Simulation of the impacts of land-use change on surface runoff of Lai Nullah Basin in Islamabad, Pakistan

Land use change has significant impact on the hydrologic and ecological processes of a watershed. This study combines an empirical land use change model and an event scale, rainfall-runoff model to quantify the impacts of potential land use change on the storm-runoff generation in the Lai Nullah Basin. The HEC-HMS rainfall-runoff model was calibrated and validated for 5 storm events in the study area, and the results showed good consistency between the simulated and measured hydrographs at the outlet (Katarian Bridge) of the basin with Nash-Sutcliffe efficiency ranging from 76 to 98%. The future land use scenario was forecasted based on Islamabad Master Plan and growth pattern. The calibrated HEC-HMS model was applied for these future land use scenarios to assess the potential land use impacts on the storm-runoff generation. The results indicated that the future land use as envisaged in the master plan is projected to increase the total runoff between 51.6 and 100.0% as well as the peak discharge between 45.4 and 83.3%, and that the magnitude of peak discharge increment relates to the expansion rate of built-up area. The results provide useful information for land use planning and management and the methods applied can serve as a useful tool for future land use impact studies. (C) 2011 Elsevier B.V. All rights reserved.