(ChLRJIS 4
Hazard Identification, Assessment,
and Mapping
             Hazard Analysis                        activities as well as much geologic information.
                                                    In addition, the availability of many types of
Recognition of the presence of active or poten-
                                                    aerial imagery (satellite, infrared, radar, etc.)
tial slope movement, and of the types and
                                                    make this a very versatile technique.
causes of the movement, is essential to land-
slide mitigation. Recognition depends on an
                                                          Analysis of Acoustic Imagery
accurate evaluation of the geology, hydrogeol-
                                                                  and Profiles*
ogy, landforms, and interrelated factors such as
                                                    Profiles of lake beds, river bottoms, and the sea
environmental conditions and human activi-
                                                    floor can be obtained using acoustic techniques
ties. Only trained professionals should conduct
                                                    such as side-scan sonar and subbottom seismic
such evaluations. However, because local gov-
                                                    profiling. Surveying of controlled grids, with
ernments may need to contract for such ser-
                                                    accurate navigation, can yield three-dimension-
vices, they should be aware of the techniques
                                                    al perspectives of subaqueous geologic phenom-
available and their advantages and limitations.
                                                    ena. Modern, high resolution techniques are
     Techniques for recognizing the presence or
                                                    used routinely in offshore shelf areas to map
potential development of landslides include:
                                                    geologic hazards for offshore engineering.
     * map analysis
                                                    Surveying and mapping standards for outer
     * analysis of aerial photography and
                                                    continental shelf regions are regulated by the
         imagery
                                                    U.S. Minerals Management Service.
     * analysis of acoustic imagery and profiles
     * field reconnaissance
                                                               Field Reconnaissance
     * aerial reconnaissance
                                                    Many of the more subtle signs of slope move-
     * drilling
                                                    ment cannot be identified on maps or photo-
     * acoustic imaging and profiling
                                                    graphs. Indeed, if an area is heavily forested or
     * geophysical studies
                                                    has been urbanized, even major features may
     * computerized landslide terrain analysis
                                                    not be evident. Furthermore, landslide features
     * instrumentation
                                                    change over time on an active slide. Thus, field
                                                    reconnaissance is necessary to verify or detect
                Map Analysis
                                                    many landslide features.
Map analysis is usually one of the first steps in
a landslide investigation. Maps that can be
                                                              Aerial Reconnaissance
used include geologic, topographic, soils, and
                                                    Low-level flights in helicopters or small air-
geomorphic. Using knowledge of geologic mat-
                                                    craft can be used to obtain a rapid and direct
erials and processes, a trained person can ob-
                                                    overview of a site.
tain a general idea of landslide susceptibility
from such maps.
                                                                        Drilling
                                                    At most sites, drilling is necessary to determine
     Analysis of Aerial Photography
                                                    the type of earth materials involved in the slide,
              and Imagery
                                                    the depth to the slip surface and thus the thick-
The analysis of aerial photography is a quick
                                                    ness and geometry of the landslide mass, the
and valuable technique for identifying land-
                                                    water-table level, and the degree of disruption
slides, because it provides a three-dimensional
                                                    *By D.B. Prior
overview of the terrain and indicates human

20
of the landslide materials. It can also provide           Anticipating the Landslide
samples for age-dating and testing the engin-
                                                                    Hazard
eering properties of landslide materials. Fin-
                                                     One of the guiding principles of geology is that
ally, drilling is needed for installation of some
                                                    the past is the key to the future. In evaluating
monitoring instruments and hydrologic obser-
                                                    landslide hazards this means that future slope
vation wells.
                                                    failures will probably occur as a result of the
            Geophysical Studies                     same geologic, geomorphic, and hydrologic
                                                    situations that led to past and present failures.
Geophysical techniques (the study of changes
                                                    Based on this assumption, it is possible to
in the earth's gravitational and electrical
                                                    estimate the types, frequency of occurrence,
fields, or measurement of induced seismic be-
                                                    extent, and consequences of slope failures that
havior) can be used to determine some subsur-
                                                    may occur in the future. However, the absence
face characteristics such as the depth to bed-
                                                    of past events in a specific area does not pre-
rock, zones of saturation, and sometimes the
                                                    clude future failures. Man-induced conditions
ground-water table. It can also be used to de-
                                                    such as changes in the natural topography or
termine the degree of consolidation of subsur-
                                                    hydrologic conditions can create or increase an
face materials and the geometry of the units
                                                    area's susceptibility to slope failure (Varnes
involved. In most instances these methods can
                                                    and the International Association of Engin-
best be used to supplement drilling informa-
                                                    eering Geology, 1984).
tion. Monitoring of natural acoustic emissions
                                                         In order to predict landslide hazards in an
from moving soil or rock has also been used in
                                                    area, the conditions and processes that pro-
landslide studies.
                                                    mote instability must be identified and their
    Computerized Landslide Terrain                  relative contributions to slope failure estimat-
              Analysis                              ed, if possible. Useful conclusions concerning
                                                    increased probability of landsliding can be
In recent years computer modeling of land-
                                                    drawn by combining geological analyses with
slides has been used to determine the volume
                                                    knowledge of short- and long-term meteor-
of landslide masses and changes in surface
                                                    ological conditions. Current technology enables
expression and cross section over time. This
                                                    persons monitoring earth movements to define
information is useful in calculating the poten-
                                                    those areas most susceptible to liandsliding and
tial for stream blockage, cost of landslide
                                                    to issue "alerts" covering time spans of hours to
removal (based on volume), and type and mech-
                                                    days when meteorological conditions known to
anism of movement. Very promising methods
                                                    increase or initiate certain types of landslides
are being developed utilizing digital elevation
                                                    occur. Alerts covering longer periods of time
models (DEMs) to evaluate areas quickly for
                                                    become proportionately less reliable.
their susceptibility to landslide/debris-flow
events (Filson, 1987; Ellen and Mark, 1988).
                                                           Translation of Technical
Computers are also being used to perform
complex stability analyses. Software programs
                                                            Information to Users
for these studies are readily available for per-
                                                    According to Kockelman (personal comnmunica-
sonal computers.
                                                    tion, 1989), the successful translation of nat-
                                                    ural hazard information for nontechnical users
               Instrumentation
                                                    conveys the following three elements in one
Sophisticated methods such as electronic
                                                    form or another:
distance measuring (EDM); instruments such
                                                         (1) likelihood of the occurrence of an event
as inclinometers, extensometers, strain meters,
                                                             of a size and location that would cause
tiltmeters, and piezometers; and simple tech-
                                                             casualties, damage, or disruption;
niques such as establishing control points
                                                         (2) location and extent of the efflects of the
using stakes can all be used to determine the
                                                             event on the ground, structures, or
mechanics of landslide movement and to warn
                                                            socioeconomic activity;
against impending slope failure.

                                                                                                     21
                                                       geologic units or environments in which addi-
      (3) estimated severity of the effects on the
          ground, structures, or socioeconomic         tional movements are most likely. Such map-
                                                       ping relies heavily on photogeology (the geolog-
          activity.
      These elements are needed because usu-           ic interpretation of aerial photography),
ally engineers, planners, and decision makers          reconnaissance field mapping, and the collec-
will not be concerned with a potential hazard if       tion and synthesis of all available pertinent
its likelihood is rare, its location is unknown,       geologic data (Leighton, 1976).
or its severity is slight.                                  Regional maps are most often prepared at
      Unfortunately, these three pieces of infor-      a scale of 1:24,000, because high-quality U.S.
mation can come in different forms with many           Geological Survey topographic base maps at
                                                       this scale are widely available, and aerial
different names, some quantitative and pre-
cise, others qualitative and general. For a pro-       photos are commonly of a comparable scale.
duct to qualify as "translated" hazard inform-         Other scales commonly used include 1:50,000
ation, the nontechnical user must be able to           (county series), 1:100,000 (30 x 60 minute
perceive likelihood, location, and severity of the     series), and 1:250,000 (1 x 2 degree series).
hazard so that he or she becomes aware of the
                                                              Community-Level Mapping
danger, can convey the risk to others, and can
use the translated information directly in a           Community-level mapping identifies both the
reduction technique.                                   three-dimensional limits of landslides and
      Maps are a useful and convenient tool for        their causes. Guidance concerning land use,
presenting information on landslide hazards.           zoning, and building, as well as recommenda-
They can present many kinds and combina-               tions for future site-specific investigations, are
tions of information at different levels of detail.    also made at this stage. Investigations should
Hazard maps used in conjunction with                   include subsurface exploratory work in order to
land-use maps are a valuable planning tool.            produce a large-scale map with cross sections
Leighton (1976) suggests a three-stage appro-          (Leighton, 1976). Map scales at this level vary
ach to landslide hazard mapping. The first             from 1:1,000 to 1:10,000.
stage is regional or reconnaissance mapping,
                                                                  Site-Specific Mapping
which synthesizes available data and identifies
general problem areas. This small-scale map-           Site-specific mapping is concerned with the
ping is usually performed by a state or federal        identification, analysis, and solution of actual
geological survey. The next stage is commun-           site-specific problems. It is usually undertaken
ity-level mapping, a more detailed surface and         by private consultants for landowners who
subsurface mapping program in complex pro-             propose site development and typically involves
blem areas. Finally, detailed site-specific            a detailed drilling program with downhole
                                                       logging, sampling, and laboratory analysis in
large-scale maps are prepared. If resources are
                                                       order to procure the necessary information for
limited, it may be more prudent to bypass re-
gional mapping and concentrate on a few                design and construction (Leighton, 1976). Map
known areas of concern.                                scales vary, but are usually not larger than one
                                                       inch equal to 50 feet.
              Regional Mapping
                                                                      Types of Maps
Regional or reconnaissance mapping supplies
                                                       The three types of landslide maps most useful
basic data for regional planning, for conducting
more detailed studies at the community and             to planners and the general public are (1)
                                                       landslide inventories, (2) landslide suscepti-
site-specific levels, and for setting priorities for
                                                       bility maps, and (3) landslide hazard maps.
future mapping.
     These maps are usually simple inventory
                                                       Landslide inventories
maps and are directed primarily toward the
                                                       Inventories identify areas that appear to have
identification and delineation of regional land-
                                                       failed by landslide processes, including debris
slide problem areas and the conditions under
                                                       flows and cut-and-fill failures. The level of
which they occur. They concentrate on those

22
                                                    with selective field checking to detect landslide
detail of these maps ranges from simple recon-
                                                    areas, and then presenting the information in
naissance inventories that only delineate broad
                                                    map form using a coded format. The maps
areas where landsliding appears to have
                                                    show any or all of the following: state of activi-
occurred (Figure 20) to complex inventories
                                                    ty, certainty of identification, dominant types of
that depict and classify each landslide and
                                                    slope movement, estimated thickness of slide
show scarps, zones of depletion and accumu-
                                                    material, and dates or periods of activity.
lation, active versus inactive slides, geological
age, rate of movement, and other pertinent
                                                    Landslide susceptibility maps
data on depth and kind of materials involved in
                                                    A landslide susceptibility map goes beyond an
sliding (U.S. Geological Survey, 1982; Brabb,
                                                    inventory map and depicts areas that have the
1984b) (Figure 21).
                                                    potential for landsliding (Figure 22). These
     Simple inventories give an overview of the
                                                    areas are determined by correlating some of
landslide hazard in an area and delineate
                                                    the principal factors that contribute to land-
areas where more detailed studies should be
                                                    sliding, such as steep slopes, weak geologic
conducted. Detailed inventories provide a
                                                    unIits that lose strength when saturated, and
better understanding of the different landslide
                                                    poorly drained rock or soil, with the past dis-
processes operating in an area and can be used
                                                    tribution of landslides. These maps indicate
to regulate or prevent development in landslide
                                                    only the relative stability of slopes; they do not
areas and to aid the design of remedial meas-
                                                    make absolute predictions (Brabb, 1984b).
ures (U.S. Geological Survey, 1982). They also
                                                         Landslide susceptibility maps can be
provide a good basis for the preparation of
                                                    considered derivatives of landslide inventory
derivative maps such as those indicating slope
                                                    maps because an inventory is essential for pre-
 stability, landslide hazard, and land use. Wiec-   paring a susceptibility map. Overlaying a geo-
zorek (1984) described how to prepare a land-
                                                    logic map with an inventory map that shows
 slide inventory map that can be used by plan-       existing landslides can identify specific land-
 ners and decision makers to assess landslide
                                                     slide-prone geologic units. This information can
hazards on a regional or community level. The
                                                    then be extrapolated to predict other areas of
process consists of using aerial photography
                                                                                EXPLANATION



                                                                             Areas inf erred to be
                                                                            underlain by landslide
                                                                                   deposits




                                                     I        r
                                                                                       1:250,000
                                                              ~~TOScale
U) T ~                           '
                            ~~
                        _
                 _WT
          A



 Figure20. Detail from the landslide inventory map of the Durango 1 x 2 degree map, Colorado
 (Colton et ad, 1975).

                                                                                                    23
                                                                                Detail from map
                                                                                showingrecently
                                (                                                    and dormant
                                                                               ~~~~~~~~~~~~~~active
                                                                                landslidesnear La
                                                                                Honda, central Santa
                                                                                Cruz Mountains,
                                                                                California. Informa-
                                                                                tion shown on this
                                        O0
                                    -

                                                                                map includes: state
                                                        NK                      of activity,dominant
                                                                   ~~~~'
                                                                                     of slope move-
                          ...                                                  ~~~~~~~~~~~~~~~type
                                                               )               ~~~~~~~ment, direction of
                                              000
                                                                                movement, scarp
      ~9504
                                        1                                      ~~~~~~~~~~location,depth and
                                                                                date of movement.
                                                                                See map for detailed
                                                                                explanation.
                                                                    /          ~~(Wieczorek, 1982.)




                                                    k                             ~~~~~~~~~~EXPLANATION
                    606


                                                                                      Stable slopes
                                                              ~~i~
                                                                 x         ~
                                                                               Liii ~Normally stable
                                                                    I
                                                                                      slopes
                                                                                   JEUnstable slopes
                                                                                      Old landslide
                                                                                     ~~~~~~~~~~~~~~~~~deposits
                     0




                                                                                    Scale 1:24,000

Figure 22. Detail from map showing relative slope stabilityin part of west-central King County,
Washington (Miller, 1973).



24
                                                now, and the likelihood in various areas that a
potential landsliding. More complex maps may
                                                landslide will occur in the future (Figure 23).
include additional information such as slope,
                                                For a given area, they contain detailed inform-
angle, and drainage.
                                                ation on the types of landslides, extent of slope
Landslide hazard maps                           subject to failure, and probable maximum ex-
Hazard maps show the areal extent of threat-    tent of ground movement. These maps can be
ening processes: where landslide processes      used to predict the relative degree of hazard in
have occurred in the past, where they occur     a landslide area.

                                                                             EXPLANATION
                                                                           Susceptibility of area
                                                          U-                        likely to fail
                                                                    1r |
                                                                               -E High
                                                                                   M Mod(3rate
                                                                                     Low
                                                                           ~
                                                                               =     Very low
                                                                                     LUquE)factio n
                                                                           m




                                                                                          N




                                                                                   Scale 1:62,50

Figure23. Detail from map showing slope stability during earthquakesin San Mateo County,
California(Wieczorek at aL, 1985).




                                                                                                      25
Transferring and Encouraging
the Use of Information
 A major part of any effective landslide loss-re-   hazard-related activities, (2) the existence of
 duction program must be the communication          enabling legislation authorizing federal, state,
 and use of technical information (information      and local hazard-reduction activities, (3) the
 transfer). Often individuals or groups do not      availability of funds and adequate, sufficiently
 take mitigative action because they do not         detailed information in a readily usable and
 understand what to do, or lack training on how     understandable form, (4) the use of effective
 to do it. The mitigation and/or avoidance of       information communication techniques, and (5)
 landslide hazards and the reduction of land-       the existence of qualified staff at all levels of
 slide losses require that appropriate informa-     government with the authority to take mitiga-
 tion be communicated to, and effectively used      tive action.
 by, planners, decision makers, and emergency
 response personnel.                                          Information Transfer
      According to Kockelman (personal com-
                                                    Methods for transferring and/or obtaining
 munication, 1989), various terms are used to
                                                    landslide information are listed in Table 3.
 describe the transfer of information to users,
                                                    These methods should be used by any landslide
 namely "disseminate," "communicate," "circu-
                                                    information collection, interpretation, and
late," "promulgate," and "distribute." Often
                                                    transferral program designed for planners and
these terms are interpreted conservatively. For
                                                    decision makers. Some of these services are
example, an agency or person might simply
                                                    provided by state agencies, map sales offices,
issue a press release on hazards or distribute
                                                    geologic inquiries staffs, public inquiries offi-
research information to potential users. Such
                                                    ces, universities, and, in the course of ordinary
activity rarely results in the adoption of effec-
                                                    day-to-day contacts with the public, by the
tive hazard reduction techniques.
                                                    producers of landslide hazard information. In
      Kockelman notes that no clear, concise de-
                                                    addition, many research workers have provided
finition or criteria for effective information
                                                    such services on a limited and informal basis.
transfer has been offered or can be found in the
literature, except by inference or by analysis of
                                                    Table 3. Examples of resources available for
what actually works for lay persons. Therefore,
                                                    obtaining/ transferringlandslide information
he uses "transfer" to mean the delivery of an
                                                    (adapted from U.S. GeologicalSurvey, 1982).
understandable product in a usable format to a
specific person or group "interested" in, or re-
                                                                 Educational Services
sponsible for, hazard reduction, plus assistance
                                                    *   Universities and their extension divisions
and encouragement in the selection and adop-
                                                        through courses, lectures, books, and dis-
tion of an appropriate reduction technique.
                                                        play materials
Only when all these criteria have been met
                                                    *   Guest speakers and participants at lectur-
have researchers, translators, and transfer
                                                        es in regional and community educational
agents fulfilled their objectives.
                                                        programs related to the application of
     The effective use of landslide information
                                                        hazard information
to reduce danger, damages, or other losses
                                                    *   Seminars, conferences, workshops, short
depends not only on the efforts of the producers
                                                        courses, technology utilization sessions,
of the information, but also on (1) the users'
                                                        training symposia, and other discussions
interest, capabilities, and experience in
                                                        involving user groups
26
                                                     Table 4. Potentialusers of landslide hazard
Table 3. Continued
                                                     information (modified from U.S. Geological
                                                     Survey, 1982).
    Oral briefings, newsletters, seminars,
*
    map-type "interpretive inventories,"
                                                            City, County, and Area-Wide
    open-file reports, reports of cooperating
                                                                 Government Users
    agencies, and "official-use only" materials
    (released via news media)                        City and county building, engineering, zoning,
    Radio and television programs that explain
*                                                       safety, planning, and environmental
    or report hazard-reduction programs and             health departments
    products                                         City and county offices of emergency services
    Meetings with local, district, and state
*                                                    County tax assessors
    agencies and their governing bodies              Local government geologists
    Field trips to potentially hazardous sites
*                                                    Mayors, county commissioners, and city council
    by state, local, or federal agencies, and           members
    professional societies                           Multicounty (regional) planning, development,
                                                        and emergency preparedness agencies
             Information Sources                     Municipal engineers, planners, and adminis-
    Annotated and indexed bibliographies of
*                                                       trators
    hazard information and lists of pertinent        Police, fire, and sheriffs departments
    reference materials                              Public works departments
    Local, state, and federal policies, procedur-
*                                                    Road departments
    es, ordinances, statutes, and regulations        School districts
    that cite or make other use of hazards           Special districts (water, sanitation, urban
    information                                         drainage)
    Hazards information incorporated into
*
    local, state, and federal studies and plans               State Government Users*
    User guides relating to earth-hazards
*                                                    Attorney General's Office
    processes, mapping, and hazard-reduction         Department of Administration
    techniques                                             State Buildings Division
                                                     Department of Health
                                                     Department of Highways
                                                     Department of Local Affairs
Users of Landslide Hazard Information
                                                     Department of Military Affairs
Among the potential users of landslide hazard
                                                           National Guard
information are people at national, state, region-
                                                     Department of Natural Resources
al, and community levels in both the public and
                                                           Geological Survey
private sectors. Three general categories can be
                                                           Water Conservation Board
identified: (1) scientists and engineers who use
                                                           Water Resources
the information directly, (2) planners and deci-
                                                     Department of Public Safety
sion makers who consider hazards among other
                                                           Emergency Management Agencies
land-use and development criteria, (3) develop-
                                                     Department of Revenue
 ers and builders; financial and insuring organi-
                                                     State Planning and Budgeting Office
zations, and (4) interested citizens, educators,
 and others with little or no technical expertise.
                                                     *NOTE: Names and functions of state agencies
These people differ widely in the kinds of infor-
                                                        vary from state to state and this list should
mation they need and in their capabilities
                                                        be adapted accordingly.
 to use that information. Examples of
 potential users are listed in Table 4.




                                                                                                   27
Table 4. Continued
                                                               Other National Users
                                                   Applied Technology Council
         Federal Government Users
                                                   American Association of State Highway and
Department of Agriculture
                                                      Transportation Officials
     Farmers' Home Administration
                                                   American Public Works Association
     Forest Service
                                                   American Red Cross
     Soil Conservation Service
                                                   Association of Engineering Geologists
Department of the Army
                                                   Association of State Geologists
     Army Corps of Engineers
                                                   Council of State Governments
Department of Commerce
                                                   Earthquake Engineering Research Institute
     National Bureau of Standards                  International Conference of Building Officials
     National Oceanic and Atmospheric
                                                   National Academy of Sciences
      Agency
                                                   National Association of Counties
Department of Housing and Urban
                                                   National Association of Insurance
  Development
                                                      Commissioners
     Federal Housing Administration
                                                   National Governors' Association
Department of the Interior
                                                   National Institute of Building Sciences
     Bureau of Land Management
                                                   Natural Hazards Research and Applications
     Bureau of Reclamation                            Information Center, University of Colorado
     Geological Survey                             National League of Cities
     National Park Service                         Professional and scientific societies (including
Department of the Navy
                                                      geologic, engineering, architecture, and
Department of Transportation                          planning societies)
     Federal Highway Administration
                                                   United States Conference of Mayors
Environmental Protection Agency
Federal Emergency Management Agency
General Services Administration
                                                         Most states have professional planners,
Members of Congress and their staffs
                                                   engineers, or geologists available who can
Nuclear Regulatory Commission
                                                   make interpretations from available hazard
Small Business Administration
                                                   information. Specialists from the federal gov-
                                                   ernment who are skilled in the translation of
            Private, Corporate, and
                                                   technical data can also assist states. As sug-
              Quasi-Public Users
                                                   gested in Chapter 4, the most effective use of
Civic and voluntary groups                         landslide information is achieved when maps
Concerned citizens, homeowners associations        are prepared that indicate the location, sever-
Construction companies                             ity, and recurrence potential of landslides.
Consulting planners, geologists, architects, and
   engineers
                                                    Developing an Information Base:
Economic development committees
                                                     Sources of Landslide Hazard
Extractive, manufacturing, and processing
   industries                                                 Information
Financial and insuring institutions                Some of the organizations that produce or
Landowners, developers, and real estate agents     provide landslide hazard information are listed
News media                                         in Table 5.
Utility and transmission companies
University departments (including geology,
   civil engineering, architecture, urban and
   regional planning, and environmental
   studies departments)

28
Table 5. Examples of producersand provid-        Journalists, commentators, editors, and other
ers of landslide hazard information (adapted         news professionals
from U.S. GeologicalSurvey, 1982).               Local seismic safety advisory groups
                                                 National Governors' Association
                                                 Natural Hazards Research and Applications
American Institute of Professional Geologists
American Society of Civil Engineers                  Information Center. University of 'Colorado
                                                 Public information offices (federal and state)
Association of Engineering Geologists
                                                 U.S. Army Corps of Engineers
County extension agents
                                                 U.S. Bureau of Land Management
Educators (university, college, high school)
                                                 U.S. Bureau of Reclamation
Museum of Natural History
                                                 U.S. Forest Service
State Department of Highways
State Geological Survey                          U.S. Geological Survey
Hazard researchers, interpreters, and mappers    U.S. Soil Conservation Service
International Conference of Building Officials




                                                                                             29
Landslide Loss-Reduction Techniques
                                      is                                i;                ;~~~~~~~~~~~~~~~~~~~~~~~~~~_


A significant reduction in landslide losses can        short supply, there is strong motivation and
be achieved by preventing or minimizing the            pressure to use the land intensively. Land-use
exposure of populations and facilities to land-        regulations must be balanced against econ-
sliding; by preventing, reducing, or managing          omic considerations, political realities, and
the actual occurrence of landslides; and by            historical rights.
physically controlling landslide-prone slopes               Various types of land-use regulations and
and protecting existing structures.                    development policies can be used to reduce
     Subsidized insurance is not considered a          landslide hazards. Some of these methods are
loss-reduction technique because it does not           listed in Table 2, Chapter 2. Responsibility
prevent or reduce losses but merely transfers          for their implementation resides primarily
the loss to other segments of the population.          with local governments, with some involve-
Indeed, it may encourage lenders to develop            ment of state and federal governments and the
hazardous lands because they are indemnified           private sector.
by uninvolved taxpayers. The insurance indus-
try could become a strong promoter of hazards              Reducing the Occurrence of
reduction if it would establish its rates to re-
                                                            Landslides and Managing
flect relative risks. Most homeowners' insur-
                                                               Landslide Events
ance policies exclude coverage for ground
movements, including landslides.                       As discussed in Chapter 3, many landslides
                                                       occur as a direct result of human activities.
       Preventing or Minimizing                        The excavation and grading associated with
                                                       the construction of buildings, highways, trans-
       Exposure to Landslides                          mission lines, and reservoirs can create
Vulnerability to landslide hazards is a function       conditions that will ultimately result in slope
of a site's location, type of activity, and frequen-   failure. The development and enforcement of
cy of landslide events. Thus, the vulnerability        codes for excavation, grading, and construction
of human life, activity, and property to land-         can prevent such landslides. A review of the
sliding can be lowered by total avoidance of           state of the art and standards of performance
landslide hazard areas or by restricting, prohi-       of hillside and flatland urban development
biting, or imposing conditions on hazard-zone          from the 1950s to the early 1980s is available
activity. Local governments can accomplish this        in a training manual (Scullin, 1982). This man-
by adopting land-use regulations and policies          ual describes the mitigation of several geologic
and restricting redevelopment.                         hazards: landsliding, subsidence, expansive
                                                       soils, drainage, and earthquakes. The concepts
           Land-Use Regulations
                                                       and technical applications described in this
Land-use regulations and policies are often the
                                                       book may be applied in short-or long-term
most economical and effective means of regula-
                                                       planning regarding geologic risks anywhere.
tion available to a community-particularly if
enacted prior to development. However, where                  Building and Grading Codes
potentially hazardous land is privately owned
                                                                Design, building, and grading codes are
with the expectation of relatively intense dev-            regulatory tools available to local government
elopment and use, or where land optimally                  agencies for achieving desired design and
suited for development in communities is in                building practices. They can be applied to both

30
    new construction and pre-existing buildings. In      slide-prone areas, with effective linkages to a
    -rare cases, such as those involving large off-      central communication warning facility and,
    shore structures, the effect of landslides can be
                                                         thence, to individuals with disaster manage-
    considered explicitly as part of the design, and
                                                         ment responsibilities, are also sometimes used.
    the facility can be built to resist landslide dam-
    age. In some cases, existing structures in land-     Warning systems can be long-term or tempor-
    slide-prone areas can be modified to be more         ary-used only when high risk conditions exist
    accommodating to landslide movement. The ex-
                                                         or while physical mitigation methods are being
    tent to which this is successfiul depends on the
                                                         designed and built (Figure 25).
    type of landsliding to which the structure is
    exposed. Facilities other than buildings (e.g.,
    gas pipelines and vater mains) can also be
    designed to tolerate ground movement. Codes                                               i
                                                              CLIMB
    and regulations governing grading and exca-
    vation can reduce the likelihood that construc-
    tion of buildings and highways will increase
                                                                   TO
    the degree to which a location is prone to
    landslides. Various codes that have been devel-
    oped for federal, state, and local implementa-
                                                           SAFETY!
    tion can be used as models for landslide-dam-
    age mitigation. A fundamental concern with
    design and building codes is their enforcement
    m a uniform and equitable way. (Committee on
    Ground Failure Hazards, 1985, p. 15).

                                                                 IN CASE OF A
          Emergency Management
                                                                  FLASH FLOOD
Emergency management and emergency plan-
ning contribute to landslide loss reduction by
saving lives and reducing injuries. Such plan-
                                                         Figure24. Sign placed in some of the hazard-
ning can also protect and preserve property in
                                                         ous mountain canyon areas of Colorado.
those cases where property is mobile or where
protective structures can be installed if suffi-
cient warning time is available.
                                                             Controlling Landslide-Prone
      Emergency management and planning
                                                               Slopes and Protecting
consist of identifying potential hazards, deter-
mining the required actions and parties respon-                  Existing Structures
sible for implementing mitigation actions, and
                                                         Physical reduction of the hazard posed by
ensuring the readiness of necessary emergency
                                                         unstable slopes can be undertaken in areas
response personnel, equipment, supplies, and
                                                         where human occupation already poses a risk,
facilities. An important element of emergency
                                                         but where measures such as zoning are pre-
management is a program of public education
                                                         cluded by the cost of resettlement, value or
and awareness informing citizens of their po-
                                                         scarcity of land, or historical rights. Physical
tential exposure, installation of warning sys-
                                                         measures can attempt to either control and
tems, types of warnings to be issued, probable
                                                         stabilize the hazard or to protect persons and
evacuation routes and times available, and
                                                         property at risk.
appropriate protective actions to be taken.
                                                              It is not possible, feasible, or -evennecessar-
      A warning system may include the moni-
                                                         ily desirable to prevent all slope movements.
toring of geologic and meteorologic conditions
                                                         Furthermore, it may not be economically fea-
(e.g., rates of landslide movement, snowmelt
                                                         sible to undertake physical modifications in
runoff, storm development) with potential for
                                                         some landslide areas. Where land is scarce,
causing a catastrophic event or the placement
                                                         however, investment in mitigation may in-
of signs instructing people within a potentially
                                                         crease land value and make more expensive
hazardous area of proper procedures (Figure
                                                         and elaborate mitigation designs feasible.
24). Automatic sensors, located within land-


                                                                                                          31
                                                            device




                                              Channel

                                        DESIGN IN Fi
                                FINAL
                                    BY INSTALLERS
                                <



           Parts List
 Strok
 Cabh
 Used
 Spea
 Solar
 Batte
 Regu
 Relal
 Cabli
 gate
 and v
 Powe
 (Donat
 Colora
 and Lii
 SubtE
 Conti
 Total                  $1351


Figure 25. Schematic of a warning system (by Robert Kistner, Kistner and Associates).

      Landslide control structures can be costly
and usually require considerable lead time for
project planning and design, land acquisition,
permitting, and construction (Figure 26). Such
structures may have significant environmental
and socioeconomic impacts that should be con-
sidered in planning.

     Precautions Concerning Reliance
            on Physical Methods
Although physical techniques may be the only
means for protecting existing land uses in haz-
ard re. solt rlianep nnthem mqv reate a
                                                                               basini 1_
                                                        Figure RuddCreek debris
                                                             26.
false sense of security. An event of greater sev-
                                                        Farmington, constructed 19n 84
                                                                                in
                                                                  Utah
erity than that for which the project was de-
                                                                                 Kistn.erand
                                                        (photograph Robert
                                                                         Kistner,
                                                                  by
signed may occur, or a structure may fail due to
                                                        Associates).
aging, changing conditions, inadequate design,

32
or improper maintenance. The result could be
catastrophic if the hazard zone has been devel-
oped intensively.

  Design Considerations and Physical
          Mitigation Methods
When designing control measures, it is essen-
tial to look well beyond the landslide mass it-
self. A translational slide may propagate over
great distances if the failure surface is suffici-
ently inclined and the shear resistance along
the surface remains lower than the driving
force. Debris flows can frequently be better
                                                     Figure 27. Retaining wall, Interstate 70,near
controlled if mitigation efforts emphasize sta-
                                                     Vail, Colorado (photograph by Colorado
bilizing the source area along with debris con-
                                                     Geological Survey).
tainment in the runout area. An understanding
of the geological processes and the surface- and
ground-water conditions, under both natural          Table 6. Physical mitigation methods (Colo-
                                                     rado Geological Survey et aL, 1988).
and human-imposed conditions, is essential to
any mitigation planning.
                                                     A. Physical Mitigation Methods for Slides and
    Some factors that determine the choice of
                                                          Slumps
physical mitigation are:
                                                         1. Drainage
    * type of movement (e.g., fall, slide, aval-
                                                            a. Surface drainage
       anche, flow);
                                                                 1) ditches
    * kinds of materials involved (rock, soil,
                                                              2) regrading
      debris);
                                                              3) surface sealing
    * size, location, depth of failure;
                                                           b. Subsurface drainage
    * process that initiated movement;
                                                                 1) horizontal drains
    * people, place(s), or thing(s) affected by
                                                                 2) vertical drains/wells
      failure;
                                                                 3) trench drains/interceptors,
    * potential for enlargement (certain types
                                                                    cut-off drains/counterforts
      of failures [e.g., rotational slides, earth-
                                                                 4) drainage galleries or tunnels
      flows, translational slides] will enlarge
                                                                 5) blanket drains
      during excavation);
                                                                 6) electro-osmosis
    * availability of resources (funding, labor
                                                                 7) blasting
      force, materials);
                                                               8) subsurface barriers
    * accessibility and space available for
                                                         2. Excavation or regrading of the slope
      physical mitigation;
                                                            a. Total removal of landslide mass
    * danger to people;
                                                            b. Regrading of the slope
    * property ownership and liability.
                                                            c. Excavation to unload the upper part
     The physical mitigation of landslides usu-                of the landslide
ally consists of a combination of methods.                  d. Excavation and replacement of the
Drainage control is used most often; slope                    toe of the landslide with other
modification by cut and fill and/or buttresses is             materials
the second most frequently used method. These            3. Restraining structures
are also, in general, the least expensive tech-             a.   Retaining walls
niques (Figure 27).                                         b.   Piles
     Various types of physical mitigation met-              c.   Buttresses and counterweight fills
hods are listed in Table 6.                                 d.   Tie rods and anchors

                                                                                                      33
                                               3. Direct protection
Table 6. Continued
                                                  a. Impact spreading walls
                                                  b. Stem walls
      e. Rock bolts/anchors/dowels
                                                  c. Vegetation barriers
   4. Vegetation
                                            C. Physical Mitigation Methods for Rockfalls
   5. Soil hardening
                                               1. Stabilization
      a. Chemical treatment
                                                  a. Excavation
      b. Freezing
                                                  b. Benching
      c. Thermal treatment
                                                  c. Scaling and trimming
      d. Grouting
                                                  d. Rock bolts/anchors/dowels
B. Physical Mitigation Methods for Debris
                                                  e. Chains and cables
      Flows and Debris Avalanches
                                                  f. Anchored mesh nets
   1. Source-area stabilization
                                                  g. Shotcrete
      a. Check dams
                                                  h. Buttresses
      b. Revegetation
                                                  j. Dentition
   2. Energy dissipation and flow control
                                               2. Protection
      a. Check dams
                                                   a. Rock-trap ditches
      b. Deflection walls
                                                  b. Catch nets and fences
      c. Debris basins
                                                   c. Catch walls
      d. Debris fences
                                                   d. Rock sheds or tunnels
      e. Deflection dams
      f. Channelization




34
                                                                            PlaIep
                                                                             P                     atio? n
                                                             Plan Preparation

          Determining the Need                              through land use management and the appli-
                                                            cation of building and grading codes is essen-
             for a State Plan                               tially a function of local government (Sangrey
                                                            and Bernstein, 1985, p. 9).
In order to determine the need for a state land-
slide hazard mitigation plan, individual states              The purpose of a state landslide hazard
must first assess the vulnerability of their pre-       mitigation plan is to encourage and support lo-
sent and future population to the hazard.               cal mitigation efforts and address serious land-
Vulnerability is the susceptibility or exposure         slide problems, beyond local capability, that
to injury or loss from a hazard. People, struc-         threaten lives and property and have potential
tures, community infrastructure systems                 regional or statewide implications. Strategies
'(transportation, water supply, communications,         and projects developed in,the planning process
and electricity), and social systems are all            are therefore based on an assessment of what
potentially vulnerable.                                 can be accomplished locally and the level of sup-
     An assessment of statewide vulnerability           plemental assistance that will be required to
to geologic hazards is a product of the technical       lessen the problem. State and federal assis-
assessment of the problem, based on scientific          tance picks up where local efforts stop; gen-
studies and investigations, and an assessment           erally local resources must first be exhausted.
of capabilities, in the public and private sec-              A key element in, the planning process and
tors, to respond to and mitigate the hazards            a major recommendation of this guidebook is
and potential impacts identified. Before re-            the establishment of a permanent state 'organi-
sources are invested in hazard mitigation               zation, representing the various levels and re-
measures, the social and economic costs and             sponsibilities of government, to focus the atten-
impacts associated with landsliding need to be          tion of state government on natural hazard
determined and put into perspective.                    mitigation issues.
     The next step in recognizing the overall
                                                        Federal Disaster Relief and Emergency
vulnerability of the state to the landslide ha-
zard is the identification of specific commun-               Assistance Act (Section 409)
ities, areas, and facilities at risk. The existence     In presidentially-declared disasters, the pre-
and effectiveness of local programs and sys-            paration of a state plan that identifies and
tems for mitigating landslide problems in com-          evaluates hazard mitigation opportunities is
munities experiencing actual or potential im-           mandated by Section 409 of the Robert T. Staf-
pacts must then be determined.                          ford Disaster Relief and Emergency Assistance
     Although landslides can potentially affect         Act (Public Law 93-288, as amended) as a
entire regions or states, the hazards them-             condition of receiving federal disaster assis-
selves are local problems first, and local gov-         tance. This requirement was originally enacted
ernments remain on the `front lines" of the             in 1974 under Section 406 of the Disaster
battle to reduce losses.                                Relief Act to encourage identification, evalua-
                                                        tion, and mitigation of hazards at the state and
          Landslide loss reduction in the United
                                                        local government levels. The requirements of
    States is primarily a local responsibility. While
    the federal government plays a key role in re-      Section 409 are triggered by a major disaster or
    search, in the development of mapping tech-
                                                        emergency declared by the President and apply
    niques, and in landslide management on feder-
                                                        to all types of declared emergencies and disas-
    al lands, the reduction of landslide losses


                                                                                                             35
                                                     government, the private sector, and academia.
ters. A hazard mitigation clause is incorporated
                                                     Typically, the group would gather, interpret,
into the FEMA/State agreement for disaster
                                                     and assemble the technical information that
assistance, thereby establishing the identifica-
                                                     forms the basic structure of the landslide haz-
tion of hazards and the evaluation of hazard
                                                     ard mitigation plan.
mitigation opportunities as a condition for re-
                                                           The interagency efforts of post-disaster
ceiving federal assistance.
                                                     hazard mitigation teams in presidentially-de-
      The Federal Emergency Management
                                                     clared disasters have demonstrated that such
Agency (FEMA) is responsible for adminis-
                                                     working groups representing a broad range of
tering the Section 409 requirements and has
                                                     state and federal agencies can successfully
prepared implementing regulations (44 CFR
                                                     develop a host of innovative and cost-effective
206, Subpart M) that specify federal, state, and
                                                     mitigation ideas.
local responsibilities under Section 409. Under
                                                           The planning team should include indivi-
the regulations, a state hazard mitigation co-
                                                     duals knowledgeable about geology, engineer-
ordinator is designated by a governor's author-
                                                     ing, emergency management, and community
ized representative to prepare a hazard mitiga-
                                                     development and planning. Depending on the
tion plan and to ensure its implementation.
                                                     nature of landslide problems, the team might
States may establish a group of individuals
                                                      also include individuals involved in natural
from state and local agencies to assist in pre-
                                                     resources management, highway construction
paring the "409 plan," which must be complet-
                                                      and maintenance, state and regional planning,
ed and submitted to FEMA within 180 days
                                                      and others as conditions warrant.
after the presidential declaration.
                                                           The responsibilities of individual team
      With the passage of the Stafford Act in
                                                      members would include researching and writ-
 1988, a hazard mitigation funding program
                                                     ing those sections of the plan that relate to
was authorized for the first time under Section
                                                     their area of expertise. Team members would
404 of the Act. This mitigation-measures fund-
                                                      also participate in meetings with planners,
ing program provides up to 50 percent federal
                                                      emergency managers, policy makers, and
funding for activities identified under Section
                                                      elected officials in local and state government
404, thus making preparation of a good hazard
                                                      and, to the extent possible, seek the input and
mitigation plan more important than ever be-
                                                      participation of private industry, professional
 fore. The identification of mitigation opportun-
                                                      and volunteer organizations, and interested
 ities under this program follows the evaluation
                                                      citizens. An initial analysis of existing mitiga-
 of natural hazards under Section 409. Total
                                                      tion plans and emergency management capa-
 federal funds available under Section 404 are
                                                      bilities in landslide-impacted jurisdictions will
 limited to 10 percent of the permanent restora-
                                                      enable the planning team to identify the most
 tive work funded under FEMA's Public Assis-
                                                      serious problems and to develop projects that
 tance Program. Implementation regulations for
                                                      build on efforts already in progress. This as-
 Section 404 can also be found in 44 CFR 206,
                                                      sessment of local landslide conditions and local
 Subpart M.
                                                      capabilities to deal with them should identify a
      In state-declared disasters, some states
                                                      wide variety of practicable mitigation solu-
 require the development of local hazard mitiga-
                                                      tions. This will facilitate the coordination of
 tion plans as an eligibility requirement of state
                                                      state support and the identification of unmet
 emergency relief.
                                                      local needs that can be presented for possible
                                                      state action.
           The Planning Team                                Local jurisdictions impacted by landslides
States undertaking plan development should            should be encouraged to form their own local
first consider assembling a state planning team       planning teams-composed of decision makers,
to manage the research and writing of the             planners, emergency managers, engineers,
plan. The planning team could be in the form of       geologists, and officials from law enforcement,
a working group, directed by state representa-        fire safety, and emergency medical services-to
tives and supported by representatives of local        formulate local plans and mitigation strategies.

36
         The Planning Process                        hazard location, description, frequency, history,
                                                     existing impacts, potential impacts, and, to the
The planning process recommended for the de-
                                                     extent possible, probability of occurrence.
velopment of a landslide hazard mitigation
                                                          The use of land-use maps in conjunction
plan follows a series of steps that are basic to
                                                     with detailed maps exhibiting the extent and
mitigation planning:
                                                     severity of landslide hazards in an area helps
     (1) analysis of the types of landslide haz-
                                                     officials to determine vulnerability to land-
           ards in the state and a general assess-
                                                     slides, mitigation priorities, and the most ap-
          ment of the vulnerability of people and
                                                     propriate mitigation measures.
          property to the state's landslide
          hazards;                                             Appropriate land use management, effec-
    (2) identification of specific areas of the          tive building and grading codes, the use of
                                                         well-designed engineering techniques for
          state where landslides have the most
                                                         landslide control and stabilization, the timely
          serious or immediate potential impacts         issuance of emergency warnings, and the avail-
          and a detailed analysis of their vulner-       ability of landslide insurance can significantly
          abilities;                                     reduce the catastrophic effects of landslides. All
    (3) translation and transfer of technical            of these approaches require, as a starting point,
                                                         the identification of areas where landslides are
          information on hazards and vulnera-
                                                         either statistically likely or immediately immin-
          bilities to users such as decision mak-        ent, and the representation of these hazardous
          ers,. community planners, and emer-            locations on maps (Committee on Ground Fail-
          gency management officials;                    ure Hazards, 1985, p. 2).
    (4) assessment of resources and mitiga-              The planning team should assemble exist-
         tion programs available in the public
                                                     ing mapped landslide susceptibility data that
          and private sectors to deal with the       portray the distribution of various types of
         identified potential impacts;               landslides and the likelihood of their occur-
    (5) determination of local capability shortt-
                                                     rence. The team will need maps sufficiently
         falls and unmet needs in order to ap-       detailed to determine the character, location,
         ply technical and financial assistance
                                                     and magnitude of landslide problems.
         where it can best contribute to the
         reduction of future losses;                           Step 2-Identification of
    (6) formulation of goals and objectives for
                                                                    Impacted Sites
         state and local landslide hazard miti-
                                                     Once the nature and distribution of the hazard
         gation plans, and the development of
                                                     and the vulnerability to landsliding of various
         cost-effective mitigation projects that
                                                     communities, areas, and facilities has been de-
         address identified vulnerabilities;
                                                     termined, site-specific evaluations of the poten-
    (7) establishment of a permanent state
                                                     tial impacts of landsliding should be perform-
         hazard mitigation system to prioritize
                                                     ed. Based on the hazard analysis, those sites
         and promote mitigation goals and ob-
                                                     determined to present the greatest threat to
         jectives and to secure and direct fund-
                                                     lives and property should be subject to further
         ing for implementation;
                                                     site analysis and mitigation planning.
    (8) periodic evaluation and modification of
                                                          Impact is the effect of a hazard event on
         the plan and planning process.
                                                     people, buildings, and the infrastructure. The
                                                     impacts of landsliding range from the incon-
         Step 1-Hazard Analysis
                                                     venience of debris cleanup to the life-threat-
A complete hazard analysis is the result of the
                                                     ening failure of a landslide-formed dam. The
identification of the state's landslide hazard
                                                     simultaneous or sequential occurrence of other
areas, the identification of the most vulnerable
                                                     hazards such as flooding or earthquakes with
locations, and the assessment of potential
                                                     landsliding can produce effects that are greater
impacts on people and property in vulnerable
                                                     or qualitatively different from those produced
areas. Where possible, the hazard analysis
                                                     by landsliding alone.
should provide planners with information about

                                                                                                              37
                                                      and cooperative agreements with other juris-
Step 3-Technical Information Transfer
                                                      dictions and private industry. Private compan-
As discussed in Chapter 5, individuals or
                                                      ies have a vested interest in the mitigation pro-
groups often do not take mitigative actions
                                                      cess because private losses often exceed public
because they do not understand the signifi-
                                                      losses in natural disasters, and also because
cance of the threat, what to do to reduce it, or
                                                      private firms may receive insurance benefits
lack information and training on how to do it.
                                                      (lower premiums, reduced liability) for a demon-
Therefore, once landslide hazard information
                                                      strated commitment to reducing future losses.
has been gathered, it must be communicated to
                                                            The assessment of local capabilities should
planners, policy makers, emergency response
                                                      identify the most vulnerable elements of the
personnel, and the public. Maps are one of the
                                                       community, the current level of mitigation act-
best methods of transferring such information.
                                                       ivity, the status of emergency management
Landslide information can be used in the de-
                                                       planning, and opportunities for state and fed-
velopment, review, and approval of land-use
                                                       eral mitigation assistance.
plans, community development plans, emer-
                                                            The checklist provided in Table 7 can assist
 gency management plans, and hazard mitiga-
                                                       local jurisdictions in preparing plans for land-
 tion plans. In order for landslide information to
                                                       slide hazard mitigation and emergency man-
 be more widely incorporated into community
                                                       agement as well as assisting state planning
 planning and planning for landslide mitigation,
                                                       teams in assessing local mitigation efforts.
 the technical staff that produces the informa-
 tion must tailor it so that it is understandable
                                                      Table 7. Types of informationthat should be
 and usable by the various parties involved in
                                                      consideredin an assessment of a commun-
 the development process. Producers of informa-
                                                      ity's landslide hazards and capabilities (mod-
 tion should also ensure that potential users are
                                                      ified from Weber et al., 1983).
 aware of available data, as well as research
 planned or in progress. Conversely, nontechni-
                                                          Maps
                                                      A.
 cal users of landslide information should take
                                                          1. Base map
  steps to improve their skills in interpreting and
                                                          2. Landslide inventories
  applying the information.
                                                          3. Landslide susceptibility maps
      The difficulty of translating technical in-
                                                          4. Landslide hazard maps
  formation for nontechnical users highlights the
                                                       B. Physical (Geologic) Information
  importance of retaining the services of qualifi-
                                                          1. Scope (boundaries of areas subject to
  ed technical experts throughout the planning
                                                                  landslides)
  process. According to Fleming and Taylor
                                                          2. Frequency (historical occurrences by
  (1980, p. 4), "solutions to the technical prob-
                                                                  date, location, description, and
  lems are only a part of the process of achieving
                                                                  impacts)
  landslide hazard reduction. The political prob-
                                                              a. Reports
  lem of transferring the information into a
                                                              b. Newspaper articles
  governmental system to reduce hazards and
                                                              c. Eyewitness accounts
  damages is perhaps more formidable than the
                                                          3. Hazard characteristics
  technical one."
                                                              a. Predictability
                                                              b. Potential speed of occurrence
      Step 4-Capability Assessment
                                                              c. Potential impact forces
 Capability assessment is a determination of
                                                              d. Magnitude
 public, private, and volunteer resources in a
                                                              e. Worst-case scenario
 community that are available to support emer-
                                                       C. Social (Human) Information
 gency management and hazard mitigation act-
                                                           1. Land Use
 ivities designed to reduce losses from a particu-
                                                               a. Existing (map)
 lar hazard. Resources include not only equip-
                                                              b. Future (map)
 ment, supplies, and materials, but, more im-
                                                               c. Zoning (map)
 portantly, people, expertise, plans, programs,


 38
                                                     2. Emergency management activities
Table 7. Continued
                                                        a. Warning systems
                                                        b. Emergency plans (life-saving,
   2. Population at risk
                                                           evacuation, facility-specific)
      a. Number of people/total dwelling
                                                        c. Public -education/hazard awareness
           units
                                                           campaigns
      b. Variability (difference in day/night
                                                        d. Training exercises
           populations)
                                                     3. Local financial capabilities and needs
   3. Property at risk (infrastructure)
                                                        a. Funds available
      a. Use/function
                                                        b. Major resource shortfalls
      b. Assessed value
                                                        c. State and federal programs and
   4. Economic activity at risk (commercial,,
                                                           grants
           industrial, tourism)
                                                        d. State and federal technical
      a. Employment
                                                           assistance
      b. Gross revenues
   5. Critical services and facilities at risk
      a. Access
                                                      By comparing local risks and possible im-
      b. Police
                                                 pacts with the capability of a jurisdiction to
      c. Fire
                                                 respond to those risks, a state planning team
      d. Communications
                                                 can identify major resource deficiencies, or
      e. Schools
                                                 unmet needs, that become the basis for projects
      f. Health care (hospitals, nursing
                                                 in the state plan. Unmet needs are technical
           homes)
                                                 and financial resource needs that exceed the
      g. Utilities
                                                 cap abilities of the communities at risk. In
      h. Emergency management facilities
                                                 many cases, these resource shortfalls represent
      i. Thansportaion
                                                 substantial obstacles to reducing the impacts of
   6. Aggravating influences (roads,
                                                 future landslides on people, property, and ess-
           structures, landscaping, removal of
                                                 ential services.
           vegetation, or other land uses that
           contribute to landslide hazard)
                                                     Step 5-Determination of Unmet
D. Landslide Hazard Management
                                                              Local Needs
      Capabilities
   1. Landslide hazard mitigation activities     Based on the analysis of local capabilities, un-
      a. Land-use regulations                    met needs that should be considered by state
      b. Land-use plans                          and federal governments are identified and a
      c. Building and grading codes              state mitigation assistance strategy is formu-
      d. Design and location standards           lated. In order to determine unmet needs,
      *e. Development and redevelopment          specific human activities should be examined
           plans                                 to evaluate potential impacts on public health
      f. Landslide control structures            and safety, public and private property, com-
      g. Monitoring/instrumentation              merce, and the community at large. Group
      h. Acquisition and relocation projects     meetings and individual interviews can yield
      i. Public utility extension guidelines     sufficient information to determine the most
      j. Planning team formation                 critical needs of local governments and to de-
      k. Land exchanges                          velop priority mitigation projects for state act-
      1. Real estate disclosure requirements     ion. Less urgent needs can be addressed in
      m. Lending and financing policies          future projects. The state planning team
      n. Additional public works                 should also identify existing local mitigation
       o. Private sector involvement             projects so that state projects can be coordinat-
       p. Special assessment districts            ed to support their efforts.
       qq. Tax adjustments


                                                                                                 39
                                                  gation face a number of important planning
     Step 6-Formulation of Goals
                                                  challenges, including: (a) the preparation of
            and Objectives
                                                  emergency management plans that ensure the
Fundamental to a mitigation program is the
                                                  timely warning and evacuation of people in
establishment of a system for landslide mitiga-
                                                  high-risk areas; (b) the formation of local
tion planning and management at the state
                                                  planning committees to identify unmet local
and local government levels. The establishment
                                                  needs and schedule the implementation of mit-
of a permanent state system to effect mitiga-
                                                  igation projects; (c) the coordination of public,
tion projects should be considered. This man-
                                                  private, and volunteer resources; and (d) the
agement system would help ensure that:
                                                  integration of landslide hazard information
   * existing hazardous conditions are dealt
                                                  into community development plans in order to
        with expeditiously,
                                                  protect existing development and guide, dis-
   * new landslide hazards are assessed and
                                                  courage, or restrict future development in
        prioritized,
                                                  landslide-prone areas.
   * new options are developed and evalu-
                                                       Local hazard mitigation and emergency
        ated,
                                                  planning are generally carried out separately
   * intergovernmental and interagency
                                                  from the basic planning of local government.
        technical advice and mitigative action
                                                  Integrating hazard information into the com-
        can be coordinated,
                                                  prehensive or master plan of a community,
   * priorities are established for high- and
                                                  however, better enables a jurisdiction to guide
        moderate-risk situations that are
                                                  the activities of builders, investors, and devel-
        beyond local government capability,
                                                  opers in areas known to be hazardous. Com-
   * decisions are made and funding
                                                  munities that have an adequate base of tech-
        obtained and spread over a period of
                                                  nical information about local landslide prob-
        time that is commensurate with state
                                                  lems, and that have succeeded in applying this
        fiscal capabilities,
                                                  information to development and planning de-
   * feedback is evaluated and needed pro-
                                                  cisions, have met an important precondition to
        gram adjustments made, and
                                                  most types of mitigation. Land-use plans that
    * a systematic approach to mitigation is
                                                  consider available hazard information demon-
        established.
                                                  strate to developers and to the public that
                                                  public health and safety concerns are import-
Local Landslide Hazard Mitigation
                                                  ant factors in community development. Accord-
Local jurisdictions should institute mitigation
                                                  ing to Olshansky and Rogers (1987, p. 957),
programs that coordinate landslide hazard in-
                                                  "By incorporating landslide hazard information
formation and mitigation needs with state gov-
                                                  into long-term local plans, local governments
ernment and the private sector. Local mitiga-
                                                  give developers advance notice of land use
tion systems should effectively employ state
                                                  policies and the reasons for those policies."
assistance and be ready to take on new prob-
lems as solutions to old problems are found.      Development of Mitigation Projects
Local mitigation plans need to be in place so     The identification of areas in the state that are
that work on mitigation projects can begin as     vulnerable to catastrophic landslide losses will
soon as funds become available.                   enable the planning team to formulate the
     Effective local systems are important to     goals and objectives of the state plan, which
state planning because they provide direction     may be expressed in the plan in the form of
for state action. A comprehensive local hazard    prioritized mitigation projects. With the sup-
mitigation program should be based on com-        port of the planning, technical, and policy-mak-
munity consensus, developed through local         ing staff of state and local agencies that have
planning committees with citizen support and      resources, capabilities, or statutory responsi-
involvement, and should conform to local goals    bilities relating to landslide hazard manage-
and objectives and budget constraints. Local      ment, the planning team should be able to
governments involved in landslide hazard miti-    develop an initial group of projects.

40
     A wide range of project ideas and opinions,    Step 7-Establishment of a Permanent
representing the perspectives of planning, geol-     State Hazard Mitigation Organization
ogy, engineering, emergency management, pri-        A permanent state hazard mitigation organi-
vate industry, elected leadership, and others,      zation should be created to coordinate the re-
should be solicited to enable the planning team     sources of state, local, and federal agencies
to determine the cost effectiveness, feasibility,   with landslide hazard mitigation responsibil-
and political and social implications of each       ities and authorities. For states with serious
possible approach. The highest initial priority     landslide problems, establishment of a perm-
should be assigned to those projects that estab-    anent organization institutionalizes in state
lish a permanent system in state government         government the consideration of opportunities
for continuous support of state hazard mitiga-      to reduce landslide losses. In Colorado, this has
tion opportunities. A second priority should be     been accomplished by an Executive Order
state support to long-term mitigation programs      (Figure 28) that formalizes landslide hazard
in local government and the private sector.         mitigation planning within a natural hazards
Another ongoing priority should be the identi-      mitigation council.
fication of and participation in state and fed-          States with no existing system for hazard
eral programs that can provide funding support      mitigation should consider establishing an
for mitigation initiatives.                         organization that also addresses and promotes
     Although implementation of many recom-         the mitigation of other hazards impacting the
mendations may be difficult if financial re-        state. Most of the public agencies involved in
sources are linited, government agencies            landslide hazard mitigation-those concerned
should be encouraged to use the plan and its        with geology, natural resources, highways,
identified projects as a resource in formulating    climatology, water resources, emergency man-
annual work programs, budgets, and policy           agement, and others-are also involved with
statements concerning landslides. Projects that     problems of flooding, drought, and, depending
modify existing programs or improve coordina-       upon location, hurricanes, and earthquakes.
tion are usually relatively low-cost and stand      Although the focus and extent of short-term
the best chance of being implemented first.         mitigation activities at any given time may
Funds to implement the more costly projects         depend upon the prevailing threats, the organ-
should be aggressively sought from state legis-     ization should maintain a broader, long-term
latures, the federal government, and the priv-      perspective on all of a state's natural hazards.
ate sector.                                         An all-hazards approach should result in an
     Projects recommended in the state plan         efficient, multi-purpose process that can gain
should include a brief statement of the prob-       the support and approval of state leadership
lem, a general statement of the recommended         and the public.
solution, a description of short- and long-term          The role of the state mitigation organiza-
initiatives, a designated lead agency; and a pre-   tion should essentially be a continuation of the
liminary estimate of cost effectiveness, where      activities performed by the state planning
possible. Projects should contribute toward an      team and those coordinating agencies with a
effective and coordinated state/local landslide     role in landslide mitigation that participated in
management system, and should be flexible           the development of the plan. One type of org-
both in content and priority to allow for modi-     anization might consist of a state mitigation
fication during the implementation process.         council supported by working groups. The
Local jurisdictions should report their accom-      council would be made up of decision makers
plishments and important unmet needs to the         selected from key state, local, and federal agen-
state mitigation organization so that new           cies and could include representatives from the
state/local strategies can be developed. New        governor's office and the state legislature. Re-
projects should be introduced into the system       presentatives from local and regional govern-
as new landslide threats are identified and as      ments and academia may also be included in
new approaches to old problems are found.           working groups.

                                                                                                  41
                                                                                                                          B 044 89
                                                                                          Executive Order
                                                                                          Page Two
                                         STATE OF COLORADO                                The Speaker of the House of Representatives, the President of the
                                                                                          Senate, the Minority Leader of the Senate and the Minority Leader of the
                                                                                                                                                       legislative
                                                                                                                                                one
                   CHAMBIERS
         EXECUTIVE
                                                                                                                                       appoint
                                                                                                                          may each
                                                                                                   of Representatives
                                                                                          House
         136SlaeCOpitol
                                                                                          representative. All members will serve for a term of two years with
                                          B 044 89
         D.on-, Colorado2v11,92
                       --
                                                                                          reappointments permitted at the pleasure of the Governor. The Governor
              (303)00003-1
         Phone
                                                                                          will appoint the chairperson.
                                                                                          2. The chairperson will appoint a steering committee and an executive
                                                                             Roy
                                                                               Rome,
                                                                                          secretary to carry on the administrative activities of the council.
                                                                             G.--rn

                                     EXECUTIVE
                                            ORDER
                                                                                               Theresponsibilities assigned to the council are to:
                                                                                          3.
                                                        OF
                              N COUNCIL THEIMPLEMENTATION
                                         FOR
                    ESTABLISHIA G
                                                 HAZARDS COLORADO
                                                      IN
                               MITIGATION OFNATURAL
               STRATEGITOMANAGE
                       ES                                                                      a. Identify vulnerability to various natural hazards and evaluate
                                                                                               the options available to mitigate such risks.
                       various natural hazards have caused physical and financial
              WHEREAS,
         impacts in Colorado and will continue to do so; and                                   b. Review current mitigation plans for such hazards as wildfires,
                                                                                               droughts and avalanches.
                        these impacts have resulted in unexpected costs to state
              WHEREAS,
         and local governments as well as degradation of the state's health,                   c. Develop a unified management strategy with recommendations
         safety, environment, infrastructure and economy; and                                  concerning state, federal or local mitigation responsibilities.
                         the opportunities to significantly manage floods,
              WHEREAS,                                                                         d. Prioritize hazards statewide.
         landslides, wildfires and other natural hazards are identifiable and
         should be executed as funding is available; and                                       e. Assist local government in seeking funding to implement hazard
                                                                                               mitigation recommendations.
                       mitigation recommendations can be effectively prioritized
              WHEREAS,
         and managed by a state council, supported by interagency working groups;              f. Meet at the call of the chairperson, but no less frequently
         and                                                                                   than once a year.
             WHEREAS,need exists to provide formal recognition, authority and
                        a                                                                      g. Prepare an annual work program and status report covering
         responsibilities to this organizational structure;                                    progress achieved and provide periodic updates to the Governor and
                                                                                               the state legislature.
                    THEREFORE,Roy Romer, Governor of the State of Colorado, by
                                1,
               NOW,
         virtue of the authority vested in me under the constitution and laws of                                                                              of the
                                                                                                                                                     public
                                                                                                    Inform local government and the general
                                                                                               h.
         the State of Colorado, including the Colorado Disaster Emergency Act of               activities and recommendations of the council.
          1973, 24-33.5-701, et seq., hereby Order:
                                                                                          The council is directed to place high priority on use of the Colorado
         1. The Colorado Natural Hazards Mitigation Council is hereby created.            Flood Hazard Mitigation Plan and Landslide Hazard Mitigation Plan, and
         The council will be.chaired by the Colorado Department of Natural                should coordinate and prioritize the projects contained in these plans
         Resources and consist of as many as 25 representatives. The following            and any other plans dealing with natural hazards.
         organizations or groups shall be appointed by the Governor:
                                                                                                                                  Given under my hand and the
                The Governor's Office
          -                                                                                                                       Executive Seal of the State
                State departments of Natural Resources, Highways, Local Affairs,
          -                                                                                                                       of Colorado, this _2,!a day
                Public Safety, Health and Agriculture
                The Colorado Municipal League and Colorado Counties, Inc.
          -
                The Natural Hazards Center, University of Colorado
          -
                Business community
          -
                The Federal Emergency Management Agency (Region VIII) and the
          -                                                                                                                       Roy Romer7 r
                                                          Oceanic and Atmospheric
                National Weather Service (National                                                                                Governor VJ
                Administration)
                U.S. ArmyCorps of Engineers
          -
                Elected local officials from areas of the state with high-risk
          -
                natural hazards
                The general public
          -




    .I                                                                                .
I
Figure 28. Executive Order establishing Colorado Natural Hazards Mitigation Council.
     The council should be responsible for prior-    implementation, (2) monitor identified land-
itizing strategies and projects, securing and        slide areas and collect and interpret informa-
 directing funding, and monitoring overall prog-     tion about emergency situations as they occur,
ram effectiveness to ensure that policies and        (3) prepare new projects as needed to meet
directed measures are implemented in a timely        changing conditions, (4) implement projects as
and efficient fashion. Since funds for the imple-   funding becomes available, (5) recommend pro-
mentation of many of the recommended pro-           jects for funding by government and the priv-
jects will not likely be immediately available,     ate sector as specific needs arise, and (6) pro-
an ongoing and aggressive search for funding        vide technical support to the council, including
sources will be a major role of the council.        recommendations on project priority.
State and federal support should be obtained
                                                          Step 8-Review and Revision
immediately for those projects that address
landslides where potentially catastrophic or        A continuous process for evaluating mitigation
serious economic impacts have been identified.      progress and for maldng adjustments to the
     The responsibilities of the working groups     program should be a part of any hazard mitiga-
will be to: (1) review risks and options and pro-   tion system. Procedures for review and revision
vide additional information to the council once     of plans and the planning process are discussed
projects have been selected from the plan for       in the following chapter.                     Ii




                                                                                                 43
                                 n~
(0111JAST                        (Q)

Review and Revision of the Plan and
the Planning Process
                                                       ways, homes and businesses, and facilities and
In order to ensure the timely implementation
                                                       services, so that decisions can be made regard-
of mitigation projects recommended in the
                                                       ing the level of mitigation assistance required
state landslide mitigation plan, the proposed
                                                       to reduce losses in an area and so that the
state hazard mitigation organization will need
                                                       cost-effectiveness of individual projects can be
to establish an ongoing system for evaluation
                                                       determined. The inventory should provide a
and modification of the planning process. In
                                                       summary of landslide incidents and associated
addition to tracking progress of the program
                                                       financial impacts on individuals, companies,
and providing a record of local and state mit-
                                                       municipalities, and local, state, and federal
igation achievements, a review process per-
                                                       governments. The inventory should include a
mits the adjustment of program priorities. It
                                                       list of occurrences, the location, type of event,
allows the state mitigation organization to
                                                       cause of event, facilities damaged, total costs of
monitor and become familiar with the types of
                                                       damages and/or repair and replacement, and
problems that are likely to be encountered in
                                                       maps and photographs of affected areas. To the
future projects, so that planning strategies can
                                                       extent possible, an estimate of indirect
be developed.
                                                       damages should also be made.
           The criteria, decisions, and methods used
     in applying the landslide research findings to             Understanding the cost and significance
     planning and decision making can be of value          of natural disasters allows officials at all levels
     to other jurisdictions in which similar hazards       of government to make decisions about how
     exist, and for which adequate landslide in-           much money should be allocated to disaster
     formation is available. The adaption to, and          prevention rather than to the repair of dam-
     adoption by, other jurisdictions depends upon         aged facilities and disaster relief after an event
     the presence of similar public awareness, en-         (Fleming and Taylor, 1980 p. 1).
     abling legislation, hazard issues, priorities,
     community interest, innovative decision
     makers, and staff capabilities (U.S. Geological
                                                        Evaluation of Mitigation Projects
     Survey, 1982, p. 44).
                                                                and Techniques
     While the exact nature of the evaluation
                                                       The state hazard mitigation organization
system should be determined by the mitiga-
                                                       should establish procedures for the periodic
tion organization in each state based on speci-
                                                       review and evaluation of the status of individ-
fic needs, it is recommended that any system
                                                       ual mitigation projects, those proposed, com-
for evaluating the success of state landslide
                                                       pleted, and in progress. The effectiveness of
hazard mitigation programs include the
                                                       landslide hazard mitigation efforts varies ac-
following components:
                                                       cording to the physical, economic, and political
     * an inventory of landslide costs,
                                                       conditions existing in the local areas. Accord-
     * an evaluation of mitigation projects and
                                                       ing to Kockelman (1986, p. 47), "Very few
        techniques,
                                                       systematic evaluations have been made of
     * cost-benefit analyses of local mitigation
                                                       hazard-reduction techniques, even fewer for
        programs.
                                                       landslides specifically." A careful assessment of
     Inventory of Landslide Costs                      the cost effectiveness of each project will help
                                                       guide decisions of the state hazard mitigation
An effort should be made to document all land-
                                                       organization about the implementation of
slide-related losses in the state as they occur,
                                                       future projects.
particularly direct damage to roads and high-

44
     The occurrence of actual landslide disas-          Analyses of Local Mitigation
ters and the identification of new landslide
                                                                 Programs
threats will also necessitate an adjustment of
                                                    A critical feature of the proposed planning pro-
planning priorities. Maintaining flexibility in
                                                     cess is the development and maintenance of
the system will enable the state organization to
                                                    lines of communication between local and state
apply limited funds and resources to efforts
                                                    mitigation systems and between state and
that are most likely to contribute to the reduc-
                                                    federal systems. In order for state mitigation
tion of future losses.
                                                    assistance to adequately support local efforts,
   Examples of Innovative Mitigation                local programs must periodically report to the
                                                    state their unmet needs, i.e., desired projects
            Approaches
                                                    that are determined locally to be needed, but
The evaluation process will produce a record of
                                                    are beyond local resource capabilities.
both mitigation achievements and failures,
                                                         Local reports of mitigation needs and
each of which will help educate officials in-
                                                    activities in progress will help state officials
volved in solving landslide problems. Examples
                                                    determine program effectiveness and funding
of innovative mitigation techniques that have
                                                    priorities. Landslides that present potenti-
been successfully implemented are not only of
                                                    ally catastrophic impacts and local mitigation
value as guidance in other jurisdictions, but
                                                    programs that have demonstrated the ability to
will also provide justification for gaining funds
                                                    produce mitigation results should be among
and support for new projects. Additionally,
                                                    the top priorities considered for state or fed-
promoting mitigation success stories increases
                                                    eral assistance.                                 U
public education and awareness of landslide
hazards, as well as public confidence in govern-
ment hazard mitigation programs.




                                                                                                  45
Approaches for Overcoming
Anticipated Problems
                                                    inating jargon and arriving at acceptable term-
The process of developing and implementing
                                                    inology for planning may require some com-
long-term state and local landslide hazard mit-
                                                    promise among team members. On-site visits
igation programs is beset with certain obsta-
                                                    to selected landslide areas within the state and
cles to success. The most significant problem is
                                                    the collection of pertinent reports and litera-
generating the resolve and motivation to or-
                                                    ture are important steps that the planning
ganize, implement, and fund such a broad-scale
                                                    team should undertake. It may also be useful
effort. The expenditure of the time and money
                                                    to organize a technical advisory committee that
necessary to derive long-term benefits is not
                                                    would meet occasionally to review draft plan
always attractive to state or local leaders. Un-
                                                    material and to provide overall guidance and
fortunately, sometimes only an actual disaster
                                                    recommendations.
will provoke action. Developing creative ap-
proaches to financing and obtaining leadership
                                                            Management Problems
support for mitigation projects is an ongoing
challenge to mitigation proponents. Neverthe-       The research and writing efforts involved in
less, it is clear that the ultimate costs to tax-   creating a state plan will involve geologists,
payers are likely to be significantly increased     engineers, planners, emergency managers,
when mitigation activities are postponed.           elected officials, and interested citizens. The
                                                    integration of these many points of view is a
       Organizational Problems                      difficult management task but necessary if the
                                                    plan is to be practical and usable for the man-
The need for the plan preparation team and
                                                    agement and mitigation of landslide hazards.
subsequent permanent hazard mitigation or-
                                                    The project manager, with guidance and help
ganization to be broadly representative, multi-
                                                    from other members of the team, must manage
disciplinary, and intergovernmental presents
                                                    this work and establish tasks, assignments,
some immediate organizational and coordina-
                                                    and completion dates. In order to obtain a clear
tion problems. An important first step in or-
                                                    and consistent document, an editor with some
ganizing such a group is to ensure that all
                                                    background in natural hazards, earth sciences,
elements of the team concur with their roles
                                                    planning and/or mitigation technology should
and assignments before work begins. This
                                                    be employed.
agreement should be formalized in a contract,
memorandum of understanding, or some other
                                                               Financial Problems
document. A further recommendation is that a
project manager be appointed early on to            Regardless of the source or sources of funding
schedule meetings, tend to administrative and       for development of the plan, careful manage-
financial details, ensure deadlines are met, and    ment of a budget will be required to ensure all
 direct and coordinate the effort.                  project expenses are accommodated (staff costs,
      The project manager should be selected        travel expenses, fees for editing, printing,
 from the state organization designated as the      graphics, etc.). Since the planning process will
 lead agency and one of his or her first tasks is   involve several agencies working on independ-
 to integrate the broad range of technical, plan-   ent tasks, periodic reviews of the budget should
 ning, community, and organizational expertise      be conducted to prevent overruns.
 available into an effective working team. Elim-


46
        Coordination Problems                       approve the plan should be kept informed of
                                                   the work and made aware of the plan well in
Because of the difficulty involved in man aging
                                                   advance of publication.
such a comprehensive effort, it is important to
                                                        Finally, in order to produce a single, clear
set realistic deadlines and to allow sufficient
                                                   draft of the plan, it is also necessary to
time for necessary coordination of involved
                                                   coordinate the word processing systems of the
agencies and integration of the various work
                                                   participating agencies. If compatibility between
-elements. The involvement of all levels of gov-
                                                   computer systems is not possible, the various
ernment will necessarily affect progress in plan
                                                   elements of the plan may have to be re-entered
preparation, and time must be allowed for
                                                   into one system. The time and expense of plan
obtaining concurrence and approval from gov-
                                                   publication (typesetting, printing, distribution)
ernmental agencies contributing to the miti-
                                                   should also be determined as soon as possible
gation process. In addition, executive and/or
                                                   to permit identification of realistic deadlines. 0
legislative leadership that will formally




                                                                                                 47
                             References Cited

                                                        um on Landslides, Toronto, Canada, Sept-
Advisory Board on the Built Environment,
                                                        ember 1984, v. 1, pp. 307-323.
    1983, Multiple hazard mitigation strate-
   gies for communities prone to multiple           Briggs, R.P., Pomeroy, J.S., and Davies, W.E.,
    natural hazards:National Research                   1975, Landslidingin Allegheny County,
    Council, National Academy Press, Wash-              Pennsylvania: Circular 728, U.S. Geologi-
    ington, D.C., 60 pp.                                cal Survey, Reston, Virginia, 18 pp.
Advisory Committee on the International Dec-        Colorado Geological Survey, Colorado Division
    ade for Natural Hazard Reduction, 1987,             of Disaster Emergency Services, and Uni-
    Confronting naturaldisasters:National               versity of Colorado Center for Community
    Research Council, U.S. National Academy             Development and Design, 1988, Colorado
    of Sciences, and U.S. National Academy of           landslide hazard mitigationplan: Bulletin
    Engineering, National Academy Press,                48, Colorado Geological Survey, Denver,
    Washington, D.C., 60 pp.                            Colorado, 149 pp.
Allen, P.M., and Flanigan, W.D., 1986, Geology      Colorado Water Conservation Board and Colo-
    of Dallas, Texas, United States of America:         rado Division of Disaster Emergency Ser-
    Bulletin of the Association of Engineering          vices, 1985, Flood hazard mitigationplan
    Geologists, v. 23, no. 4, pp. 363-418.              for Colorado: Colorado Water Conservation
                                                        Board, Denver, Colorado, 234 pp.
Alfors, J.T., Burnett, J.L., and Gay, T.E., 1973,
    Urbangeology masterplan for Californ-           Colton, R.B., Holligan, J.A., Anderson, L.W.,
    ia-the nature, magnitude and costs of               and Patterson, P.E., 1975, Preliminary
    geologic hazards in Californiaand recom-            map of landslide deposits, Durango 10 x 2
    mendations for their mitigation:Bulletin            Quadrangle, Colorado:Map MF-703 U.S.
     198, California Division of Mines and              Geological Survey, Reston, Virginia.
    Geology, Sacramento, California, 112 pp.
                                                    Committee on Ground Failure Hazards, 1985a,
Bernknopf, R.L., Brookshire, D.S., Campbell,           Reducing losses from landslidingin the
    R.H., Shapiro, C.D., and Fleming, R.W.,            United States: National Research Council,
    1985, The economics of landslide mitiga-           Commission on Engineering and Technical
    tion strategies in Cincinnati, Ohio: A meth-       Systems, National Academy Press, Wash-
    odology for benefit-cost analysis: Chapter         ington, D.C., 41 pp.
    D, in Feasibilityof a nationwideprogram
                                                    Eisbacher, G.H., and Clague, J.J., 1984, Des-
    for the identificationand delineationof
                                                        tructive mass movements in high moun-
    hazardsfrom mud flows and other land-
                                                        tains-hazardand management: Paper
    slides: Open File Report 85-276D, U.S.
                                                        84-16, Geological Survey of Canada,
     Geological Survey, Reston, Virginia, 16 pp.
                                                        Ottawa, Canada, 230 pp.
Brabb, E.E., 1984a, Minimum landslide dam-
                                                    Ellen, S.D., and Mark, R.K., 1988, Automated
    age in the United States, 1973-1983: Open-
                                                        modeling of debris-flow hazard using
    File Report 84-486, U.S. Geological Sur-
                                                        digitalelevation models: EOS Transactions
    vey, Reston, Virginia 8 pp.
                                                        of the American Geophysical Union, v. 69,
        ,_1984b, Innovative approaches to land-         no. 16, 347 pp..
      slide hazard and risk mapping, in Pro-
      ceedings of the 4th InternationalSymposi-


 48
     Erley, D., and Kockelman, W.J., 1981, Reduc-      Miller, R.D., 1973, Map showing relative slope
         ing lands/ide hazards-aguide for plan-             stability in part of west-central King
         ners: Planning Advisory Service Report no.         County, Washington: Miscellaneous
         359, American Planning Association, 29 pp.         Geologic Investigations Map I-852A, U.S.
                                                            Geological Survey, Washington, D.C.
    Filson, J.R., 1987, Geo/ogica/ hazardspro-
        gramsand research in the U.SA.: Episodes,      Ministry of Construction '(Japan), 1983, Refer-
        v. 10, no. 4, pp. 292-295.                        ence manual on erosion control works [in
                                                          Japanese]:Erosion Control Department,
    Fleming, R.W., and Taylor, F.A., 1980, Estimat-
                                                          Tokyo, Japan, 386 pp.
        ing the costs of landslide damage in the
        UnitedStates: Circular 832, U.S. Geologi-      Nilsen, T.H., and Thrner, B.L., 1975, Influence
        cal Survey, Reston, Virginia, 21 pp.               of rainfalland ancient landslide deposits
                                                           on recent landslides (1950-71) in urban
    Gray, R.E. and Gardner, G.D., 1977, Processes
                                                           areasof Contra Costa County, California:
        of colluvial slope development of Mc-
                                                           Bulletin 1388, U.S. Geological Survey,
        Mechen, West Virginia: Bulletin of the
                                                           Reston, Virginia, 18 pp.
        International Association of Engineering
        Geology, no. 16, pp. 29-32.                    Olshansky, R.B., and Rogers, J.D., 1987, Uns-
                                                           table ground: landslidepolicy in the Unit-
    Kaliser B.N. and Slosson, J.E., 1988, Geologic
                                                           ed States: Ecology Law Quarterly, v. 13,
        consequences of the 1983 wet year in
                                                           no. 4, pp. 939-1006.
        *Utah:Miscellaneous Report 88-3, Utah
        Geological and Mineral Survey, Salt Lake       Rogers, W.P., Ladwig,. L.R., Hornbaker, A.L.,
        City, Utah.                                       Schwochow, S.D., Hart, S.S., Shelton, D.C.,
                                                          Scroggs, D.L., and Soule, J.M., 1974,
    Keefer, D.K., Wilson, R.C., Mark, R.K, Brabb,
                                                          Guidelines and criteriafor identification
        E.E., Brown, W.M. Il, Ellen, S.D., Harp,
                                                          and land-use controls of geologic hazard
        E.L., Wieczorek, G.F., Alger, C.S., and
                                                          and mineral resource areas:Special Publi-
        Zatkin, R.S., 1 987, Real-time landslide
                                                          cation 6, Colorado Geological Survey,
        warning-during    heavy rainfall:Science,
                                                          Denver, Colorado, 146 pp.
        v. 238, pp. 921-925.
                                                       Sangrey, D.A. and Bernstein, AB., 1985,
    Kockelman, W.J., 1986, Some techniques for
                                                          Landsliding-a hazard that can be miti-
       reducing landslide hazards:Bulletin of the
                                                          gated: Ground Failure, n o. 1, Winter
       Association of Engineering Geologists,
                                                           1984-85, pp. 6-10.
       v. 23, no. 1, pp. 29-52.
                                                       Schuster, R.L., and Fleming, R.W:, 1986, Econ-
    Krohn, J.P., and Slosson, J.E., 1976, Landslide
                                                          omic losses and fatalities due to landslides:
       Potential in the United States: California
                                                          Bulletin of the Association of Engineering
        Geology, October, 1976, pp. 224-231.
                                                           Geologists, v. 23, no. 1, pp. 11-28.
    Leighton, F.B., 1976, Urban landslides: targets
                                                       Scullin, C.M., 1982, Excavation and grading
        for land-use planning in California, in
                                                           code administration,inspection and en-
        Coates, D.R., ed., Urban Geomorphology:
                                                           forcement: Prentice-Hall, Englewood Cliffs,
        Special Paper 174, Geological Society of
                                                           New Jersey, 405 pp.
        America, Boulder, Colorado, pp. 37-60.
-
                                                       Slosson, J.E., 1969, The role of engineering
    Lessing, P., Kulander, B.R., Wilson, B.D., Dean,
                                                           geology in urbanplanning: The Governor's
        S.L., and Woodring, S.M., 1976, West
                                                           Conference on Environmental Geology:
        Virginia landslides and slide-prone areas:
                                                           Special Publication 1, Colorado Geological
        West Virginia Geological Survey, Environ-
                                                           Survey, Denver, Colorado, pp. 8-15.
        mental Geology Bulletin 15, 64 pp.



                                                                                                     49
                                                                   Slopes, 1984, Landslide hazard zona-
Slosson, J.E., and Krohn, J.P., 1982, Southern
                                                                   tion- a review of principles and practice,
    California landslides of 1978 and 1980, in
                                                                   in Natural Hazards, v. 3, 63 pp.
    Storms, Floods and Debris Flows in
    Southern Californiaand Arizona, 1978                 Watters, R.J., 1988, Slide Mountain, Nevada:
    and 1980: Proceedingsof a Symposium:                    a landslide-induced, water flood-debris
    National Academy Press, Washington,                     flow: Ground Failure, no.4, Spring 1988,
    D.C., pp. 291-319.                                      pp 18-19.
University of Utah, Bureau of Economic and                Weber, G., von Schulez, W., and Czerniak, R.,
    Business Research; Utah Department of                     1983, Flood hazard management plan for
    Community and Economic Development;                       the Sheridan watershed area:Sheridan,
    and Utah Office of Planning and Budget,                   Wyoming: Geographic Applications and
    1984, Flooding and Landslides in                          Research Group, Boulder, Colorado, 113
    Utah-aneconomic impact analysis:
                                                              PP.
    University of Utah, Bureau of Economic
                                                          Wieczorek, G.F., 1982, Map showing recently
    and Business Research, Salt Lake City,
                                                              active and dormant landslides near La
    Utah 123 pp.
                                                              Honda, Central Santa Cruz Mountains,
U.S. Geological Survey, 1981a, Facinggeologic                 California:Miscellaneous Field Studies
    and hydrologic hazards-earthsciences                      Map MF-1422, U.S. Geological Survey,
    considerations:Professional Paper 1240B,                  Reston, Virginia.
    U.S. Geological Survey, Reston, Virginia,
                                                                        1984, Preparinga detailed land-
     108 pp.                                              ______

                                                                   slide-inventory map for hazard evaluation
             , 1981b, The 1980 eruptions of Mount                  and reduction: Bulletin of the Association
         St. Helens, Washington, edited by Lipman,                 of Engineering Geologists, v. 21, no. 3,
         P.W., Mullineaux, D.R., Professional Paper                pp. 337-342.
         1250, U.S. Geological Survey, Reston,
                                                          Wieczorek, G.F., Wilson, R.C., and Harp, E.L.,
         Virginia, 844 pp.
                                                              1985, Map showing slope stability during
             1982, Goals and tasks of the landslide           earthquakes in San Mateo County, Calif-
______


         partof a ground-failurehazards-reduction             ornia: Miscellaneous Investigations Series
         program: Circular 880, U.S. Geological               Map I-1257E, U.S. Geological Survey,
         Survey, Reston, Virginia, 48 pp.                     Reston, Virginia.
Varnes, D.J., 1978, Slope movement types and              Wiggins, J.H., Slosson, J.E., and Krohn, J.P.,
    processes in Schuster, R.L. and Krizek,                  1978, National hazards-earthquake,
    R.J., eds., Landslides-Analysis and                      landslide, expansive soil loss models:
    Control: Special Report 176, Transporta-                 Techincal Report, J.H. Wiggins Company
    tion Research Board, National Academy of                 Redondo Beach, California, 162 pp.
    Sciences, Washington, D.C., pp. 11-33.
                                                          Youd, T.L., 1978, Major cause of earthquake
Varnes, D.J., and the International Association               damage is ground failure: Civil Engin-
    of Engineering Geology Commission on                      eering, v. 48, no. 4, pp. 47-51.
    Landslides and Other Mass Movements on




 50                                         *U.S. GOVERNMENT PRINTING OFFICE: 1998 -- 617 -998/ 90587