Intellectual Merit - The objective of this proposal is to acquire and analyze highresolution digital topography data for an ~18km2 field site in the Colorado high plains that represents a natural experiment in scarp retreat and drainage divide migration. The site offers a unique opportunity to document landform development and test physically based landscape evolution theory under differential baselevel control. The larger importance is two-fold. First, drainage divide migration is a fundamental aspect of landscape response to tectonics, eustasy, and other forms of baselevel control. Second, testing physically based landscape evolution models requires natural experiments that involve a transient response to a known forcing factor, such as baselevel. High-resolution, research-grade laser altimetry data are essential to achieving these goals because standard USGS digital elevation data lack the necessary resolution and accuracy to document the topographic signatures of the governing processes, extract statistics for model-data comparison, and map incised surfaces. The project is timely because the National Center for Airborne Laser Mapping (NCALM) will launch a mission to acquire data from other sites in Colorado this summer. The cost of data will be significantly lower if the data for the study area are collected during NCALM's 2006 Colorado mission. The data will be analyzed to determine characteristic topographic signatures, including slope and curvature maps and frequency distributions, slope-area diagrams, area aggregation indices, and related metics. They will also be used to reconstruct the former extent of a series of incised valley fills and upland surfaces. These data, when combined with timing constraints on cut and fill events, will provide a unique method for testing landscape evolution models and their predictions about divide migration in response to differential baselevel lowering. Exploratory iterative forward modeling using the CHILD model will be used to identify process laws and parameter sets that can and cannot account for the observed topography and soil thickness. Success in this project is expected to seed a larger effort that will generate geochronology data, real-time process monitoring, and sediment-yield estimates, resulting in a comprehensive data set for use by the research community in testing other landform evolution models. Note that in addition to the budget requested in this proposal, funds are also requested for data acquisition by NCALM. If funded, the University of Florida will request a supplemental budget for these expenses. Broader Impacts - The broader impacts of this research fall into several categories. The high-resolution altimetry data will directly support the dissertation research of a Ph.D. student at the University of Colorado, thus contributing to teaching, training, and learning. The project enhances infrastructure by providing the scientific community with altimetry data and associated information for a valuable research site; in addition to its geomorphic importance, the area encompasses a world-famous terrestrial Cretaceous-Tertiary boundary section. Broad dissemination will be ensured not only through the usual routes of publications and conferences, but also by providing data and images to the Plains Conservation Center, a non-profit land conservation and public education organization that owns the site, and to the Denver Museum of Natural Science, which leads research on the K-T boundary section and has a strong track record in research-based public outreach related to the geology of the Denver Basin. Benefits to society include advances in our understanding of soil erosion, transport, and deposition, which is applicable to land management.
