In the Pacific northwest, the pattern of succession is reported to 

 consist first of grasses, then willows, elderberry (Sarrbucjus sp.)» and black- 

 berries (Rubus sp.). Later, larger trees such as red alder ( Alnus rubra ), 

 green ash ( Fraxinus subi nteoerrima ), and hemlock ( Tsuga sp.) may appear (U.S. 

 Army Corps of Engineers, Portland District 1975). 



Brady (1976) concluded that it was better to dispose of dredged material 

 onto early successional stages, such as v/eedy herbaceous plants or willow-cot- 

 tonwood stands rather than into mature forests of later serai stages. The for- 

 mer will revegetate more quickly. 



Stream Margin and Wetland Disposal 



Frequently, dredged material is placed in shallow waters or wetlands 

 where it forms islands or extends land masses (Figures 6 and 7) or it may be 

 placed on existing islands or land masses but spills over into the backwaters. 

 Productive shallow water habitat is changed to sandy, initially barren areas. 

 The dredged material also may block running sloughs or feeder channels that 

 feed fresh water through backv/ater areas, or the outwash may fill in backwater 

 sloughs and lakes. In either instance, the productivity and useful life of 

 backwaters is lessened (U.S. Army Corps of Engineers, St. Paul District 1974). 



The findings of Colbert et al. (1975), Simons et al. (1975), and Grunwald 

 (1976) indicate that on the Upper Mississippi River the long-term impacts of 

 dredged m.aterial placement are often not immediately recognizable and are po- 

 tentially more severe than the direct short-term impacts. Dredged material 

 placed along the shoreline is subject to erosion and reintroduction to the 

 stream course. The material is often carried into side channels where, when 

 the current diminishes, it is deposited, blocking water flow to backwater 

 areas or is carried into backwaters where it blankets biologically productive 

 habitat. Fremling et al. (1979) noted several instances in which dredged 

 material that had been transported considerable distances from the original 

 deposit areas had blocked side channels or moved into backwaters. Ragland 

 (1974), Schramm and Lewis (1974), and Terpening et al. (1975) demonstrated the 

 high value of backwaters to fish and wildlife. 



Strategically placed dredged material can be used to develop favorable 

 habitat by creating lagoons or other quiet-water areas behind newly created 

 islands (U.S. Army Corps of Engineers, Portland District 1975). 



Coastal Zone Resources Corporation (1977) studied a historic disposal 

 area along the Whiskey Bay Pilot Channel, an artificial channel of the Atcha- 

 falaya River in southern Louisiana. Dredged material was disposed parallel to 

 the channel during construction in 1935 to 1936 and again in 1961 to 1962. 

 The disposal area was originally swamp and bottomland forest with several 

 small streams. Following disposal, the elevation increased and the area became 

 nonwetland habitat. 



An analysis of vegetational changes at the site and in other disposal 

 areas in the Atchafalaya Basin indicated the following possible sere on dis- 

 posal sites: (a) unvegetated dredged material; (b) ragweed (and other forbs); 

 (c) willow-cottonwood or willow-sycamore-mixed forest; (d) sycamore-mixed 

 forest; (e) red maple-sweetgum-sugarberry; and (f) sweetgum-sugarberry-oak. 



61 



