Drainage Density as Index of Watershed Development

Studies have been completed on watersheds in Florida, and a methodology developed to predict environmental impacts using drainage characteristics of developing watersheds. The drainage density index, a measure of total length of waterways observed on aerial photographs per unit area, was computed for various watersheds in order to relate land-use changes and drainage patterns to hydrologic and water quality responses. Results indicate significant increases in drainage density over the past 19 yr in the Kissimmee River Basin. Water quality concentrations and loading rates of total phosphorus from seven watersheds indicate a significant correlation with the drainage density index. Differences in available nonpoint source loads were found to reflect only a small fraction of observed difference in measured total phosphorus loads.