Runoff Impacts of Land-Use Change in Indian River Lagoon Watershed

Changes in land use can have significant impacts on hydrology and the environment. The Long-Term Hydrologic Impact Analysis model and a geographic information system-based Soil Conservation Service curve number method were used to estimate average annual runoff and runoff for rainfall events with varying return periods, respectively, for NASA’s John F. Kennedy Space Center (KSC) within the Indian River Lagoon watershed (IRL), Florida, for 1920, 1943, and 1990 land uses. Changes in estimated runoff depths due to land-use alteration between 1920 and 1990—for design rainfall events ranging from a 24 h/1 year to a 24 h/100 year return period—ranged from 7–17% for KSC to 22–55% for the IRL watershed. The percentage changes in average annual runoff due to land-use changes were much greater. Between 1920 and 1990, estimated average annual runoff for the KSC increased about 49%, and the IRL runoff increased nearly 113%. For the KSC and IRL, most of the increase in runoff between 1920 and 1990, both for single events and annually, came from landscape urbanization, although increased agricultural land uses in the IRL also contributed to increased runoff. Large differences in estimated runoff between the KSC and IRL are due to differences in the amount of urban land use within the respective areas (1990 urban land uses for the IRL are 34.8 versus 20.5% for KSC). Land-use change can have a dramatic impact on annual runoff volume, as demonstrated in this study; thus the effects of land-use change on annual or long-term runoff should be considered in land-use planning.