Saranya Sasindran

Development of a Blue-Green Infrastructure opportunity mapping tool for Kerala (India)

Urban flooding has become a recurring issue in India with the increasing intensity and variability of rainfall. Anthropogenic climate change has resulted in the increased frequency and severity of natural phenomena such as heavy rainfall, tidal surges, and land subsidence, which when combined with the rapid expansion and reduced permeability of urban regions, and outdated water management infrastructure are responsible for frequent inundation events in urban areas. The city of Kochi on the south western coast of India has faced major incidences of heavy rainfall and consequent severe flooding in recent years. Research shows that sustainable systems for storm-water management such as Blue Green Infrastructure (BGI) is a viable solution for cities facing the multiple challenges of climate change and rapid urbanisation.

BGI is an integrated systems approach to storm water management using an interconnected network of natural and designed interventions. It has a significant impact in improving flood resilience by reconnecting the urban hydrological cycle with the landscape and has a proven track record of providing multiple environmental and socio-economic benefits. Such interventions can replace the need for expensive grey infrastructure while simultaneously improving urban resilience, preserving biodiversity and enhancing liveability. Examples of BGI include infiltration trenches, vegetated swales, bio-retention areas, permeable pavements and green roofs. These interventions are highly specific and dependent on the physical and socio-economic characteristics of an area. This project uses a GIS-based Multi Criteria Analysis to find the optimal location for the placement of BGI for effective storm-water management. It also looks at the feasibility of adopting BGI, identifying options that are best suited and most efficient for the study area.

The resulting suitability maps show the optimal locations for the placement of swales, bio-retention cells, permeable pavements and bioretention cells. The applicability of these solutions were then tested on a smaller catchment within the study area using SWMM software. The results from runoff modelling demonstrates that BGI has potential to be applied in the context of the study area.