As a student of Holy Cross Institute at Quepem (1965-1969),our major excitement during peak monsoons was: “padde budlem”. This refers to the flooding of Paroda village near Quepem, a phenomenon that has been occurring almost every year. The large wetland up to the foothills of the Chandranath mountain is invaded by surplus waters discharged by the river Kushavati as well as rain water that cannot empty into the river. The narrow bridge connecting Paroda to Avedem and the main road to Margao gets submerged, thus cutting off Paroda from the neighbouring town. This natural hazard has inflicted this region for more than 50-60 years. As such, the recent advisory from the Indian Meteorological Department (IMD) about the impending heavy rainfall that may lead to swelling of rivers in the hinterland, is a cause for concern specially for flood-prone Paroda village and adjoining wetlands. Goa has received 125 cm total rainfall; and following torrential rains of 12 cm on 5 July, 2018, river Kushavati did overspill and Paroda indeed got waterlogged. Inundation is thus a recurring phenomenon.
The town of Quepem is blessed with natural as well as priceless man-made heritage. A unique dam across river Kushavati is located close to the main church and behind ‘Palacio de Deão’. Built more than 100 years ago, a man-made waterway lined with concrete originates from the lock-water gate, operated manually, at the dam site. The canal underpasses Quepem town, traverses Paroda and Gudi at ground level, and ends somewhere near Guirdolim. The canal has a gradient of ½ degree; excess water in the river is released through this canal. The gentle slope ensures that water flows as a placid mass, and thus supplies fresh water to the vast expanse of paddy fields along its course as far as Chandor. The uniqueness of the Kushawati river system with an engineering marvel of yesteryears, a heritage dam and a linked waterway, has rarely been explored before.
But a 60 year history of flooding at Paroda is the issue. A look at Google Earth (GE) satellite images reveals some peculiar morphology and vegetation related features along a 5 km meandering river from Quepem to Paroda. Consider this:
1. Upstream of Quepem dam: Behind the dam, up to about 3 kilometres upstream, the waterway presents a perfectly natural character; the river never dries, but acts as a perennial fresh water reservoir; both banks are wooded and marked by private orchards.
2. From dam to Quepem bridge: Along this portion of about 500 metres, the Kushavati river bed comprises prominent huge detached boulders and extensive deposits of pebbles and gravel; such a substrate (now stabilised) has promoted dense vegetation as tall trees with large girth are noted within the river; some of these trees may be 50-60 years old; if left unattended, this part of the Kushavati may get converted into a mature forest, thus entirely blocking the river flow.
3. From Quepem bridge to Paroda bridge: With a few patches of accreted sediment and plant growth, this 3.5 kmlong segment of the river bed presents large rocky exposures at six different places; obviously, such a bed morphology will not allow water to flow easily; also, the role of a small check dam in blocking flood waters may need attention.
4. Downstream of Paroda bridge: Again, a 100 metre long stretch marks the river bed in the vicinity; such a geological disposition, along with a low bridge, will by itself restrict the functions of fast flowing flood waters; arise in water level thus submerges the bridge every year.
A comparison with the older GE satellite images of 2002 confirm the present scenario, indicating that sediment deposits and dense tree growth within the river are not of recent origin, but existed since decades. Therefore, a combination of antecedent rock exposures, huge boulders at several places, and gravel/sediment substrate that promotes luxuriant vegetation on the river bed is bound to impede normal water flow. A swollen river thus makes it doubly impossible for excess rain water to empty into the river; hence the inundations.
The development of, and human actions in, the town is not the cause of overtopping of river banks at Paroda (although a low bridge may be partly at fault). Inundation is a purely natural process caused due to natural morphological barriers within the river. From a scientific viewpoint, management of rivers in the hinterland has rarely been discussed before. Instead, we hear about “nationalisation” of waterways. The recent announcements of projects about rivers have created a flutter across Goa.
A whatsapp group called ‘Our Rivers Our Rights’ is extremely active with incessant posts across the world. Discussions within the group, however, indicate that certain issues are not understood by the society in general and stakeholders in particular. Nevertheless, there seems to be no respite for our water ways. Since a river management policy does not exist, the case of Kushavati needs urgent attention.
In summary, river Kushavati constitutes a perfectly preserved natural river system upstream of the dam. In comparison, the downstream segment, up to a little beyond the Quepem bridge, the river is choked in totality; free flow is severely hampered due to siltation and dense vegetation. Huge rock outcrops that occur at eight places within the river, up to and beyond the Paroda bridge, tend to severely slacken the excessive discharge of rain water.
These natural features explain why the Kushavati swells during peak monsoon, drowns the narrow bridge at Paroda, and converts the village into a (temporary) island. Since flooding has been occurring since the 1960’s at least, it is obvious that river management imperatives were never thought about. River Kushavati is losing its uniqueness.
(Dr Antonio Mascarenhas is a former scientist, NIO, Goa)
