My views are based on my observations in Chennai (floods) and in Goa (the topography of coastal villages60 years back). It is an appeal to the experts to review their ideas about coastal management. The observations are a fact; the analysis and conclusions are hypothetical.
For illustration sake I shall use one area in Chennai : the ECR – OMR corridor. In Goa I shall pick two areas (which are very similar) : the Miramar – Caranzalem – Taleigao area and the Carmona – Fatrade Beach – Varca area. The near beach coastal topographies in Chennai and Goa seem to bear a strong similarity as you see in the topo maps.
Let us begin with the topographic profile of a typical coastal zone. In the figure below there is a line marked as ‘the original gradient’. This is how the land must have sloped towards the sea at some point of time, before the action of wind and water created the ‘sand dunes’. There may be one or more lines of sand dunes (in the Chennai illustration given below, you see two lines of sand dunes). The result is formation of a dip or a bowl between the dunes and the ‘original high ground’. You can identify this profile in all three illustrations given below: the ECR-OMR corridor in Chennai, and the Miramar – Caranzalem – Taleigao / Carmona – Fatrade Beach – Varca areas in Goa. The Chennai is a little more complex as here the marshlands are not always confined to ribbons parallel to the coastline; they extend inland between the uneven contours of the high ground.
The dip or the bowl has a very important function in water management: to hold the rain water runoff from the high ground; this both prevents flooding during heavy rain and recharges the ground water aquifers. The overflow from these marshlands is drained out through the rivers that cut through them and empty into the sea -for instance the Adyar and Coom rivers in Chennai, and Sal river and Santa Inez Creek of Mandovi in Goa). Though originally these bowls may present themselves as marshlands, in most of the places these have been reclaimed for kharif cultivation. The water therein is further managed by building canals connecting the individual water bodies; the Buckingham Canal in Chennai is an example of this; you find a canal running across the fields between the sand dunes and high ground in Carmona – Fatrade Beach – Varca area popularly called the ‘danga-holli’. But such reclamation does not pose any problem, as it neither reduces their capacity for holding the runoff nor impairs their ability to recharge the ground water. Of course, some parts of these bowls may continue to remain as marshlands.
The problem comes when these marshlands are filled up and built upon. Almost all the areas that experienced excessive flooding during the Chennai floods are the areas where marshlands have been filled up and built upon.
OMR (Old Mahabalipuram Road) connects Adyar in South Chennai to Mahabalipuram in Kanchipuram district. Around year 2000 it was decided to convert the road into an IT corridor – a six-lane expressway with service lanes and landscaping; it was named Rajiv Gandhi I T Expressway. The first phase of the road – Adyar to Siruseri was completed by 2008, and subsequently a vast maze of IT Parks developed in the bowl on either sides of the road; the roads and new developments are now slowly encroaching into the Pallikaranai Wetland Reserve. This IT district is a home to one of the largest IT parks in Asia. All the IT activity had to close down till the waters receded after the December floods.
Now let us turn to the CRZ (Coastal Regulation Zone). The CRZ Regulations of 1991 and subsequent amendments restrict themselves to ‘coastal stretches within 500 metres of High Tide Line on the landward side’. This covers a part of what we have called the sand dunes, but nothing of what we have called the marshlands. The Chennai experience shows that it is the latter that needs to be more vigorously and still more rigorously regulated; replacing sand dunes with RCC dunes can do far less long term damage than draining out and filling up marshlands. The CRZ regulations have fatally glossed over the water management function of the coastal marshlands.
Fortunately relatively less development has happened in the marshland zone in Carmona – Fatrade Beach – Varca area, or, for that matter, in the entire coastal stretch of Salcete. But the Miramar – Caranzalem – Taleigao area is fast going the Chennai way.
(All topo maps are from www.arcgis.com)
