Planning for sustainable stormwater management: a case of Surat

Abstract

Urban flooding is well-known event all around the world. This issue arises due to uneven rainfall distribution, rapid urbanization, dumping of solid waste in drains, and climate change is at top of these. Urban areas have the dynamic entities where social, environmental, economic systems and infrastructure overlap. Urban infrastructure increases the interaction of human population with cities and its environment. Urbanisation is one of the glaring realities of 21st century. From 28.1% (in 2001), it has reached to 31.16% (in 2011) are living in urban areas. In case of Surat which is also known Diamond city and Textile market of India has grown from 2.8 million (in 2001) to 4.5 million (in 2011). Surat is India’s 8th most populous city with the potential sectors in textile markets. With the growing economy, it is therefore becoming important to safeguard the city and it’s people from the risk of uncertain disaster and unpredictable climate change. Surat is in similar situation, where traditional storm water management is failing in front of extreme climatic changes. The study aims to develop strategies for managing storm water and water logging in sustainable manner to make Surat city more resilient. Firstly, the phenomenon of flooding in Surat have been studied in which water logging areas are being marked based on the mapping of flood, existing storm water network and topography of the place. To understand the phenomenon, the rainfall trend of past 28 years (i.e. 1990 to 2018) was also studied. Secondly, critical factors contributing to flooding were identified. These were lack of drainage capacity, increased built up area, reduced green spaces in certain areas. Land use changes were also studied from 2000 to 2018 in which built up increased from 67.46 sq.m to 98.6 sq.m. of the total land area and vegetative cover reduced from 182.32 sq.m to 149.9 sq.m. The runoff generation of year 2018 for whole city was calculated by Rational Method for each micro watershed. In which higher the built up and low vegetative cover has high surface runoff. The urban flood vulnerability and risk mapping has been done to identify the critical areas using pairwise scoring using multi-criteria method and GIS. For this various parameter such as Land use v and landcover, drainage density, slope, soil infiltration rate, surface runoff, and vegetation change were taken and given weightages. Strategies would be applied to tackle critical areas where the vulnerability to flooding is high. The sustainable storm water system was applied to critical watershed area. The main objective of proposed strategies is to reduce runoff rates through source control, site control and regional control. Sustainable storm water management system includes system for water conservation, infiltration, filtration, retention, detention and constructed wetlands. Through these sustainable systems, runoff rates can be reduced and water quality and vegetation cover, can be enhanced in the critical areas of Surat and further may be applied to other cities having similar challenges.