AN ARC/INFO PROGRAM TO MODEL STREAM MANAGEMENT ZONES (SMZ’s) AS DEFINED BY SOUTH CAROLINA FORESTRY BEST MANAGEMENT PRACTICES

 
Donald J. Lipscomb
Research/Demonstration Forester
Department of Forest Resources
Clemson University
Clemson, SC
 
Thomas M. Williams
The Belle W. Baruch Institute of Coastal Ecology and Forest Science
Clemson University
Georgetown, SC
 

ABSTRACT

South Carolina’s forestry best management practices (BMP’s) are published guidelines for silvicultural practices which are intended to minimize their impacts on water quality (SC FOR. COMM., 1994). Like the recommended practices for many other southeastern states, South Carolina’s guidelines call for stream management zones (SMZ’s) that very in width with slope to filter run-off and provide other benefits to stream water quality (Florida, Georgia, Virginia and SC BMP’s). Because of their relationship to slope, South Carolina’s SMZ’s are difficult to map using standard buffer functions in a GIS environment. However, it is possible to use the buffer function in a variable mode if the widths resulting from perpendicular slope on each side of the stream have been calculated and placed in an attribute table for a stream network. This requires special interpretation of a slope surface developed from a digital elevation model to determine the SMZ width because the slope sought is a linear slope for each segment on each side of the stream. The slope of the grid intersected does not necessarily correspond to the slope on either side of the stream, in fact it probably represents the in-stream slope. Zonal and focal functions account for area (eg. rectangle and polygon) means, not slope along a line perpendicular to the stream.

This paper presents an ARC/INFO AML program that will arbitrarily segment a stream net work into one hundred foot segments and interpret the slope perpendicular to each side of those segments into attribute tables of SMZ widths. These table values are then used by the program to map variable width buffers for each side of the stream network independently. The zones for each side are combined to map the area and location of the SMZ as defined by South Carolina’s forestry best management practices. The program can be used on whole stream net works or small segments of streams.