Of all the river systems of Goa, the Mandovi is the most severely impacted. The northern and southern (Panjim city) banks are built-up with multiple jetties and related structures and, as such, hardly any natural features remain. In comparison, in the Zuari River, the northern bank is relatively natural; however, the opposite bank from Mormugao port to Vasco city, and even beyond Chicalim village, the entire bank is taken over by barge repair yards with high walls abutting the highway. A traveller cannot even get a glimpse of the river all along this 10 kilometre long stretch. It is obvious that the geomorphological characteristics of the Mandovi – Zuari estuarine banks have undergone drastic human intervention over the last few decades.
And yet, the recent proposals for marinas at Sancoale and Nauxi bays have come as a shocker that has to be viewed with extreme caution. Sancoale constitutes a back water complex with a network of creeks and lagoons influenced by the tide, twice daily. Dense fringing mangroves adorn the river bank and the lagoon system, as can be observed from the Zuari bridge.
The Survey of India (SoI) Toposheets of 1964 and Naval Hydrographic Office (NHO) charts drawn subsequently can be used to study the morphology and the areal extent of these mud flats. Presently, the river bank of Sancoale is marked by a prominent mud flat that gets fully exposed during the low tide. This geological feature in fact extends from Zuari bridge up to Chicalim bay, a distance of about 6 kilometres. Visual megascopic observations indicate that the sediment is composed of sand near the bank where as silty clay dominates the deeper strip. This marine deposit forms the second largest tidal flat within the estuarine systems of Goa.
Similarly, along the opposite bank, the stretch from Agassaim to Siridao is again characterized by another tidal flat which gets sub-aerially exposed at low tide. This feature also extends up to around 1.6 kilometres into the Zuari River. The Sancoale and the Siridao mud flats make this part of the river extremely shallow. The shipping channel of less than a kilometre in width cuts across the river bed. The shallowness of this area with a very narrow channel can also be viewed from the Zuari bridge.
A comparison of SoI and NHO maps indicate that both the tidal flats formed over the last 60 years at least. The Siridao flat has extended considerably in space and time, the Sancoale – Chicalim linear deposit has remained unchanged. Generally, tidal flats are located in estuaries and low energy marine environments and at places where fine-grain sediments accumulate. The Sancoale mud flat could be termed as inter-tidal, as a maximum of around 1 kilometre (from the bank into the river) gets exposed during low tides owing to the shallow nature of such habitats.
The functions of riverine tidal flats are documented globally. These accreted sediments perform the functions of a buffer zone between the land and the deeper sea thereby protecting inter-tidal habitats by dissipating wave energy. More importantly, such habitats reduce and even eliminate erosion.
Under the CRZ 2011 notification, mud flats are classified under CRZ I since they are biologically active and hence ecologically sensitive; no interference is permitted in such environments. Being a tidally influenced water body and a mangrove marsh setting adjacent to a saline river, the entire area also falls within the No Development Zone (NDZ) according to the CRZ 2011 notification. Therefore, the Sancoale mud flat is one such sensitive ecosystem that cannot be tampered with.
Therefore, any unwarranted interference in the mud flat system can have a drastic long term ramification – sediment deficit, consequent deepening, rapid erosion of an erstwhile stable river bank, and invasion of river water into the hinterland. It is precisely due to the fragile nature and ecological sensitivity of mud flats that these habitats are protected by law.
Based on the data of Goa State Biodiversity Board, the Sancoale – Chicalim strip is a confirmed site for Window Pane Oyster and a habitat for diverse marine organisms such as shrimps, clams and crabs. Independent research by NIO scientists had also confirmed the richness of benthic population as this bay is not only the habitat but also a breeding site for the Window Pane Oyster species, listed as endangered by the Wildlife Protection Act 1972. Therefore, the impact of dredging on the habitat, bathymetry and evolution of the fragile mud flats of Sancoale bay is manifold. Remobilization of sediment will endanger the stability of the bank and the population dynamics of diverse bivalves in the bay as well as the permanently established clam bed in the vicinity. Scouring of an established and productive mud flat can be frightening and can be the worst environmental impact that one can expect.
Should a marina be banned? Or, alternatively, can our river systems which are already under stress, accommodate hundreds of yachts or sail boats that will keep drifting in and out of the estuary? What will be the fate of the local trawlers, canoes or fisher folk that traditionally used and routinely utilize this area for their livelihood? And, above all, what will be the benefit of this activity to the state of Goa in general and the local populace in particular? In CRZ 2011 laws, the term ‘marina’ is not found. Also, there are no guidelines for such an activity and no provisions based on which such a project can be conceived.
It is a foregone conclusion that infrastructure intensive marinas only cater to the bold and the beautiful of tourism industry. It appears that the fate of a massive marinas in close proximity, within a sensitive estuary, has already been planned, albeit surreptitiously. Apparently, the marina project is being sanctioned by the Investment Board of Goa that operates under the umbrella of Goa Investment Policy. This document is not freely available; at least the general public does not seem to be aware of it. According to media reports, the board consists of a couple of politicians and some businessmen who apparently decide among themselves what may /may not be good for the state. For obvious reasons, scientists or technical experts do not exist in the board. No debate or seminar has ever been held to explain the nuances of having such mind boggling ventures, the consequences of which only few of us may live to see.
In summary, (a) ecologically sensitive mud flats within river systems have to be imperatively protected at all costs, (b) faunal assemblages need to be conserved for posterity, and (c) irrespective of what type of an activity is envisaged, the ultimate beneficiary of coastal management is the common man and not the business man.
(Dr Antonio Mascarenhas is a former
Scientist, NIO, Goa)
