Implementing LID Techniques for Runoff Reduction Through the Curve Number Method Considering Slope Variation in Uttarakhand

Uttarakhand, a Himalayan state in India, is significantly affected by the flooding in urban regions due to high intensity rainfall, varied land use/ land cover (LULC) and steep topography. This chapter calculates direct runoff estimation by Soil Conservation Service Curve Number (SCS-CN) technique combining LULC, hydrological soil groups (HSG), rainfall and slope data, in ArcMap. Curve Number method formula was used to introduce slope effect on Curve Number (CN) values. In order to reduce runoffs, the Low Impact Development Techniques have been implemented through installing permeable and rain gardens by adjusting CN to capture greater infiltration. The runoff was recalculated after the implementation of LIDs. The results emphasize the effectiveness of integrating slope-based CN modifications and LID practices to reduce surface runoff. This method is used to illustrate the way that sustainable land use planning and hydrological modelling can be combined for better flood risk management in mountainous areas. The methodology offers a replicable model for other regions that are experiencing similar stresses of rapid urbanization and climate change-induced hydrological extremes.