Urban Flood Model for Bangalore City

Abstract:

With a rise in urbanization, frequency and intensity of flash floods in urban regions has increased exponentially in India. In the recent past, Bangalore, which was once the garden city of India, has seen a rapid increase in urbanization and industrialization. This has caused a decrease in the surface area for water to infiltrate or to be stored as water bodies. The urbanization has caused the city to face flood inundations in the extreme rainfall events during the annual monsoon season. Bangalore is at an average elevation of 900m and receives an average annual rainfall of about 900mm The Monsoon season of 2020 saw a very heavy cumulative daily rainfall of 185mm, observed to be highest in the past century. There have been frequent occurrences of such events annually and multiple events in a season causing flash floods. Hence, a multi-modular scientific approach to address this issue, with the active participation of governmental bodies as stakeholders for mitigation and management of the impacts of the devastating floods is documented here. The rainfall is forecast at a high resolution of 1 km by developing and using an advanced Weather Research and Forecasting model validated with the observed data from 100 telemetric rain gauge stations set up for real-time data recording. Fine resolution digital elevation model (DEM), along with the fine resolution urban land use maps serve as input for the robust flood models, which are developed using PCSWMM and MIKE platforms. These models are calibrated using the observed rainfall data and the water level data sensors installed across Bangalore city. The flood model is applied to study various scenarios and the flood inundation. The effect of employment of low impact developments (LIDs) Porous pavements and porous bed channels as a mitigation strategy and as a method to recharge the groundwater is studied critically using the developed models for using floods as a resource The study intends to create a package of solutions as a transferable tool to address the increasing problem of urban floods in the various developed and developing cities of India.