Offshore breakwater project at Poonthura shows positive results

A performance assessment of the offshore breakwater project at Poonthura in Thiruvananthapuram district has yielded encouraging results, prompting the Kerala government undertaking, the State Coastal Area Development Corporation (KSCADC), to consider expanding the programme to more locations along the Kerala coast.

A June 2026 report prepared for KSCADC by Chennai-based National Institute of Ocean Technology (NIOT) pointed to “significant buildup” of beach area at Poonthura after the construction of the submerged breakwater (SBW) comprising geotextile tubes, particularly from 2024 onwards.

KSCADC is now examining model studies conducted by NIOT for Shangumugham and Valiyathura in Thiruvananthapuram district and studies by Indian Institute of Technology-Madras for Kollam beach and Cherai in Ernakulam district, KSCADC managing director Sheikh Pareed said.

Satellite imagery analysis comparing the pre-construction (2022) and post-construction conditions (2026) indicates “substantial beach accretion” behind the submerged breakwater segments, the NIOT report on Poonthura said. “Overall, the analysis shows an average increase in beach width of approximately 37 metres in the sheltered areas behind the dyke segments, demonstrating the effectiveness of the submerged breakwaters in reducing wave energy, promoting sediment deposition, and enhancing beach formation along the project site,” it said.

Preserving coastline

Shore protection measures in Poonthura using geotextile tubes filled with sand slurry were launched with the aim of preserving the coastline while creating a stable beach. The State government has sanctioned ₹20 crore through the Kerala Infrastructure Investment Fund Board (KIIFB) to deploy custom-designed geotube technology along the Poonthura coastal stretch. This ambitious initiative was entrusted to KSCADC and the model study was done by NIOT.

The geotubes have varying lengths (20 metres, 16 metres and 12 metres) and a circumference of 15 metres. When filled with sand, they weigh between 200 tonnes to 250 tonnes. The project involved deploying them in five segments, each measuring 100 metres, with a 50-meter gap between them, over a total distance of 700 metres. KSCADC began the implementation at Poonthura in 2022.

“The reduction in wave energy caused by wave breaking behind the SBW structures has promoted sediment accumulation and beach formation in the sheltered region. These findings are consistent with feedback from local fishermen, who have reported positive impacts associated with the construction of the SBW segments,” the NIOT report said. Overall, the five segments exhibited an average increase in sediment deposition of approximately 1.6 metres in height behind the segments, indicating significant sediment accumulation and shoreline stabilisation in the project area, it said.