Evaluating remote sensing methods for targeting erosion in riparian corridors

The Oklahoma Conservation Commission has begun using satellite imagery with hydrologic/water quality modeling to identify potential critical source areas of pollutants. Implementation of best management practices in these critical source areas is essential to the improvement of Oklahoma's impaired waters. To more efficiently use available funds, it is necessary for the Oklahoma Conservation Commission to quantitatively target areas with the highest potential for water quality improvement. For large watersheds, aerial photography and satellite imagery are far less expensive and less time consuming to develop a detailed land cover compared to on-site inspection. The objective of this research was to compare the accuracy of SPOT 5 and Landsat 7 imagery with aerial photography to identify land covers thought to be critical sources of erosion in riparian corridors. The study area was Turkey Creek, a 108,000 ha watershed in northwest Oklahoma. Land cover for 2,400 ha of riparian corridor was manually digitized from existing color aerial photograph and used as a truth layer for comparing the satellite images. Land cover percentages derived from each type of image were compared. In addition, a statistical method using weighting factors based on the type of land cover classification error was used to evaluate the magnitude and spatial distribution of errors. We concluded that manual classification using aerial photography was the best option for areas up to twice the study size. For areas that exceed this critical size, we recommend Landsat 7 over SPOT 5 as the best satellite option.