HIGH RESOLUTION LIDAR DIGITAL ELEVATION MAPS OF NEBRASKA'S RAINWATER BASINS; VISUALIZING THE PLANFORMS OF THE CAROLINA BAYS' WESTERN COUSINS

While there has been a great deal effort expended in researching the "Carolina bays" on the eastern seaboard of the United States, little attention has been paid to the significant quantity of elliptical-shaped landforms in Nebraska, United States. William Zanner (2001) proposed a relationship between the Rainwater Basins of Nebraska and the Carolina bays, based prior core sampling through overburden loess layers (Mark Kuzila, 1994), which suggested the ancestral depressions were created sometime prior to 27 ka. Since that time a significant blanket of late Wisconsin glacial loess have been deposited, rounding off the originally sharp edges of the basins. In 2010, the Nebraska Department of Natural Resources released high-resolution 2-meter Ground Sample Distance (GSD) LiDAR data with 0.36 m vertical accuracy for much of the southeastern region of their state. We present digital elevation maps (DEMs) generated with this data. These clearly exhibit the presence of significant quantities of elliptical planform depressions with many facets in common with those in the East. The use of these LiDAR maps has enabled this identification with their sub-meter relief fidelity, as the characteristic planforms are rarely seen or identified on the ground or in satellite imagery. Their distinct closed elliptical circumpheral rims, variety of sizes, and common alignments in any one area are considered by us to be as enigmatic as the Carolina bays’ planforms. In some areas, local dunes visible in the LiDAR maps have breached the landforms, but the underling ancestral basin structure continues to show through. Our use of LiDAR elevation data includes the generation of elevation profile maps, which attempt to document basin rim relief, as well as the disparate altitudes of basins in a region. As is the case on the East coast, the basins were generated on a continuum, without regard to altitude above sea level. The Rainwater Basins are spatially large landforms, correlating well with the larger Carolina bays. We speculate that, if ever existent, smaller basins have been inundated with overburden and no longer map through. While not found in quantities as extensive as those in the East, we hold the geospatial mapping of the surviving basins to be critical to our triangulation attempt, when correlated to their Eastern brethren.