Urbanization in Koramangala-Challaghatta Valley Increases Flood Risk

The Koramangala-Challaghatta (KC) valley in Bengaluru is facing significant flood risks due to extreme urbanization, according to a study by RV College of Architecture. The built-up area in the valley has increased from 62.74% in 2000 to a projected 87% by 2025, resulting in a 3.4-fold increase in runoff rates. This surge in impervious surfaces, such as concrete roads and buildings, has drastically reduced the area's capacity for rainwater infiltration, posing a high risk of flooding.

Researchers conducted rainfall-runoff simulations comparing pre-development and post-development scenarios. The results showed that peak runoff increased from 72.60 m³/s to 248.00 m³/s, highlighting the impact of urban expansion on the valley's hydrology. Experts emphasize the need for flood-resilient urban planning, advocating for the preservation and enhancement of natural ecosystems. They suggest implementing nature-based solutions like rain gardens, green roofs, and permeable pavements to improve water absorption and reduce flood risks.

The study also points out that the concretization of stormwater drains has hindered natural groundwater recharge, exacerbating surface runoff issues. Additionally, the degradation of the lake network in the KC Valley, with many drains carrying untreated sewage, further compromises the water system's effectiveness. To address these challenges, experts recommend restoring the interconnected lake network and ensuring that stormwater drains carry only stormwater, not sewage. The research findings are published on papers.ssrn.com.