Using remote sensing and GIS techniques to determine the tectonic significance of small-scale surface water runoff in Canyonlands National Park

The Needles District of Canyonlands National Park consists of brittle strata overlying plastically flowing evaporite deposits. These deposits are primary drivers of active extensional deformation in the overlying sandstone. Previous studies have analyzed the evolution of fault arrays at the surface and the plasticity of the evaporites. Initial research was done to show that surface water runoff, especially when piped into dilating faults, correlates with areas of higher rates of subsidence. In order to make these correlations, surface drainage networks (especially where crossing faults) needed to be analyzed at large and small scales. The best available data in the area are limited to a 5-meter resolution auto-correlated digital elevation model (DEM), stereo film imagery, high-resolution digital air photos, and a differential interferometric SAR data map. Several methodologies for mapping surface features were explored, including photogrammetry, aerial photo analysis, and hydrologic modeling. By using the available datasets and testing various software packages, we have determined a comprehensive and time-effective methodology for mapping, analyzing, and interpreting large- and small-scale hydrologic features. In order to obtain better small-scale modeling, a test DEM using photogrammetric methods successfully created a high-resolution model of the area, but was ultimately not used because the overall accuracy of the DEM was not as high as other available elevation data in the area. Maps of stream order, catchment boundaries, drainages piping directly into faults, and sinkholes were created at varying scales using the most accurate available DEMs and hydrologic modeling software. Piping drainages and sinkhole maps were made by hand. Each map was draped over the InSAR map and aerial imagery, and mapped surface features such as trunk streams at fault crossings, piping drainages, and catchment areas were correlated with areas of highest rates of subsidence (as defined by InSAR). These data confirm the influence of surface water runoff on tectonic subsidence in at least 30% of cases, and close to 100% where high-order streams cross faults. Although our work suggests that infiltration of surface water runoff increases localized areas of subsidence by 100-200%, large-scale patterns of strain (~20-30% of the fault array) are likely driven by contributions from other processes such as groundwater influx.