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.

► HEC-HMS model effectively simulates effects of land use change on runoff generation.
► Significant increase in runoff volumes associated with increase in urbanization.
► Expansion rate of built-up area is of utmost importance to avoid future flood risk.