HR: 0800h
AN: H51C-1141    [Abstracts]
TI: Challenges in Parameterizing a Landscape Evolution Model to Predict 1000 Years of Erosion on a Mesa-top Waste Repository
AU: * Wilson, C J
EM: cjw@lanl.gov
AF: Los Alamos National Laboratory, EES-2 MS J495, Los Alamos, NM 87545 United States
AU: Crowell, K J
EM: crowell@lanl.gov
AF: Los Alamos National Laboratory, EES-2 MS J495, Los Alamos, NM 87545 United States
AU: Lane, L J
EM: ljlane2@msn.com
AF: Los Alamos National Laboratory, EES-2 MS J495, Los Alamos, NM 87545 United States
AB: Low-level radioactive waste from operations at Los Alamos National Laboratory is currently being disposed in pits excavated into mesa-top repositories. One requirement for operation of the repositories is that no release of radioactive material will occur for up to 1000 years following closure of the repository. LANL is required to demonstrate that the repository can be successfully closed; including demonstrating that the waste pits will not be excavated by long term surface erosion processes. Here we describe the parameterization and application of the Siberia landscape evolution model in the optimization of the closure cap design for the Material Disposal Site G at LANL. The closure design is particularly challenging since some of the older waste pits are located near the edges of a slender finger mesa with complex topography. LANL scientists worked with the cap design engineer at URS in an iterative process to develop a stable design. In addition to design challenges, we faced significant challenges parameterizing the Siberia model for our site. Although we had multiple rainfall, runoff and sediment data sets at a range of scales (plot, first order basin and watershed), these data were not complete enough to develop the relationships required to parameterize Siberia. The data did however provide a strong realty-check on rainfall-runoff and runoff-sediment yield relationships derived from the IRS9 and Hillslope Erosion (HEM) models respectively, which were ultimately used to develop parameter values for the fluvial erosion in Siberia. Diffusion was constrained by eye-balling a match between Siberia generated topography and the observed topography (field and ALSM data) at the heads of first order channels. Siberia runs that generated colluvial hollows (non-existent at this site) indicated that the diffusion coefficient was too high. LA-UR-04-6328.
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting