Modelling effects of land use/cover changes under limited data



Watershed models are valuable tools used in the study of impacts of land use/cover (LULC) changes on hydrology. We use the Soil and Water Assessment Tool (SWAT) to study the impacts of LULC changes in a coastal Alabama watershed, where flow data did not exist at the onset of the study. We set up and calibrated the model in the neighbouring Magnolia River watershed. Relevant model parameters were then transferred to the Wolf Bay watershed. Impacts of LULC changes on hydrology are studied in the Wolf Bay watershed by running the model with the default parameters, transferred model parameters (from the Magnolia River watershed), and calibrated parameters at the Wolf Bay watershed with limited data that became available later during the study. The relative changes in flow duration curves (FDCs) due to differing LULC showed a similar pattern with each parameter set: There is a clear threshold of around 1% probability of exceedance where the relative change is at its maximum. The relative change in flow due to LULC change drops drastically with increasing probability of exceedance of beyond 2% until it reaches a plateau at p = 20%. Hence, small to medium range flows are less sensitive to the parameter set. Further, the impact of LULC change on flow gradually decreases with the size of the storm for very large events (probability of exceedance < 1%). Copyright © 2010 John Wiley & Sons, Ltd.