Landslide Hazards and Planning
PAS Report 533/534
By James Schwab, FAICP, Paula Gori, Sanjay Jeer
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Is a landslide waiting to happen in your community? Landslides occur primarily in mountainous regions, but flatter parts of the country are not immune. Landslides often go hand-in-hand with other natural disasters such as wildfires and floods, making them an important consideration in hazard mitigation planning and comprehensive plans.
This report will help planners minimize the risk landslides pose to life and property. It offers basic knowledge of the natural and manmade factors that trigger landslides, as well as information needed to identify at-risk areas and determine whether development should be permitted there.
Landslide risks clearly affect land-use decisions, but planners must also consider how landslides might affect other elements of their comprehensive plan, including housing, transportation, and economic development.
When development is permitted in areas at risk of landslides, the best practices described here can mitigate losses, an important consideration given the lack of insurance for landslide losses. The report also explains remedial tactics for landslide areas where development already exists and regulatory tools for preventing development or ensuring the safest possible development.
Table of Contents
1. A primer on landslide hazards for planners
The nature of landslide hazards • Scope and consequences • Key planning issues
2. Planning to address landslide hazards
Trends in hazard planning • Landslide hazards and the comprehensive plan • Hazard identification and risk management • Policy responses
3. Development regulations for landslide hazards
Zoning and landslide mitigation • Use restrictions • Grading ordinances • Maintenance requirements • Subdivision and planned unit development standards • Transfer of development rights • Bonds and insurance • Hillside development ordinances
4. Geologic hazard abatement districts (GHADs)
California's experience with hazard mitigation through geologic hazard abatement districts • Weighing the benefits of GHADs
5. Technical tools to assist planners in combating landslide hazards
New quantitative landslide hazard assessment tools for planners • Growth, geology, and GIS: Mapping, modeling and living with geologic hazards in Moab-Spanish Valley, Grand County, Utah
6. Case studies: how local governments respond to the challenge of planning for landslide hazards
A model of effective use of geology in planning, Portola Valley, California • The Kelso, Washington, Aldercrest-Banyon Landslide • Policy tools for addressing landslide hazards in Pittsburgh, Pennsylvania • Green Mountain Landslide: A case history of geologic hazards planning in Colorado
7. State and federal roles in landslide hazard planning and mitigation
California's seismic hazards mapping act: A statewide approach to landslide hazard mitigation • Landslide Hazards and federal lands: The United States Department of Agriculture Forest Service experience • The role of government in landslide hazards loss reduction with a discussion of role of the United States Geological Survey and other federal agencies