Spatial and temporal variability in floodplain sedimentation during individual hydrologic events on a lowland, meandering river: Allerton Park, Monticello, Illinois

Flooding;Sedimentation

Arnott, Donald Ryan ; Anders ; Alison M.

关键词: Flooding;    Sedimentation;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/88120/ARNOTT-THESIS-2015.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Floodplains are major sinks and sources for sediment within the fluvial system and are constructed through two main processes: lateral and vertical accretion. In fine grained systems, vertical accretion dominates. Overbank flooding and floodplain inundation are dependent on bank height and local topographic variability and this leads to highly variable deposition both spatially and temporally. In order to better understand the dynamics of flooding, single flooding events need to be observed and characterized. Using artificial turf mats as sediment traps, I measured floodplain deposition during five flood events on the floodplain of the Sangamon River at Allerton Park in Monticello, Illinois. The five events observed had peak discharges of 40-250 m3/s. During each event, deposition was found to occur most frequently and with greatest magnitude in and adjacent to floodplain channels. Sediment thicknesses accumulated during each flood event vary from 0-4.5 mm with the largest deposition, equivalent to ~14 mm/year, being observed near a crevasse splay which may be evolving toward a meander cut-off.Flow simulations using the iRIC open source 2-dimensional solver of the St-Venant shallow water equations show how water inundates the floodplain during the rising limb of the largest discharge event observed. Geomorphic features such as floodplain channels, scroll bar topography, and, depressions drastically impact the routing of water over the floodplain and, ultimately, the location and amount of deposition.