9405757 Mertes The research will test working hypotheses on relationships among the geomorphology of an alluvial of floodplain/wetland, geomorphic processes active on the inundated floodplain surface, and the hysteresis between water discharge and sediment concentration during floods. Data for the Central Amazon River show that the conceptual model adequately describes the characteristic patterns of water and sediment transport and the related patterns of erosion and disposition during flood on the largest river in the world. The proposed work is to test the conceptual model at a smaller spatial scale by collecting hydrologic, hydraulic, and sediment transport data for the Altamaha River, Georgia. The work is a step in a larger study to develop a physically based model of the construction of landforms on inundated floodplains for rivers across all scales. It is anticipated that the results from the Altamaha River, with a drainage basin area of 35,200 Km2 will significantly advance understanding of the hydrologic and geomorphic processes controlling the development and maintenance of its floodplain and wetland. Limited water discharge sediment concentration data for the Altamaha River indicate that it is similar to the Amazon River, in that the peak sediment concentration precedes the peak water discharge. One hypothesis to be tested is that the rates of deposition on a non-channelized floodplain surface are a monotonic function of the rate of water and sediment discharge supplied from the main channel. The second hypothesis is that the rate of deposition increases at the crest of the flood as the pressure distribution across the channel-floodplain boundary equalizes. The third is that the rates and loci of deposition and erosion in drainage channels shift from the upstream end during initial stages of inundated to the downstream end during the falling -water period. Data from field studies, remote sensing, and numerical simulations of hydr odynamics will be used numerical simulations of the hydrodynamics of the field sites for floods with different magnitudes and durations the hypotheses. The data from each source will constrain the interpretation of the results from the other techniques.
