22 



Fig. 21. Wetland drainage and filling increase the potential for damaging floods. 



This flood storage value of wetlands has also been 

 reported for other areas. In eastern Pennsylvania, the 

 1955 floods washed out all but two bridges along one 

 stream; the remaining bridges lay immediately down- 

 stream of the Cranberry Bog (Goodwin and Niering 

 1975). A Wisconsin study projected that floods may be 

 lowered as much as 80% in watersheds with many wet- 

 lands compared with similar basins with little or no wet- 

 lands (Novitski 1978). Pothole wetlands in the Devils 

 Lake basin of North Dakota store nearly 75% of the total 

 ninoff (Ludden. et al. 1983). 



Recent studies at National Wildlife Refuges in North 

 Dakota and Minnesota have demonstrated the role of 

 wetlands in reducing streamflow. Inflow into the Agassiz 

 National Wildlife Refuge and the Thief River Wildlife 

 Management Area was 5.000 cubic feet per second (cfs). 



while outflow was only 1.400 cfs. Storage capacity of 

 those areas reduced flood peaks at Crookston, Minnesota, 

 by 1 .5 feet and at Grand Forks. North Dakota, by 0.5 feet 

 (Bemot 1979). Drainage of wetlands was the most impor- 

 tant land-use practice causing flood problems in a North 

 Dakota watershed (Malcolm 1978; Malcolm 1979). Even 

 northern peat bogs reduce peak rates of streamflow from 

 snow melt and heavy summer rains (Verry and Boelter 

 1979). Destruction of wetlands through floodplain devel- 

 opment and drainage has been partly responsible for re- 

 cent major flood disasters throughout the country (Figure 

 21). 



Besides reducing flood levels and potential damage, 

 wetlands may buffer the land from storm wave damage. 

 Mangrove swamps are so effective in this regard that the 

 Federal Insurance Administration's regulations state that 



