prohibited sedimentation within the central delta, forcing silt-laden waters to the Outer Continental 

 Shelf. Thus, subsidence within the central delta has not been counterbalanced by sedimentation, 

 so large shallow freshwater bays have been created. In addition, channelization and canal dredging 

 have diverted the sheet flow from the freshwater areas and allowed saltwater intrusion from the 

 Gulf of Mexico, accelerating the decline in the freshwater marshes. 



Aerial photographs of the central delta taken during the past 10 years show that downstream 

 from levee breaches there has been rapid land buildup in limited areas within several of the large 

 freshwater ponds and bays. Rapidly these inner delta splays become colonized by various local 

 freshwater plants, some of which are highly desirable wildlife food. The Fish and Wildlife Service, 

 which manages most of the northeastern delta, has seen dramatic use of these splays by wildlife. 

 So, during October 1983 a levee crevasse was made along Octave Pass to further induce land 

 buildup within a huge freshwater pond that had formed from subsidence since 1956. 



This study monitored plant colonization and succession on the inner delta splay that formed as 

 a result of the levee breach. Also, this study measured the rate of sedimentation on this artificial 

 splay. For comparison, this study also monitored the sedimentation rate, plant colonization, and 

 succession on a nearby splay near Brant Pass that formed naturally in 1978 from another levee 

 breach. 



METHODS AND MATERIALS 



Plant colonization, succession, and sedimentation on these two inner delta splays were monitored 

 for a period of 3 years. Both splays are located within the Delta National Wildlife Refuge, which 

 occupies most of the northeastern quadrant of the Mississippi River Delta. Both splays receive 

 water in sheet flow from Octave Pass and are located within 4 km of the river. 



Three study sites were established at the very down flow end of one finger or lobe of the splays. 

 In the summer of 1984, one site was located on the Octave Pass splay and another on the south 

 end of the Brant Pass splay. Because of their age differences, the Brant Pass splay is many times 

 larger than the Octave Pass splay, so a third site was chosen on the Brant Pass splay in spring 

 1985, approximately 2.5 km north of the first site. 



At each of the three sites, sedimentation rates were quantified by using the procedures of 

 Baumann (1980). Beginning in the fall of 1984 and periodically thereafter, white silica marker 

 horizons were placed in transects parallel and perpendicular to the developing mudflat to mark 

 mudflat levels. Cores through the horizons months and years later gave estimates of the amounts 

 of sedimentation. 



To study plant colonization and succession, vegetation was sampled by using 0.25-m 2 plots, 

 placed along transects perpendicular to the long axis of the mudflat. The vegetation in each plot 

 was sorted by species, oven-dried, and weighed to determine biomass. In addition, an estimate of 

 belowground growth and organic matter accumulation was determined by collecting the sediment 

 within 0.25-m ? plots well below rhizome growth; washing the mud away; and drying and weighing 

 the remaining live and dead organic material. No attempt was made to separate roots and 

 rhizomes from dead material, or to separate species. 



With each new growing season additional transects of five 0.25-m 2 plots were established at the 

 leading edge of mudflat development. Each August from 1984 to 1987 the plots along the new 



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