A NEW METHOD FOR EXTRACTING RIVER PROFILES AND NORMALIZED STEEPNESS VALUES WITH OPEN SOURCE R SCRIPT
HILL, Jesse S., Department of Geological Sciences, University of North Carolina at Chapel Hill, Mitchell Hall, Campus Box 3315, Chapel Hill, NC 27599, hilljs@live.unc.edu
Streams in the Cullasaja River basin were the focus of a recent study in which plots were produced using the StreamProfiler tool (http://www.geomorphtools.org) and Matlab, and were interpreted to have experienced a base-level change in the Miocene (Gallen et. al, 2013). The extraction of longitudinal profiles using R, an open-source computing language, instead of Matlab offers an alternative method to investigate uplift history. ArcMap v.10 hydrology tools were used to find the steepest path from the headwaters of each stream and the results were imported into R to draw stream profiles and calculate normalized steepness values (ksn) along multiple stream networks in the Blue Ridge of western North Carolina. A detailed description of the normalized steepness analysis of stream profiles can be found in many recent geomorphology papers (e.g. Kirby and Whipple, 2001; 2012, Duvall et al., 2004, Gallen et al., 2013).
With high-resolution LIDAR data (horizontal resolution of ~6 m and a vertical resolution of ~1/3 m) obtained from the NC Floodmaps program (http://www.ncfloodmaps.com/) a discretized slope map was produced using three topographic parameters. The first parameter was defined as areas with both elevations less than 1000 m and slopes less than 3 degrees. These areas correspond to possible lineaments. The second topographic style was defined as areas with elevations greater than 1000 m and slopes less than 10 degrees, and was used to find possible relict landscapes in the upper reaches of drainage basins. The third topographic style was defined as areas higher than 1000 m with slopes greater than 10 degrees. These areas correspond to high topography that is steep.
To establish a relative sequence of local uplift, a geomorphological study of knickpoint migration may be utilized (Gallen et al., 2011, Gallen et al., 2013, Miller et al, 2013). The addition of the discretized slope maps offers a new way to find relict landscapes and compare these with knickpoint locations.
