An aerial view of the 2015 Chennai floods. © Indian Air Force
Researchers in the coastal Indian city of Chennai have evaluated how climate change might impact storm water drainage and pinpointed vulnerable hotspots that if redesigned could reduce future monsoon flooding events. The study in the Tamil Nadu capital, which was crippled by unprecedented monsoon flooding in 2015, could offer a climate-resilient model to renovate storm water networks of other Indian cities, such as Mumbai and Kolkata, prone to flooding after a heavy rainfall.
The civil engineers from Anna University in Chennai used the Global Climate Model dataset of the Intergovernmental Panel on Climate Change (IPCC) and daily rainfall data of the past 45 years from the India Meteorological Department to develop their model. They created a base map and digital elevation model using data procured from the National Remote Sensing Centre (NRSC) in Hyderabad.
From the Greater Chennai Corporation, the researchers collected details of the existing storm water drainage network of Velachery, one of the most flood prone areas in the city. They outlined the storm drainage network of the area with a Differential Geographic Positioning System (DGPS) survey. The researchers then carried out integrated hydraulic and hydrological modelling to assess the flood carrying capacity of storm drainage under present and future climate scenarios. This led them to identify the vulnerable hotspots, create a vulnerability map and suggest measures that could reduce flood risk.
Managing storm water under climate uncertainty is a major concern in urban areas throughout the world. The researchers say scientific knowledge will help city planners design futuristic and intelligent climate-proof urban storm water drainage systems.
Their recommendations to the city planners include proper maintenance of the 'hotspot' junctions for free drainage, construction of new roads away from inlets of storm drains, widening of downstream channels, increasing carrying capacity of channels by removing vegetation and blockages and lining them with stone. The researchers also call for incorporation of real time flood forecasting with practices such as permeable pavements, rain gardens, green roofs, street planters, rain barrels, infiltration trenches and vegetative swales.
References
1. Andimuthu, R. et al. Performance of urban storm drainage network under changing climate scenarios: Flood mitigation in Indian coastal city. Sci. Rep. 9, 7783 (2019) doi: 10.1038/s41598-019-43859-3
