PRELIMINARY LIDAR ANALYSIS OF CHANNEL MORPHOLOGY AND ASSOCIATED LANDFORMS OF THE LOWER WISCONSIN RIVER VALLEY, SAUK COUNTY, WISCONSIN

Light detection and ranging (LiDAR) imagery has become a crucial tool for geomorphologists because it makes possible more accurate landscape analysis, and, in many instances, the identification of features previously not visible on coarser (and older) resolution data. This project presents a study in Sauk County, Wisconsin, where new LiDAR imagery is used to assess and catalog a variety of landforms in the county, most notably those in the lower Wisconsin River valley. County-wide LiDAR imagery was requisitioned in 2005 for updating FEMA flood insurance maps. While this LiDAR imagery was intended for flood mapping, these data make possible landform analysis, especially in the lower Wisconsin River valley where land use and vegetation has made it nearly impossible observe the topography with more traditional sensors.

As the Wisconsin River leaves the Johnstown Moraine in eastern Sauk County, it immediately cuts westward through sandy glacial outwash. Several millennia of river incision has created multiple high terraces and a broad, highly-meandered flood plain. Farther west, the river meanders back and forth through a bedrock-constrained reach. In this region, the flood plain is not as well-defined, nevertheless, several terraces and meander scars are observed. Along the southern edge of Sauk County, the river valley widens to its broadest span (~10 km wide). In this area, high terraces are found adjacent to the bedrock uplands, several lower terraces are observed across the valley, and numerous meander scrolls and sand bars are present in the modern flood plain. In addition to the fluvial landforms, large areas of eastward-trending parabolic sand dunes are found mantling the terrace deposits.

Sauk County, Wisconsin has several unique landscapes, and LiDAR imagery has highlighted several areas that should be investigated in the future. For example, further stratigraphic investigations of terraces and sand dunes of the lower Wisconsin River valley may yield important clues into the late-Quaternary history of the region. In addition, new chronological investigation may yield new information on the timing of the Last Glacial Maximum (Johnstown Moraine) and the deglaciation of the Green Bay lobe.