A study conducted by the Department of Civil Engineering of BITS Pilani, Hyderabad has revealed that half of the land in the Greater Hyderabad Municipal Corporation region would be submerged if it rained continuously for 17 days. The study ‘Urban flood risk analysis of buildings’ made an estimation using the historic extreme rainfall which occurred for 8 days in 2016 in Hyderabad. According to the study, if Hyderabad received a rainfall of 440.30 mm for 17 days, 334.23 square kilometres of GHMC would be submerged. GHMC covers an area of 650 square kilometres. Similarly, if 624.2 mm occurred in 19 days, 357.97 square kilometres of GHMC would be submerged.
The study further revealed that the areas located near Musi river and Hussain Sagar are most vulnerable to flooding. The areas, which are most vulnerable to flooding, are in the northern sections of zones 1 and 5 -- Kapra and Saroorngar falling under LB Nagar zone and southern sections of zones 13 and 15 -- Karwan and Musheerabad.
The study was conducted to assess the flood depth, building risk analysis and the effectiveness of various flood adaptation strategies to attenuate building risk caused by urban floods in a climate change scenario.
The study was conducted based on a hydraulic model. The Hydrologic Engineering Center's-River Analysis System 2D (HEC-RAS 2D) was applied for two-dimensional flood modelling to estimate the submerged areas, the flood depth, and building risk for extreme events.
As per the study, the percentages of buildings in GHMC under high, medium, and low risks in case it rains for 17 days are estimated to be 38.19, 9.91, and 51.9% respectively. Similarly, in case it rains for 19 days, 40.82% of buildings would be under high risk, 10.55 % of them under medium, and 48.63% of buildings under low risk. The study said that flood depths were found to vary from zone to zone. High flood depth values near buildings were observed in zones 1 (Kapra), 5 (Saroorngar), 6 (Malakpet), 7 (Santoshnagar), 13 (Karwan), and 15 (Musheerabad); low flood depth values near buildings exist in zone 9 (Charminar).
The study suggested flood proofing as one of the strategies to tackle the disaster. The capital investment required for flood proofing has been calculated as Rs 3,740 × 107 and Rs 3,800 × 107 to achieve the ideal situation of no risk for all buildings.