In addition to climatic factors, frequent floods in Bengaluru city are a direct consequence of rapid urbanisation, shrinking green spaces, poor sewerage system  and inadequate stormwater  infrastructure. In this regard, the water and society programme at ATREE conducted a one year long study to develop a comprehensive strategy and action plan aimed at building long-term flood resilience. The report was released on March 26, 2024.

This study employed IPCC AR5 flood risk assessment framework to evaluate flood hazard, vulnerability and exposure. A case of subcatchment in Yelahanka (21 sq.km) was used to generate a detailed flood risk map. Hydrologic and hydraulic modeling tools were used to simulate the flooding conditions (inundated area and depth)in the subcatchment. Additionally, citizen science data was used to calibrate and validate the model results.

Nature based solutions are termed as one of the most effective solutions to address risk and build resilience to urban floods . We evaluated the efficacy of various NbS solutions such as green roofs, bioswales and recharge wells by running multiple scenario-based simulations. The results showed that NbS has significant potential to  reduce runoff volume and flood risk. In the most effective scenario( 25% recharge wells and 25% green roofs), runoff volume reduced by 45% and the area under very high risk to flooding dropped by 77%.

This action plan proposes five strategic focus areas: early warning and preparedness, lake and stormwater management, scaling blue-green infrastructure, better maintenance of drainage systems, and active community engagement. The co-creation process included input from Bangalore Water Supply and Sewerage Board (BWSSB), Karnataka State Natural Disaster Monitoring Center(KSNDMC), academic experts, citizen groups, and NGOs, ensuring the plan is both practical and inclusive.