Alappuzha: The breach of the sandbag bund being constructed in the Kanakassery paddy polders in Kuttanad on Monday has raised fears of an ecological imbalance following the drainage of tonnes of sea sand into the river and paddy fields. The salty sand spread across the area will decrease the carrying capacity of the river leading to floods, according to experts.
The presence of sea sand will also affect the fertility of the soil.
The district administration said that at least 57,000 sandbags had been brought from Thottappally estuary to construct the bunds with 25-feet depth, 20-metre width and 40-metre length. Last year's floods had already decreased the carrying capacity of the river due to the deposition of silt from highland.
Dr. K.G. Padmakumar, director, International Research and Training Centre for Below Sea-level Farming, has suggested bund construction with impervious clay deposited in the river basin itself instead of using sand bags. The rivers and water bodies should be dredged instead of dumping more sand from outside resulting in the ecological imbalance, he said. The real impact of the salty sand drained into the paddy land could be assessed only during the next season, he added.
According to him, sand is no longer a scientific solution for Kuttanad bunds since it is pervious. The government should encourage clay mining for the bund construction instead of treating it as illegal activity, he said. The silt that reached the river during the floods in 2018 is yet to be cleared.
Mr. Kumar also asked the government to study the water saving irrigation (WSI) techniques being experimented across the world for flood reduction.
Dr. Priyadarsanan Dharma Rajan, senior fellow, Ashoka Trust for Ecology and Environment (ATREE), a Bangaluru-based NGO working for the protection of Vembanad river habitat, questioned the practicability of dumping salty sand in Kuttanad to construct bunds. "The salty soil will affect the soil structure of paddy lands. The plastic bags will decay and plastic particles will react with soil structure and resist its fertility. In the post-flood context, the carrying capacity of the river should be increased. The government should set up an expert panel to study the situation and avoid future flooding in Kuttanad and elsewhere," Dr. Rajan said.