EARTH-SCIENCE 

INFORMATION 

IN LAND-USE 

PLANNI.NG 

CIRCULAR '721 

WORK DONE IN COOPERATION WITH 

U.S. DEPARTMENT OF HOUSING AND URBAN DEVELOPMENT, 

OFFICE OF POLICY DEVELOPMENT AND RESEARCH 

Earth-Science Information in 

Land-Use Planning-Guidelines for 

Earth Scientists and Planners 

By William Spangle and Associates; F. Beach Leighton and 

Associates; and Baxter, McDonald and Company 

G E 0 L 0 G I C A L S U R V E Y C I R C U LA R 721 

Jointly supported by the U.S. Geological Survey 

and the Department of Housing and Urban Development, 

Office of Policy Development and Research, 

as a part of a program to develop and apply earth-science 

information in support of land-use planning and decisionmaking 

1976 
United States Department of the Interior 

JAMES G. WATT, Secretary 

Geological Survey 

Doyle G. Frederick, Acting Director 

First printing 1976 

Second printing 1976 

Third printing 1977 

Fourth printing 1981 

Library of Congress Cataloging in Publication Data 

William Spangle_ and Associates. 

Earth-science information in land-use planning. 

(Geological Survey Circular 721) "Jointly supported by the lJ.S. Geological Survey and the Department of Housing 

and Urban Development, Office of Policy Development and Research." 

Bibliography: p. 26-2 7. 

Supt. of Docs. No.: I 19.16:721 

1. Earth sciences-California-San Francisco Bay region. 2. Land-California-San Francisco Bay region. 3. Environmental 

protection-California-San Francisco Bay region. I. Leighton_(F. Beach) and Associates. II. Baxter,McDonald and 

Company. III. Title. IV. Series: United States Geological Survey£ircular 721. 

QE75.C5 no. 721 [QE90.S12) 557.3'0~s [333.7'09794'6] 75-619436 

Free on application to Distribution Branch, Text Products Section, 

U.S. Geological Survey, 604 South Pickett Street, Alexandria, VA 22304 
FOREWORD 

This report is a product of the San Francisco Bay Region Environment and 

Resources Planning Study, an experimental program that is designed to 

facilitate the use· of earth-science information in regional planning and 

decisionmaking. The study is jointly supported by the U.S. Geological Survey, 

Department of the Interior, and the Office of Policy Development and Research, 

Department of Housing and Urban Development. The Association of Bay Area 

Governments participates in the study and provides a liaison and communication link with other regional planning agencies and with county and local 

governments. 

Although the study focuses on the nine-county 7 ,400-square-mile San 

Francisco Bay region, it bears on an issue that is of national concern. This 

issue-how best to accommodate orderly development and growth while 

conserving our natural resource base, insuring public health and safety, and 

minimizing degradation of our natural and manmade environment-is difficult 

and complex. The complexity, however, can be greatly reduced if we understand 

the natural characteristics of the land, the processes that snape it, its resource 

potential, and its natural hazards. These subjects are chiefly within the domain 

of the earth sciences: geology' geophysics, hydrology' and the soil sciences. 

Appropriate earth-science information, if available, can be rationally applied in 

guiding growth and development, but the existence of the information does not 

assure its effective use in the day-to-day decisions that shape development. 

Planners, elected officials, and the public rarely have the training or experience 

needed to recognize the significance of basic earth-science information, and 

many of the conventional methods of communicating earth-science information 

are ill suited to their needs. 

The study is intended to aid the planning and decisionmaking community by 

(1) identifying important earth-science problems related to growth and 

development in the bay region, (2) providing the earth-science information that 

is needed to solve these problems, (3) interpreting and publishing findings in 

forms understandable to and usable by nonscientists, ( 4) establishing new 

avenues of communication between scientists and users, and (5) exploring 

alternate ways of applying earth-science information in planning and 

decisionmaking. 

Since the study was started in 1970, it has produced more than 70 reports and 

maps. These cover a wide range of topics: reduction of flood and earthquake 

hazards, unstable slopes, engineering characteristics of hillside and low land 

areas, mineral and water resources management, solid and liquid waste 

disposal, erosion and sedimentation problems, bay water circulation patterns, 

and others. The methods used in the study and the results it has produced have 

elicited broad interest and a wide range of applications from planners, 

government officials, industry, universities, and from the general public. 

III 
This report, uEarth-Science Information in Land-Use Planning," results fron 

a nationwide sampling of applications of earth-science information to urban 

land-use planning. It is intended to acquaint planners and earth scientists with 

the needs and problems each faces in working with the other. To identify an~ 

evaluate these, the authors of the report examined earth-science applications in 

several urbanizing regions in different parts of the United States. Although th~ 

problems, methods, and political structure differ in each of these regions, many 

needs and problems that were found frequently appeared to be general in nature 

and of fundamental importance to communication between planners an~ 

scientists. 

The report is a summary and is structured as a series of recommendations that 

are based on current methods and practices in those parts of the United State~? 

where earth-science information has been used successfully in planning. TherP. 

recommendations are offered not as a set of directives, but as guidelines that 

provide a starting point for planners and earth scientists who wish to work 

together more effectively .1 

Because the use of the earth-science information in planning is evolvirg 

rapidly and because needs and practices differ from one planning jurisdiction to 

the next, no single set of guidelines can be final and definitive. Both planners 

and scientists may wish to view the guidelines given here as a set of postulates to 

be tested and refined against· the background of their own experience. 

AJ~,o.~~ Project Director 

San Francisco Bay Region Study 

IV 
CONTENTS 

Page 

Forevvord -------------------------------------------- III Guidelines for utilizing earth-science 

Page 

Introduction ________________ ------------______________ 1 

Guidelines for utilizing earth-science information in landuse planning ---------------------------------- 3 

ESI in the planning process ---------------------- 3 

Sources, types, ~nd interpretation of ESI for planinformation in land-use planning-Continued 

Planning for natural resources--Continued 

Environmental and economic impact ---------- 17 

ning -------------------------------------- Sources of ESL ______________________________ _ 5 

5 

Scale, accuracy, and detail of ESI -------------- 6 

Limitations and qualifications on ESI ---------- 9 

Types of ESI for planners -------------------- 10 

ESI in a form usable by planners ___ ----------- 13 

Planning for natural resources -------------------- 13 

Need for national policies -------------------- 13 

Natural-resource plans ________________________ 15 

Planning for reduction of natural hazards ---------- 18 

Identification of hazardous areas -------------- 18 

Impacts of hazard-mitigation methods---------- 18 

Mitigation methods and acceptable risks ------ 20 

Integration of ESI in the planning process ______________ 20 

Land-capability studies basic to land-use planning-- 20 

Interdisciplinary relationships -------------------- 23 

Public participation------------------------------- 26 

Conclusion ------------------------------------------ 26 

References cited-------------------------------------- 26 

Selected readings ------------------------------------ 27 

ILLUSTRATIONS 

Page 

FIGURE 1. Aerial photograph shovving suburban development extending into the hills in 

Hayvvard, Calif ________________ -------------------------------------- 2 

2. Diagram of the land-use planning process------------------------------------ 4 

3. Tvvo topographic maps identical except for scale ------------------------------ 7 

4. Three geologic maps differing in both scale and amount of detail -------------- 8 

5. Qualifying note on a geologic hazard maP------------------------------------ 9 

6. Typical soils map ---------------------------------------------------------- 11 

7. Typical hydrologic map ---------------------------------------------------- "12 

8. Map shovving landslide susceptibility in San Mateo County, Calif., and aerial 

photograph of part of the same area ---------------------------------- 14 

9. Photograph of a strip-mined area after reclamation -------------------------- 17 

10. Graph shovving estimated dollar losses from selected environmental problems and 

costs of reducing losses ________________________ :._ _____________________ 19 

11. Risk-zone map of part of Santa Clara County, Calif -------------------------- 21 

12. Land suitability map, Palo Alto, Calif -------------------------------------- 24 

TABLES 

Page 

TABLE 1. General guidelines for utilizing earth-science information in land-use planning 1 

2. Some sources of earth-science information____________________________________ 5 

3. Natural processes important to land-use planning ---------------------------- 19 

4. Rating system for land-capability factors ------------------------------------ 22 

v 

Earth-Science Information in Land-Use PlanningGuidelines for Earth Scientists and Planners 

By William Spangle and Associates; F. Beach Leighton and Associates; 

and Baxter, McDonald and Company 

INTRODUCTION 

The principal question facing those responsible 

for land-use decisions is clearly expressed in the 

recently published report of the Task Force on 

Land Use and Urban Growth created by the 

President's Citizens' Advisory Committee on Environmental Quality (1973, p. 14) and funded by 

the Rockefeller Brothers Fund: 

How shall we organize, control, and coordinate the process of 

urban development so as to protect what we most value in the 

environmental, cultural, and aesthetic characteristics of the 

land while meeting the essential needs of the changing U.S. 

population for new housing, roads, power plants, shopping 

centers, parks, businesses, and industrial facilities? 

The land itself is a resource that must be used 

with wisdom. The needs of our growing population 

require that we conscientiously plan for the use of 

land, not only to protect its resources and esthetic 

values but also to reduce the exposure of urban 

development to natural hazards by giving explicit 

consideration to natural conditions and processes 

in land-use decisions. In this task, the work of the 

planner and the earth scientist can be mutually 

reinforcing. 

From the earliest times the natural environment has influenced the location and form of 

human settlement (fig. 1). The land and its 

features present, in varying degrees, opportunities 

and constraints for various human activities. As 

expressed by Robert F. Legget (Legget, 1973, p. 

70-71), 

When planning starts, for urban community or region, the area 

to be developed is not the equivalent*** of a piece ofblank paper 

ready for the free materialization of the ideas of the designer, 

but it is rather an environment that has been exposed for a very 

long period to the effects of many natural modifying factors***. 

Development of new communities and the charting of regional 

development must, therefore, take account of this fundamental 

organic and dynamic character of Nature so that the works of 

man may fit as harmoniously as possible into the environment*** 

1 

To achieve harmonious blending of man's works 

and nature requires knowledge of resources to be 

developed and conserved and awareness ofhazards 

to to be avoided or mitigated. Information from the 

earth sciences is thus essential. Earth-science 

information (ESI) pertains to the natural materials, features, and processes of the land. It 

includes basic information from geology, soils, 

hydrology, and a large number of related scientific 

and engineering fields, together with interpretations of that basic information. ESI thus encompasses much of the information concerning the 

physical nature and interactions of land and 

water. Because of the focus of the study, and these 

guidelines, information from chemical and biological sciences, meteorology, and climatology is not 

considered, although it, too, is highly relevant to 

land-use planning. 

This circular presents and discusses a set of 

general guidelines for utilizing ESI in land-use 

planning (table 1). The guidelines concern subject 

areas of interest to both planners and earth 

scientists. Planners should find the report useful 

as a brief introduction to the kinds and sources of 

ESI available and to techniques for applying ESI 

to planning. For earth scientists, the report defines 

in broad terms the needs of planners and how ESI 

can be made more useful to planners. The report 

is intended to stimulate the development of effective communication between planners and earth 

scientists. 

The main purpose of this report, however, is to 

introduce decisionmakers and interested citizens 

to the potential uses ofESI in a planning program. 

The desires of the community as perceived by 

decisionmakers are frequently reflected in landuse decisions. Both planners and earth scientists 
FIGURE I.-Suburban development extending into the hills in Hayward, Calif. The natural constraints and opportunities 

should be evaluated before further development of these hillsides. 

TABLE 1.-General guidelines for utilizing earth-science 

information in land-use planning 

ESI in the planning process 

• ESI should be integrated into all phases of the land-use 

planning process (see section "ESI in the Planning 

Process"). 

Sources, types, and interpretation of ESI for planning 

• Planning agencies can obtain ESI from a variety of 

sources (see section "Sources of ESI"). 

• Scale, accuracy, and detail of the ESI required for 

planning vary according to jurisdictional level, environmental diversity, and rate of development of the 

area (see section "Scale, Accuracy, and Detail ofESI"). 

• Planners should be aware of the limitations of data and 

any qualifications placed on its use and accuracy (see 

section "Limitations and Qualifications on ESI"). 

• Basic ESI concerning topography, geology, soils, and 

hydrology is fundamental to any land-use planning 

effort (see section "Types of ESI for Planners"). 

2 

TABLE I.-General guidelines for utilizing earth-science 

information in land-use planning-Continued 

• Planners need ESI relevant to, and in a form suitable for, 

application in land-use planning (see section "ESI in a 

Form Usable by Planners"). 

Planning for natural resources 

• Ideally, planning for the wise use of natural resources at 

the state, regional, and local levels should be 

consistent with national policies on resource conservation and development (see section "Need for National 

Policies"). 

• Natural-resource planning is a necessary function of 

agencies at all jurisdictional levels with land-use 

planning responsibilities (see section "NaturalResource Plans"). 

• Proposals involving resource conservation and development should be subjected to both environmental and 

economic impact analyses (see section "Environmental and Economic Impact"). 
T ABL,E 1.-General guidelines for utilizing earth-science 

information in land-use planning-Continued 

Planning for reduction of natural hazards 

• Hazardous areas should be identified and evaluated for 

level of risk (see section "Identification of Hazardous 

Areas"). 

• Alternative measures to mitigate hazards should be 

evaluated for both environmental and economic 

impacts (see section "Impacts of Hazard-Mitigation 

Methods"). 

• Selection of measures to mitigate hazards should be 

consistent with acceptable levels of risk (see section 

"Mitigation Methods and Acceptable Risks"). 

Integration of ESI in planning process 

• Land-capability studies to evaluate natural opportunities and constraints are basic to the integration of 

ESI in land-use planning (see section "LandCapability Studies Basic to Land-Use Planning"). 

• Successful integration of ESI in land-use planning 

requires the establishment of a close working relationship between planners and earth scientists (see 

section "Interdisciplinary Relationships"). 

• Public participation in decisionmaking should be encouraged throughout the planning process to insure 

effective results (see section "Public Participation"). 

can be expected to respond to public pressures for 

land-use planning that recognizes natural opportunities and constraints. 

This circular is a condensation of a technical 

report prepared after a 14-month study funded by 

the U.S. Department of the Interior, Geological 

Survey, and the Department of Housing and 

Urban Development, Office of Policy Development 

and Research. The study, called ttApplication of 

Earth-Science Information in Urban Land-Use 

Planning-State-of-the-Art Review and Analysis," investigated the experience of selected city, 

county, and regional agencies in the application of 

earth-science information to land-use planning. 

The study was undertaken by a multidisciplinary team composed of professionals in urban and 

regional planning, the earth sciences, and public 

administration. The team members interviewed 

planners and earth scientists across the country in 

agencies identified as making effective use of ESI 

in their planning programs. From this investigation, an understanding of conditions favoring the 

use of ESI in land-use planning was developed. 

The reader is referred to the full technical report 

for more detailed discussion of the material 

presented in this summary (Spangle and others, 

1973). 

3 

GUIDELINES FOR UTILIZING 

EARTH-SCIENCE INFORMATION 

IN LAND-USE PLANNING 

ESI IN THE PLANNING PROCESS 

Land-use planning is an integral part of a 

broader planning process variously termed comprehensive, general, or master planning. Whereas 

comprehensive planning treats the future development of an area in terms of all major determinants of growth and change-economic, political, 

social, and physical-land-use planning highlights the physical expression of the plan on the 

land. As such, it is primarily concerned with the 

arrangement and types of land uses, their impact 

on the landscape, and relation to transportation 

and community facilities and utilities. 

The land-use planning process consists of five 

conceptually distinct phases: (1) identification of 

problems and definition of goals and objectives; 

(2) data collection and interpretation; (3) plan 

formulation; (4) review and adoption ofplans; and 

(5) plan. implementation. Figure 2 depicts the 

land-use planning process and lists typical studies 

and documents associated with three phases. As 

shown by the arrows, each phase is interrelated 

with all others, and the sequence, while logical, is 

often varied especially in response to crises, 

political opportunities, or legal requirements. 

Interaction among the phases, however, should be 

virtually continuous. Plan formulation often indicates the need for additional information, and 

additional information may alter the concept of 

the objectives and problems; moreover, plan 

implementation may reveal the need for additional information or modification of the plan. 

Public initiative and response is a key part of 

every phase of land-use planning. ttPublic" may 

refer to elective political bodies, special-interest 

groups, or interested individuals. Elected public 

officials have final responsibility for most key 

policy decisions, although persons in nonelective 

positions actually make many important day-today decisions. Decisions occur throughout the 

process, ranging from the decision to engage in a 

planning effort to the final approval of a plan and 

adoption of implementing regulations, programs, 

and procedures. 

ESI is necessary in each phase of the land-use 

planning process. The following outline lists the 

basic steps for integrating ESI in each phase of 
information 

Background studies 

Existing land use 

Transportation 

Economic 

Political 

Social 

Zoning and subdivision regulations 

Erosion and sedimentation control 1 

ordinances 

Building and housing codes 

Environmental impact statements 

A-95 review procedures 

Capital improvement programs 

Health and sanitation codes 

FIGURE 2.-Diagram of the land-use planning process. 

land-use planning; planners and earth scientists 

should work together in carrying out each step: 

1. Identify problems and define goals and objectives. 

a. Obtain readily available ESI for preliminary identification of natural hazards 

and resources. 

b. Review this ESI in relation to existing 

land-use plans and policies, projected 

growth trends, and anticipated changes 

to develop a tentative set of objectives 

and priorities, giving special consideration to hazards and resources. 

2. Collect and interpret data. 

a . Develop a program for utilizing available 

ESI and compiling new data. 

b. Arrange with earth scientists to prepare 

basic and interpretive maps and texts. 

Map information should relate in scale 

and detail to other basic planning information. 

c. Estimate the probable future demand for 

land considering projections of population growth and distribution, economic 

activity, social and cultural needs, and 

transportation requirements. 

4 

d. Prepare land-capability maps showing the 

natural capability of each land unit to 

accommodate each potential use. 

3. Formulate plans. 

a . On the basis of land-capability maps, 

appropriate projections, and economic, 

social, and political analyses, consider 

feasible alternative arrangements of 

land uses. 

b. Evaluate alternative land-use possibilities, selecting the most desirable. 

c. Prepare a land-use plan incorporating as 

much detail as necessary to serve as a 

basis for decisionmaking. 

d. Evaluate land-use proposals for environmental, economic, and social impacts. 

Make any indicated revisions in the plan. 

4. Review and adopt a plan. Obtain official 

approval of plan from public decisionmaking 

bodies. 

5. Implement the plan. 

a. Prepare and seek adoption of land-use 

regulations and any land-acquisition 

and capital-improvement programs 

needed to carry out the plan. 

b. Establish guidelines and a procedure for 
conducting the earth-science investigations needed to evaluate each development proposal. 

c. Develop procedures and staff capability for 

reviewing soils and geology reports, 

environmental impact assessments, and 

project proposals. 

d. Arrange for modification of previous steps 

as new or more detailed ESI becomes 

available. 

SOURCES, TYPES, AND INTERPRETATION 

OF ESI FOR PLANNING 

SOCRCES OF ESI 

A variety of agencies at all jurisdictional levels 

in the United States produce ESI (table 2). Two 

Federal agencies-the United States Geological 

Survey (USGS), Department of the Interior, and 

the Soil Conservation Service (SCS), Department 

of Agriculture -are prime sources of information, 

and their publications are widely available 

throughout the country. 

The USGS has a broad research base in the earth 

sciences covering work in topography, geology, 

and mineral and water resources. Major offices in 

Reston, Va., Denver, Colo:, and Menlo Park, Calif., 

have professional staffs and extensive facilities for 

basic earth-science research. The USGS is specifically charged with the preparation of topographic 

and geologic quadrangle maps of the United 

States. The Water Resources Division of USGS 

(with district offices throughout the United States) 

produces basic hydrologic data, inventories the 

nation's water supply, monitors its quality, and 

engages in other hydrologic research. 

The USGS recently has placed an increased 

emphasis on production of ESI specifically applicable to planning and decisionmaking. Through a 

series of pilot projects, studies have been undertaken to interpret basic ESI in terms of its 

implications for various land uses. These products 

are particularly useful to planners. 

The SCS is responsible for many soil and water 

conservation programs throughout the United 

States. Over 3,000 soil conservation districts 

established under enabling legislation in all 50 

states are served by SCS field offices, each headed 

by a ''district conservationist." District boundaries 

in most cases conform to county lines. 

The SCS field offices are staffed largely by soil 

scientists invvlved primarily in classifying soils 

5 

TABLE 2.~ome sources of earth-science inform-..tion 

Federal agencies 

U.S. Department of the Interior 

Geological Survey 

Bureau of Mines 

Bureau of Reclamation 

Bureau of Land Management 

U.S. Department of Agriculture 

Extension Service 

Soil Conservation Service 

Forest Service 

U.S. Department of Commerce 

National Oceanic and Atmospheric Administration 

U.S. Department of Army 

Army Corps of Engineers 

Energy Research and Development Administretion 

Environmental Protection Agency 

National Aeronautics and Space Administration 

Tennessee Valley Authority 

State divisions or departments 

Agriculture 

Conservation 

Forestry 

Geological Surveys 

Oil and Gas 

Soil Conservation 

Fish and Game 

Water·Resources 

Water Quality 

Mineral Resources 

Colleges and universities 

County or city departments or special districts 

Planning 

Water 

Flood Control 

Agriculture 

Parks and Recreation 

Engineering 

Building and Safety 

Public Works 

Private producers 

Consulting firms 

Private colleges and universities 

Professional societies 

Industries with in-house capabilities 

and evaluating their suitability for agri~ultural 

purposes. Because soil classifications have some 

engineering significance and because much agricultural land has been converted to ur":lan and 

suburban uses, SCS products are often used in 

land-use planning. For this reason, and as agricultural applications of SCS products have been 

satisfied, SCS soil scientists are incr~~asingly 

orienting their work to the needs of ur":lan and 

regional planners. 

The decentralization of work by the sc:: brings 

its soil conservationists into close personal contact 
with local persons and agencies requiring technical assistance. Each SCS district responds to local 

needs and circumstances, leading to considerable 

innovation and flexibility in presenting and 

interpreting soil data. Such data are of particular 

value in assessing foundation conditions and 

supporting systems near the surface for light 

structures such as single-family residences, 

utilities, and streets. Where foundation conditions 

at greater depths are of concern and natural 

processes such as landslides may be active, soil 

data can be a helpful supplement to the geologic 

and hydrologic information needed to characterize 

problem areas. 

State geological surveys can be important 

sources of ESI for planners. These agencies may 

undertake geological surveys, publish statewide 

earth-science maps, and serve . as information 

bureaus for the people of the state. All states, 

except Rhode Island, have geological surveys, but 

staff size, facilities, organizational structure, and 

areas of emphasis vary considerably from state to 

state. 

Many state governments also have departtnents 

or divisions that are responsible for soil and water 

conservation. Such a department or division may 

work largely through the state SCS office or may 

act independently in developing a separate program of its own. It may be an excellent source of 

ESI related to soil and water resources. 

Earth-science departments at public and private 

universities and private consultants are other 

sources ofESI. If the need is for fairly detailed data 

related to a specialized problem or particular site, 

a special study will ordinarily be required. 

SCALE, ACCURACY, AND DETAIL OF ESI 

A major consideration in building a data base of 

ESI for land-use planning is the relationship of 

scale, detail, and accuracy to an agency's planning 

responsibilities and requirements. There is often 

misunderstanding over the fact that scale, accuracy, and detail do not refer to the same thing and 

may not even be related to each other in a 

consistent manner. 

Map scale is the relationship between corresponding distances on a map and on the earth. A 

scale of 1:24,000 means that 1 map-inch iii 

equivalent to 24,000 inches on the ground. 

Planners would normally translate this to 1 

map-inch is equivalent to 2,000 feet. A map's scale 

is considered usmall" if the second figure of this 

6 

ratio is ularge"; a scale of 1:62,500 is thus smaller 

than a scale of 1:24,000 (fig. 3). A s"llall-scale map 

does not usually show as mucl:t detail as a 

large-scale map (fig. 4). 

Accuracy has two distinct meanings. First, it 

refers to whether the information is. right or 

wrong. Accurate information is correct, free from 

error. Second, accuracy in a relative sense refers to 

the degree of precision with which the information 

was obtained, measured, and recm·ded. 

Although scale and accuracy are important in 

planning, obtaining data of an appropriate level of 

detail for the task at hand is usually the most 

significant informational concern of the planner. 

Confusion occurs when the common but sometimes 

unwarranted assumption is made. that a largescale map (say of scale 1:24,000) shows more detail 

and is more accurate than a small-scale map (say 

of scale 1: 125,000). The planner Vl'ho indicates a 

need for ularger scale" may really mean that he 

needs more detailed or more accurate maps. A map 

may easily be enlarged to a larger scale, but the 

enlargement process will result in a map no more 

detailed nor accurate than the original. Enlarging 

a map may, however, Pender detail p]ready present 

in the original more legible and hence make it 

more useful. Data plotted on the enlarged map 

cannot be located any more accurately than on the 

small-scale map. In fact, the enlarged map does not 

have the accuracy of a map prepared specifically at 

the enlarged scale. 

The term umap detail" refers to the amount of 

information presented in a given map area-the 

more information per map unit, the more detailed 

the map. Map production techniques and legibility 

requirements impose physical limits on the level of 

detail that can be shown on a map cf a given scale. 

Within these limits, however, two maps of identica] scale may present data with diFerent levels of 

detail. 

Successful application of ESI to land-use planning requires that ESI be available in sufficient 

detail to meet the planning needs of an agency. 

The level of detail required varies in a general way 

with the jurisdictional level and phase of the 

planning process. The need for detailed data in 

plan formulation is generally hierarchical with 

respect to governmental level; that is, more 

detailed data are needed at the local level than at 

the state or national level. More detailed data are 

ordinarily required for plan implementation regardless of jurisdictional level. Administration of 
FIGURE 3.-The top map is a basic topographic map at a scale of 1:62,500 (Provo quadrangle, 1949). The bottom map is a part of 

the top map enlarged to a scale of 1:24,000. The enlarged map has no greater detail and is no more accurate than the smaller scale map. 

7 
FIGURE 4.-Three geologic maps that differ both in scale and amount of detail. A, Part of geologic map of Palo Alto 7 .5-minute 

quadrangle, California, scale 1:24,000 (Pampeyan, 1970). B, The same area at a scale of 1:62,500 (Dibblee, 1966). C, The 

same area at a still smaller scale, 1:250,000 (Jennings and Burnett, 1961 ). 

8 
land-use regulations ultimately depends on decisions made at the site level where the need for 

detail is greatest. 

The level of detail ofESI needed also depends on 

the environmental diversity of the planning area. 

It is generally true that the more varied the 

natural environment of a planning area, the more 

detailed its ESI requirements. Generalized data on 

geology, soils; and hydrology may be sufficient for 

land-use planning in relatively flat agricultural 

areas of the Midwest where similar natural 

conditions may prevail throughout the planning 

area. In parts of California, on the other hand, 

many single J?lanning jurisdictions include mountains, coastsides, deserts, and valleys with a great 

variety of geologic conditions. The very diversity of 

terrain poses planning constraints and opportunities that can be identified only with detailed 

information. 

The present and anticipated rate of development 

within a jurisdiction also determines its ESI 

requirements. Generalized ESI is usually sufficient for areas that are relatively unchanging, 

clearly inaccessible, or otherwise undesirable for 

urban development. Detailed ESI is needed in 

rapidly growing areas for effective, almost daily, 

evaluation of project proposals. In areas where 

growth pressures are especially strong, development may be guided primarily by the economic 

judgments of private landowners without regard 

for the natural features of the land. When an area 

is under growth pressure, the planner needs great 

persistence and accurate and detailed ESI to 

insure consideration of earth-science factors in 

land-use decisions. 

LIMITATIONS AND QUALIFICATIONS ON ESI 

Planners should always read the notes on an ESI 

document before use. They may discover, for 

instance, that there is considerable variation in 

the precision or completeness of data for different 

parts of the same map. Inaccessible areas may be 

less thoroughly mapped than accessible ones; 

important assumptions may have been made 

about the relationship of certain features; or the 

data may have been derived from different 

sources. Such information should always be 

included with a map or report, and a planner 

should always heed it. The disclaimer in figure 5 is 

part of the legend provided by the California 

Division ofMines and Geology for a recently issued 

map on special studies zones for the State of 

WOODSIDE -OUADRANGLE , 

1) 

2) 

3) 

have 

howiv'er, 

IMPORTANT..:. PL~ASE NOTE ~~~f;i : \ ;I ' /' < ·: :• ~ :: I 

have not duJiog this map compiliiltlon. 

4) Faalt ~r:\formati~ ·:. ~ this map .is oot'suffi~(ent to serve a~ a sub-· 

stitute f9r nf()rm~ti9n ~~velo ~ed by ~he sp~~ i~l s~uc1,i,s. tbat rr-ay. be· 

required under. Chipter :7'.5', Division 2·,·$Qctidn 2G23 6f" 1~e Cahfdr' · ' '. . '·.· • •J;;.: i•' t • 

nia Public Resources Code. · · · 

FIGURE 5.-Example of a qualifying note on a geologic hazard map (State of California, 1974). 

9 
California. The disclaimer makes it clear that for 

most planning purposes, supplementary information will be necessary. 

The planner must also note the scale and detail 

of a map. For instance, a highly generalized 

landslide map at a regional level may show an 

entire mountainside as being in a high landslidesusceptibility category, whereas additional, more 

detailed information may reveal a range of 

conditions incltiding stable areas within the more 

generalized hazardous areas. 

The degree of specificity of a planning decision 

should be no greater than warranted by the data 

upon which it is based. Planners, in seeking firm 

data on which. to base decisions, may risk placing 

undue reliance on ESI that is too generalized for 

their purpose. The planner is well advised to write 

plans or regulations to accommodate more specific 

data as they become available. For example, the 

Portola Valley, Calif., zoning ordinance (Article II, 

Section 6209.2) prohibits structures for human 

occupancy within 50 feet of a Hknown" fault trace 

and 100 feet of an ninferred" fault trace. The 

ordinance provides that ((when geologic studies 

acceptable to the Planning Commission identify 

an (inferred' segment of a trace at a level of 

accuracy equivalent to previously mapped (known' 

traces, such fault trace segments shall be automatically reclassified as a (known' location." 

TYPES OF ESI FOR PLANNERS 

The standard Geological Survey topographic 

map in the quadrangle series is one of the most 

basic and valuable sources of ESI and is of great 

use as a planning tool (fig. 3). It _not only shows 

terrain features, such as the shape and elevation of 

the land, and cultural features, such as transportation networks and areas of urbanization, but 

also serves as a good base map on which to record 

both earth-science and planning information. 

Topographic maps are readily available for most 

areas of the United States at very modest prices. 

With these maps, the knowledgeable planner can, 

among other things, calculate slope, inventory 

surface water resources, identify some obviously 

hazardous areas, and make a good preliminary 

assessment of where land-use conflicts may occur. 

In addition to standard topographic maps, the 

Geological Survey is now producing orthophotoquads and hopes to have within the next 

few years complete coverage of all conterminous 

areas of the United States that are not already 

10 

mapped at 1:24,000 scale. An orthophotoquad is a 

vertical aerial photograph in quadrangle format, 

corrected for position distortion related to differences in elevation and camera angle. A planimetrically accurate and detailed photoprint is produced providing planners with geographic and 

topographic information (with the exception of 

contours and elevations) more quickly than is 

possible with a standard topographic map. The 

Survey also has orthophotoquads overprinted with 

contours and elevations for some areas. 

Geologic maps show the kinds, distribution, and 

some physical characteristics of geologic units at 

or near the earth's surface and can be especially 

useful to planners when supplemented by engineering and planning interpretation. Areas susceptible to such geologic hazards as faults, 

landslides, and subsidence can be identified from 

these maps. The most commonly used basic 

geologic maps are 1:24,000-scale geologic quadrangle maps published by the Federal and state 

geological surveys (fig. 4A). These may be 

supplemented by more detailed information available from local sources. Other important sources of 

geologic maps are listed in table 2. 

Soil classification maps show the distribution of 

different types of surface soils (fig. 6). The Soil 

Conservation Service soils surveys, which provide 

information pertaining to the upper 5-6 feet of 

earth materials, are widely used by planners. 

SCS publications may also include tabulations of 

basic data and interpretation of the data. Recent 

soil surveys provide soil ratings (limitations and 

capabilities) for a variety of agricultural, urban, 

and engineering uses. Soils information is frequently more readily available to planners than 

many other categories of ESI. When used in 

conjunction with geologic, hydrologic, and engineering data, it pr~wides the basis for many 

studies on the natural limitations and potentials of 

the land for particular uses. 

Data describing the hydrologic system of an area 

are always needed for land-use planning. Available from the Geological Survey, state and local 

water resources agencies br local flood-control and 

water districts, hydrologic maps depict the character of, and interrelationships between, surface and 

ground-water resources (fig. 7). They are useful for 

delineating and evaluating water supply, floodprone areas, water quality, areas of potential 

subsidence, seepage areas, and areas where 

erosion or sedimentation is a potential p!'oblem. 
..... 

..... 

FIGURE 6.-A typical soils map from southeastern Wisconsin. Map furnished by courtesy of Southeastern Wisconsin Regional Planning Commission. 
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FIGURE 7 -A typical hydrologic map from Greater Anchorage Area Borough, Alaska (Barnwell and others, 1972, p. 25). 
ESI I;\; A FORM USABLE BY PLAN:'IJERS 

Earth-science data applicable to land-use planning are often presented in map form. These maps 

may contain only basic data, or they may provide 

interpretive material as well. Actually, no sharp 

break separates basic and interpretive data. There 

is, instead, a continuum of information ranging 

from the very basic, such as bedrock material, to 

the highly interpretive, such as relative slope 

stability. When a planner says interpretive data 

are needed, he means, in a general sense, that a 

description of a natural feature or process is not 

very helpful to him unless accompanied by 

information concerning its probable behavior 

under certain natural and manmade conditions or 

by the implications regarding capability ofland to 

accommodate par!icular uses. 

An example from an environmental geologic 

study of the Santa Cruz Mountains in California 

illustrates this point. Basic geologic units mapped 

for the Santa Cruz Mountains were combined into 

six categories of relative geologic stability (D, H, L, 

P, S, W) and mapped. Each category was described 

in terms of its basic geologic composition and 

nature. For example, category ((S" is described as 

((Unconsolidated to semi-consolidated sand and 

gravel, locally clay rich, interbedded with clay, 

Quaternary-Tertiary age. Unconsolidated alluvium, Quaternary age, ranges from P to S 

categories (QTscsc' QTsc5 , QTscu' Qoal, Qal)" (Rogers 

and Armstrong, 1973). Such a geologic description 

becomes meaningful to a planner only when its 

implications are spelled out. The same map 

category C(S") is interpreted for ((anticipated 

response to earthquakes" in the following terms: 

((Ground shaking-slightly more intense than L 

category' possible severe shaking in watersaturated Qoal and Qal; ground failurelandslides may occur as in H category and in 

poorly consolidated units along steep margins of 

stream channels. Severe lurch cracks may occur in 

water-saturated Qoal and Qal (as near Congress 

Springs in the 1906 earthquake)." 

Interpretations such as this give the planner a 

feel for the specific nature of the problem involved 

on land containing these geologic units. Maps 

combining data on several natural conditions to 

provide i:pterpretations related to complex natural 

processes can be particularly useful to the planner. 

One such example is a landslide-susceptibility 

map of another part of the Santa Cruz Mountains 

(fig. 8) that synthesizes information from geology, 

13 

slope, and landslide inventory maps (Brabb and 

others, 1972). Such a map is a very important 

planning tool, useful both in developing land-use 

policy and plans and in identifying areas that 

require detailed site investigation. 

PLANNING FOR NATURAL RESOURCES 

NEED FOR NATIONAL POLICIES 

Natural resources include earth materials such 

as minerals, soil, and water that are either 

consumed or altered by man. The combination of 

growing population and rising per capita consumption is leading to the real possibility of 

serious shortages of essential nonrenewable 

natural resources in the not-too-distant future. As 

a nation, we have not developed a systematic, 

comprehensive approach to resource planning. 

Planning and regulatory authority are dispersed; 

costs and benefits-both environmental and 

economic-fall unevenly on different jurisdictions 

and communities; and mechanisms for resolving 

basic conflicts over whether or not to develop a 

particular resource are lacking. 

There ·is need for broad, national policies to 

guide state and local jurisdictions in making 

land-use decisions related to resources. Except for 

the most widespread resources, the questions of 

adequacy and quality of resource supply are 

national, even global, concerns, while the direct 

environmental impacts from extraction are often 

localized. For instance, a decision to strip mine for 

coal may be a logical response to the growing 

national demand for energy, but the attending 

destruction of the land and loss of air quality may 

have a devastating local impact. Resource planning must address both the broad question of need 

and the more localized question of environmental 

impact. 

The adequacy of known resources to meet 

present and projected needs is difficult to determine. There may be significant undiscovered 

sources for some materials, and moreover, 

technological advances may render the need for 

certain resources obsolete or make possible the 

utilization of presently inaccessible or unusable 

resources. Also, the location of a resource with 

respect to national or even regional boundaries 

influences the judgment of its adequacy. 

National and state policy is needed to prevent 

the loss of resources through local decisions that, 

while individually rather insignificant, have a 

great combined impact. For example, one com-
A 

B 

FIGURE 8-Landslide susceptibility in San Mateo County, California. A, Map specifically prepared for application 

in land-use planning studies. It was derived from a basic geologic map, an inventory oflandslides, and a slope map 

(Brabb and others, 1972). Explanation on facing page . B , Aerial photograph showing the area outlined in the 

landslide-susceptibility map. 

munity's decision to permit the subdivision of 

agricultural land may yield local benefits and have 

little negative impact on the nation's food supply. 

If, however, many communities make this same 

decision, the impact on food supply may become 

14 

critical. Such choices regarding alternative uses of 

land need to be made on the basis of established 

national, state, and regional priorities that consider the long-term as well as short-term consequences. 
Explanation of Map Units 

Areas least susceptible to landslldlng. Very few small 

landslides have formed in these areas. Formation of 

large landslides is possible but unlikely, except during 

earthquakes. Slopes generally less than 15 percent, but 

may include small areas of steap slopes that could have 

higher susceptibility. Includes soma areas with 30 percent 

to mora than 70 percent slopes that seam to be underlain 

by stable rock units. Additional slope stability problems; 

some of the areas may be mora suscaptlbila to landsliding 

If they are overlain by thick deposits of soil, slopawash, or 

ravine fill. Rockfalls may also occur on steep slopes. Also 

includes areas along creaks, rivers, sloughs, and lakes that 

may fail by landsliding during earthquakes. If area is 

adjacent to area with higher susceptibility, a landslide may 

encroach into the area, or the area may fail if a landslide 

undercuts It, such as the flat area adjacent to sea cliffs. 

Low susceptibility to landsliding. Several small landslides 

have formed in these areas and soma of these have caused 

extensive damage to homes and roads. A few large land· 

slides may occur. Slopes vary from 5-15 percent for unstable rock units to more than 70 percent for rock units 

that seem to be stable. The statements about additional 

slope stability problems mentioned in l above also apply in 

this category. 

Moderate susceptibility to landsliding. Many small landslides have formed in these areas and several of these have 

caused extensive damage to homes and roads. Some large 

landslides likely. Slopes generally greater than 30 percent 

but includes some slopes 15-30 percent in llreas underlain 

by unstable rock units. See l for additional slope stabil ity 

problems. 

r.:1 Moderately high susceptibility to landslidlng. Slopes all 

~ greater than 30 percent. These areas are mostly in undeveloped parts of the County. Several large landslides likely. 

See l for additional slope stability problems. 

High susceptibility to landslidlng. Slopes all greater than 

30 percent. Many . large and small landslides may form. 

These areas are mostly in undeveloped parts of the 

County. Sea l for additional slope stability problems. 

f':::1 Very high susceptibility to landsliding. Slopes all greater 

~ than 30 percent. Development of many large and small 

landslides is likely. The areas are mainly in undeveloped 

parts of the County. Seal for additional slope stability 

problems. 

r.-1 Highest susceptibility to landsliding. Consists of landslide 

~ and possible landslide deposits. No small landslide deposits 

are shown. Some of these areas may be relatively stable 

and suitable for development, whereas others are active 

and causing damage to roads, houses and other cultural 

features. 

Definitions: Large landslide - mora than 500 feat in 

maximum dimension 

Small landslide - 50 to 500 feet in 

maximum dimension 

FIGURE B.-Continued. 

:-.IATCRAL-RF:SOURCE PLANS 

Decisions regarding the use ofland are decisions 

concerning the allocation of a very important 

resource. This statement is true whether or not 

explicit policies and priorities regarding natural15 

resource conservation or development are adopted 

and adhered to. Obviously, however, it is desirable 

for decisions to be made in the context of full 

information and clearly stated policies. 

Natural-resource planning is presently carried 
out to some degree by all levels of government. 

Federal and state agencies become most directly 

involved in resource planning in the management 

of government-owned land. For example, the U.S. 

Forest Service and Bureau of Land Management 

each plan for the use of significant parts of the 

nation's important natural resources. At the 

regional and local level, resource planning is more 

likely to be an integral part of general land-use 

planning. However, the nature of the planning 

process and requirements for ESI differ less with 

jurisdictional level than with the particular 

resource involved. 

Natural-resource planning is a prerequisite to 

development and administration of a resource 

management program. A natural-resource plan 

provides policies covering the basic question of 

whether or not particular resources should be 

developed or utilized. Such plans usually have 

three broad objectives: (1) Conservation of natural 

resources such as timber, water, agricultural land, 

and sand and gravel to provide a sustained yield 

for man's use, (2) preservation of areas with special 

scenic, scientific, ecological, and historical value, 

and (3) utilization of resources for the benefit of 

man. 

Natural-resource management programs deal 

more specifically with the rate of resource utilization, the impacts of resource development or 

extraction, and the means of conserving or 

preserving certain natural resources. Management programs provide the basis for review of 

specific proposals for resource extraction and for 

administration of regulations pertaining to resource utilization. 

Natural-resource planning requires an inventory of the resources of a planning area. Typically, 

resource areas are described, mapped, and classified according to resource potential. Special 

attention is given to areas with extractive resource 

potential or areas of special scenic, scientific, or 

cultural value. Policy recommendations are then 

developed to resolve possible conflicts between 

resource conservation and dev~lopment. 

The Natural Resources Plan produced by Bucks 

County, Pa., is an example of natural-resources 

planning appropriate to regional and local planning agencies. Phase I (1971) presented an 

inventory of natural resources, including prime 

agricultural soils, forests, wetlands, steep slopes, 

lakes and ponds, flood plains, extractive resources, 

scenic areas, and aquifers. In this phase, each 

16 

natural feature was defined, weighted, and computer mapped on a grid. Phase II (1972) ofthe plan set 

forth specific policies for the protection of each 

natural resource in terms of the percentage of each 

grid cell containing a particular natural resource 

that should remain in open-space use. The 

land-use consequences of carrying out the policies 

are depicted on the Nat ural Resource Protection 

Map, which shows prime agricultural lands, 

existing parks, scenic areas, and open space 

required for resource protection. 

The Bucks County planning effort was an 

integral part of a comprehensive land-use planning program. It is a particularly relevant 

example because the natural resources considered 

are those that occur to some extent in most local 

areas. The study and resulting plan respond 

primarily to concerns regarding resource preservation. As such, the Natural Resources Plan is an 

important contribution to open-space planning in 

Bucks County. 

Usually the economics of resource development 

is calculated on a fairly short-term basis. This 

tends to militate against the conservation of 

resources for the use of future generations and, in 

addition, creates conflicts when resource potentials overlap. For example, fine agricultural land 

in some areas overlies rich coal deposits. In the 

short term, the gain from development of the coal 

may exceed that from the productive use of the 

agricultural land. It is possible that the reverse 

would be true in the long term. Each use of land 

has its economic effects. Careful assessment of 

both long- and short-term economic costs and 

benefits are needed to develop sound resource 

policy. In addition, any effort to balance economic 

costs and benefits must consider both costs and 

benefits as they relate to different economic and 

social groups and jurisdictions. Only recently have 

operators been required to assume the external 

costs of extracting and processing natural resources. In the past, it was legally and politically 

acceptable for the costs of air, water, and noise 

pollution to be passed on to the owners and 

occupants of adjoining lands and downstream, 

downwind areas. 

Planning for the conservation and utilization of 

commonly occurring natural resources such as 

agricultural land, sand and gravel, timber, water 

resources, and scenic areas has been left primarily 

to regional and local agencies. Regional agencies 

can be particularly effective in carrying out 
regionwide inventories of natural resources, for 

areas of significant resource potential often transcend local political boundaries. In addition, the 

production of resource inventories is often beyond 

the financial and technical capabilities of local 

government. The inventories form a foundation for 

preparation of regional policies concerning resource conservation and development that provide 

a useful context for local planning efforts. The 

implementation of natural-resources plans, 

whether formulated by regional or local agencies, 

depends primarily on local government under the 

present allocation of governmental powers. The 

key implementation mechanisms are land use, 

land division, land-development regulations, and 

land acquisition. 

To assure that natural resources are utilized in a 

way that mini1nizes environmental damage requires a detailed resource management program. 

The National Environmental Policy Act of 1969 

and various state requirements provide a 

framework for regional and local consideration of 

the environmental impacts accompanying resource development and use. The regulation of the 

utilization process is a part of the administrative 

process of project review. It is possible, for 

example, to plan for sequential multiple use of an 

excavation site. Issuance of a permit to extract the 

resource can be conditioned on the developer's 

commitment to leave the site usable for another 

purpose once the resource has been exhausted (fig. 

9). For example, some exhausted sand and gravel 

pits can be used for sanitary landfills and later 

converted to open space and recreational uses with 

adequate planning and controls at the outset. 

Many states have passed legislation requiring the 

mine operator, after mining, to restore the land to 

a semblance of its original state. However, the 

responsibility for regulating resource development operations to prevent environmental degradation historically has rested primarily with local 

government. The effort frequently requires extensive and detailed ESI and agency capacity to 

review earth-science reports that may be highly 

technical. 

ENVIRONMENTAL AND ECONOMIC IMPACT 

Most decisions to develop natural resources are 

based on e·conomic judgments made by private 

FIGURE 9.-Strip-mined area in Washington after land reclamation. The area in the foreground has been mined, refilled, and 

recontoured. New topsoil was added and fertilized, and grass was planted. With proper planning, the long-term environmental effects of such operations can be minimized. (Source: Bureau of Outdoor Recreation, 1974.) 

17 
and, in some cases, public entities. This fact affects 

the degree and sequence of development. Those 

resources that can be obtained with the least cost, 

closest to the user, are usually developed first. For 

example, a community usually looks first to the 

most immediately available water source of 

adequate quality-ground or surface. If the initial 

source proves to be inadequate, cost considerations 

will be dominant in choosing among alternative 

means of assuring a firm supply-to impound, 

import, increase the level of treatment of the local 

source, or recycle. 

Judgments concerning the economics of resource development cannot be adequately made 

without thorough and accurate earth-science 

information. The cost of utilizing a given resource 

directly reflects natural conditions that must be 

understood. For example, information concerning 

geologic struct\}re, ground-water level, and soil 

depth is needed to estimate the cost of extracting 

coal from a given location. 

Adverse environmental effects often accompany 

the extraction and utilization of resources. The 

withdrawal of ground water may result in the 

subsidence ofland; the overcultivation of soil may 

destroy its fertility or contribute to its loss through 

erosion; strip mining sharply alters the surface of 

the land; leaks from offshore oil wells may destroy 

beaches, pollute the water, and kill marine life. 

There is some environmental cost to be borne with 

almost any resource use. Assessment of the 

environmental impacts associated with the utilization of a resource should be made prior to its 

extraction and balanced against the net economic 

gains. Where utilization is clearly desirable, a 

thorough assessment of environmental impacts 

can lead to proper actions to reduce environmental 

degradation to an acceptable level. 

PLANNING FOR REDUCTION OF NATURAL HAZARDS 

IDENTIFICATION OF HAZARDOUS AREAS 

The natural features of the earth are created by, 

and constantly altered by, natural processes. Some 

of these processes are potentially hazardous to 

man and his works. Man himself is an important 

hazard-creating agent. In fact, almost every 

natural hazard is aggravated by man's actions. 

Disturbance of the ground may increase storm 

run off and erosion and decrease slope stability. 

Subsidence of land is often directly attributable to 

acts of man. There is even evidence that the 

18 

injection of waste materials below the earth's 

surface near Denver, Colo., increased seismic 

activity in that area (Raleigh and others, 1972). 

Thus, not only is man acted upon by natural 

processes, he is also a prime agent in determining 

the course, speed, and nature of some processes. In 

this complex relationship, man and his activities 

must be viewed as part of the natural environment. 

Table 3 lists widespread natural processes that 

are hazardous to man and his works. In areas 

where these processes occur, the identification of 

the hazards and evaluation of the potential for risk 

from natural hazards is an important part of 

land-use planning. Once an area has been identified as hazardous, appropriate land-use designations can be made. Intensive land uses; high-rise 

buildings, hospitals, schools, or other institutions 

with involuntary occupancy; critical public 

facilities such as dams or highway overpasses; and 

major utility installations should be prohibited or 

located and designed so as to withstand the hazard 

in areas determined to have high risk. Such areas 

should be considered for open-space uses, such as 

as agriculture or recreation. 

IMPACTS OF HAZARD-MITIGATION METHODS 

There are four basic ways to reduce the risks 

associated with natural hazards. First, land use 

may be regulated to restrict man's use and 

occupancy of potentially hazardous areas. Flood 

plains and unstable slopes, for example, can be 

recommended for open space or very low intensity 

uses. Second, efforts can be made to control the 

hazardous processes. For example, channel improvements or holding ponds may be constructed 

to control floodwaters. And, since man is an agent 

in aggravating natural occurrences, regulation of 

how he treats the land can reduce risks. Third, 

measures can be taken not toward controlling the 

processes, but toward reducing their impact. Such 

measures inch.ide special foundation requirements 

and construction techniques for landslide-prone 

slopes, artificial recharge of ground water to 

prevent subsidence, or special structural safety 

standards for seismically active areas. Fourth, 

monitoring of natural processes may permit the 

development of warning systems to allow evacuation of hazardous areas when disaster appears 

imminent. This method is especially effective in 

reducing loss of life and property damage from 

flooding. 
TABLE 3.-Natural processes important to land-use planning 

Process Description of hazard 

Flooding ________ ____ Overtopping of river and stream banks 

Erosion and 

sedimentation. 

by water produced by sudden cloudbursts, prolonged rains, tropical 

storms or seasonal thaws; breakage 

or overtopping of dams; ponding or 

backing up of water because of inadequate drainage. 

Removal of soil and rock materials by 

surface water and depositing of these 

materials on flood plains and deltas. 

Landsliding ___ ___ __ Perceptible downslope movement of 

earth masses. 

Faulting------------ Relative displacement of adjacent rock 

masses along a major fracture in the 

earth's crust. 

Ground motion ______ Shaking of the ground caused by an 

earthquake. 

Subsidence---------- Sinking of the ground surface caused by 

compression or collapse of earth 

materials; common in areas with 

poorly compacted, organic, or collapsible soils and commonly caused by 

withdrawal of ground water, oil, or 

gas; or collapse over underground 

openings, such as mine workings or 

natural caverns. 

Expansive soils ______ Soils that swell when they absorb water 

and shrink when they dry out. 

High water table ____ Upper level of underground water close 

Seacliff retreat 

Beach 

destruction. 

Migration of 

sand dunes. 

to ground surface causing submergence of underground structures, 

such as septic tank systems, foundations, utility lines, and storage tanks. 

Recession of seacliffs by erosion and 

landsliding. 

Loss of beaches owing to erosion and 

(or) loss of sand supply. 

Wind-induced inland movement of sand 

accelerated by the disturbance of 

vegetative cover. 

Salt-water Subsurface migration of seawater inintrusion. land into areas from which freshwater has been withdrawn, contaminating freshwater supplies. 

Liquefaction ___ ___ __ Temporary change of certain soils to a 

fluid state, commonly from earthquake-induced ground motion causing the ground to flow or lose its 

strength. 

There is often a fortuitous overlapping of hazardous areas and areas suitable for open-space 

uses. For example, areas subject to flooding are 

often ide'al for water-related recreational uses, 

hiking trails, wildlife refuges, parking areas, or 

outdoor storage. Land-use planners can often 

achieve dual objectives of hazard mitigation and 

19 

open-space preservation by recommending nonin; 

tensive uses for such areas. 

Losses from some natural hazards can be reduced more readily than from others, but in most 

cases, the dollar savings from efforts to reduce 

losses are significant. Figure 10 shows the estimated total losses due to the five most costly 

natural hazards in California for the period 

1970-2000 under current hazard-reduction practices, the amount of loss reduction possible if the 

Ill 

a: 

ct 

...J 

22 

20 

18 

16 

14 

6 12 

0 

u.. 

0 

Ill 

15 10 

...J 

...J 

al 

8 

6 

4 

2 

Ill 

w 

u 

a: 

:::1 

0 

Ill 

w 

a: 

...1 

ct 

a: 

w 

z 

::1! 

EXPLANATION 

Total losses

-, 1970-2000, 

under current practices 

Loss reduction possible, 

1970-2000 

Cost of loss-reduction 

measures, 1970-2000 

FIGURE 10.-Estimated dollar losses from environmental 

problems that could be alleviated by the use of earthscience information and technology. Amounts that such 

losses could be reduced and the estimated cost of 

loss-reduction measures are also shown. (Modified slightly 

from State of California, 1973, p. 6). 
best of known practices were followed, and the cost 

of applying such measures. 

Man's ability to predict hazardous events varies 

considerably. For example, earth scientists can 

predict quite reliably where fault activity will 

occur but are less able to predict frequency or 

severity. Flooding, on the other hand, can be more 

exactly predicted with respect to location, severity, 

and statistical frequency, but the time of a flood 

cannot be determined very far in advance. 

The selection of approach or combination of approaches appropriate to each situation should be 

based on a careful weighing of environmental, 

social, and economic costs and benefits. Costs of 

controlling natural processes may be very high. 

All four ways of reducing risks have social, 

environmental, and economic effects that need to 

be balanced against the nature of the risk and the 

degree to which it can in fact be mitigated. 

MITIGATION METHODS A:'\D .\CCEPT/\BLE RISKS 

The development of public policy to deal with 

natural hazards and the appropriate allocation of 

public resources to mitigate them require an 

answer to the question uHow safe is safe enough?" 

Each individual may be able to answer this 

question for himself in any given circumstance, 

but planners and earth scientists share responsibility for providing a framework on which to base a 

communitywide response to the question (fig. 11). 

Several steps appear to be essential to the public 

process of judging acceptable levels of risk. First of 

all, the presence of a hazard must be recognized. 

Development frequently has proceeded without 

explicit recognition of the natural forces at play. 

Towns have been built on flood plains, on unstable 

hillsides, astride faults, and on subsiding ground. 

The results are well documented in accounts of 

many of our nation's worst natural disasters. 

Second, considerable effort may be required to 

characterize the hazard. It is important to know its 

likely severity and the frequency of its occurrence, 

as well as the physical and cultural characteristics 

of the area that may be affected. Third, the degree 

of risk must then be evaluated. This step should 

take into account what can be done to reduce the 

hazards and balance these possibilities against 

public costs and benefits. 

The accumulation and interpretation of detailed 

information as to the nature, severity, and 

frequency of the r~sk and as to the alternative 

responses to the hazard are necessary. Public 

20 

decisionmakers can then balance risk against the 

economic and environmental costs of mitigating 

risk to decide the level of risk acceptable to the 

community. 

INTEGRATION OF ESI 

IN THE PLANNING PROCESS 

LA;\;D-CAPABILITY STUDIES BASIC TO 

LAND-USE PLANNING 

In any area the existing natural features and 

processes present a range of advantages and 

disadvantages for different uses of land. It is well 

recognized that the natural characteristics of different parcels of land vary. Different uses of the 

land also have different physical requirements. 

For example, farmers seek fertile soils; manufacturers in heavy industry want level sites with good 

foundation conditions; golf course developers look 

for rolling terrain with adequate surface and 

subsurface soil conditions. An important part of 

land-use planning is matching land uses with the 

appropriate physical characteristics of the land. 

Evaluating the physical features of an area with 

regard to different types of land use is termed a 

((land-capability study." The natural features and 

processes considered usually include topography, 

hydrology, geology, soils, vegetation, climate, and 

ecology. Although this report emphasizes the 

earth-science factors (mainly geology, hydrology, 

and soils), the concepts and methods discussed are 

applicable to land-capability studies involving a 

full range of natural factors. 

Land-capability studies are a means of determining the relative physical merits of lands for a 

specified land use. However, such determination 

usually provides only a· part of the information 

needed to make land-use decisions. Economic, 

social, and political considerations are also essential. A parcel of land may have a low physical 

capability for supporting intensive use, but other 

factors, such as location and accessibility, land 

cost, absence of alternative lands, and overriding 

public need, may well indicate that it should be 

intensively developed. In this report, a study that 

considers economic, social, and political factors in 

addition to land-capability factors is called a ((land 

suitability study." 1 Thus, land-capability studies 

may be undertaken as part of a broader landsuitability study. 

'The terms "capahil ity" and "suitability" are often used without precise definition 

and are sometimes used interchangl'ably. 
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"TU£ 8AYLANO~ OF SANTA Cf..AQ"' 

FIGURE 11.-A risk-zone map that provided important information for the preparation of the Santa Clara County (Calif.) Policy Plan for the Bay lands (Planning Policy 

Committee of Santa Clara County, 1972). The map represents an explicit attempt to evaluate risk from natural processes as an integral part of land-use planning. 

The risk is lowest in zone A and highest in zone D. The subscripts indicate the nature ofthe risk (see legend at lower left; Woodward-Clyde and others, 1970, part II, 

fig. 4). 
Many different methods are employed in making land-capability studies. A study may be 

largely descriptive, stating in narrative form 

information concerning the natural features and 

processes relevant to a particular land use. Such 

descriptive analyses are often used when the 

capability of a given site or alternative sites for 

a specific use are being considered. A landcapability study may also involve a fairly sophisticated effort to quantify, weight, and aggregate the 

earth-science information relevant to specific uses 

for all lands within a planning area. Regional 

land-use planning agencies and those with computers for data processing are most likely to 

undertake such studies. 

An example of a land-capability study integrated within a land-suitability study is contain'ed 

in the report prepared by the consulting firm 

Livingston and Blayney (1971) for Palo Alto, Calif. 

Although the study is properly termed a landsuitability study, it provides a good example.ofthe 

general methods employed in land-capability 

studies. Material adapted from the report i& used 

below to illustrate each of the following five basic 

steps usually involved in a land-capability study: 

1. Identify the types of land use for which land 

capability is to be determined.-In the Palo 

Alto study, land uses range from low-density 

residential to industrial. In formulating a 

land-use plan, the capability of the lands 

within the planning area for the reasonable 

alternative types ofland use would need to b~ 

evaluated. 

2. Determine the natural factors having a significant effect on the capability of the land to 

accommodate each use.-The choice of factors 

depends on the physical requirements of the 

land use under consideration. In the Palo Alto 

suitability study, 23 factors were selected and 

categorized2 as geologic and soils factors (10 

factors), ecologic factors (4 factors), visual 

and recreation factors (4 factors), and planning and market factors (5 factors). Most of 

the capability factors involving earth-science 

information were included in the first category, geologic and soils factors. These 10 

factors were average slope, San Andreas fault 

zone, other fault zones, landslides, natural 

slope stability, cut slope stability, excavation 

2 For purposes of illustration, the factor "average slope" was moved from the 

"planning and market" category in the original study to the "geologic and soils'' 

category, since slope is a major determinant of land capability. 

22 

difficulty, soil suitability as fill, soil erosion, 

and soil expansion. 

3. Develop a scale of values for rating each natural 

factor in relation to its effect on land 

capability.-Two operations are involved in 

this step. First, the relevant range of conditions of each factor is determined. The 

expression of this range may be cuite precise, 

as for average slope (table 4), or very general, 

as in the poor, fair, and good ratir~s shown for 

several factors on the table. T!"'e degree of 

precision depends on the degree C'frefinement 

needed (or possible, given the level of detail of 

data available) to make judgments regarding 

land capability for the selected use. 

Second, a scale of values is established to 

quantify the different condition~:· within each 

factor. In the example from tl"~ Palo Alto 

study, the significant differenceF within each 

factor were rated on a scale of1-E (column 2 of 

table 4). 

4. Assign a weight to each natural factor indicating its importance relative to the other factors 

as a determinant of land capability.-In the 

Palo Alto example, each factor was given a 

weight ranging from 1 to a possible 10 

(column 3 of table 4). The weight represents a 

judgment of the relative importance of each 

factor for Hdevelopment." 

5. Establish land units, rate each land unit for each 

TABLE 4.-Rating system for land-capability factors 

[Source: Adapted from Livingston and Blayney and otherr,, 1971, p. 59--65] 

Geologic and soils factors 

2 

Rating 

Average slope: 

Over 50 percent._. _ . 1 } 31-50 percent_ ______ _ 16-30 percent. _____ . ____ .. ___ _ 

~15 percent.. ______ .. __ ... __ _ 

San Andreas fault zone: Within zone __________ .. Not within zone _______________ _ 

Landslides: Within slide area ___________ _ Not within slide area _____ .. __ _ 

Natural slope stability: Poor ______________ _ 

Fair ________________ ------

Good--------------------------

~ } 

~ } 

Cut-slope stability: Poor __ ___________ ______ __ __ __ ~1 } 

Fair ------------------- _____ ---

Good------------------ ------- Soil suitability as fill: Poor ___ ------------------ --- Fair ______________ . ________ _ Good ______________________ _ ! } Soil erosion: 

Severe _____ . ---. - . ---- . ------ 5

1 } Moderate ___________ . ___ . ____ _ 

Soil expansion: High ______________________ --

Modt>rate _____________________ _ 

Low -------------------------- ~ } 

3 

Weight 

LO 

6 

5 

4 

6 

3 

4 

We1ghted 

rating 

{ 20 10 

40 

50 

{ 7 

35 

{ 6 

30 

{ 5 

15 

25 

{ 1~ 20 

{ 2 

6 

10 

{ 6 

30 

{ 3 

9 

15 
factor, calculate the weighted ratings for each 

factor, and aggregate the weighted ratings for 

each land unit.-This step involves the 

application of the rating system developed in 

the previous steps to the land under consideration. The study area is divided into land 

units for evaluation. The size and configuration of the land units depends on the diversity 

of physical conditions within the study area, 

the physical requirements for the land use 

under consideration, and the kind ofland-use 

policy needed. The Palo Alto study area was 

divided by a grid into 330 cells each of 20 

acres. Each cell was evaluated and rated for 

each factor (that is, was assigned a number 

from column 2 on table 4). The rating for each 

factor was multiplied by the weight assigned 

to the factor in column 3 of table 4 to yield the 

weighted rating as shown in column 4. The 

weighted ratings for all factors were then 

added for each cell. The total is a score 

reflecting the capability of the cell for the 

selected land use. 

In the Palo Alto study, the weighted ratings for 

the other suitability factors were added to those for 

capability factors shown on the table to produce 

the total score for each cell. The range of possible 

total scores for each category of factors was 

planning and market factors, 19--95; ecological 

factors, 18-90; visual and recreational factors, 

11-55; and geologic and soils factors, 4g_:.240. It is 

clear that the capability factors related to earth 

science are very important in the determination of 

land suitability. The total scores for all factors 

ranged from 96 to 480. These scores were divided 

into six groups and mapped as shown in figure 12. 

Land-capability studies such as the one described above are increasingly important to 

land-use planning at all governmental levels. 

They assure that physical characteristics of the 

land will be given systematic consideration in the 

development of plans and policies. The earthscience information requirements for such studies 

vary with the total land area and the specific use to 

be studied. At the regional level, for example, 

fairly generalized data may be appropriate for an 

analysis of land capability for open space. On the 

other hand, a study undertaken, at any governmental level, to locate a specific site with a high 

capability for use as a sanitary landfill will require 

detailed information. 

In most cases, the land-capability analysis 

provides only part of the information needed for 

land-use decisions, but on occasion capability 

factors are, or should be, determining. The studies 

can be useful in eliminating areas with very low 

capability for a particular use from further 

consideration and allow the planner to focus 

attention on more realistic options. 

INTERDISCIPLINARY RELATIONSHIPS 

Integrating man's works and activities with his 

natural environment is an objective generally 

shared by planners and earth scientists. To 

effectively attain this objective requires the 

contributions of both professions, and since it is 

unreasonable to expect either planner or earth 

scientist to become proficient in the other's area of 

expertise, the establishment of a cooperative 

working relationship is a prerequisite for a 

successful program. 

There are, however, several obstacles to the 

establishment of such relationships arising from 

three factors, the education, working environment, and terminology of each profession. First, 

planners are generalists by education and are 

taught to draw information from a wide variety of 

subjects including architecture, engineering, 

landscape design, economics, sociology, public 

administration, and political science. Yet planning curriculums frequently offer little or no 

exposure to the earth sciences. Earth scientists, 

although conversant with related scientific fields, 

typically are not required to draw on the extensive 

range of subject matter normally dealt with by 

planners. 

23 

Second, a professional career is normally pursued within an institutional framework that 

limits opportunities for interdisciplinary effort. In 

addition, professional adva.ncement in both fields 

usually requires an ever-increasing degree of 

specialization. Since specialists may be reluctant 

to tread on each other's professional territory, 

interdisciplinary contact is even further inhibited. 

Perhaps more important .is the fact that, until 

recently, the earth scientist has not regarded the 

planner as a ucustomer" for his product. In turn, 

the planner has not recognized the need for ESI in 

land-use planning. Until fairly recently, natural 

resources were conside:red inexhaustible, the 

effects of natural hazards were viewed as uacts of 

God," and governmental bodies tended to place the 

rights of the private property owner above those of 

the puolic at large. Under these circumstances, 
Suitability for 

Development 

Ratings 

• MOST SUITABLE 

(340-480) 

Ill 2ND MOST SUITABLE 

(315-339) 

=::::~ 3RD MOST SUITABLE 

(295-314) 

[ill 4TH MOST SUITABLE 

(275-294) 

[I] 5TH MOST SUITABLE 

(255-274) 

D LEAST SUITABLE 

(94-254) 

N 

cr z,ooo· 

-- FIGURE 12.-Land-suitability map of part of Palo Alto, Calif., prepared by Livingston and Blayney and others (1971). 

24 
economic and political considerations easily become the primary determinants of land use. Only 

with acceptance by public agencies of some 

responsibility for resource conservation and mitigation of dangers and damages from natural 

hazards has the planner needed ESI. The need for 

interdisciplinary efforts is being recognized by 

both f>rofessions. 

Another working-environment problem arises 

from the fact that planning is a public undertaking 

usually culminating in decisions made by political 

bodies. The planner's role in the political process 

requires the ability and willingness to respond to 

the needs of conflicting interests of different 

segments of a community. The earth scientist's 

work is usually evaluated by fellow earth scientists according to §Cientific standards of truth. He 

is often uncomfortable when faced with the reality 

of political compromise and dismayed when a 

recommendation supported by exacting earthscience analysis is rejected by decisionmakers on 

political, social, or economic grounds. 

The third obstacle to establishing interdisciplinary relationships is that each profession has its 

own jargon, which, though it may facilitate 

exchange of ideas within the profession, tends to 

inhibit communication with outsiders. Earth 

scientists employ a technical vocabulary that 

includes many words not in common usage. Even 

with a glossary, it is difficult for a person who is not 

an earth scientist to read and understand a report 

prepared for a professional audience of earth 

scientists. Planners, on the other hand, lack 

precision and consistency in their use of terms. 

They frequently use everyday words in specialized 

senses or borrow terms from other disciplines, 

altering their definitions. 

Planners and earth scientists will find, however, 

that many of these problems will diminish rapidly 

once they are working together. With a little effort 

on both sides, they will find that their effectiveness 

in solving common problems and achieving common objectives greatly increases. The planner who 

joins the earth scientist in the field gains a new 

perspective not only of the natural characteristics 

of his planning area but also the application of the 

earth scientist's wort\.. The earth scientist, similarly, gains insight into the nature and perspectives of planning. The result can be a creative 

synthesis in which innovative interpretations and 

appli<;ations ofESI are much more likely to occur. 

A variety of arrangements permit the earth 

25 

scientist and planner to work together directly. 

For the most part, the responsibility for eftablishing such arrangements rests with the ]and-use 

planning agency. With the growing awareness of 

environmental problems, all land-use p 1anning 

agencies have some need for earth-scienc~ expertise. Some may require a full-time staff person; 

others may find that part-time or consultant 

services will suffice. However, for large agencies 

involved with varied and complex enviroTimental 

problems, the addition of an earth scientiqt to the 

planning staff may prove valuable. 

The presence of an earth scientist on the 

planning staff encourages the consider~tion of 

earth science in all phases of the planning process. 

The staff earth scientist would typically perform 

the following functions: Help develop and carry 

out a realistic data-acquisition and interpretation 

program, including advising on costs and 

priorities; assist in the determination and evaluation of land capabilities; help formulate p'.q,ns and 

policy regarding such topics as geologic hazards 

and mineral and water resources; urqertake 

detailed studies of particular development issues, 

such as the impact of urbanization OTt water 

pollution or the geologic stability ofhillsicle areas; 

assist in the formulation and administration of 

land-use regulations, such as subdivision. zoning, 

grading, and erosion-sediment control ord~nances; 

make field checks in connection with particular 

projects and prepare and (or) review soils reports, 

geologic reports, and environmental impact assessments prior to development approval; assist in 

presenting technical information direct]~, to decisionmakers to facilitate evaluation of alternatives, prepare slides, models, or other graphic 

materials for these purposes, and respond directly 

to questions arising from the presentation; advise 

when additional earth-science expertise i~ needed 

and know where and how to obtain it. 

While few planning agencies intervie,..,ed during the course of this study employed a pe ... manent 

earth scientist on the staff, considerable benefits 

were derived in those cases where planners 

established a close working relationsl'ip with 

earth scientists outside the agency. For example, 

in many areas, earth scientists are in frequent 

contact with planning agencies and perform a 

number of-the functions discussed above. In many 

areas, private consultants and universi~y scientists, on a contractual or informal basis- provide 

similar services. 
PUBLIC PARTICIPATION 

As a governmental function, planning is inextricably bound to the political process. Land-use 

decisions have a strong influence oh 'the qu.ality of 

life. Whether or not a freeway is constructed, a new 

shopping center approved, or land zoned for open 

space is of concern to the whole community as well 

as to the property owners and residents whose land 

is directly involved. Land-use decisions affect 

different segments of the community in different 

ways and are commonly the subject of much 

controversy, for it is through the political process 

that conflicting interests and differences of opinion 

are resolved. Effective resolution' requires the 

informed participation of all segments of the · 

community at all stages in the planning process. 

The professional planner may serve solely as a 

technical advisor to the decisionmakers or may be 

a more active advocate with respect to planning 

proposals or particular issues. The planner, however, rarely makes the decisions; this is the 

function of elected public officials. Even though 

the planner's information may be complete and 

accurate and his logic impeccable, there is no 

guarantee that his advice will be taken. 

Both the earth scientist and the planner need to 

be aware that providing accurate and wellinterpreted ESI for use in the planning process is 

only a first step. To assure that ESI will influence 

actual decisions requires public understanding of 

the issues. It is encouraging that in recent years 

much of the impetus for the use ofESI in planning 

has come from citizen groups concerned about 

environmental quality. 

CONCLUSION 

It is a human tendency to assume that the land 

upon which we live, work, and play is one 

permanent aspect of an otherwise constantly 

changing world. Yet the land itself undergoes 

continuous alteration as a result of natural 

processes and the actions of man. This report 

points to the importance of reconciling man's use of 

the land with its natural characteristics. Implementation of land-use plans formulated with 

full awareness of natural features and processes is 

the key to achieving such reconciliation. 

The state-of-the-art in applying earth-science 

information to land-use planning and decisionmaking is currently undergoing rapid evolution. 

In the last few years, agencies producing ESI have 

dramatically increased efforts to provide data 

26 

specifically for land-use planning. r:'he new information is just now becoming widely available to 

planners, and it is too early to evaluate in detail its 

impact on land-use plans and decisi9ns. Certainly 

the impact will be great. In most metropolitan 

areas the need to preserve open space, protect 

natural resources, and maintain high standards of 

environmental quality often conf~~ts with the 

need to expand employment opportunities, the 

housing stock, and the tax base. Land-use planners are faced with resolving l: :t1sic land-use 

conflicts with what is now recognized as a finite 

supply of land. The decisions are becoming 

increasingly important and subject to controversy. 

In this context, the planner will seek out and use 

all relevant information, including ESI. 

Studies of land capability are becoming much 

more common and serve to formaliz~ the consideration of natural factors in land-use planning. ESI 

is increasingly translated into quartitative terms 

allowing aggregation of data relevant to a particular site or area. Quantification and weighting of 

physical factors is becoming an imp'lrtant feature 

of capability studies, especially in agencies with 

computer data-processing capacity. 

Although the guidelines presenter.! here are very 

general, they provide a framework for the effective 

utilization of ESI in land-use planning. However, 

no single set of guidelines can possil'ly include the 

wide range of conditions and problems encompassed by the fields of planning and the earth sciences. 

The essential point, however, is the need to foster 

an institutional, legal, and political climate 

favorable to full and effective interplay between 

planners and earth scientists on the one hand and 

professionals and public decisionmakers on the 

other. Ultimately, it is the public, through its 

representatives, who must assume the responsibility for considering long-term as wel1 as short-term 

social, economic, and political impacts from the 

land-use decisions made today. 

REFERENCES CITEI' 

Barnwell, W. W., George, R. S. Dearborn, L. L., and others, 

1972, Water for Anchorage: Anchora,?e, Alaska, U.S. 

Geological Survey, in cooperation with the City of 

Anchorage, 77 p. 

Brabb, E. E., Pampeyan, E. H., and Bonilla, M. G., 1972, 

Landslide suscepti\>ility in San Mateo County, California: 

U.S. Geol. Survey Misc. Field Studies Map MF-350, scale 

1:62,500. 

Citizens' Advisory Committee on Environmer+.al Quality, Task 

Force on Land Use and Urban Growth, 1973, The use of 
lands-a citizens' policy guide to urban growth: New York, 

Thomas Y. Crowell, 304 p. 

Dibblee, T. W., 1966, Geologic map and sections of the Palo Alto 

15-minute quadrangle, California: Calif. Div. Mines and 

Geology, map sheet 8, scale 1:62,500. 

Jennings, C. W., and Burnett, J. L., 1961, Geologic map of 

California, Olaf P. Jenkins edition, San Francisco sheet: 

Calif. Div. Mines and Geology, scale 1:250,000. 

Legget; R. F., 1973, Cities and geology: New York, McGrawHill, 552 p. 

Livingston and Blayney and others, 1971, Environmental 

design study-open space vs. development, final report to 

the City of Palo Alto: Palo Alto, Calif., 190 p. 

Pampeyan, E. H., 1970, Geologic map of the Palo Alto 7Yz 

minute quadrangle, San Mateo and Santa Clara Counties, 

Calif: U.S. Geol. Survey open-file map,. scale 1:24,000. 

Planning Policy Committee of Santa Clara County, 1972, A 

policy plan for the bay lands of Santa Clara Co.: County of 

Santa Clara Planning Dept., San Jose, Calif., 76 p. 

Raleigh, C. B., Healy, J. H., and Bredehoeft, J. D., 1972, 

Faulting and crustal stress at Rangely, Colo: Geophys. 

Mon. Ser., v. 16, p. 275-284. 

Rogers, T. H., and Armstrong, C. F., 1973, Relative geologic 

stability map, Montebello Ridge study area: Calif. Div. 

Mines and Geology. 

Spangle, William and Associates, Leighton, F. B., and 

Associates, and Baxter, McDonald and Company, 1973, 

Application of earth science information in land-use 

planning-preliminary technical report: U.S. Dept. Housing and Urban Development and U.S. Dept. Interior, 330 

p.; available from the Natl. Tech. Inf. Service, U.S. Dept. 

Commerce, Springfield, Va., NTIS PB-238-081/AS. 

State of California, 1973, Urban geology master plan for 

California: Calif. Div. Mines and Geology Bull. 198, 112 p. 

---1974, Special Studies Zones delineated in compliance 

with Ch. 7.5, Div. 2, Calif. Pub. Resources Code, Woodside 

quadrangle, official map: scale 1:24,000. 

Woodward-Clyde and Associates, and McClure and Messinger, 

1970, Geology and structural engineering: Prepared for 

the Baylands Subcommittee of the Planning Policy 

Committee of Santa Clara County, Part 1, 48 p,; Part II, 

74 p. 

SELECTED READINGS 

American Society of Planning Officials, Planning Advisory 

Service, 1970, Environmental planning-A selected annotated bibliography: Chicago, Report No. 264, Prepared by 

Michael J. Meshenberg, 79 p. 

An excellent bibliography of books, reports, and articles 

published through 1970 listed under 15 subject categories 

covering a wide range of environmental issues. Emphasis 

on reports and plans of public agencies. No indexes. 

Bair, F. H., Jr., 1970, Planning cities-selected writings on 

principles and practice: Chicago, Am. Soc. Planning 

Officials, 491 p. 

A wide-ranging review and discussion of planning 

practice drawn from the writings of a planner with 30 years 

of experience. 

Belknap, R. K., and Furtado, J. G., 1967, Three approaches to 

environmental resource analysis: Washington, D.C., Conserv. Found., 103 p. 

27 

A discussion and evaluation of the theories ar.d methods 

of resource analysis developed and employed by Ian L. 

McHarg, G. Angus Hills, and Philip H. Lewis, Jr. 

Bestor, G. C., and Jones, H. R., 1972, City planning 

bibliography [3d ed.]: New York, Am. Soc. Civil Engineers, 

518 p. 

An annotated bibliography of over 1,800 pt,blications 

relating to city and regional planning. 

Bosselman, Fred, and Callies, David, 1971, The quiet revolution in land use control: Council on Envi-onmental 

Quality, 327 p. 

A .discussion of evolving new techniques of land-use 

regulation, primarily at the state and regknal level. 

Reviews in detail specific examples. 

Branch, M. C., 1970, Comprehensive urban phoning, a 

selective annotated bibliography with related materials: 

Beverly Hills, Calif., Sage Publications, 480 p. 

A list of 1,500 titles on virtually all aspects of planning, 

indexed by subject, author, and title; provides a table of 

contents or brief description of each publicatio~. 

Citizens' Advisory Committee on Environmental Qu~ility, Task 

Force on Land Use and Urban Growth, 1973, The use of 

land-a citizens' policy guide to urban growth: New York, 

Thomas Y. Crowell, 304 p. 

A discussion of evolving new techniques of land-use 

regulation, primarily at the state and regional level. 

Reviews in detail specific examples. 

Detwyler, T. R., and Marcus, M. G., and oth,~rs, 1972, 

Urbanization and environment-The geograrhy of the 

city: Belmont, Calif., Duxbury Press, 277 p. 

A collection of articles on the influence of physical 

geographic factors on urban location and de,·~lopment. 

Geology, climate, water, soil, natural hazards, noise, and 

vegetation are among the topics discussed. 

Flawn, P. T., 1970, Environmental geology-Conservation, 

land-use planning, and resource management: New York, 

Harper & Row, 311 p. 

A basic reference work on geology, soils, and hydrology 

for planners and others who are not earth scientio;.,ts but are 

concerned with land-use planning and develop~ent. 

Legget, R. F., 1973, Cities and geology: New York. McGrawHill, 552 p., references, indexes. 

Discussion by a geologist of the planning impHcations of 

geology with extensive use of examples drawn from all over 

the world and many periods of history. 

McHarg, I. L., 1969, Design with nature: Garden City, N.Y., 

Nat ural History Press, 197 p. 

Well-illustrated book presenting a comb~nation of 

theory, philosophy, and case studies of planning projects 

illustrating the application of the theories and techniques 

of considering natural features and processes i..,. land-use 

planning. 

Nichols, D. R., and Campbell, C. C., eds., 1970, Envi-onmental 

planning and geology: U.S. Dept. Housing and Urban 

Devel. and U.S. Dept. Interior, 204 p. 

A collection of papers describing planning problems 

posed by geologic conditions, the responsibility of various 

governmental levels for solving the problems, and examples of planning approaches to the solution of the problems. 

U.S. Department ofthe Interior, Bureau of Land Management, 

1968, Where not to build, A guide for open space planning: 

Tech. Bull. No. 1, 96 p. 
A general discussion of the concept and functions of open 

space including an open-space classification system and 

standaJ1ls as well as suggestions concerning means of 

implementing open-space plans. The concepts are illustrated by a case study of open space in Washington Co., 

Utah. 

28 

Way, Douglas, 1973, Terrain analysis-A guide to site 

selection using aerial photographic interpretation: 

Stroudsburg, Pa., Dowden, Hutchinson, & Roo;.s, Inc., 356 

p., glossary, appendixes, index. 

A well-illustrated reference work describing the 

techniques of aerial photographic interpreta~ion of land 

features for application in site-development rlanning. 

*U.S. GOVERNMENT PRINTING OFFICE: 1981- J.*1-6l·V155