Agenda - Planning Commission - 12/02/1997

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OCTOBER 1997 IY/H ews AMERICAN PLANNING ASSOCIATION II Zoning for Flood Hazards By Jim Schwab, AICP Among natural hazards, flooding remains a dominant concern for planners and emergency management officials alike. According to the Federal Emergency Management Agency (FEMA), more than 80 percent of the nation's presidentially declared disasters involve floods. Although the other 20 percent-involving such hazards as earthquakes, hurricanes, wildfires, and tornadoes-often produce a disproporttonate share of the overall damages from natural disasters, floods continue to generate most disaster-related costs in most years. They also pose one of the most manageable and predictable problems connected with natural disasters. Flood mitigation lends itself to land-use planning solutions because, with few exceptions, floods follow the contours of riverbanks and shorelines. Improvements in mapping and other technologies useful to planners have helped improve the effectiveness of mitigation efforts. Flood Insurance and Local-Planning This issue of Zoning News examines the ways in which zoning and other land-use controls can be used to reduce flood losses in communities as part of a comprehensive attack on flood problems. Land-use regulations are just one part of a larger package of mitigation tools available to local planners and other officials involved in disaster issues. Emergency managers and engineers have long played vital roles in planning for disaster relief and evacuation and in designing flood-control structures to relieve t4e threat of flooding. Since its)nception in 1968, the National Flood Insurance Program (NFIP) has shaped the basic structure of most floodplain management at the local level. The program had two initial purposes: to provide affordable insurance to flood victims and to promote zoning and land-use regulations that would prevent development in flood-prone areas. Because the program tended to serve the first objective better than the second, FEMA initiated a number of changes in recent years to improve its effectiveness "in encouraging sound local land-use planning. Among these changes was the creation of the Community Rating System (CRS), launched in 1990 to provide incentives in the form of flood insurance rate reductions for local flood management efforts (see box on page 2). NFIP regulations, however, simply provide a framework for local programs and do not prevent communities from creating innovadve means to solve their flood problems, even though it may not always be easy to get credit for some innovations within the CRS guidelines. More often than not, when communities have limited the scope of their efforts, it was because they asked only what they were required to do and did not consider what they could be doing. Floodplain management consultant French Wetmore has noted that most communities rely on engineers and emergency managers to construct their floodplain programs. When so planners are not part of the process, it is likely that no one will ask what types of floodplain land uses are most appropriate to help prevent or reduce property losses from flooding (see "Flooding and Planners," Environment 6- Development, July! August 1996). Thus, structural solutions often prevail at the expense of a serious examination of which land uses really need to be in the floodplain in the first place. For instance, a floodplain management ordinance may go no further than to create an overlay zoning district for the floodplain within which structures must be elevated to a certain level-typically, one foot-above the base flood elevation, defined as the level to which water would rise in a 100-year flood. Such measures serve a purpose but often do not address more fundamental questions about locating land uses in the floodplain. ~~ .D ~ -e V) Ii =. Even after the waters receded from the 1993 Midwest floods, this house in Johnson County, Iowa, remained perilously close to the Iowa River. A number of other publications already detail NFIP requirements (see list on page 4), and the first chapter of PAS Report No. 473, by Marya Morris, Subdivision Design in Flood Hazard Areas, also summarizes the program's operations. What follows here is a summary of details essential for understanding how the program relates to the mechanics of zoning for floodplain land uses. The one element on which NFIP rests is the program's function of mapping floodplains. Flood Insurance Rate Maps (FIRMs) outline Special Flood Hazard Areas (SFHAs) by determining how high water would rise in a flood with a I percent chance of occurring in a given year. Although these are known as I OO-year floods, the definition makes clear to anyone with a knowledge of statistics that such floods can occur more often than once in a century. It is also true, however, that, in some areas, floods occur with greatet frequency not only because of bad luck, but because development after the maps were drawn may have exacerbated the conditions that can lead to ~.