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Persistent distribution patterns of woody vegetation within the bottomland forest of Passage Creek, Virginia, were related to fluvial landforms, channel geometry, streamflow characteristics, and sediment-size characteristics. Vegetation patterns were determined from species presence a~ oJ:>se~ed in transects and traverses on landforms developed along the stream. Distinct species distnbubonal patterns were found on four common fluvial geomorphic landforms: depositional bar, active-channel shelf, floodplain, and terrace. Independent hydrologic characteristics (flow duration a':ld floo? fr~q~:~ency) were _dete~i~ed for each of the landforms. Vegetation data were analyzed by bmary discnmmant analysis, pnnc1pal components analysis, and detrended correspondence analysis. Results and related field observations suggest that certain species are significantly associated with specific fluvial landforms. Vegetation patterns appear to develop more as a result of hydrologic processes associated with each fluvial landform rather than from sediment-size characteristics. Flood disturbance may be an important factor in maintaining the vegetation patterns, which may therefore be used as indicators for particular hydrogeomorphic site conditions. F!G. 2. Block diagram showing fluvial landforms. From the lowest, the features are: CB = channel bed, DB = depositional bar, AB =channel-shelf bank, AS= channel shelf, FB =floodplain bank, FP =floodplain, T1 =lower terrace, T" =upper terrace, and HL = hillslope. From Osterkamp and Hupp (1984).

Rivers of the Coastal Plain of the southeastern United States are characteristically low-gradient meandering systems that develop broad floodplains subjected to frequent and prolonged flooding. These floodplains support a relatively unique forested wetland (Bottomland Hardwoods), which have received considerable ecological study, but distinctly less hydrogeomorphic study. The hydroperiod, or annual period of inundation, largely controls the development of characteristic fluvial landforms, sediment deposition, and vegetation distribution patterns. Order of magnitude differences in wetted perimeter, width/depth, suspended sediment load, and hydraulic roughness may exist between "dry" in-channel seasons and the hydyoperiod. Substantial sediment (and adsorbed contaminants) retention and storage through lateral and bertical accretion is common (where not heavily impacted by flow regulation) along these Coastal PI&n rivers. The present chapter summarizes our current understanding of the hydrology, fluvial geomorphology, general and local sedimentation patterns, and related plant ecological patterns of these Coastal Plain bottomlands.

Hundreds of kilometres of West Tennessee streams have been channelized since the turn of the century. After a stream is straightened, dredged, or cleared, basinwide ecologic, hydrologic, and geomorphic processes bring about an integrated, characteristic recovery sequence. The rapid pace of channel responses to channelization provides an opportunity to document and interpret vegetation recovery patterns relative to otherwise long—term, concomitant evolution of river geomorphology. Nearly 150 sites along 15 streams were studied in the Obion, Forked Deer, Hatchie, and Wolf River basins. Channels of these streams, except that of the Hatchie River main stem, have undergone major modifications along all or parts of their courses. This paper presents the eco—geomorphic analyses and interpretation of a large multidisciplinary study, with special reference to their interrelated hydrogeomorphic aspects of channel recovery. Quantitative plant ecological analyses were conducted to infer relative bank stability, to identify indicator recovery species, and to determine patterns of vegetation development through the course of accelerated channel evolution. Binary—discriminant and ordination analyses show that distinctive riparian—species patterns reflect a six—stage model of channel evolution and can be used to infer channel stability and hydrogeomorphic conditions. Woody vegetation initially establishes on low— and mid—bank surfaces at the same location and time that bank accretion begins, and corresponds to the site of initial geomorphic restabilization. The linkage of channel bed aggradation, woody vegetation establishment, and bank accretion all lead to recovery of the channel. Pioneer species are hardy and fast growing, and can tolerate moderate amounts of slope instability and sediment deposition; these species include river birch (Betula nigra), black willow (Salix nigra), boxelder (Acer negundo), and silver maple (Acer saccharinum). High stem densities and root—mass development appear to enhance bank stability. Tree—ring analyses suggest that on average 65 yr may be required for recovery after channelization.