The northern part of the Mahanadi delta in eastern India is a high-risk zone for severe cyclones and heavy floods, researchers at Jadavpur University have found1.
Mahanadi delta in Odisha is drained by three rivers — Mahanadi, Brahmani and Baitarani — that pour into the Bay of Bengal. It has a population of 8 million, and a population density that is higher than that of the state of Odisha.
Floods and cyclones are the most common extreme events in this delta, with about 2–3 flood events every year. The flood hazard in the study was assessed using the flow rate of water and artificial neural networks. The probability of the storms was also simulated for various time periods.
In the case of flood events that have a one per cent probability of occurrence in one year, more than 80 per cent of the land and 88 per cent of cropland in the northern part is likely to be affected.
The study found that a seven-metre storm surge — a storm surge is the abnormal rise in sea level due to cyclone — could affect up to 95 per cent of the population and 88 per cent of cropland in the low-lying northern region of the delta. This region is also more susceptible to high wind speeds during cyclones.
The northern districts have a high dependence on agriculture (71 per cent), and a high percentage of kutcha (mud brick) houses (50–70 per cent), making them more vulnerable to extreme events.
Dykes, storm-surge barriers, vegetation canopy and salt-tolerant crop species are some of the adaptation and mitigation strategies proposed by the authors.
1. Ghosh, A. et al. Risk of extreme events in delta environment: A case study of the Mahanadi Delta. Sci. Total Environ. (2019) doi: 10.1016/j.scitotenv.2019.01.390