CHENNAI: Indian Institute of Technology Madras (IIT-M) researchers have studied flooding in and around Chennai and have proposed the construction of ‘straight training walls’ at the mouth of Ennore Creek to minimise flood risk significantly on its upstream.
The study was commissioned by Kamarajar Port (formerly Ennore Port) in Chennai to propose solutions to reduce flooding around the banks of the Kosathalaiyar, a statement from the institution on Monday said. It was undertaken by K Murali, SA. Sannasiraj and V Sundar from the Department of Ocean Engineering, IIT-Madras.
The study focused on extreme storm surge scenarios and high tide levels along with flooding in the river. It found that heavy siltation in the creek mouth and narrow opening in the mouth posed a flood threat to the areas adjoining the river.
The study showed straight training walls at the creek mouth and some regular de-silting of the river will improve the situation and minimise flood risk significantly in North Chennai.
It also showed that an alternative proposal of curved training walls proposed earlier will worsen the situation, by blocking the free exchange of Seawater with the creek, thereby, increasing the flood risk.
Sannasiraj, said, “The proposal has been made to construct a pair of training walls extending perpendicular from the shore up to a water depth of 5m on either side of the creek.” Further, the straight training walls would act in complement with the present series of groynes which were designed by IIT-Madras for shore protection.”
In the history of flooding in and around Chennai, the three creeks — Adyar, Cooum and Ennore— remain major bottlenecks due to sand bar formation at their mouths this results in significant flooding over the settlement along its banks affecting coastal villages, disrupting fishing activity, industrial network on the upstream, road encroachments and illegal waste disposal.
In a well-balanced ecosystem, the mouth of the inlet should remain open and continuous exchange of water is to be ensured. Owing to large volumes of sediments transported along the bed as well as suspended in water, such inlets act as a sediment sink resulting in sand bar formation. Like a chain reaction, the hydrodynamics are altered; the inlet stability fails; and, flooding on riverbanks follows.
The comprehensive report of IIT-Madras examined different possibilities of extreme event cases both from the land and the sea.
The studies reveal that it could lead to an overflow in the region of elevation lesser than 2.71 m with respective MSL. A detailed study for the Adyar and the Cooum estuaries will also be taken up for investigation by IIT-Madras, the statement said.
Source: https://www.newindianexpress.com/cities/chennai/2020/sep/15/walls-can-protect-chennai-from-floods-iit-madras-study-2196936.html
