AN APPLICATION OF GIS TO KARST TERRAINS: STREAM NETWORK MODELING (CARTER CAVES STATE RESORT AND PARK)

In GIS software, a digital elevation model (DEM), raster data representing elevations for a given area, can be used to delineate a stream network (vector data). Raster data sets have connected cells where each cell has its own value or number and vector data are represented as points, lines, or polygons that are not necessarily connected. In GIS, the conversion from a raster to a vector is easily done. Stream flow through a karst system is not always surficial; flow can also be subterranean. When a stream starts at the surface, eventually goes underground, and resurfaces along the flow path it is deemed a sinking stream. These streams are characteristic of karst terrains and can augment karstification of the area. This type of stream complicates the modeling of a stream network because most models assume the flow of the streams is at the surface. This paper discusses the delineation of a stream network for Carter Caves State Resort and Park (CCSRP) using a 30m x 30m DEM. The CCSRP is a karstified region and contains many sinking streams, which masks the stream network. The streams in the park seem fragmented, not connected and the stream network is not obvious. Using ESRI's ArcMap, a Stream Network Model was created using sub routines to delineate the stream network from a DEM. The key to an accurate model is finding best the threshold value for the given area. The threshold is the minimum number of cells that must flow into one cell in order for that cell to become part of the stream network. The model was run three times with different threshold numbers (10,000 cells, 1,000 cells, and 100 cells) because the threshold number depends on the relief in a given area and the resolution of the DEM. The resulting stream networks were compared to the KGS stream data to calibrate the model. Delineation of a stream network in a karst terrain can be done with the use of GIS software. Once a stream network is derived a watershed can be delineated.