Mapping seasonal snow melting is crucial for assessing its impacts on water resources, natural hazards, and regional climate in Karakoram. However, complex terrain in the high mountain region posed great challenges to remote sensing based wet snow mapping methods. In this study, we developed a novel framework that incorporated Synthetic Aperture Radar (SAR) and topographic data for robust and accurate mapping of wet snow over the Karakoram. Our method adopted the Gaussian Mixture Model (GMM) to adaptively determine the Wet Snow Index (WSI), and computed the Topographic Snow Index (TSI) considering the impact of terrain on wet snow distribution to improve the accuracy of mapping. We validated the mapping results against Sentinel-2 snow cover maps, which demonstrated significantly improved accuracy using the proposed method. Applied across three major water basins in Karakoram, our method generated large-scale wet snow maps and provided valuable insights into the temporal dynamics of regional snow melting extent and duration. This study offers a practical and robust method for snow melting monitoring over challenging terrains. It can contribute to a significant step forward in better managing water resources under the climate change in vulnerable regions.