Spatially distributed storm runoff depth estimation using Landsat images and GIS

The use of geographic information systems (GISs) and remote sensing to facilitate the estimation of runoff from watershed and agricultural fields has gained increasing attention in recent years. This is mainly due to the fact that rainfall-runoff models include both spatial and geomorphologic variations. The US Department of Agriculture, Natural Resources Conservation Service Curve Number (USDA-NRCS-CN) method was used in this study for determining the runoff depth. Runoff curve number was determined based on the factors of hydrologic soil group, land use, land treatment, and hydrologic conditions. GIS and remote sensing were used to provide quantitative measurements of drainage basin morphology for input into runoff models so as to estimate runoff response. The study was conducted on the S-65A sub-basin of the Kissimmee River basin in south Florida. Land use from Landsat images for 1980, 1990 and 2000 were considered in the study. The process of determining spatially distributed runoff curve numbers from Landsat images is presented in this study using GIS and image processing software. Spatially distributed runoff curve numbers and runoff depth were determined for the watershed for different land use classes. Results of the study show that land use changes determined from Landsat images are useful in studying the runoff response of the basin. It is shown that the S-65A sub-basin has undergone land use and runoff response changes over the 20 years period of time. The area covered by water and wetlands in 2000 is higher than in 1980 and 1990. In 2000 areas having CN of greater than 90 accounted for 3% compared to 0.9 and 0.6% in 1980 and 1990 respectively. This was due to the increase in wetlands and water covered areas attributed to the Kissimmee River restoration work, which started in 1997 and aimed at restoring lost wetlands and floodplains.