Developing strategies for managing PLUVIAL FLOODING in Gurugram (Gurgaon)

Abstract

Urban flooding is not an unknown event and is one of the growing concern around the world. This happens mainly due to uneven distribution of rainfall, rapid urbanization, encroachments, and solid waste dumping in drainage, drying of lakes and filling of natural drainage. In case of Gurgaon, even with is rainfall of 94cm or 3% less rainfall than normal rainfall, it results in flooding and city get water logged. 60% of city is concreted which don’t allow water to penetrate into the ground. Construction of projects in low lying areas, insufficient drainage system and poor infrastructure lead to water logging in this city. The study aims to develop strategies for managing PLUVIAL FLOODING in Gurgaon. Pluvial flooding occurs when the capacity of local drainage system completely gets saturated.Firstly the phenomenon and characteristics of flooding in Gurgaon have been studied in which water logging areas of 2016 were studied at sub-basin level and existing urban drainage system of the city have been understood. 100 yrs. of rainfall has been studied. Secondly, Critical factors contributing to flooding in Gurgaon were identified. These are reduced drainage capacity in certain stretches, absence of Pre-monsoon desilting of drains, illegal encroachments and solid waste dumping. Land utilization changes were also studied from 2000 to 2016 in which built up area has increased from 26.54% in 2000 to 48.32% in 2016 and cropland area has also reduced by 35.85% from 2000 to 2016.The runoff generations of year 2016 for whole city at micro watershed level was calculated using CN method in which land use and soil map were used. Higher the CN number, higher is the run off potential. Then runoff volume was also calculated at micro watershed level. The urban flood vulnerability and risk mapping has also done to identify the critical areas using integrated Multi-parametric AHP and GIS. For this, various parameters such as drainage density, rainfall, elevations, soil, land use and slope were taken and given weightages. Strategies would be applied to manage critical areas which are highly vulnerable to flooding with high runoff depths. The sustainable urban drainage systems (SuDS) were applied to the critical areas. Their main objective is to reduce runoff rates through source control, site control and regional control. SuDs include system for water conservation (source control), infiltration (source control), filtration (Source control), retention (Site/Regional control), detention (Site/Regional control) and constructed wetlands (regional control). Through these urban drainage systems, run off rates can be reduced and water quality can be increased in the critical areas of Gurgaon and further may be applied to other cities having similar challenges vis-a- vis storm water management.