Imaging a Natural Experiment in Drainage Divide Migration

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Imaging a Natural Experiment in Drainage Divide MigrationIntellectual Merit - The objective of this proposal is to acquire and analyze highresolutiondigital topography data for an ~18km2 field site in the Colorado high plainsthat represents a natural experiment in scarp retreat and drainage divide migration.The site offers a unique opportunity to document landform development and testphysically based landscape evolution theory under differential baselevel control. Thelarger importance is two-fold. First, drainage divide migration is a fundamental aspectof landscape response to tectonics, eustasy, and other forms of baselevel control.Second, testing physically based landscape evolution models requires naturalexperiments that involve a transient response to a known forcing factor, such asbaselevel. High-resolution, research-grade laser altimetry data are essential toachieving these goals because standard USGS digital elevation data lack the necessaryresolution and accuracy to document the topographic signatures of the governingprocesses, extract statistics for model-data comparison, and map incised surfaces. Theproject 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. Thecost of data will be significantly lower if the data for the study area are collectedduring NCALM's 2006 Colorado mission. The data will be analyzed to determinecharacteristic topographic signatures, including slope and curvature maps andfrequency distributions, slope-area diagrams, area aggregation indices, and relatedmetics. They will also be used to reconstruct the former extent of a series of incisedvalley fills and upland surfaces. These data, when combined with timing constraintson cut and fill events, will provide a unique method for testing landscape evolutionmodels and their predictions about divide migration in response to differentialbaselevel lowering. Exploratory iterative forward modeling using the CHILD modelwill be used to identify process laws and parameter sets that can and cannot accountfor the observed topography and soil thickness. Success in this project is expected toseed a larger effort that will generate geochronology data, real-time processmonitoring, and sediment-yield estimates, resulting in a comprehensive data set foruse by the research community in testing other landform evolution models. Note thatin addition to the budget requested in this proposal, funds are also requested for dataacquisition by NCALM. If funded, the University of Florida will request asupplemental 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 aPh.D. student at the University of Colorado, thus contributing to teaching, training,and learning. The project enhances infrastructure by providing the scientificcommunity with altimetry data and associated information for a valuable researchsite; in addition to its geomorphic importance, the area encompasses a world-famousterrestrial Cretaceous-Tertiary boundary section. Broad dissemination will be ensurednot only through the usual routes of publications and conferences, but also byproviding data and images to the Plains Conservation Center, a non-profit landconservation and public education organization that owns the site, and to the DenverMuseum of Natural Science, which leads research on the K-T boundary section andhas a strong track record in research-based public outreach related to the geology ofthe Denver Basin. Benefits to society include advances in our understanding of soilerosion, transport, and deposition, which is applicable to land management.