Because the flood control function of wetlands hinges on their capacity to detain water for hours or at most a couple of days, the ability to hold water for 15 continuous days has virtually no relevance to flood control. Their loss results in directing new sources of potential floodwaters into rivers. Studies in the southeast have demonstrated that loss of these wetlands increases flooding in coastal areas. The proposed manual would exclude 86 percent of the similar kinds of wetlands in the western portion of the county- an area that today retains many wetlands and suffers from little flooding. They play a particularly important role filtering sediments and nutrients, which cause roughly 75 percent of the degradation of streams and lakes and half the degradation of estuaries.
Nutrients also contaminate groundwater drinking supplies in many rural areas.
Replacing these natural wetlands functions with artificial means of controlling pollutants would be extremely expensive. The Chesapeake Bay, America's largest estuary, illustrates estuaries that already suffer widepsread degradation from excess nutrients. The proposed manual revisions would sharply set back restoration efforts by excluding protection for more than 50 percent of the freshwater wetlands surrounding the bay. Biological Diveristy Wetlands that would be excluded are among the most biologically diverse areas in the United States and are centers of rare, threatened and endangered species. The loss of these wetlands would adversely affect and potentially jeopardize at least 79 species of animals and plants listed as threatened or endangered by the federal government and more than 120 species that are candidates for listing.