finishes. Surfaces

should be nonporous in order to minimize absorption

and facilitate cleaning (eg., concrete, metal, plastic, or

glass). Pumping clean water in as flood waters rise, rather

than allowing flood water to enter, will simplify clean-up.

All interior spaces must be allowed to fill with water, including any cavity walls, and must be able to drain and be

cleaned after the water recedes.

It is essential in wet floodproofing that utility and

mechanical systems be accessible and operable before,

during, and after flooding Thus they must be either

above the base flood elevation or waterproofed and anchored Fuel and chemical storage tanks must be elevated

or located on upper floors above flooding levels, or evacuated prior to flooding Valves that maintain equalized

water pressure and clean-up equipment must be included

in a wet-floodproofed building

The many special requirements of wet-floodproofing

and its limited effectiveness in reducing damage to contents limit the number of situations to which it can be ap- plied However it could be useful in some industrial

buildings and may be appropriate for limited-use basement areas that are below the base flood elevation

The foregoing techniques are not all-encompassing,

but indicate the design issues involved in reducing flood

damage, ranging from site selection to control of storm

water runoff and from building configuration to

structural requirements. They are outlined to provide an

overview of the general information needed and the

tools that are available for design in flood-prone areas.

More detailed information is available from the literature

references cited and from the relevant government

agencies listed in the Resource Index.

The designer with a firm grasp of these flood-related

issues and techniques is better prepared to generate ap- propriate design responses for each specific project and

site Increased knowledge allows the designer to accept

the creative challenge of designing to meet programmatic

and aesthetic standards while simultaneously reducing

flood losses throughout the natural and built environment The designer is thus able to meet professional responsibilities while benefiting both the client and the

community

72

F___J
Literature Resources

Design and Construction Manualfor Residential

Buildings in Coastal High Hazard Areas. Dames &

Moore, Inc. Washington, D.C.: U.S. Department of

Housing and Urban Development; Federal Emergency

Management Agency, Federal Insurance

Administration, 1981.

Elevated Residential Structures: Reducing Flood Damage Through Building Design. AIA Research Corporation. Washington, D.C.: Federal Insurance Administration, 1976.

Earthscape: AManual of Environmental Planning. John

0. Simonds. New York: McGraw-Hill Book Company,

1978.

Flood Proofing Regulations. Washington, D.C.: U.S.

Army, Office of the Chief of Engineers, 1972.

Introduction to Floodproofing. John R. Sheaffer.

Chicago: Center for Urban Studies, University of

Chicago, 1967.

Lakes and Ponds. Joachim Tourhier and Richard

Westmacott. Washington, D.C.: Urban Land Institute,

Technical Bulletin 72,1976.

Manualfor the Construction of Residential Basements

in Non-Coastal Flood Environs. National Association

of Home Builders Research Foundation, Inc. Washington, D.C.: Federal Insurance Administration, 1977.

Michigan Soil Erosion and Sedimentation Control

Guidebook. Lansing, Michigan: Bureau of Water Management, Michigan Department of Natural Resources,

n.d.

Residential Storm Water Management. New York, N.Y

and Washington, D.C.: American Society of Civil Engineers, National Association of Home Builders, and

the Urban Land Institute, 1975.

The Role of Vegetation in Shoreline Management. Great

Lakes Basin Commission. Chicago: U.S. Army Corps of

Engineers, North Central Division.

73
il.

III

hull I IIVITIIIT!TI

mmmrT7 
Resource Index

Glossary

Actuarial Rates. Rates established by the Federal Insurance Administration pursuant to Flood Insurance

Studies for individual communities. These rates are

set in accordance with the National Flood Insurance

Program (NFIP) and accepted actuarial principles.

Subject to various other limitations, actuarial rates are

applicable only after the publication and effective date

of a community's Flood Insurance Rate Map (FIRM).

Base Flood Elevation (BFE). The elevation for which

there is a one-percent chance in any given year that

flood levels will equal or exceed it. The BFE is determined by statistical analysis of streamflow records

for the watershed and rainfall and runoff characteristics in the general region of the watershed.

Coastal High Hazard Area. The portion of a coastal

floodplain that is subject to high velocity waters

caused by tropical storms, hurricanes, northeasters,

or tsunamis. NFIP regulations for Coastal High I lazard

Areas apply where tides, storm waves and surges, and

local geographic characteristics combine to produce a

breaking wave of three feet or more.

Debris Impact Loads. Loads induced on a structure

by solid objects carried by flood water. Debris can

include trees, lumber, displaced sections of structures, tanks, runaway boats, and chunks of ice. Debris

impact loads are difficult to predict accurately, yet reasonable allowances must be made for them in the design of potentially affected structures.

Encroachment. Any physical object placed in a floodplain that hinders the passage of water or otherwise

affects flood flows.

Existing Construction. Those structures already existing or on which construction or substantial improvement was started prior to the effective date of a

community's floodplain management regulations.

First Floor. The floor that is level with or immediately

above the main point of entry into the building. For

residences, it is additionally that floor that comprises

the main living area of the dwelling.

Flood or Flooding. A general and temporary condition of partial or complete inundation of normally dry

land areas. Flooding results from the overflow of inland or tidal waters or the unusual and rapid accumulation of surface water runoff from any source,

Flood Fringe. The area within the floodplain (as determined by the reach of the one-percent-probability

flood) that is outside the floodway.

Flood Hazard Boundary Map (FHBM). An official

map of a community, issued or approved by the

Federal Emergency Management Agency on which

the boundaries of the floodplain and special flood

hazard areas have been designated. This map is

prepared according to the best flood data available

at the time of its preparation, and is superseded by

the Flood Insurance Rate Map after more detailed

studies have been completed.

Flood Insurance Rate Map (FIRM). An otticial map

of a community, issued or approved by the Federal

Insurance Administration, that delineates both the

special hazard areas and the risk premium zones applicable to the community.

Flood Insurance Study (FIS). A study, funded by the

Federal Insurance Administration and carried out by

any of a variety of agencies and consultants, to delineate the special flood hazard areas, base flood elevations, and NFIP actuarial insurance rate zones. The

study is based on detailed site surveys and analysis of

site-specific hydrologic characteristics.

Floodplain. Any normally dry land area that is susceptible to being inundated by water from any natural

source. This area is usually low land adjacent to a

river, stream, watercourse, ocean, or lake.

Floodplain Management. The operation of a program of corrective and preventive measures for reducing flood damage, including but not limited to

flood control projects, floodplain land use regulations, floodproofing of buildings, and emergency

preparedness plans.

Flood Profile. A graph showing the relationship of

water surface elevation to a specific location, the latter generally expressed as distance above the mouth

of a stream of water flowing in an open channel. It is

generally drawn to show surface elevation for the

crest of a specific magnitude of flooding, but may be

prepared for conditions at any given time or stage.

Floodprooflng. Any combination of structural provisions and/or other modifications incorporated into

individual buildings or properties primarily for the

purpose of reducing or eliminating flood damages.

75 U.S. Gc<(Iogical Survey
Floodway. The channel of a river or watercourse and

the adjacent land areas that must be reserved to discharge the one-percent-probability flood without

cumulatively increasing the water surface elevation

more than a designated height, generally one foot.

Flood Boundary and Floodway Map. An official map

of a community, issued or approved by the Federal

Emergency Management Agency, on which floodplain

and floodway boundaries have been designated.

Hydrograph. A graph that charts the passage of water

as a function of time. It shows flood stages, depicted

in feet above mean sea level or gage height, plotted

against stated time intervals.

Hydrology. The science of the behavior of water in the

atmosphere, on the earth's surface, and underground.

Hydrodynamic Loads. As flood water flows around a

structure at moderate-to-high velocities it imposes

loads on the structure. These loads consist of frontal

impact by the mass of moving water against the structure, drag effect along the sides of the structure, and

eddies or negative pressures on the structure's downstream side.

Hydrostatic Loads. Those loads or pressures resulting

from the static mass of water at any point of flood

water contact with a structure. They are equal in all

directions and always act perpendicular to the surface

on which they are applied. Hydrostatic loads can act

vertically on structural members such as floors, decks,

and roofs, and can act laterally on upright structural

members such as walls, piers, and foundations.

Infiltration. The flow of fluid into a substance through

pores or small openings. The word is commonly used

to denote the flow of water into soil.

Mean Sea Level. The average height of the sea for all

stages of the tide, usually determined from hourly

height observations over a nineteen-year period on

an open coast or in adjacent waters having free access

to the sea.

New Construction. Structures on which construction

or substantial improvement was started after the effective date of a community's floodplain management

regulations.

One-Hundred-Year Flood. See Special Flood Hazard

Areas.

Permeability. The property of soil or rock that allows

passage of water through it.

Regulatory Floodway. Any floodway referenced in a

floodplain ordinance for the purpose of applying

floodway regulations.

Special Flood Hazard Areas. Areas in a community

that have been identified as susceptible to a onepercent or greater chance of flooding in any given

year. A one-percent-probability flood is also known as

the 100-year flood or the base flood. Special Flood

Hazard Areas are usually designated on the Flood

Hazard Boundary Map (FHBM) as Zone A. After detailed evaluation of local flooding characteristics, the

Flood Insurance Rate Map (FIRM) will refine this

categorization into Zones A, A0, A1-30, and V1-30.

Transpiration. The process by which water vapor escapes from a plant through its leaf system and enters

the atmosphere.

Watershed. An area from which water drains to a

single point; in a natural basin, the watershed is the

area contributing flow to a given place or a given

point on a stream.

Water Table. The uppermost zone of water saturation

in the ground.

76
Federl Emergency Management Agency Regional Offices

The Federal Emergency Management Agency (FEMA) was

created in 1978 to provide a

single point of accountability

for all federal activities related to disaster mitigation

and emergency preparedness

and response. It was established as an independent

agency in the executive

branch to consolidate a variety of existing agencies and

offices performing related

functions. The Federal Insurance Administration (FIA),

formerly a part of the Department of Housing and

Urban Development, is only

responsible for insurance

activities. FEMA is responsible for administering the

National Flood Insurance

Program. This responsibility

includes assisting state and

local governments in the

implementation of floodplain management programs

and providing information

on flooding to communities

and individuals. Regional offices are the primary means

by which FEMA's programs

are carried out at the state

and local level.

Federal Emergency Mnm nt Agency

Regional Officee and Boundare

Region I Connecticut, Maine,

Massachusetts, New

Hampshire, Rhode Island &

Vermont

442 J. W MacCormack Office

Building

Boston, Massachusetts

02109

(617) 223-2616

Region II New Jersey, New York, Puerto

Rico & Virgin Islands

26 Federal Plaza

Rm. 1349

New York, New York

10007

(212) 264-4756

Region III Delaware, District of

Columbia, Maryland,

Pennsylvania, Virginia & West

Virginia

Curtis Building

Sixth & Walnut Streets

Philadelphia, Pennsylvania

19106

(215)-597-9416

Region IV Alabama, Florida, Georgia,

Kentucky, Mississippi, North

Carolina, South Carolina &

Tennessee

1375 Peachtree Street, N.W

Suite 778

Atlanta, Georgia

31792

(404) 881-2391

77
Region V Illinois, Indiana, Michigan,

Minnesota, Ohio & Wisconsin

1 North Dearborn Street

Chicago, Illinois

60602

(312) 353-0757

Region VI Arkansas, Louisiana, New

Mexico, Oklahoma & Texas

Federal Regional Center

Rm. 206

Denton, Texas

76201

(817) 387-5811

Region IX Arizona, California, Hawaii &

Nevada

211 Main St.

Rm. 220

San Francisco, California

94105

(415) 556-3543

Region X Alaska, Idaho, Oregon &

Washington

Federal Regional Center

Bothell, Washington

98011

(206) 486-0721

Iowa, Kansas, Missouri &

Nebraska

Federal Office Building

Rm. 405

Kansas City, Missouri

64106

(816) 374-2161

Region VIII Colorado, Montana, North

Dakota, South Dakota, Utah &

Wyoming

Federal Regional Center

Building 17

Denver, Colorado

80225

(303) 234-6582

I

I

78

Region VII

::00 :0: f:00S;0000000:000:; fft 000000000000000 dS fffff:0S

F Si$ 00 dd -t f :S700:(:ffSH- e00:0S *0 0 C :S: O) ;SSSfff;S:0 0000S;0j; I: -f:f~tS:0

I=S0000 IffffAAtA :fffE ENn \ ; .'g-.11
U.S. Army Corps of Engineers District Offices

The Corps of Engineers is involved in a variety of floodrelated activities, including

research and development,

planning, design, construction, operation and maintenance. It also engages in real

estate activities related to rivers, harbors, and waterways

and administers laws for protection and preservation of

navigable waters and related

resources such as wetlands.

The Corps is organized

into 11 divisions and 36 districts based on riverbasins

and watersheds. The districts

are the principal planning

and implementation offices

of the Corps, and include an

office of Floodplain Management Services. It is authorized to provide information, technical assistance, and

guidance to nonfederal entities in identifying the magnitude and extent of flood

hazards and in planning wise

use of floodplains. It can

identify areas subject to

flooding and describe flood

hazards at specific sites. This

* Anchorage

U.S. Army Corps of Engineers

District Offices and Boundaries

information is a basis for

planning floodplain use, delineating boundaries for

floodplain regulations, and

setting appropriate elevations

for floodproofing.

Missouri River Diviuion Kansas City

U.S. Army Engr. Dist.

700 Federal Bldg.

Kansas City, Mo. 64106

Omaha

U.S. Army Engr. Dist.

6014 USPO & Courthouse

Omaha, Ne. 68102

North Atlantic Division

Memphis

U.S. Army Engr. Dist.

668 Clifford Davis Federal

Building

Memphis, Tn. 38103

New England

U.S. Army Engineering Division,

424 Trapelo Road

Waltham, Ma. 02154

Baltimore

U.S. Army Engr. Dist.

PO. Box 1715

New Orleans Baltimore, Md. 21203

U.S. Army Engr. Dist.

PO. Box 60267

New Orleans, La. 70160

New York

U.S. Army Engr. Dist.

26 Federal Plaza

St. Louis New York, NY 10007

U.S. Army Engr. Dist.

210 Tucker Blvd. N.

St. Louis, Mo. 63101

Norfolk

U.S. Army Engr. Dist.

803 Front St.

Vicksburg Norfolk, Va. 23510

U.S. Army Engr. Dist.

PC). Box 60

Vicksburg, Ms. 39180

Philadelphia

U.S. Army Engr. Dist.

79

Lower Mississippi Valley Division
U.S. Custom House

2nd & Chestnut St.

Philadelphia, Pa. 19106

Pacific Ocean Division Honolulu

U.S. Army Engr. Dist.

Bldg. 230, Fort Shafter

Honolulu, Hi. 96858

North Central Division Buffalo

U.S. Army Engr. Dist.

1776 Niagaeh St.

Buffalo, NY 14207

South Atlantic Division

Chicago

U.S. Army Engr. Dist.

219 S. Dearborn St.

Chicago, II. 60604

Detroit

U.S. Army Engr. Dist.

PO. Box 1027

Detroit, Mi. 48231

Rock Island

U.S. Army Engr. Dist.

Clock Tower Bldg.

Rock Island, II. 61201

St. Paul

U.S. Army Engr. Dist.

1135 USPO & Custom House

St. Paul, Mn. 55101

North Pacific Division Alaska

U.S. Army Engr. Dist.

PO. Box 7002

Anchorage, Ak. 99510

South Pacific Division

Portland

U.S. Army Engr. Dist.

PO. Box 2946

Portland, Or. 97208

Seattle

U.S. Army Engr. Dist.

PO. Box C-3755

Seattle, Wa. 98124

Walla Walla

U.S. Army Engr. Dist.

Bldg. 602, City-County Airport

Walla Walla, Wa. 99362

Ohio River Division

Charleston

U.S. Army Engr. Dist.

PO. Box 919

Charleston, SC 29402

Jacksonville

U.S. Army Engr. Dist.

PO. Box 4970

Jacksonville, Fl. 32201

Mobile

U.S. Army Engr. Dist.

PO. Box 2288

Mobile, Al. 36628

Savannah

U.S. Army Engr. Dist.

PO. Box 889

Savannah, Ga. 31402

Wilmington

U.S. Army Engr. Dist.

PO. Box 1890

Wilmington, NC 28402

Los Angeles

U.S. Army Engr. Dist.

PO. Box 2711

Los Angeles, Ca. 90053

Sacramento

U.S. Army Engr. Dist.

650 Capital Mall

Sacramento, Ca. 95814

San Francisco

U.S. Army Engr. Dist.

211 Main Street

San Francisco, Ca. 94105

South Western Division

Huntington

U.S. Army Engr. Dist.

PO. Box 2127

Huntington, WV. 25721

Louisville

U.S. Army Engr. Dist.

PO. Box 59

Louisville, Ky. 40201

Nashville

U.S. Army Engr. Dist.

PO. Box 1070

Nashville, Tn. 37202

Pittsburgh

U.S. Army Engr. Dist.

Federal Bldg.

1000 Liberty Ave.

Pittsburgh, Pa. 15222

s0

Albuquerque

U.S. Army Engr. Dist.

PO. Box 1580

Albuquerque, NM 87103

Fort Worth

U.S. Army Engr. Dist.

PO. Box 17300

Ft. Worth, Texas 76102

Galveston

U.S. Army Engr. Dist.

PO. Box 1229

Galveston, Texas 77553

Little Rock

U.S. Army Engr. Dist.

PO. Box 867

Little Rock, Ar. 72203

Tulsa

U.S. Army Engr. Dist.

PO. Box 61

Tulsa, Ok. 74102
U.S. Department of Agrulture

Soil Conservation Service

The Soil Conservation Service (SCS) was established in

1935 to develop a national

soil and water conservation

program. SCS provides technical assistance to local conservation districts, sponsors

of watershed protection projects, and other individuals

and groups.

The SCS technical services

include a number of floodrelated activities. Soil surveys

are made to determine soil

use potentials and conservation strategies. SCS's plant

materials centers are operated to assemble, test, and

encourage the use of promising plant species in conservation programs. An inventory

and monitoring system is

maintained for planning the

use of water and land resources. Snow surveys in

western states are made to

develop stream-flow forecasts. SCS's watershed studies

provide a basis for developing coordinated water resource programs, and its

floodplain management

studies furnish technical data,

assistance, and information

for local floodplain management programs.

SoNI Coneervato Servie

Rqlidn Soundwdy.

S.C.S. Montana Office

Federal Building

PO. Box 970

Bozeman, Montana 59715

(406) 587-5271 Ext. 4322

S.C.S. North Dakota Office

Federal Building

Rosser Avenue & Third St.

PO. Box 1458

Bismark North Dakota 58501

(701) 255-4011 Ext. 421

Northwest S.C.S. Alaska Office

Suite 129, Professional Bldg.

2221 E. Northern Lights Blvd.

Anchorage, Alaska 99504

(907) 276-4246

S.C.S. Oregon Office

Federal Office Building

1220 S.W 3rd Avenue

Portland, Oregon 97209

(503) 221-2751

S.C.S. Colorado Office

Room 313

2490 West 26th Avenue

PO. Box 17107

Denver, Colorado 80217

(303) 837-4275

S.C.S. South Dakota Office

Federal Building

200 4th Street, S.W

PO. Box 1357

Huron, South Dakota 57350

(605) 352-8651

S.C.S. Idaho Office

Room 345

304 North 8th St.

Boise, Idaho 83702

(208) 384-1601 Ext. 1601

S.C.S. Utah Office

4012 Federal Building

125 South State St.

Salt Lake City, Utah 84138

(801) 524-5051

81
S.C.S. Washington Office

360 U.S. Courthouse

W 920 Riverside Avenue

Spokane, Washington 99201

(509) 456-3711

S.C.S. Wyoming Office

Federal Office Building

PO. Box 2440

Casper, Wyoming 82601

(307) 265-5550

S.C.S. Arkansas Office

Federal Building, Room 5029

700 West Capitol Street

PO. Box 2323

Little Rock, Arkansas 72203

(501) 378-5445

S.C.S. Arizona Office

3008 Federal Building

230 N. 1st. Ave.

Phoenix, Arizona 85025

(602) 261-6711

S.C.S. California Office

2828 Chiles Road

Davis, California 95616

(916) 758-2200 Ext. 210

S.C.S. Hawaii Office

300 Ala Moana Blvd.

Room 4316

PO. Box 5004

Honolulu, Hawaii 96850

(808) 546-3165

S.C.S. Louisiana Office

3737 Government Street

PO. Box 1630

Alexandria, Louisiana 71301

(318) 448-3421

S.C.S. Nevada Office

U.S. Post Office Building

PO. Box 4850

Reno, Nevada 89505

(702) 784-5304

S.C.S. New Mexico Office

517 Gold Avenue, S.W

PO. Box 2007

Albuquerque, New Mexico

87103

(505) 766-2173

S.C.S. Oklahoma Office

Agriculture Building

Farm Road & Brumley Street

Stillwater, Oklahoma 74074

(405) 624-4360

S.C.S. Texas Office

WB. Poage Federal Building

101 S. Main Street

PO. Box 648

Temple, Texas 76501

(817) 773-1711

Midwest S.C.S. Illinois Office

Federal Building

200 W. Church Street

PO. Box 678

Champaign, Illinois 61820

(217) 356-3785

S.C.S. Indiana Office

Atkinson Square West

Suite 2200

5610 Crawfordsville Road

Indianapolis, Indiana 46224

(317) 269-3785

S.C.S. Iowa Office

693 Federal Building

210 Walnut St.

Des Moines, Iowa 50309

(515) 862-4260

S.C.S. Kansas Office

760 South Broadway

PO. Box 600

Salina, Kansas 67401

(913) 825-9535

Southwest

0

Ji

82
S.C.S. Ohio Office

Room 522

200 North High St.

Columbus, Ohio 43215

(614) 469-6785

S.C.S. Michigan Office

Room 101

1405 South Harrison Road

East Lansing, Michigan 48823

(517) 372-1910

S.C.S. Minnesota Office

200 Federal Bldg., &

U.S. Courthouse

316 North Robert St.

St. Paul, Minnesota 55101

(612) 725-7675

S.C.S. Missouri Office

555 Vandiver Drive

Columbia, Missouri 65201

(314) 442-2271

S.C.S. Nebraska Office

Federal Building

I.S. Courthouse, Room 345

Lincoln, Nebraska 68508

(402) 471-5301

S.C.S. Wisconsin Office

4601 Hammersvey Road

Madison, Wisconsin 53711

(608) 252-5351

Southeast S.C.S. Alabama Office

Wright Building

138 South Gay St.

PO. Box 311

Auburn, Alabama 36830

(205) 821-8070

S.C.S. Florida Office

Federal Building

Room 248

PO. Box 1208

Gainesville, Florida 32602

(904) 377-8732

S.C.S. Georgia Office

Federal Building

355 E. Hancock Avenue

PO. Box 832

Athens, Georgia 30603

(404) 546-2274

S.C.S. Kentucky Office

333 Waller Ave.

Lexington, Kentucky 40504

(606) 233-2749 Ext. 2749

S.C.S. Mississippi Office

Milner Building, Room 590

210 South Lamar St.

PO. Box 610

Jackson, Mississippi 39205

(601) 969-4330

S.C.S. North Carolina Office

310 New Bern Ave.,

Federal Building

Fifth Floor, PO. Box 27307

Raleigh, North Carolina 27611

(919) 755-4165

S.C.S. Puerto Rico Office

Caribbean Area

Federal Office Bldg.,

Room 633, 6th Floor

Hato Rey, Puerto Rico, 0)0918

(809) 753-4206

S.C.S. South Carolina

240 Stoneridge Drive

Columbia, South Carolina 29210

(803) 765-5681

S.C.S. Tennessee Office

675 U.S. Courthouse

Nashville, Tennessee 37203

(615) 749-5471

83

NIt ft  -1. $minimal"

- - 'a- , .
Northeast S.C.S. Connecticut Office

Mansfield Professional Park

Route 44A

Storrs, Connecticut 06268

(203) 429-9361/9326

S.C.S. Delaware Office

Treadway Towers, Suite 2-4

9 East Loockerman St.

Dover, Delaware 19901

(302) 678-0750

S.C.S. Maine Office

USDA Building

University of Maine

Orono, Maine 04473

(207) 866-2132/2133

S.C.S. Maryland Office

Room 522, Hartwick Building

4321 Hartwick Road

College Park, Maryland 20740

(301) 344-4180

S.C.S. Massachusetts Office

29 Cottage St.

Amherst, Massachusetts 01002

(413) 549-0650

S.C.S. New Hampshire Office

Federal Building

Durham, New Hampshire 03824

(603) 868-7581

S.C.S. New Jersey Office

1370 Hamilton St.

PO. Box 219

Somerset, New Jersey 08873

(201) 246-1205 Ext. 20

S.C.S. New York Office

U.S. Courthouse & Federal Bldg.

100 S. Clinton St., Room 771

Syracuse, New York 13260

(315) 423-5493

S.C.S. Pennsylvania Office

Federal Bldg. & Courthouse

Box 985, Federal Square Station

Harrisburg, Pennsylvania 17108

(717) 782-4403

S.C.S. Rhode Island Office

222 Quaker Lane

West Warwick, Rhode Island 02893

(401) 828-1300

S.C.S. Vermont Office

Burlington Square, Suite 205

Burlington, Vermont 05401

(802) 862-6501 Ext. 6261

S.C.S. Virginia Office

Federal Bldg., Room 9201

400 N. 8th St.

PO. Box 10026

Richmond, Virginia 23240

(804) 782-2457

S.C.S. West Virginia Office

75 High St.

P0. Box 865

Morgantown, West Virginia 26505

(304) 599-7151

84
U.S. Department of the Interior

Water and Power Resources Service

(Formerly, the Bureau of Redamation)

Since 1902 the Department of

the Interior has been authorized to construct and

maintain facilities to develop

water resources for the reclamation of arid and semiarid

lands in 17 western states

(see map). This responsibility

has been fulfilled by the

Bureau of Reclamation since

1907. In 1979 its name was

changed to the Water and

Power Resources Service. Included among the agency's

activities are programs for

water conservation and flood

control, as well as studies of

riverbasins and watersheds.

The Service can provide

water-related information

and technical assistance for

areas in the states in which it

operates.

Bureau of Reclamation

Whter and Power Reourcs Service Offless

Pacific Northwest

Mid-Pacfic

Lower Colorado

Regional Director, Federal Bldg.

and U.S. Courthouse

Box 043-550, West Fort St.

Boise, Idaho 83724

Regional Director, Federal Bldg.

2800 Cottage Way

Sacramento, California

95825

Upper Missouri

Lower Missouri

Regional Director

PO. Box 427

Administration Bldg.

Boulder City, Nevada

89005

Regional Director

PO. Box 2553

Federal Bldg.

316 No. 26th St.

Billings, Montana

59103

Director

PO. Box 25247

Building 20

Denver, Colorado

80225

Upper Colorado

Southwest

Regional Director

PO. Box 11568

125 So. State St.

Salt Lake City, Utah

84147

Regional Director

Herring Plaza

Box H-4377

Amarillo, Texas

79101

85
U.S. Geological Survey

State Offices

The U.S. Geological Survey

(USGS) has existed since

1879, carrying out research

throughout the country on

topography, geology, and

mineral and water resources.

USGS has a number of interests, including resource conservation, geologic studies,

mapping, and land and water

analysis.

The USGS provides hydrologic data for optimum management of the nation's water resources. It collects data for

the evaluation of water quality and quantity conducts

water resource appraisals of

the characteristics of surface

and ground water, coordinates other federal agencies'

water-related research, and

provides technical assistance

on hydrologic issues to federal, state, and local agencies.

As part of its mission, the

USGS disseminates water

data and research results

through reports, maps, and

computerized information

services.

Connecticut

Delaware

Florida

Hartford

District Chief

Connecticut District Office USGS WRD

RM 235 Post Office Bldg.

FTS 244-2528 COM 203-244-2528

Dover

Subdistrict Chief

Subdistrict Office IJSGS WRD

300 S. New St., Federal Bldg.

Rm. 1201

FTS 487-5128 COM 302-734-2506

Tallahassee

District Chief

Florida District Office USGS WRD

Suite F-240, 325 John Knox D.

FTS 946-4251 COM 904-386-l1lA

University

t)istrict Chief

Alabama District Office LUSGS WRD

PO. Box V

FTS 229-2957 COM 205-752-8104

Anchorage

District Chief

District Office USGS WRD

Skyline Bldg., 218 E. Street

F-TS 339-0150 COM 907-277-5526

Tucson

District Chief

Arizona District Office USGS WRD

Fed. Bldg., 301 West Congress

FFS 762-6671 COM 602-792-6671

Little Rock

District Chief

Arkansas District Office USGS WRD

2301 Federal Bldg.

700 W Capitol Ave.

FTS 740-5246 COM 501-378-5246

Menlo Park

District Chief

California District Office USGS WRD

855 Oak Grove Avenue

FTS 467-2328 COM 415-323-8111

Lakewood

District Chief

Colorado District Office IJSGS WRD

Denver Fed Center MS 415

PO. Box 25046

FTS 234-5092 COM 303-234-5092

Georgia

Hawaii

Idaho

Illinois

Indiana

Iowa

Doravi l le

District Chief

Georgia District Office UJSGS WRD

6481 Peachtree Indust. Blvd. Suite 8

FTS 285-4858 COM 404-526-4858

Honolulu

District Chief

Hawaii District Office USGS WRD

5th Floor, 1833 Kalakawa Ave.

FTS 556-022USAKCOM 955-0251

Boise

District Chief

Idaho District Office IJSGS WRD

PO. Box 036, Rm 365 FEd. Bldg.

550 W. Fort St.

FT'S 554-1750 COM 208-384-1750

Champaign

District Chief

Illinois District Office USGS WRD

PO. Box 1026, 605 N. Neil St.

FT'S 958-9137 COM 217-359-3918

Indianapolis

District Chief

Indiana District Office USGS WRD

1819 North Meridian St.

F'S 313-7101 COM 317-269-7101

Iowa City

District Chief

Iowa District Office USGS WRD

Rm 269 Fed. Bldg., 400 S. Capitol St.

PO. Box 1230

FTS 863-6521 COM 319-338-05A1

Alabama

Alaska

Arizona

Arkansas

California

Colorado

86
Kansas Lawrence Minnesota

District Chief

Kansas District Office USGS WRD

1990 Ave., "A' Campus West

Univ. of Kansas

FTS 752-2300 COM 913-864-4321

Kentucky

Louisiana

Maine

Maryland

Massachusetts

Louisville

District Chief

Kentucky District Office USGS WRD

572 Federal Bldg., 600 Federal Place

5l'S 352-5241 COM 502-582-5241

Baton Rouge

District Chief

Louisiana District Office USGS WRD

P0. Box 66492, 6554 Florida Blvd.

FTS 687-4281 COM 504-387-0181

Augusta

Subdistrict Chief

Subdistrict Office USGS WRD

State House Annex-Capitol Shopping Ctr.

FT'S 833-6280 COM 207-289-3484

Towson

District Chief

District Office LUSGS WRD

208 Carroll Building, 8600 La Salle Rd.

VTS 920-3311 COM 301-828-1535

Boston

District Chief

Central New England District

Office USGS W C

Suite 1001,150 Causeway St., 10th Floor

FTS 223-2822 COM 617-223-2822

Mississippi

Missouri

Montana

Nebraska

Nevada

St. Paul

District Chief

Minnesota District Office USGS WRD

Room 1033 PO. Bldg.

FTS 725-7841 COM 612-725-7841

Jackson

District Chief

Mississippi District Office USGS WRD

430 Bounds Street

FT'S 490-4600 COM 601-969-4600

Rolla

District Chief

Missouri District Office USGS WRD

P0. Box 340

FrS 276-9185 COM 314-364-36HO

Helena

District Chief

District Office USGS WRD

Rmn 421 Fed. Bldg., 316 N. Park Ave.

PO. Box 1696

FrS 585-5263 COM 406-449-5011

Lincoln

District Chief

Nebraska District Office USGS WRD

Rm 406 Fed. Bldg. & US CRTIIS

100 Centenial Mall N.

FTS 867-5082 COM 402-471-5082

Carson City

District chief

Nevada District Office USGS WRD

229 Federal Bldg., 705 N. Plaza St.

FTS 598-5911 ASKCOM 702-882-1388

Okemos

District Chief

Michigan District Office USGS WRD

2400 Science Pkwy, Red Cedar Research

FTS 374-1561 COM 517-372-1910

New Hampshire Concord

Subdistrict Chief

Subdistrict Office USGS WRD

Rm 307 Federal Bldg 55 Pleasant St.

FTS 834-4740 COM 603-224-7273

87

.E

v)

9

v'

I!

Michigan
New Jersey Trenton

District Chief

District Office USGS WRD

Rm 420 Fed. Bldg., 402 E. State St.

PO. Box 123A

FTS 340-3212 COM 609-599-3511

Huron

District Chief

South Dakota District

Office USGS WRD

Po. Box 1412, Rm 231 Fed. Bldg.

FTS 782-2258 COM 605-352-8651

Albuquerque

District Chief

New Mexico District Office USGS WRD

PO. Box 26659

FTS 474-2246 COM 505-766-3357

Albany

District Chief

New York District Office USGS WRD

PO. Box 1350, 343 PO & Court House

FTS 562-3107 COM 518-472-3107

Raleigh

District Chief

North Carolina District Office USGS WRD

PO. Box 2857, Rm 440 Century Sta.,

PO. Bldg

FTS 672-4510 COM 919-755-4510

Bismarck

District Chief

North Dakota District Office WRD

PO. Box 778, Rm. 332 New Fed. Bldg.

FTS 783-4227 COM 701-255-4011

Columbus

District Chief

Ohio District Office USGS WRD

975 West Third Ave.

FTS 943-5553 COM 614-469-5553

Oklahoma City

District Chief

Oklahoma District Office USGS WRD

Rm 621, 201 N.W 3rd St.

FTS 736-4256 COM 405-231-4256

Portland

District Chief

Oregon District Office USGS WRD

830 NE Holladay St., PO. Box 3202

FTS 429-4776 COM 503-234-3361

Tennessee

Texas

Utah

Vermont

Virginia

Washington

West Virginia

Nashville

District Chief

Tennessee District Office USGS WRD

A-413 Federal Bldg.

FlS 852-5424 COM 615-749-5424

Austin

District Chief

Texas District Office USGS WRD

649 Federal Bldg., 300 East 8th

FTS 734-5766 COM 512-397-5766

Salt Lake City

District Chief

Utah District Office USGS WRD

8002 Federal Bldg., 125 So. State St.

FTS 588-5663 COM 801-524-5663

Montpelier

Hydrologist In Charge

Field Headquarters USGS WRD

8 E. State St., PO. Box 628

FTS 832-2393 COM 802-223-8610

Richmond

District Chief

Virginia District Office USGS WRD

Room 304, 200 West Grace St.

FTS 925-2427 COM 804-782-2427

Tacoma

District Chief

Washington District Office USGS WRD

Room 300, 1305 Tacoma Ave., South

FTS 390-6510 COM 206-593-6510

Charleston

District Chief

West Virginia District Office USGS WRD

3303 Fed. Bldg. & US Courthouse

500 Quarrier St E.

FTS 924-1310 COM 304-343-6181

Carnegie

Hydrologist In Charge

Field Unit USGS WRD

Box 420

FTS 590-3468 COM 717-782-3468

Providence

Subdistrict Chief

Subdistrict Office USGS WRD

224 Federal Building and

U.S. Post Office

FTS 838-4387

Wisconsin

Wyoming

Madison

District Chief

Wisconsin District Office USGS WRD

Room 200,1815 University Ave.

FTS 262-2488 COM 608-262-2488

Cheyenne

District Chief

Wyoming District Office USGS WRD

PO. Box 2087, 4015 Warren Ave.

FTS 328-2111 COM 307-778-2220

South Carolina Columbia

District Chief

South Carolina District

Office USGS WRD

Suite 200, 2001 Assembly St.

FTS 677-5966 COM 803-765-5966

88

New Mexico

New York

North Carolina

North Dakota

Ohio

Oklahoma

Oregon

Pennsylvania

Rhode Island

South Dakota
State Coordinating Offices for the

National Flood Insurance Program

Each of the states, in cooperation with the Federal

Emergency Management

Agency, has designated a specific agency to coordinate

implementation of the National Flood Insurance Program. This agency provides a

link between federal, state,

and local levels of government and between different

state agencies with floodrelated responsibilities. The

designated agency will typically be a department responsible for natural resources, emergency services,

Alabama

Alaska

Arizona

Arkansas

California

Colorado

or physical development,

and is a focal point for information relating to flood

insurance and floodplain

management. It can be an

important source of physical

data, information on community eligibility for flood

insurance, relevant state regulations, references to other

agencies, and, in some instances, technical assistance.

The authority of each state's

coordinating agency varies,

and can best be determined

through direct contact.

Connecticut

Delaware

Florida

Georgia

Alabama Development Office

State Planning Division

State Capitol Bldg.

Montgomery, Alabama 36130

(205) 832-6400

Department of Community

& Regional Affairs

Pouch B

Juneau, Alaska 99811

(907) 276-1721

Emergency Services Director

State of Arizona

Division of Emergency Services

5636 E. McDowell Rd.

Phoenix, Arizona 85008

(602) 258-8596

Division of Soil & Water Resources

State Department of Commerce

1818 W Capitol Building A

Little Rock, Arkansas 72202

(501) 371-1611

State of California

Department of Water Resources

PO. Box 388

Sacramento, California 95802

(916) 445-2985

Hawaii

Idaho

Iinois

Indiana

Iowa

Colorado Water Conservation Board

Rm. 823

State Centennial Building

1313 Sherman Street

Denver, Colorado 80202

(303) 839-3441

Connecticut Department of

Environmental Protection

State Office Bldg., Rm. 207

Hartford, Connecticut 06115

(203) 566-7245

Office of Management, Budget,

and Planning

Townsend Bldg., Third Floor

Dover, Delaware 19901

Department of Community Affairs

2571 Executive Ctr. Circle East

Howard Bldg.

Tallahassee, Florida 32301

(904) 488-7956

Georgia Department of Natural

Resources Environmental Protection

Division

270 Washington Street, S.W

Atlanta, Georgia 30334

(404) 656-5164

Hawaii Board of Land & Natural

Resources

PO. Box 621

Honolulu, Hawaii 96809

(808) 548-7642

Idaho Department of Water Resources

Statehouse

Boise, Idaho 83720

(208) 384-2215

Illinois Department of Transportation

Division of Water Resources

Local Floodplain Programs

300 North State Street

Room 1010

Chicago, Illinois 60610

(312) 793-3864

Department of Natural Resources

608 State Office Building

Indianapolis, Indiana 46204

(317) 633-5267

Iowa Natural Resources Council

Wallace State Office Building

Des Moines, Iowa 50319

(515) 281-5029

89
K21088

Kentucky

Louisiman

Maine

Marylmad

Division of Water Resources

Kansas State Board of Agriculture

1720 South Topeka Avenue

Topeka, Kansas 66612

(913) 757-3717

Division of Water Resources

Kentucky Department of

Natural Resources

950 Leestown Road

Frankfort, Kentucky 40601

(502) 564-3980

Louisiana Department of Urban

& Community Affairs

5790 Florida Boulevard

Baton Rouge, Louisiana 70806

(504) 925-3718

Bureau of Civil Emergency

Preparedness

State House

Augusta, Maine 04330

(207) 622-6201

Maryland Water Resources

Administration

Fkxld Control Section

Tawes State Office Building

D-2

Annapolis, Maryland 21401

(301) 269-3826

Massachusetts Water

Resources Commission

State Office Building

100 Cambridge Street

Boston, Massachusetts 02202

(617) 727-3267

Water Management Division

Michigan Department of Natural

Resources

Post Office Box 30028

Lansing, Michigan 48909

(517) 373-3930

Minnesota Department of Natural

Resources

Land Use Management Section

Division of Waters

St. Paul, Minnesota 55101

(612) 296-4803

Mississippi Research & Development

Center

Post Office Drawer 2470

Jackson, Mississippi 39205

(601) 982-6376

Disaster Planning & Operations

Office

Post Office Box 116

Jefferson City, Missouri 65102

(314) 751-2321

Montana

Nebrska

Nevada

New Hazpshire

Montana Department of Natural

Resources & Conservation

32 South Ewing Street

Helena, Montana 59601

(406) 449-2864

Nebraska Natural Resources

Commission

Post Office Box 94876

Lincoln, Nebraska 68509

(402) 471-2081

Department of Conservation

& Natural Resources

Capitol Complex

201 S. Fall Street

Carson City, Nevada 89710

(702) 885-4380

New Hampshire Office of State

Planning

21⁄2/ Beacon Street

Concord, New Hampshire 03301

(603) 271-2155

* -F I \\ C0 A7 , -" C AN * E *~% ofi - ; t%? o

x. I

- n, -CE

Michigan

Minnesota

MI-ouril

8 i. :bn 

I I

&I IS; \

,0fE 

l '

I E 

9
North Dakota

Ohio

Oklahoma

Oregon

State Water Commission

State Office Building

900 E. Boulevard

Bismark, North Dakota 58501

(701) 224-2750

Ohio Department of Natural

Resources

Flood Plain Management Unit

Fountain Square & Building E

Columbus, Ohio 43224

(614) 466-6020

Oklahoma Water Resources

Board

12th Floor, Northeast

10th & Stonewall

Oklahoma City, Oklahoma 73105

(405) 271-2959

Oregon Water Resources

Department

Milcreek Office Park

Salem, Oregon 97310

(503) 378-3671

New Jersey Department of

Environmental Protection

Post Office Box CN 029

Trenton, New jersey 08625

(609) 292-2296

State Engineer's Office

Bataan Memorial Building

Santa Fe, New Mexico 87501

(505) 827-2135

New York State Department of

Environmental Conservation

Water Management

50 Wolf Road-Room 618

Albany, New York 12233

(518) 457-3157

Pennsylvania

Puerto Rico

Rhode Island

South Carolina

South Dakota

Department of Community

Affairs

216 South Office Building

Capitol Complex-Room 506

Harrisburg, Pennsylvania 17120

(717) 787-7400

Puerto Rico Department

of Natural Resources

Post Office Box 5887

Puerta de Trera, Puerto Rico 00906

(809) 726-5710

Statewide Planning Program

Rhode Island Office of

State Planning

265 Melrose Street

Providence, Rhode Island 02907

(401) 277-2656

South Carolina Water Resources

Commission

Post Office Box 4915

3830 Fore Drive

Columbia, South Carolina 29240

(803) 758-2514

South Dakota Planning Bureau

State Capitol

Pierre, South Dakota 97501

(605) 224-3661

Division of Community

Assistance

Department of Natural &

Economic Resource

PO. Box 27687

Raleigh, North Carolina

(919) 733-2850

Tennessee Tennessee State Planning

Office

660 Capitol Hill Building

Nashville, lTnnessee 37219

(615) 741-2211

New Jersey

New Mexico

New York

North Carolina

91
Pennsylvania

Rhode Island

Texas

Utah

Division of Industrialized and

Mobile Housing

Education Building, Room 503

PO. Box 155

Harrisburg, Pennsylvania 17120

(717) 787-9682

(Mobile Homes)

State Building Commissioner

State Building Commission

12 Humbert Street

North Providence, Rhode Island 02911

(401) 277-3032

(Mobile Homes)

Division of Disaster Emergency

Services

Texas Department of Public

Safety

5805 N. Lamar Boulevard

Post Office Box 4087

Austin, Texas 78773

(512) 475-2171

Virginia

Washington

West Virginia

Wisconsin

Wyoming

Utah Department of Public Safety

317 State Office Building

Salt Lake City, Utah 84114

(801) 533-5401

Virginia State Water Control Board

Post Office Box 71143

Richmond, Virginia 23220

(804) 257-0056

Department of Ecology

St. Martinis College

Abbot Raphael Hall

Olympia, Washington 98504

(206) 754-2040

Disaster Recovery Office

1591 Washington Street, East

Charleston, West Virginia 23505

(304) 348-2246

Department of Natural Resources

Flood Plain-Shoreline

Post Office Box 7921

Madison, Wisconsin 53707

(608) 266-0161

Wyoming Disaster & Civil Defense

Agency

PO. Box 1709

5500 Bishop Boulevard

Cheyenne, Wyoming 82001

(307) 777-7566

Department of Water Resources

Vermont Agency of Environmental

Conservation

State Office Building

Montpelier, Vermont 05602

(802) 828-2761

I.

I

I

Vermont

92
Flood-Related Buiding Codes

Building codes can be part of a community's legal mechanisms for reducing flood damage. The Building Officials

and Code Administrators (BOCA) model code, which is

used as a guide in many parts of the country, includes

several sections meant to mitigate flood damage. Many

communities may have similar requirements, and the designer should consult with local or state building officials

to ascertain the flood-related codes that are in effect.

Below are relevant excerpts from the BOCA model code,

followed by a list of the state agencies that coordinate or

enforce building codes within their respective jurisdictions.

Excerpts for the Building Code Officials

and Code Administrators (BOCA)

Model Code

Section 709.0 Special Loads

709.1 General: Provisions shall be made for all special

loads herein prescribed and all other special loads to

which the building or structure may be subjected.

709.2 Below Grade: All retaining walls and other walls

below grade shall be designed to resist lateral soil

pressures with due allowance for hydrostatic pressure and

for all superimposed vertical loads.

709.3 Hydrostatic Uplift: All foundation slabs and other

footings subjected to water pressure shall be designed to

resist a uniformly distributed uplift equal to the full hydrostatic pressure.

Section 870.0 Retaining walls

870.1 General: Walls built to retain or support the lateral

pressure of earth or water or other superimposed loads

shall be designed and constructed of approved masonry,

reinforced concrete, steel sheet piling, or other approved

materials within the allowable stresses of accepted engineering practice....

870.2 Design: Retaining walls shall be designed to resist

the pressure of the retained material, including both dead

and live load surcharges to which they may be subjected,

and to insure stability against overturning, sliding, excessive foundation pressure, and water uplift.

870.3 Hydrostatic Pressure: Unless drainage is provided,

the hydrostatic head of water pressure shall be assumed

equal to the height of the wall.

cordance with the approved rules.

872.2 Steel Frame: Exterior steel columns and girders,

before embedment in masonry of the required fireresistance rating specified. . ., shall be protected from

moisture by approved waterproofing material, a parging

coat of cement mortar or by a minimum of eight (8) inches

of weather-tight masonry.

872.3 Chases: The backs and sides of all chases in exterior walls with less than eight (8) inches of approved

masonry to the exterior surface shall be insulated and

waterproofed.

872.4 Foundations: Exterior walls below grade and the

cellar floors of all buildings for institutional and residential uses (use groups I and R) enclosing habitable or

occupiable rooms or spaces below grade shall be made

watertight, and when necessary shall be reinforced to

withstand water pressure as prescribed in Sections 709.0

and 870.0. The basement walls of buildings in the residential use groups and the walls of all habitable and occupiable rooms and spaces below grade shall be protected

with not less than a one (1) coat application of approved

waterproofing paint, or a one-half (%) inch parging coat of

portland cement mortar or other approved dampproof

covering.

872.4.1 Subsoil Drains: Subsoil drains shall be provided

around foundations enclosing habitable or usable spaces

located below grade and which are subjected to ground

water conditions. Drains shall be installed at or below the

area to be protected and shall discharge by gravity or by

mechanical means into an approved drainage system

complying with the plumbing code listed in Appendix B

(of the codes).

872.5 Types of Waterproofing: The processes and

methods used to render buildings, structures or parts

thereof watertight as herein required shall comply with

accepted engineering practice covering types of

waterproofing.

872.6 Floodproofing: Where a structure is located within

a floodplain as determined by the building official or the

governmental body having jurisdiction, such a structure

must be designed to resist or overcome the anticipated

flood conditions.

Section 872.0 Waterproofing and Floodproofing

872.1 General: The exterior structural elements of all

buildings herein specified shall be waterproofed in ac93
State Building Code Offices

Alabama Director of Technical Staff

State Building Commission

800 South McDonough Street

Montgomery, Alabama 36104

(205) 832-3404

Arizona Division of Mobile and

Manufactured Housing Standards

1645 West Jefferson

Phoenix, Arizona 85007

(602) 255-4072

(Recreational Vehicles & Mobile Homes)

State Building Services

700 Medical Arts Building

12th and Marshall

Little Rock, Arkansas 72202

Division of Codes and Standards

Department of Housing and

Community Development

921 Tenth Street

Sacramento, California 95814

(916) 445-9471

(Recreational Vehicles)

r

U

E*

In

State Building Inspection

Department of Public Safety

294 Colony Street

Meriden, Connecticut 06450

(203) 238-6011

Comptroller General

State Capitol, Room 238

Atlanta, Georgia 30334

(404) 656-2056

Department of Labor and

Industrial Relations

825 Miliani Street

Honolulu, Hawaii 96813

(808) 548-3150

Director and Fire Marshal

Department of Labor and

Industrial Services

317 Main Street, Room 400

Boise, Idaho 83720

Institute of Natural Resources

325 Adams Street

Room 300

Springfield, Illinois 62706

(217) 785-2002

Iowa

Kansas

Kentucky

Maine

Maryland

State Building Commissioner

300 Graphic Arts Building

215 North Senate Avenue

Indianapolis, Indiana 46204

(317) 232-1400

State Building Codes Commissioner

State Capitol Complex

523 East Twelfth Street

Des Moines, Iowa 50319

(515) 281-3807

Architectural Services Divison

Department of Administration

State Office Building

10 East H larrison

Tbpeka, Kansas 66612

(913) 296-3811

Commissioner

Department of Housing

Route 127 South

Frankfort, Kentucky 40601

(50)2) 564-8044

Department of Business Regulation

Station 35

State I louse

Augusta, Maine 04333

(207) 289-3916

Director

Codes Administration

Maryland Department of Economic

and Community Development

2525 Riva Rd.

Annapolis, Maryland 21401

(301) 269-2701

94

Arkansas

California

Connecticut

Georgia

Hawaii

Idaho

Illinois

Indiana
State Building Code Commission

McCormack State Office Building

1 Ashburton Place

Room 1309

Boston, Massachusetts 02108

(617) 727-6916

(Mobile Homes)

Bureau of Construction Codes

Department of Labor

7150 Harris Drive

Lansing, Michigan 48909

(517) 322-1701

(Mobile Homes)

Department of Administration

200 State Administration Building

St, Paul, Minnesota 55195

(612) 296-3862

Division of Mobile Homes

Missouri Public Service Commission

P0. Box 360

Jefferson City, Missouri 65102

(314) 751-2557

(Recreational Vehicles & Mobile Homes)

Nebraska

Nevada

New Hampshire

New Jersey

New Mexico

New York

North Carolina

Ohio

Oklahoma

Oregon

Administrator, Building ('odes Division

Department of Administration

State of Montana

Capitol Station

Helena, Montana 59601

(4.06) 449-3933

Division of Housing and

Environmental Health

301 Centennial Mall South

Lincoln, Nebraska 68509

(402) 471-2541

(Recreational Vehicles & Mobile Homes)

Manufactured Ilousing Division

Department of Commerce

201 South Fall Street

Room 325

Carson City, Nevada 89710

(702) 885-4298

(Recreational Vehicles & Mobile Homes)

State Fire Marshal

Department of Public Safety

James Hayes Safety Building

Ilayes Drive

Concord, New Hampshire 03301

(603) 271-3336

Division of Housing

363 West State Street

Trenton, New jersey 08625

(609) 292-7898

General Construction Bureau

Bataan Memorial Building

Santa Fe, New Mexico 87503

(905) 827-5571

Ilousing and Building Codes Bureau

Division of Housing and

Community Renewal

Two World Trade Center

New York, New York 10047

(212) 488-7080

Deputy Commissioner of Insurance

North Carolina Department of Insurance

PO. Box 26387

Raleigh, North Carolina 27611

(919) 733-3901

Board of Building Standards

PO. Box 825

2323 West 5th Avenue

Columbus, Ohio 43216

(614) 466-3316

Engineering Department

State Board of Public Affairs

Room 306, State of Capitol

Oklahoma City, Oklahoma 73105

(405) 521-2121

Building Codes Division

Department of Commerce

401 Labor and Industries Building

Salem, Oregon 97310

(903) 378-3176

95

SN

Massachusetts

Michigan

Minnesota

Missouri

Montana
Division of Industrialized and

Mobile Housing

Education Building, Room 503

PO. Box 155

Harrisburg, Pennsylvania 17120

(717) 787-9682

(Mobile Homes)

State Building Commissioner

State Building Commission

12 Humbert Street

North Providence, Rhode Island 02911

(401) 277-3032

(Mobile Homes)

Facilities Planning &

Construction Division

1028 Stephen F. Austin State

Office Building

Austin, 12xas 78711

(512) 475-2270

Department of Labor and Industry

120 State Street

Montpelier, Vermont 05602

(802) 828-2286

Office of Uniform Building Code

Division of Building Regulatory

Services

205 North Fourth Street

Richmond, Virginia 23219

(804) 786-5041

Washington

West Virginia

Wisconsin

Wyoming

Puerto Rico

Department of Labor & Industries

Building Construction Safety

Inspection Services

300 West Harrison Street

Room 504

Seattle, Washington 98119

(206) 464-7204

State Fire Marshal

2000 Quarrier Street

Charleston, West Virginia 25305

(304) 348-2191

Safety and Building Division

Department of Industry, Labor &

Human Relations

PO. Box 7969

Madison, Wisconsin 53707

(608) 266-7319

State Fire Marshal

Department of Fire Prevention and

Electrical Safety

720 West 18th Street

Cheyenne, Wyoming 82002

(307) 777-7288

Regulations and Permits Administration

PO. Box 41179

Minillas Station

Santurce, Puerto Rico 00940

(809) 726-6200

U.S. Army Corps of Enginccrs

96

Pennsylvania

Rhode Island

Texas

Vermont

Virginia
National Flood Insurance Program:

Rules, Buiding and Insurance Rate Information

The National Flood Insurance Program (NFIP) is the

principal administrative mechanism for reducing flood

damage, providing an incentive to local governments to

implement sound floodplain management controls.

Using the limited availability of flood insurance as

leverage, the NFIP has established requirements and

guidelines for development in flood-prone areas. The

rate structure of insurance premiums reinforces the

intent of these regulations by charging higher insurance

rates for buildings subject to greater hazard. Insurance

rates are set on the basis of designated hazard zones and

the elevation of the building or structure in relation to

the Base Flood Elevation (BFE) in that particular zone.

The effect of this differential rate structure is to provide

an incentive to increase the safety of buildings beyond

the minimum standards by giving significant financial

benefits to buildings at higher elevations and in less

hazardous zones. Insurance rates are an important

element in analysis of life-cycle costs and can be the

designer's best argument for proper siting and design of

a proposed project.

It is thus vital that designers, before approaching any

design, familiarize themselves with the nature and extent

of the NFIP This should specifically include those components of the NFIP rules and building and insurance

rate information that can directly influence building design. This information can be obtained from local insurance agents, public officials and FEMA regional offices.

97
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