Wednesday , 14 November 2018

Kerala floods – Lessons for Goa

Nandkumar M Kamat


Kerala is experiencing an unprecedented flooding disaster with just 40 per cent excess monsoon rainfall. Although lack of a prolonged dry spell is cited as a reason, the red or orange colour of the floodwater shows that there is heavy sediment load everywhere – a stark indicator of soil erosion in steep hilly areas.

This situation is an excellent eye opener for the Goa government, local politicians, contractors, engineers and architects. Some of them have combined forces in the past 30 years to dismantle most of the pre existing, pre liberation life support systems. Unhindered flow of water from land to sea and encroachment free flood plains marked the pre liberation drainage systems. It is easy to predict a situation like Kerala in Goa next month as the monsoon departs because September brings with it high intensity rains short of cloudbursts.

On October 1 and October 2, 2009 it rained almost 500 millimeters in Canacona. The flooding disaster in the first week of October 2009 in Canacona was not different than what we saw in Kerala past week. Only long dry spells between high intensity rains would be able to save Goa from flooding next month. These spells help in clearing excess water flow.

As experts interested in understanding combination of local impacts of global climate change with human interference in ecosystems and landscape we are closely monitoring the final few weeks of south west monsoon which officially terminates on September 30. But post monsoon rains continue till the middle of November when sometimes Goa gets hit by a passing cyclone in Bay of Bengal.

Except the type of rock formations, Goa and Kerala have several things in common. The eastern part of both the states is traversed by the Western Ghats. Goa has 11 and Kerala has 44 rivers among which 41 originate in the Western Ghats. Kerala has 42 dams and reservoirs whereas Goa has only five dams and reservoirs. Kerala has land mass from 5 meters below sea level in the west to an altitude of 2695 meters in the east within the short span of 120 kilometres. The picture is similar in Goa as the altitude rises from the coast (1 to 4 metres below sea level) to the ghats (Sonsagar, 1166 meters) within 65 kilometres. Kerala has 4000 square kilometres of low lying land whereas Goa has 500 square kilometres of estuarine, Khazans and mangroves falling in low lying area.

If coastal Goa has not seen unprecedented floods like Kerala the credit goes to Goa’s 225 ancient communidades. They built massive coastal embankments along all the 11 estuaries and controlled the tidal flow through an intricate system of deep backwaters, sluice gates and 30 coastal creeks. But the communidades had planned for a population of less than half a million and had not factored in the sediment load due to man-made erosion. So the picture when Goa gets flooded with high intensity rains would show how a combination of factors-open cast ore mining, laterite and basalt quarrying, deforestation and terracing of hills, filling up of flood offset reservoirs, exploitation of river and stream sand would combine to increase the sediment load thus further increasing the kinetic energy of the erosive flood waters.

None of the constructions in lateritic sub-soils in Goa without any solid foundation rocks have factored in how heavy subsoil percolation of water would cause collapse of buildings. Most of these buildings don’t go more than 10 metres deep which is insufficient to withstand heavy percolation and would face slope instabilities and may come tumbling down with a river of lateritic mud. The Portuguese architects and engineers had realised this in 16th century while learning to build under demanding tropical environment and had erected strong deep, heavy buttresses to support large structures from collapse. The greatest threat to all the towns and villages in Goa is a record increase in impermeable or impervious surface area. Architects and engineers are totally clueless about the need of natural rainwater percolation in subsoil and drainage budget of Goa’s towns and villages as populist pseudo-beautification schemes are being pushed forward blindly and aggressively.

Both London and Paris had admitted their mistakes after heavy floods in their rivers. But Goa has learnt nothing from their experiences. Almost all the towns with open rainwater percolation areas are being covered under a carpet of either cement or concrete, asphalt or tiles. Almost all the experts in Kerala are unanimous about the reasons for recent floods – the heavy human interference in natural ecosystems and landscapes. If a state like Kerala which has some of the best land utilisation policies, an active state land use board and a plethora of active, vigilant NGOs, faces such a situation then one can imagine the magnitude of flooding disaster in Goa.

The fundamental planning units for Goa should have been the river basins and the micro watersheds. This also helps in rainwater conservation and aquifer recharge. But micro-watersheds are being converted into commercial and residential projects and flood plains have been totally destroyed. So it is just matter of time when forces of nature may combine with man-made factors to bring the people of Goa to their knees. The ecological history of three ruined ancient capitals of Goa-  Chandrapur/Chandor (100 BC to AD 900), Govapuri/Goa Velha (AD 900-1350) and Old Goa (AD 1350 to 1842) shows that it takes Goans several decades to learn their lessons from disasters.

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