Gabion walls to shield Ranganathittu islands from erosion

Mandya: Authorities at Ranganathittu Bird Sanctuary in Mandya district have begun constructing eco-friendly gabion structures to protect vulnerable river islands from flood-induced erosion.

The sanctuary, on the Cauvery River, has 25 islands that serve as key nesting and breeding grounds for resident and migratory birds. In the first phase, five of the most flood-prone islands are being fortified with gabion walls designed to withstand strong currents.

For several years, the forest department relied on temporary sandbag barriers. However, when large volumes of water were released from the Krishna Raja Sagar (KRS) dam, the sandbags were often washed away, leading to severe erosion. This reduced island size and destroyed nests, eggs and chicks, threatening bird populations, particularly migratory species, said the authorities.

Officials have now adopted gabion technology as a long-term solution. The system uses boulders and stones enclosed in corrosion-resistant galvanised iron wire mesh to form retaining walls that remain stable during floods while blending with the riverine ecosystem.

Syed Nadeem, range forest officer, Ranganathittu Bird Sanctuary, said earlier soil-based protective structures frequently failed during high water release from KRS. “Whenever large quantities of water were released from KRS, the islands protected by sandbags suffered erosion and damage. After consulting experts, we decided to implement the gabion shield system as a permanent solution.”

He said five major islands have been prioritised and work is nearing completion. The protection system will be extended to the remaining islands in phases.

Constructed using stones within corrosion-resistant mesh, the gabion walls are expected to provide long-lasting protection to the islands and the bird population.