Development of an ArcGIS-pollutant load application (PLOAD) tool
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Many of the findings of previous studies have indicated that there is a direct correlation between water quality and urbanization. Increasing impervious coverage typically results in a decrease in water quality. The purpose of this study was to adapt an automated tool for assessing the Pollutant Load Application (PLOAD). Created by CH2M HILL, a fullservice engineering and construction enterprise, PLOAD is a simplified GIS-based model used to calculate pollutants within a watershed. The so-called “simple method” implemented by PLOAD and discussed in this thesis has been endorsed by the EPA as a viable screening tool for National Pollutant Discharge Elimination System (NPDES) stormwater projects. This model was designed to be used with ArcView 3.3. ArcView 3.3 is a depreciated product, the capabilities of which have been replaced by ArcGIS 9.1. Using the same GIS data and tabular data required by PLOAD and custom ArcObjects scripting, a replacement, ArcGIS-PLOAD, was created. The current version of ArcGISPLOAD implements the “simple method” to calculate total pollutant load in pounds per year based on basin boundaries, precipitation in inches per year, ratio of storms producing runoff, parcel land use and parcel area, runoff coefficient for each land use, event mean pollutant concentrations for each land use. Time comparisons between the original PLOAD and the new ArcGIS-PLOAD revealed significant improvements. Both versions of PLOAD produce an intersection between the basin boundary and the land use layer. Calculations are actually done to the intersect layer. It was also found that the original PLOAD disregarded an albeit small portion of the intersection polygons. The new version does not. With the creation of ArcGIS-PLOAD, it is anticipated that it will become a small step in assist the State of Texas in improving water quality.
Young, De'Etra Jenra (2006). Development of an ArcGIS-pollutant load application (PLOAD) tool. Master's thesis, Texas A&M University. Available electronically from