Chapter 9: Natural Hazard Mitigation

Discussion Questions
Exercises
Links

Summary:
Effective hazard mitigation requires understanding the hazard, mapping relative hazard based on that understanding, and formulating and implementing enforceable measures to mitigate exposure and vulnerability. These measures include land use and building regulations that preclude development in high hazard areas and require stringent standards in moderate hazard areas; property acquisition and relocation in high hazard areas; education; and emergency preparedness. Natural hazard mitigation plans should address multiple hazards, be prepared in anticipation rather than after a natural disaster, and be reevaluated and modified as necessary after each hazard event. Inland flooding hazard mitigation requires quality mapping and land use controls.
Through FEMA, the U.S. NFIP has made flood hazard boundary maps available to all flood-prone communities. In addition, the availability of flood insurance is conditional on local floodplain management, including restrictive zoning in the 100-year floodplain. These standards provide a baseline of protection for new development, but many communities have gone beyond these requirements to protect more flood-prone and riparian areas and have addressed existing exposed developments through relocation. Coastal hazards result from the dynamic nature of beach, dune, and bluff processes and exposure to coastal storms including hurricanes. Restricting development in hazard areas and preserving natural protection mechanisms like dune systems are important elements of coastal hazard mitigation.
Slope-stability hazards are a function of slope steepness and underlying materials. Mapping these features as well as evidence of past landslides can give a good spatial representation of slope stability and provide information on which to base land use regulation to reduce exposure and vulnerability.
Likewise, support problems like karst and sinkholes can be assessed, mapped, and controlled. Subsidence problems are usually caused by human activities like groundwater, oil, or natural gas pumping and subsurface mining. Hazard mitigation requires understanding the processes involved and controlling the activities to reduce the hazard, exposure, and vulnerability.
Unlike slope and support problems, earthquake hazards affect entire regions. More pervasive hazards from earthquake groundshaking require more widespread controls, like building standards for all new development. Still, there are areas within earthquake regions that are more susceptible to roundshaking hazards than others due to underlying materials such an unconsolidated materials, clays, and muds. Effective mitigation requires identifying and mapping these areas of higher relative hazard and applying more stringent mitigation measures.

Discussion questions

1. Natural hazard mitigation involves understanding and addressing hazards, exposure, vulnerability, and risk. Briefly distinguish these four elements, and illustrate how hazard mitigation can address each.
8. Hazard:
9. Exposure:
10. Vulnerability:
11. Risk:

a. Using a diagram and some words, explain the difference between the floodway, the floodway fringe, and the 100-year and 500-year flood plains.

b. Draw a hypothetical flood profile and a hypothetical flood plain map and describe how they relate to one another.

c. Frequent flood damages are a problem in the Town of Highwater, an urbanizing community along the Fuller River 10 miles upstream from the City of Lowater. About half of the land within the Town limits is developed and about half is in forest and farmland but this area is poised for development. The following three alternatives have been suggested for dealing with the current and future flooding problems in both communities. As an environmental planning consultant you have been asked (a) to comment on one or two "pros" (advantages) and "cons" (limitations) of the three alternatives, and (b) to give your recommendation, which need not be limited to the three options.
a. Comment on alternatives: Pros Cons
1. Flood plain zoning through Highwater:
2. Build levee to protect existing development
in Highwater:
3. Widen river channel through Highwater
to improve drainage:
12. What would you recommend to the Town? (not limited by the above alternatives) (Hint: consult with chapters 13 and 14)

Exercises

a. In fall 2003, wildfires in California destroyed more than 3500 homes and killed more than 20 people, including fire fighters. This follows an equally devastating wildfire year in 2002, principally in Florida, Colorado, and Oregon. The Firewise Community program aims to educate and prepare communities for this natural (and sometimes man-made) hazard by providing an assessment tool. Download the assessment form from http://www.firewise.org/communities and do the assessment for a neighborhood in the rural fringe of your community.

b. Go to the FEMA Project Impact website http://www.fema.gov/impact/, select a participating community, and write a one page synopsis of their hazard problems and their response.

c. Go to the Institute for Business and Home Safety website http://www.ibhs.org, retrieve the full Community Land Use Evaluation Questionnaire (CLUE) and use it to evaluate your community’s comprehensive plan for natural hazard mitigation.

d. Go to the FEMA Map Store (give website), find your community’s Flood Insurance Study, and find and print a Flood Hazard Boundary Map (FHBM), flood profile, and Flood Insurance Rate Map (FIRM) for a stream reach in the community similar to figures 9.8 and 9.10.

e. Using information from the Internet and the literature, update the chapter’s discussion of one of the following natural hazard policies:
i. The 1888 Stafford Act, as amended
ii. FEMA’s policy for rebuilding in the flood plain after inland or coastal flooding damage.

f. Risk assessment has become one of the most important analytical methods for a wide range of risks facing communities, not only for natural hazards but also for man-made hazards including industrial and transportation accidents but terrorism. Expand on the chapter’s discussion of risk assessment but finding useful references on the Internet and the literature and writing a four page synopsis of the basic approach to risk assessment along with an illustration.