GEOMORPHIC MAP OF THE LOWER WABASH VALLEY, IL-IN-KY

Landforms of the lower 140 km (4,800 km²) of the Wabash Valley (~87.49 E, 38.91 N to 88.01 E, 37.76 N) and adjacent uplands were interpreted from lidar digital terrain models (DTM). Lidar point cloud data, typically with a nominal point spacing (NPS) of 1 meter, were compiled for 9 counties in Illinois, Indiana, and Kentucky, comprising collection years of 2010-2013. Although DTM gridded data are readily available from each state, they vary in horizontal resolution and vertical accuracy, and grid data exhibit poor fit along boundaries. Thus, a regional-scale DTM was processed using the classified LAS point cloud data to produce a grid with a horizontal spacing of 1.5 m. Subsequently, the entire 9-county compilation was interpolated into a seamless DTM with a horizontal spacing of 3 m. The 3 m grid spacing is less intensive on computing resources for medium-scale, valley-wide analysis in 3D GIS software and constitutes a seamless cartographic layer with acceptable loss in detail at the intended publication scale of 1:62,500. Initially, gross features such as valley margins were digitized at 1:50,000. All other features were digitized at 1:15,000. The 1.5 m lidar-derived DTM supports additional analysis at scales up to 1:2,500. Landform delineation was supported by direct interpretation using digital orthophotography, recent 1:24,000 geologic mapping over portions of the study area, and existing soils and well bore data. The landforms delineated include unglaciated bedrock uplands in the southern portion, bedrock uplands glaciated during the Illinois Episode in the northern portion, Wisconsin Episode proglacial lacustrine terraces, outwash terraces, and eolian dunes, and Hudson Episode meandering stream forms. The map constitutes a geospatial lexicon of features to inspire and plan geologic investigations based on landform dimension, elevation, spatial distribution, and cross-cutting relationships.