HR: 0800h
AN: H51C-1142    [Abstracts]
TI: Constraining Uncertainty in the Application of a Landscape Evolution Model to Predict 1000 Years of Erosion at a Mesa-top Waste Repository
AU: * Crowell, K J
EM: crowell@lanl.gov
AF: Los Alamos National Laboratory, EES-2 MS J495 PO Box 1663, Los Alamos, NM 87544 United States
AU: Wilson, C J
EM: cjw@lanl.gov
AF: Los Alamos National Laboratory, EES-2 MS J495 PO Box 1663, Los Alamos, NM 87544 United States
AU: Lane, L J
EM: ljlane2@msn.com
AF: Los Alamos National Laboratory, EES-2 MS J495 PO Box 1663, Los Alamos, NM 87544 United States
AB: A landscape evolution model (SIBERIA) is being applied to assess long term erosion of cap designs proposed for eventual closure of a waste disposal area atop a mesa, under the design requirement that waste remain buried beneath a prescribed minimum thickness of cap material at 1000 years. Here we describe a first-cut at constraining uncertainty in the landscape evolution model, so that predicted erosion rates are realistic within the bounds of the likely physical conditions at the site. A profile-based hillslope erosion, sediment transport, and erosion model (HEM) which has been subject to extensive validation on rangeland conditions is used to simulate sediment yield on hillslope profiles under a range of conditions that promote high, moderate, and low erosion rates. HEM uses a small set of parameters, including canopy- and ground-coverage, slope, and soil properties along the profiles, data for which are easily obtained in the field. Such a field dataset has been developed for profiles on disturbed and undisturbed hillslopes on the mesa and on an existing closure cap. The profiles included canopy- and ground-cover conditions which encompass the range of conditions expected to be present during the evolution of the ecosystem on the closure cap. A series of 64 HEM simulations were run with parameters obtained from the field dataset and properties of two soil types chosen to represent cap material properties on profile geometries constructed using a range of slopes. SIBERIA parameters were chosen so that resulting sediment yields on the profiles were bounded by the extremes of the HEM field based simulations. This represents a first step in assessing uncertainty in the application of SIBERIA as a predecessor to a more formal uncertainty analysis. LA-UR-6329
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting