THE USE OF GIS IN EVALUATING LONGITUDINAL PROFILES OF KARST STREAMS

Southeastern Minnesota is characterized by an extensive karst network. In Kentucky, Carter Caves State Resort Park is a similar karst area that has exhibited karst anomalies, or ‘bumps,’ in a longitudinal stream profile. This study aimed to determine if these same karst anomalies can be found in southeast Minnesota, where LiDAR data are available, and if these bumps are actually karst features. Profiles of carbonate and siliciclastic streams were observed to determine if the presence of anomalies in only carbonate streams, both lithologies, or neither. Another objective was to determine if GIS could be an effective method at generating these profiles. Field data were collected to verify the GIS derived profiles. Stream shapes were also analyzed to determine what dominant processes occur in the area. No karst features were identified within profiles of streams in southeast Minnesota. However, GIS proved to be a useful tool in creating profiles from 1- and 3-meter DEMs. GIS was able to locate where changes in slope occurred; this was verified by field data. Some differences in profile can be attributed to the continuously changing morphology due to scour and fill processes that occur in these streams. Filled DEMs were also created, but ultimately not used because they eliminated some important features. Stream gradient index values were calculated that accounts for the distance from the source, length of reach, and elevation change of the reach. Values were calculated for carbonate and siliciclastic reaches of streams and were found to be statistically similar to each other, indicating that stream bed lithology is not a dominant process affecting the stream shape in this area. Four main stream shapes were identified: linear, concave, convex, and stepped. Linear streams were the dominant shape, followed by concave. There was no statistically significant difference between shapes for the carbonate and siliciclastic rocks. This further supports the claim that lithology is not playing a role in the streams’ morphology in this study area. It is likely that the erosion of legacy sediments from past farming practices is playing the largest role in sculpting the streams. Another factor affecting shape is land use, which increases erosion in this area.