‘Sea walls do not ensure beach stability’
Experts participating in a consultative meeting on bringing comprehensive development to the coastal village of Chellanam through scientific intervention under the aegis of the Kerala University of Fisheries and Ocean Studies (Kufos) mooted a variety of options on Sunday.
The meet was held in the wake of widespread flooding of homes triggered by cyclone Tauktae.
N. Chandra Mohan Kumar of Sasthra Sahithya Parishad, former registrar of the Cochin University of Science and Technology and professor of chemical oceanography, suggested a combination of hard and soft engineering options to protect the shoreline.
He said that coastal erosion was a natural process, and the problem of erosion occurred when people built structures on the coastal zone, and any shoreline construction caused changes and that once constructed, coastal structures produced a trend in coastal development that was difficult, if not impossible, to reverse.
A combination of hard and soft structures is most suited to protecting the coast.
Hard structures include sea walls, groynes, breakwaters or artificial headlands. Sea walls, built parallel to the coast, protect the coast from wave action but creates wave reflection and transportation of sediments offshore.
Seawalls do not ensure beach stability, said Dr. Mohan Kumar.
He said that geotextile tubes were now being widely used, and they can help control erosion as these tubes protect soil surfaces from the forces of moving water or wind and rainfall erosion.
The soft engineering options are meant to dissipate wave energy by mirroring natural forces and maintaining the natural topography of the coast. These include beach nourishment/feeding, dune building, revegetation, and other non-structural management options.
He said studies had shown that the presence of vegetation in coastal areas improved slope stability, consolidated sediments and reduced wave energy and protected the shore from erosion.
He said that wave size decreased considerably through denser mangrove areas.
K.K. Raghuraj of Kufos, an expert in mangroves, said that Chellanam suffered extensive loss of the shoreline and bioshielding the coast was an option. However, the coastal line between Fort Kochi and Chellanam did not have substantial beach formation for allowing mangroves or mangrove associates to grow and that beach restoration was needed for bioshielding the coast.
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