Dr V M Meher-Homji outlines a proposed action plan for the small fishing town of Udvada on the west coast of India.
BEACH EROSION which has ravaged Kerala and other parts of the west coast of India has, in recent years, begun to adversely affect the small town of Udvada. Udvada is located between the Union Territory of Daman and the district town of Valsad (Bulsar).
Region of Udvada
The town’s shore is lined with the hamlets of fishermen as well as with the houses, hotels and bungalows of residents, some of these dating back to 1870.
Udvada is also an important heritage site and pilgrim centre. The town houses the oldest Fire Temple of the Parsis. In 1742 the holy fire that came to India from Iran in 720 AD following the migration of the Zoroastrians finally found its base at Udvada.
The problem of beach erosion at Udvada was first observed about five decades ago with the demolition of a few fishermens’ huts. Over the ensuing years the erosion has spread northwards, affecting the backyards of the coastal settlement.
Shoreline oscillation is a natural hazard like seismic movement. The shoreline representing the land-sea interface does not remain stationary over long periods such as centuries or millennia.
A comparison of the topsheet of the Pichavaram mangrove area (South Arcot District) based on the Survey of 1930 with an aerial photograph taken in 1970 shows that in the southern area of the mangrove beach sand has moved in. In the northern area, the sea has invaded 500m of the mangrove forest. Palynology (the study of living and fossil pollen grains and plant spores) is a useful tool in making out the shifts in the shoreline.
Environmentalists have been issuing warnings that in the wake of the increasing levels of carbon dioxide in the atmosphere, global warming will lead to a rise in the sea level not only because of melting glaciers but there would also be expansion of ocean water as well.
Scientists are of the opinion that the beach erosion encountered on the west coast of India is not as yet the result of global warming but is more likely the consequence of geotectonic movements like the tilting or up-lifting of the coastal margin. Nevertheless, experience gained in dealing with this present-day problem could prove invaluable in responding to the longer-term threat of sea-level rise induced by climate change.
Any obstruction, natural or human-made, in the path of the along-shore movement of sand may cause erosion on the downdrift side and deposition of sand on the updrift side. It would, therefore, be interesting to ascertain the role of the bridge or jetty in a southerly region like Daman.
The most popular belief amongst the residents is that it is land reclamation carried out around Bombay that is the root cause of the devastation of the beach. However, the fact that the sea erosion takes place only for a few days at the peak of the monsoon, corresponding to the spells of torrential rains, points a finger at the run-off water of land origin rushing into the sea through the neighbouring rivers, streams and overflow from the tanks (lakes). The debris washed ashore by the high tides include plant materials growing in the interior areas and also occasional carcasses of cattle.
The northern part of the beach not affected by erosion still shelters mounds of sand covered with sand-binders such as Ipomoea pes-caprae and a few other trailers such as Cyperus arenarius and Spinifex littoreus. Among the fast-depleting biodiversity of the region, vestiges are still available of plant resources like Agave Sp., Aloe Sp., and Pandanus Sp., all of which can effectively bind the sand.
Whereas engineering works like the construction of a suitable wall in the most affected parts where tons of sand with parts of houses have been washed away seems the only solution, the available land all along the shoreline should be protected by a green belt, in which Casuarina equisaetifolia has to play a key role. Among other species particularly suitable to the littoral zone that have to be tried are: Terminalia catapa; Barringtonia Sp.; Thespesia populnea; Calophyllum inophyllum; Cocoloba uvifera; and Hyphaene indica.
Walls constructed around individual houses have not been able to withstand the fury of the giant waves. Sea walls offer solutions which are of value for a limited time. Vertically impermeable walls have been used in the past with little success. Sloping permeable sea walls give better results, however they require continuous maintenance.
Since sea-walls restrict the use of the beach, sand nourishment is a new concept. Dredgers have been used to nourish eroding beaches from sources of sand offshore. Except in the case of major ports, this method is not very popular in India as it is an expensive means of beach protection. An alternative is an offshore disconnected submerged barrier.
The marine assault is two-pronged. Whereas in the southern part of the settlement the sea is invading the land, in the low-lying land just north a creek is making an inroad. During the high tides this low-lying Khar land (salty terrain) gets inundated by brackish water and tends to render the soil and well-water salty.
The vicinity of the creek could be planted with available mangrove species such as Avicennia marina and Acanthus ilicifolius. For the brackish marshy wasteland, species of back-mangrove like Clerodendrum inermis, Salvadora persica, Excoeraria agallocha and others like Thespesia populnea, Pongamia glabra, Acacia holosericea and even Prosopis juliflora, an aggressive exotic weed, may be tried.
Prosopis juliflora has managed to colonize even the periphery of the Rann of Kutch and has a good coppicing capacity to provide fuel wood. In the drier districts of Tamil Nadu it is not only the sole source of firewood but of income for the weaker sections of the society.
As fuel wood shortage leads to the cutting down of trees and shrubs, additional energy plantations with species like Casuarnia, P. juliflora and Acacia holosericea have to be provided for the survival of the shoreline plantations. Acacia holosericea, introduced at Auroville, Pondicherry, has proved successful over sub-desertic tract with little irrigation and fertilizer. An added value for the local community is that it has good calorific value for burning.
Wall exposed by sea erosion
In summary, a green belt – the greening of the saline marshy land – would lead to a reduction in the salinity of the area and also would arrest its extension. Such an action plan would greatly enhance the security and livelihoods of the small local community.
Original article here