by Rajendra P. Kerkar
KERI (SATTARI) – Deforestation undertaken for various purposes in the watershed of the tributaries of Mandovi, Zuari, and Colvale intensified the flooding situation in different parts of Goa.
Though there was a heavy downpour of monsoonal rain during the last week, on Thursday repeated heavy rainfall coupled with the destruction of the watershed of the various tributaries have intensified floods in the low-lying areas of Bicholim, Dharbandora, Pernem, Sattari, and its vicinity.
Massive deforestation for the quarter-century in the various basins of the Mandovi, Zuari, and Colvale resulted in increasing sediment load.
Also, encroachment done in the river’s flood plains, heavy runoff from mining dumps, and stone quarries worsen the situation.
In many riverine villages, Goa villagers have reclaimed land from the flood plains for agricultural and horticultural crops. Also, the mining of sand, pebbles, stones, and unscientific dredging inside the river has changed rivers’ hydrodynamics.
In the watershed of the Mhadei, Kotrachi, Ragado, Zarme, Velus, Dudhsagar, Tillari, Kalane and the Nanoda rivulets forest clearance have been illegally done for the cashew plantation and also felling of trees have been done.
Deforestation to clear land for undertaking plantations and building farmhouses in Virdi of Dodamarg taluka have caused soil erosion and siltation in the Valvonti river. In Talekhol of Dodamarg, stone quarries have increased the silt in the Bicholim river.
The havoc caused due to floods is not only on account of natural factors, but various anthropogenic activities have led to intensifying floods.
Water Resources Department have already undertaken anti-flooding embankments without understanding the vulnerability and ecology of the river, and these have increased the erosion; also work of desiltation have been done with unscientific dredging that has been posing a threat to the natural vegetations inside the river.
In the watershed of Tillari, large-scale monoculture plantations of rubber, sugarcane, pineapple, banana, herbal medicine, cashew, and others have been undertaken. This has caused soil erosion, thereby leading to rapid siltation affecting the water storage capacity of the Tillari river. Despite a ban on tree felling in the Dodamarg-Sawantwadi wildlife corridor, deforestation, stone quarries, mining of laterite and metabasalt stones are going on, which has badly affected water holding capacity of Tillari dams reservoirs.
While dredging and desiltation the species of sherni plants that protect the riverine coarse and beds have been degraded. Sherani plays a vital role in minimizing the destructive role of floods.
The Sherni plant Homonia riparian have a role in enriching freshwater ecosystems.
From 1960 to 1980 for two decades, Sattari taluka lost the forest cover of 8,848 ha, whereas Sanguem, along with Dharbandora 9,933 ha of forests for various developmental projects and anthropogenic activities. Under the social forestry of the Forest Department of Goa had undertaken a massive monoculture plantation of the exotic species, which has drastically affected the groundwater recharge natural system along with percolation of rainwater.
India accounts for one-fifth of the global flood deaths; an average of 1650 Indians lost their lives every year between 1953 and 2016. About 40 million ha in India are prone to flooding and economic losses.
Climate change, sea-level rise, the intensity and frequency of flood events and the predictability of heavy downpours affect flood management in India. In Goa, every year, floods in urban areas are a particularly evolving risk due to planned city growth and poor drainage infrastructure.
India’s current flood management strategy largely focuses on structural measures such as embankments and dykes. However, in the coastal state of Goa where many of the west-flowing rivers originates in the Western Ghats, the embankment, flood protection wall and the Vasant bandharas along with tree felling on either bank of the river, have been revealed intensifying flooding threat. There is an urgent need for a planning strategy to protect flood-prone areas and flood forecasting and flood risk management activities.
Though, Indian Meteorological Department observatory in Goa had released forecasting of heavy downpour, the local administration has been seen unable to use it properly on account of seriousness and lack of skilled personnel. To address the increasing threat of flooding, there is a need for an improved drainage system, a real-time flood forecasting system, strict implementation of building codes and demarcation of flood zones. It has been revealed that afforestation undertaken in rivers’ watershed areas have helped prevent soil erosion and sediment deposition.
In Goa, the flood-carrying capacity of the river network is rapidly decreasing because of bank erosion and rise in sedimentation. There is a need for early forecasting system, land use planning, warning outreach and flood plain mapping, and implementing a unique insurance scheme for the people residing in flood-prone areas.