Urban Footprints in the Storm: Land-Use Sensitivity of Extreme Rainfall over Chennai

Urbanization significantly changes land surface features, affecting local weather and increasing extreme rainfall events (EREs) in cities like Chennai. Improving urban resilience to climate-related extremes requires understanding how land-use patterns influence heavy rainfall in fast-growing cities. Greening concrete grids with vegetation or converting them to cropland can reduce convective strength and change moisture flows, helping to moderate extreme rainfall. To explore this, we performed high-resolution simulations using the Weather & Research Forecasting Model (WRF), combined with an urban canopy model, for three land-use scenarios: fully urbanized (UCM), cropland replacement (Crop (UCM)), and flooded surface (Water (UCM)). These experiments showed that urban surfaces increase both the frequency and severity of heavy rainfall, while replacing urban areas with cropland significantly decreases rainfall and surface runoff. The Water (UCM) scenario displayed mixed results, with shifts in rainfall patterns and increased runoff compared to Crop (UCM). Additionally, urbanization boosted sea-breeze circulation and moisture transport, which contributed to localized rainfall intensification. These results emphasize the important role of land-use planning in influencing ERE behavior.