Abstract
Leon Creek's riparian vegetation was evaluated through the use of Landsat TM data, where different methods were compared and integrated. Through the use of an Image Difference Calculation, areas of 20% or more change in pixel value from 1987 to 1999 were determined. These areas show the most intense loss or gain of dense vegetation and whether these intense changes are occurring in rural or urban zones. Unsupervised and supervised classifications on 1987 Landsat and 1999 Landsat images were performed of major land use/ land cover types to determine areas of dense vegetation in the riparian areas. The class of dense vegetation was analyzed for their percent area in defined riparian zones surrounding Leon Creek between 1987 and 1999 in both rural and urban zones. Results for both Image Difference Calculation and Percent Area Calculation suggest that for the total watershed, there are higher rates of decreases in vegetation occurring in rural and urban zones. Less vegetation overall in the 0.5 mi. buffer zone in the urban zone suggests that development activity may have affected productive vegetative growth, especially in the urban zone. The 100 ft. buffer zone, closest to Leon Creek, has the greatest fluctuations between increases and decreases in vegetation, suggesting that natural causation (flooding, change in stream morphology) may be affecting vegetative growth or non-growth rather than human-induced disturbances. Spatial landscape indices were used to compare 1987-99 changes in the riparian vegetation area. A land cover theme was created from the supervised classification images where only the dense vegetation theme was analyzed for fragmentation patterns from landscape metrics. The shape indices seem to be indicating that there is an overall decrease in shape complexity in all buffer zones from 1987 to 1999, suggesting there has been more human-induced change. The fragmentation of dense vegetation in urban zone may indeed be due to increased development, which would result in smaller patches.
Cummins, Karen Leigh (2000). The temporal mapping of riparian vegetation at Leon Creek in Bexar County, Texas from 1987 to 1999. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -2000 -THESIS -C846.