The recent proposal of installing tetrapods in Velsao beach by Cortalim MLA Alina Saldana which was made after villagers had approached her to resolve the issue of beach erosion, has been vehemently opposed by Olensio Simoes, General Secretary of Goemchea Ramponkaracho Ekvott. Herald dug deeper into the issues that cause erosion, the impact of tetrapods /beachwalls and the real solution which can help protect Goa’s precious and pristine beaches.
While beach erosion is a seasonal phenomenon, the decline extreme levels of erosion witnessed in the last few years is a direct impact of reckless human activities. India is losing its beaches fast and Goa may be no exception.
Beach sand is not a static geological feature like rocks but is in continuous motion and is shifted from one place to another by waves and sea currents. This phenomenon can’t be perceived easily because the “longshore drift” immediately replenishes the sand that is moved with more sand brought to the coast by our rivers. In fact, the longshore drift can be affected by manmade structures and activities which can lead to an imbalance in the erosion – restoration cycle. The intensity of the erosion increases during monsoon but post-monsoon the sea restores the sand on the beach provided it is not obstructed with man-made structures.
When sea erosion is witnessed during monsoon, hard structures such as tetrapods, seawalls and groins are installed without any study, probably because it is a lucrative project for contractors. But these structures are not the solution are not the answer to erosion because they disrupt natural patterns of sand movement and often accelerate erosion. They don’t solve the problem but simply transfer the problem to the next beach. Once hard structures are created, the cycle never ends since the structures keep sinking and this solution is unsustainable.
Instead of triggering erosions and then creating seawalls, the State needs to plan coastal development with great care. The only way to stop erosion from spreading like cancer along Goa’s coastline is prevention. It is imperative that we strictly regulate port activities and other coastal structures which are the root causes of man-made erosion.
Goa can learn from Puducherry’s mistakes and solutions
The beach erosion of Puducherry began when a harbour was constructed south of the town in 1986. A breakwater was constructed jutting into the sea. This obstructed the free movement of the longshore drift and caused sand to accumulate in the beach south of the breakwater. However, the beach north of the breakwater was starved of sand because of the obstruction.
With the longshore drift taking sand away from the north side and with no new sand replacing that what was lost, the north side beach kept eroding more and more in the direction of the town. As a result, within 4 years of constructing the harbour, the 4 km beach that was the pride of Puducherry completely disappeared and was replaced with an ugly seawall to protect the town. Since then 10km of the beach was lost completely. Puducherry also had to cut several hills to source the rocks for sea walls.
Herald spoke to Probir Banerjee, a Civil Engineer at the Sri Aurobindo International Center of Education in Puducherry, who has been actively involved in the campaign to restore Puducherry beach. He said that any hard structure blocks the movement of sand which is always in continuous motion. Once tetrapods are installed the sand adjacent to the tetrapod start eroding.
He stated that the severe erosion caused in Goa could be a natural phenomenon but it could also be caused due to extreme climate and River sand mining which prevents fresh sand from reaching the shore.
After an intense campaign by the citizens of Puducherry, Ministry of Earth Sciences got involved and provided innovative solutions to protect coastal areas. In Puducherry, the MoES developed a Shoreline Management Plan in collaboration with National Institute of Ocean Technology. The shoreline changes along the Puducherry beach were analysed using remote sensing data and field measurements, and a plan was submitted to the Puducherry Government.
A pilot beach nourishment project was carried out on the north side of the port using 50000 cum of dredged sand from the harbour mouth. This resulted in the formation of a 60m beach. Upon the success of the pilot project, they expanded their goal to restore the beach further along the town.
Further, oceanographic measurements were taken during various seasons for a period of 3 years and based on the data, computer-based numerical models were constructed to develop innovative solutions to restore the beach along the city. The project included construction of submerged reefs.
Offshore sandbars have also been created using a method called rainbow nourishment using section dredgers and the beaches are nourished by cutter dredgers which spray sand on the beaches in a process called pipeline nourishment. The sand is collected by the dredgers from the harbour mouth. The beach has already begun recovery and is well on its way to achieving is past glory. This initiative taken by MoES can easily be adopted in coastal areas of Goa.
