Elevation Time Series Analysis and Its Impact On Soil Hydraulic Properties At Lake Lynn, Raleigh, NC.

The Southern Piedmont region is characterized by a sandy surface over a subsurface that contains an accumulation of clay (Bt horizon).  The lower horizons provide a natural barrier to water movement, and generally have very low saturated hydraulic conductivity (Ksat) values.  The area around Raleigh, North Carolina experienced a 48% population increase in the last ten years.  The influx of people require new infrastructure.  These building projects can vastly alter the landscape, exposing the lower Bt and BC horizons. These horizons have a lower permeability, and their exposure can decrease infiltration rates. The objective of this study was to assess how elevation and infiltration capacity changes with development.  In 1968, the Centennial Campus of North Carolina State in Raleigh was forested. Today, it contains nearly 40 buildings, a middle school, and a golf course.  A 1968 contour map with a ten foot interval was digitized and georeferenced.  Between 1999 and 2012, there were six contour maps taken. The surface elevation, curvature, and slope for all time periods were recreated using a spline with a tension function.  Preliminary development soils data was used to determine the overall infiltration capacity.  A majority of the buildings were cut into the slopes, altering hydrology and relief. A new infiltration potential was calculated from the modeled soil horizons. For a five year storm, development can drastically reduce the infiltration capacity of soil. A reduced infiltration potential can cause pooling and runoff.