The Water Resources Department (WRD) has deferred the levelling of the river bed in front of the Opa barrage due to the inability to empty the Khandepar river basin because of tidal water. The work will now be taken up after the monsoon season. However, WRD Executive Engineer Mario Rebello confirmed that the construction of the river bank erosion protection wall will be completed as planned.
Retaining Wall Construction
A retaining wall is being built along the Khandepar river basin on the downstream side of the Opa barrage. Rebello stated that the department has prepared 1 cubic meter square concrete blocks, each weighing approximately 1.5 tonnes, to be placed in areas where soil has been washed away, creating deep ravines.
Natural Erosion Process
The senior officer explained that soil erosion is a natural phenomenon caused by water current. During the monsoon, when the barrage gates are opened to release excess rainwater, the high-velocity water washes away river bed soil, leading to the formation of ravines.
To address this, concrete blocks are placed inside the ravines to level the river bed. However, due to tidal water, the river basin could not be fully emptied to install a geosynthetic membrane that stabilizes the concrete blocks.
Project Details
After discovering significant erosion near the Opa Water Works, the WRD initiated the construction of a retaining wall to prevent further damage. The tender for the retaining wall and concrete blocks was awarded to Unique Construction, Quepem, at a cost of Rs 5 crore.
The barrage is 8 meters high and approximately 40 meters wide, with six gates capable of holding water up to 8 meters. Rebello noted that during monsoon overflow, the WRD does not open the first and last gates to minimize river bank erosion.
