Meeting:Abstract 2011 CSDMS meeting-028


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CSDMS all hands meeting 2011

Floodplain Deposition Modeling: Time and Spatial Scale Issues

Irina Overeem, CSDMS, University of Colorado Boulder Colorado, .

[[Image:|300px|right|link=File:]]Floodplain deposition maintains and builds up low-lying lands along rivers and in deltas. Floodplain aggradation processes and patterns determine how vulnerability of low-lying land changes over timescales of decades to hundreds of years. Over the longterm, floodplain deposition and channel migration determine the depositional architecture with impacts on groundwater and hydrocarbon reservoirs.

We build and enhanced a 3D floodplain architecture model, AquaTellUs. AquaTellUs uses a nested model approach; a 2D longitudinal profile, embedded as a dynamical flowpath in a 3D grid-based space. A main channel belt is modeled as a 2D longitudinal profile that responds dynamically to changes in discharge, sediment load and sea level. Sediment flux is described with a modified Exner equation by separate erosion and sedimentation components. Erosion flux along the main flowpath depends on river discharge and channel slope, and is independent of grain-size. Depositional flux along the channel path as well as in the lateral direction into the floodplain depends on the local stream velocity, and on grainsize-dependant settling rates. Multiple grainsize classes are independently tracked. Floodplain deposition is an event-driven system, only peak discharge events cause overbanking, flooding and perhaps channel avulsion. The computational architecture of AquaTellUs preserves stratigraphy by event, allowing for preservation of information of depositional layers of variable thickness and composition.

We here present experiments that show the pronounced effect of different probability density functions for river discharge and sediment load, i.e. flooding recurrence times, on the stratigraphic architecture.