IMPACTS OF LAND USE CHANGE ON SURFACE RUNOFF OF LAI NULLAH BASIN

Abstract

Land use change has significant impact on hydrologic processes at the watershed level. This study combines an empirical land use change and an event scale, rainfall-runoff model to quantify the impacts of potential land use change on the storm-runoff generation in the Lei 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) of the basin with NashSutcliff 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 (51.6-100.0 %) as well as the peak discharge (45.483.3 %), and that the magnitude of increment relates to the expansion rate of built-up area. The results of this study can provide useful information for land use planning and management, and the methods applied here can be useful for land use impact studies.