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IIT-M study of water flow in the Adyar river to prevent flooding

The Indian Institute of Technology, Madras, researchers and students braved cyclone Nivar to collect real-time data on Adyar river discharge which could help prevent floods in Chennai.

Led by Balaji Narasimhan of the Department of Civil Engineering, IIT-M, two teams equipped with Acoustic Current Profiler, measured river currents and flow depths across the width of the river to get the integrated flow rate.

During the floods of 2015, such critical ground truth data and a reservoir inflow forecasting system through numerical models could have helped mitigate the impact. The catchments of Somangalam, Manimangalam, Adhanur and Guduvanchery in Chennai with a large network of tanks received a record amount of rainfall during the monsoon of December 2015.

K Phanindra Reddy, Commissioner, Revenue Administration, Disaster Management and Mitigation, Government of Tamil Nadu, said that the data collected during this field campaign by IIT Madras in close coordination with Tamil Nadu State Disaster Management Authority (TNSDMA) would be very useful to operationalise the Real Time Flood Forecasting and Spatial Decision Support System being coordinated by TNUIFLS under World Bank assisted Tamil Nadu Sustainable Urban Development Project.

Narasimhan said, “As part of a robust flood management, rating curves at critical sections of the rivers are especially important to understand the volumetric flow rate for different flow depths. Once a rating curve is developed, an integrated network of water level sensors could be used to monitor the river discharges remotely and automatically at these critical river stretches.

Some preliminary model runs showed that the catchments alone could have contributed to up to 70 to 80 per cent of flood flows realised in Adyar river. Unlike the Chembarambakkam reservoir with flood gates to regulate the water level, the control measures available in the tanks in this part of the catchment was almost nil in 2015. Realising this lacuna, the State Public Works Department has begun installing sluice gates in many of the small tanks to regulate the water levels prior to the incoming floods, the release said.

Although Chennai did not encounter large scale flooding during Cyclone Nivar, certain localities in the city experienced some flooding and water logging. The data collected during the field campaign, which continued till December 11, could give insights into the hydrological behaviour of this catchment and find remedies to mitigate future floods.

Narasimhan said even more critical is, the collected data would be useful to manage and moderate the reservoir releases from Chembarambakkam, giving sufficient lead time for officials from TNSDMA to issue warnings to the public in low-lying regions and coordinate flood mitigation and relief measures.