Wetland development . To date, most wetland development from dredged ma- 

 terial has consisted of salt marsh establishment. However, freshwater wetland 

 development or enhancement offers considerable potential. In fact, freshwater 

 marsh vegetation will quickly establish itself under favorable conditions; 

 whereas salt marsh plants often have to be seeded or sprigged. In a greenhouse 

 study, Barko et al. (1977) obtained good growth of freshwater marsh plants on 

 fine-grained material and considerably slower growth on sandy material. In the 

 James River (Virginia), at a freshwater tidal location, dense freshwater marsh 

 vegetation quickly invaded a disposal area consisting of fine-grained material 

 retained by a dike of sandy material (Lunz 1977). 



Some general considerations for freshwater marsh development are: (a) 

 type of dredged material including grain size and contaminants present; (b) 

 site characteristics including elevation and hydrologic regim.e; (c)value of 

 the habitat to be replaced or altered at the disposal site; (d) energy level 

 at the disposal site -- can the site be protected?; and (e) is the proposed 

 site within dredged material transport distance?. Size, shape, and orientation 

 are important considerations and relate to the in situ volume and location of 

 the material to be dredged. 



In the absence of specific guidelines for freshwater marsh development, 

 the reader is referred to the section on coastal wetlands habitat development 

 and to Lunz et al. (1978), Smith (1978), and Environmental Laboratory (1978). 

 For a discussion on potential contaminant uptake, see "contaminant uptake" in 

 "wetland development" (Part III), remembering possible differences in uptake 

 between freshwater and saltwater sites due to physical-chemical differences 

 (Gambrell et al. 1977). 



Studies of uptake of the contaminants in fresh waters are generally lack- 

 ing. In an artificial marsh in the James River, Virginia, nickel, of several 

 available metals, and chlorinated hydrocarbons, were taken up by marsh plants 

 (Lunz 1978). 



Fremling et al. (1976) and Nielsen et al. (1978) noted that the con- 

 struction of a navigational pool at Weaver Bottoms, Wisconsin, in the Upper 

 Mississippi River resulted in an elevated water level. The water overtopped 

 the natural levees, converting natural marsh to wind-swept open water. They 

 also noted possible ways dredged material could be used to aid rehabilitation 

 of the marsh. Modifications to dredging operations could increase water 

 clarity and decrease wind fetch which would make the area more condusive to 

 aquatic plant growth. The Fish and Wildlife Work Group of GREAT I (Vanderford 

 1979) discussed the concept of rehabilitation of backwater areas of the Upper 

 Mississippi River. 



Aquatic development . At this time aquatic habitat development does not 

 appear to have wide application in riverine systems. However, in the Upper 

 Mississippi River, the opening or closing of cuts to side channels and back- 

 waters to direct or obstruct water flows appears to offer considerable poten- 

 tial (Fremling et al. 1979). The modifications are designed to permit suffi- 

 cient movement of freshwater through backwaters to prevent stagnation and win- 

 ter-kills, yet prevent the movement of sediments into the backwaters. 



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