APPLICATIONS OF GIS IN GEOMORPHOLOGY

Visualization and analysis of spatially oriented data are the primary strengths of a geographic information system (GIS). These attributes have assisted a variety of ongoing geomorphology studies in the Oregon District of the U.S. Geological Survey. Three examples are (1) flow modeling with LIDAR elevation data for the Snoqualmie River, Washington; (2) determining temporal and spatial rates of channel migration for several rivers in western Washington; and (3) calculation of sediment budget for the Deschutes River Basin, Oregon. The flow modeling application required modification of a digital raster elevation model (DEM) that did not adequately represent the channel geometry or the channel water surface. Superimposing vector topographic data on the DEM and creating a water surface for the channel resulted in a product that could be used in the flow modeling process. The channel migration study required a compilation of various statistics on channel characteristics for cross-sections at specific intervals such as cumulative length and area, width, and area of gravel deposits or riparian vegetation. Additionally, historical maps were digitized into the GIS, which easily allowed distance and direction of migration over time to be measured along cross-sections. For the Deschutes River Basin, a spatially explicit map of relative sediment production was created in the GIS for use in assessing the effects of the Pelton-Round Butte dam complex on the lower Deschutes River channel. The entire basin was divided into 100 approximately equal hydrologically based units. For each unit, the average slope and drainage density were computed and used to calculate the relative potential for sediment production.