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Simulating Sub-Decadal Channel Morphologic Change in Ephemeral Stream Networks

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Abstract:A distributed watershed model was modified to simulate cumulative channel morphologic
change from multiple runoff events in ephemeral stream networks. The model incorporates the general design of the event-based Kinematic Runoff and" Erosion Model (KINEROS), which describes the processes of interception, infiltration, surface runoff, and erosion from small watersheds predominantly characterized by overland flow; A geomorphic sub-model was added to compute geometric adjustment of the channel reaches in response to computed changes in sediment storage by minimizing the total stream power. The event-based watershed model framework permits exceptional temporal resolution of channel response to ephemeral water and sediment fluxes, including impacts resulting from distributed land-use/cover management. A GIS-based interface was developed to facilitate parameterization of the model, track cumulative geomorphic change and errors resulting from multiple distributed rainfall events. In addition the interface allows visualization of the spatial patterns of computed geomorphic adjustment, and permits comparisons of results from different simulations.

Results from multiple-event simulations indicate that morphologic adjustment within channel networks is predominantly controlled by the frequency and magnitude of rainfall events. In ephemeral stream networks transmission losses progressively decrease the transport capa.city of flows as they move downstream. Drier periods, characterized by small runoff events, thus produce aggradation and increasing width-to-depth ratios within the smallest headwater
channels. As rainfall and the number of large events increases, headwater channels begin to incise and sediment is progressively redistributed further downstream. Disturbance within a portion of the watershed can interfere with this response pattern, with significant alterations to channel morphology extending well downstream of the disturbance. Comparisons of simulated patterns of morphologic adjustment with and without localized urbanization demonstrate the anticipatedgeomorphic response of incision within the urbanized area and increasing width-to-depth ratios downstream.
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Citation:Semmens, D. J., W. R. Osterkamp, P. Guertin, and D. C. Goodrich. Simulating Sub-Decadal Channel Morphologic Change in Ephemeral Stream Networks. Presented at American Geophysical Union Conference, San Francisco, CA, December 13-17, 2004.
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Contact: Chris Siebert - (702) 798-2234 or siebert.christopher@epa.gov
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Division: Environmental Sciences Division
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Branch: Landscape Ecology Branch
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Product Type: Abstrct/Oral
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Presented: 12/13/2004
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Related Entries:
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Bullet Item Development of Landscape Indicators for Use in Regional Ecological Risk Assessments
spacer Relationship Reason:   A Project of the Product
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Last Updated on Monday, October 22, 2007
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