Agenda - Planning Commission - 04/03/2008

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underlying zoning designations, the floodplain area becomes the overlay zone with additional regulations. Racine County, Wisconsin; Roseville, California; Exeter, New Hampshire; and Auburn, Maine, all have floodplain over- lay ordinances. This allows them not only to set minimum standards for construction but also to limit the uses that are constructed in these at-risk areas. This is a more realistic way to regulate areas that are in floodplains. Setbacks. Some communities require that any structures built in a floodplain be set back from the center line of the stream, the channel of the stream, orthe floodway. This setback is added to the ordinance because encourage them to purchase the high-risk areas for their natural and beneficial values. When FEMA purchases damaged structures and their underlying land, it requires that acquired land and structures remain in perpetual open space. Once a community purchases the land, it can be used for parks and open space. Minor improve- ments can be made, such as constructing open shelters, rustic parking lots, and playground equipment. Some communities require setbacks from streams, while others such as Racine County, Roseville, Maricopa County, Central Point, Oregon, and all of the northeastern Illinois communities that have adopted the the communities understand that there is no guarantee that today's stream channel will carry all the water that comes down a stream under all flood conditions. The closer a struc- ture is to a channel, the more likely it is that the structure will be flooded. Some communi- ties modify this setback requirement slightly by not allowing principal structures in the set- back area but allowing cheaper accessory structures there. Maricopa County, Arizona, and Mecklenberg County, North Carolina, include setback requirements in their flood- plain ordinances, but they are stand-alone ordinances rather then overlay ordinances. Open space zones. Open space zones are widely accepted as a mitigation tool for flood- plains. Some communities require that develop- ers dedicate areas along high-risk zones such as floodplains as open space for local parks. Other communities work with environmental groups to 154 state model floodplain ordinance limit the use of areas that are in the floodway to either open space or to those uses with low damage potential. In effect, these areas serve the same purpose as keeping the land in open space while allowing residents to have some use of the land. Not only do these areas reduce damages, but they also provide larger areas to hold floodwaters with minimal dam- age to the built environment. _ Density controls. Density controls can be used in multiple ways to reduce the risks from flooding. One way is to reduce the densities allowed in the floodplain. If a house is built on a larger lot, it first reduces the number of structures at risk. It also gives the developer additional space, allowing more innovative ways to elevate structures above the flood- plain by allowing fill below the structure to elevate it above the base flood elevation (BFE). When fill is placed below a structure, a 3:1 slope should be included as the ground slopes below the BFE to help ensure that the soil doesn't erode as readily. In addition, by limiting the density, fewer residences and their occupants are put at risk. Another way is to use density confrols to reduce flood risk as Mecklenberg County does. It allows develop- ers to increase densities on sites that are out- side the floodplain areas in return for keeping the at-risk floodplain as open space. Nonconforming use regulations/substan- tial improvement regulations. One additional way that communities can use their zoning- ordinances to reduce flood damages is to rig- orously enforce the nonconforming use sec- tion of their zoning ordinance and the sub- stantial improvement section of their floodplain ordinance. Nonconforming use reg- ulations can be used to help bring structures into compliance with current regulations, including floodplain regulations. The substan- tial improvement section requires that, if the value of improvements to a structure equals or exceeds a 50 percent threshold, the structure must be brought into compliance with current regulations. If a structure predates the com- munity's participation in NFIP or predates the current base flood elevations, it may have been constructed well below BFE and be at risk of flooding. By using nonconforming use regula- tions, communities can require owners who want to change uses or significantly modify a structure to bring the structure into com- pliance with floodplain regulations. A num- ber of communities across the country have dropped the 50 percent threshold for sub- stantial improvements to a lower percent- age. This, along with the nonconforming use section, can significantly affect the number of structures at risk. CONCLUSION Communities have all the tools they need to make their neighborhoods safer. The question is whether they have the will to use them. Open space zones are widely accepted as a mitigation tool for floodplains. ZONING PRACTICE 3.08 AMERICAN PLANNING ASSOCIATION I page 6