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Flood Hazard Mitigation For more information: Technical assistance is provided by the Office of Water Resources and NIPC. The basic references are Model Flood Plain Ordinance for Communities Within Northeastern Illinois. Floodplain Regulations. and Floodplain Compliance. 2.1.5 Wetland regulations Wetlands are usually located in floodplains or depressed storage areas. They provide certain natural and beneficial functions that warrant their protection. Wetlands provide habitat for species that cannot live or breed anywhere else. They reduce flood velocities and erosion. Wetland vegetation filters water. making it cleaner for those downstream. While some communities have their own wetland protection programs. all areas of northeastern Illinois are subject to the Corps of Engineers' Section 404 regulations. Corps permits are required for projects that will place fill or dredged materials in a wetland. Before a permit is issued. the plans are reviewed by several agencies. including the US Fish and Wildlife Service and the US Environmental Protection Agency. A ppropriate for: Preserving the natural beneficial functions of wetlands. Problems: In many areas. wetlands subject to regulation are not mapped. so projects may be built without knowing the area should be protected. The Corps' authortty is generally limited to filling wetlands. They can be impounded or otherwise damaged without a 404 permit Therefore. communities should consider their own more comprehensive regulations. For more information: Technical advice can be found at the county planning agencies. the Northeastern llIinois Planning Commission. the US Army Corps of Engineers. the US Fish and Wildlife Service. and the Department of Natural Resources, A basic reference for northeastern Illinois communities is Environmental Considerations in Comprehensive Planning. 2.1.6 Stormwater management Floodplain regulations address development in the path of flooding. Flooding can also be increased by development outside the floodplain. The history of flooding in northeastern Illinois (section 1.3) descrtbes what happens when an area is urbanized. Figure 2-2 illustrates the increase in runoff when natural ground cover is replaced by urban development. Not only does unconstrained watershed development aggravate downstream flooding, it often overloads the community's drainage system. Effective stormwater management requires developers to build detention basins and utilize other "best management practices" to ensure that the rate of runoff after development is no greater than under pre-development conditions.