Response
Effective response and action
The following points can be used to plan and implement an effective
hazard analysis:
- Closely define the purpose of the investigation: Landslide zonation
investigations are a type of special-purpose geological or geomorphological
study. A different approach will taken depending on whether the
slope instability problem affects agricultural or urban developments,
roading, railways or forestry management. Zonation will also be
determined by legislative requirements.
- Determine what should be done by purpose of the study and the
processes involved: A recognition of the prevailing processes
of slope failure combined with a well-defined purpose for the
investigation should determine the technical requirements of the
hazard investigation, and these should be established at the outset.
Constraints of time, funding and available personnel will inevitably
constrain what can be done. But should not be the overriding consideration
in the design of the investigation.
- Identify, if possible, the users: The content and presentation
of landslide zonation should be appropriate to the user's requirements
and technical capabilities. The product of the zonation results
should be directly applicable to decisive action regarding preventative
or corrective measures, landuse planning, development and construction,
legislation, insurance etc.
- Plan a phased investigation: Start with a review of the available
data, e.g. aerial photograph interpretation, and proceed from
there as technical requirements and capabilities are better defined.
- Include the basic information on which the interpretation is
based: Although the content of hazard analyses may be intended
for the lay person in many instances an experienced engineer or
geomorphologist will use the zonation and will need to know how
it was derived. Maps showing the individual factors which were
compiled in developing the hazard scheme should be included in
the presentation, together with an explanation of the method used.
- Involve the user in all phases of the programme: It is important
that the end users who actually implement the hazard zonation
are involved in all phases of the investigations from definition
of the problem, through choosing the methods of investigation
to the conclusions reached. Allowing the end user some influence
in the programme design and development ensures that the end user
will better understand the importance of the results obtained
and will better identify with the project and be motivated to
apply the results of the programme. Furthermore, if the end user
is involved in all phases of the programme then they will be well
informed about the combined factors of the analysis and will not
need expensive and time-consuming training sessions in which they
will have to try and absorb and understand all the many different
and complex elements which the researchers have utilised.
- Use the best skills that can be obtained: The areal evaluation
of landslide hazards requires researchers and investigators who
are skilled and have experience in the techniques of engineering
geology and geomorphology. They also need the interest, time and
ability to be able to transmit the findings of their investigations
to a wide range of audiences, including planners, engineers, local
and regional government, or the general public. This may lead
to a long term commitment to become involved in the technical,
social and economic consequences which will evolve through implementation
of the hazard zonation.
Responses to slope stability hazards
In general demands for better information and improvements and
changes to regulations follow destructive events The response to
actual or potential hazardous events usually includes a combination
of the following (Varnes, 1984, p. 28-31):
- Fact-finding - delineating the location or extent of the hazard
and the degree of risk it may present.
- Disseminating the information to the appropriate government
bodies and public through education and warnings
- Avoiding utilising the hazardous area through landuse regulations,
acquiring the land for low risk use and through evacuation.
- Removal or control of the hazard
- Relief and reconstruction
In New Zealand the Earthquake and War Damages Fund, originally
established to cover war damages, has been extended to cover earthquakes
and, in the aftermath of the Abbotsford landslide, landslides. This
fund provides for scientific research into the hazards, public awareness
and education campaigns and financial relief and insurance against
the hazardous events should they occur. In Los Angeles following
heavy rains in 1951/52, which caused widespread landsliding, the
citizens, together with advice from earth-moving contractors, professionals
in private industry and city officials established a grading ordinance
(which was adopted into law) which required some soil engineering
and geology for hillslope development. These regulations were made
stricter following further rains and damage in 1957/58. A comparison
of damage in storms prior to 1952 and damage sustained during heavy
rain in 1968/69 showed that damage had been 18 times higher before
the law was introduced. In Austria the 1975 forestry law requires
landslide hazard zonation before general planning.
In Japan where slope stability problems are widespread the Law on
Landslide Prevention provides for designation of hazardous areas,
restrictions on land use and construction of preventative works.
There are three essential elements to a regulatory response to recognised
land instability:
1. An able and concerned local government
2. A solid base of reliable technical information about the
hazards
3. A recognition of the need for regulation on the part of
the landusers.
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