DEVELOPING GEOMORPHIC LANDFORM MAPS OF CENTRAL KENTUCKY USING LIDAR-BASED TERRAIN INTERPRETATION

Kentucky has statewide 1:24,000 bedrock geologic map coverage and a 1:24,000 materials-based surficial geologic mapping program is underway, but the state lacks equivalent quadrangle-scale geomorphic landform maps. Geomorphic maps are important for studying erosional and depositional processes, delineating areas of hazard occurrence, and understanding landscape evolution. We mapped geomorphic landforms across a catchment in central Kentucky using high resolution LiDAR DEMs and derivative maps (such as flow direction/accumulation maps, slope angle and curvature maps and hillshade images) with three objectives in mind. First, to develop a framework for future landform mapping that can be used in different physiographic regions across the eastern midcontinent and into Appalachia. Second, to identify correlations between landforms and topography that can be used to infer landscape evolution using time-space substitution. Third, to create a GIS-based workflow using topographic position index (TPI) and slope angle that can be used as a first order model of landform distribution and enable the creation of a statewide landform map. Our mapping framework includes head slopes, side slopes, base slopes, summits, interfluvial ridges, alluvial fans, terraces, free faces, several types of landslides, and anthropogenic landforms. Thus far, our observations include correlation of landslide activity, presence of base slopes, and other landforms to the maturity of the fluvial network, prediction of bank collapse, and presence of knick zones based on TPI of the fluvial network, identification of relict karstic side slopes that are hydraulically disconnected from the contemporary fluvial system, and a relationship between the presence of well-developed head slopes and alluvial fans at the mouth of tributary catchments. One hypothesis is that head slopes, which are dominated by sheetwash, sap headward into low angle summits – with longer head slopes presumably moving faster and effectively driving stream capture.