Mangaluru

Rampant sand extraction in rivers aiding sea erosion

It may be stretching the fact when the burgeoning construction activities in Bengaluru is linked to the aggravated sea erosion around Mangaluru. But fishermen in Mangaluru claimed that unabated sand extraction in the last few years within the Coastal Regulatory Zone from the Netravathi and the Gurupura (Phalguni) is the reason for the Arabian Sea inching several meters into the mainland every year.

A major quantum of the CRZ sand, which is cheaper to other varieties because of its salinity, was being transported to the Bengaluru region with an average of 300 truckloads per day till February. The government had directed the district administration to allow inter-district transportation following severe sand shortage in Bengaluru.

Sand deposits hit

The claims made by the fishermen are not unfounded, with some experts backing them. Indiscriminate sand extraction to the tune of lakhs of tonnes every year has prevented strengthening of the beachfront every year, say experts in marine geology.

K. Jayappa, Professor in Marine Geology, Mangalore University, said that sand extraction in the CRZ limits has prevented sand accumulation on beaches, which had been the natural course. And, because of the weak beachfront, the sea is advancing with vigour, he said.

Vented dams along the river course as well as the breakwaters near harbours too contribute to sea erosion; but not on the scale of what sand extraction has done, he told The Hindu . There has also been illegal sand extraction from the river mouths aggravating the problem, Prof. Jayappa added.

Overexploitation

Sand from the rivers in the CRZ areas was being removed across the coast earlier too; but it was for local consumption and only small wooden boats were being used by traditional extractors. When the demand for sand escalated in the last few years, the administration designed a novel method — dredging the riverbed for smooth boat movement — to circumvent the strong CRZ regulations.

As a result, the number of traditional sand extractors rose spontaneously, from just about 60 before 2004 to about 400 in 2016, in Dakshina Kannada district. This naturally leads to overexploitation, said S.G. Mayya, retired professor in Applied Mechanics and Hydrology with NITK.

Sand has to be removed from the riverbed, but not at the present scale, and only under traditional method. How could there be 400 traditional extractors on about a 3-km riverbank, he wondered.

Besides transporting sand to the Bengaluru region, unscrupulous elements have rampantly been transporting sand to neighbouring Kerala where there has been a total ban on sand extraction.



Sand extraction in CRZ areas

About 23 lakh tonnes of sand extracted in three coastal districts in 2015

Another 18 lakh tonnes expected to be extracted in 2016

Sea erosion

Sea erosion has aggravated since about five years along several sections of the coast

Uchchila, Ullal, Hejamadi, Gangolli, Kirimanjeshwara, Bhatkal, Honnavar are some of the affected areas

Union and State governments are taking Asian Development Bank loan to protect the seafront

Rs. 216-crore work under way at Ullal under first tranche work

Work in other areas to be taken up subsequently



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Printable version | Jan 22, 2021 10:13:43 AM | https://www.thehindu.com/news/cities/Mangalore/Rampant-sand-extraction-in-rivers-aiding-sea-erosion/article14469770.ece

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