Why rivers like Ganga are more prone to flooding and overflowing come monsoons
The monsoon is around the corner and so is the threat of floods in some parts of the country. One of the main reasons for flooding and overflowing of river waters is the accumulation of silt in riverbeds, besides other factors like encroachments in flood plains. The problem is more acute in the river Ganga which passes through several states in the north.
Besides the need to take steps to prevent dumping of untreated waste into the river, the current campaign to clean Ganga has also brought into focus the issue of silt in the river. For the river to be really clean, it has to achieve the twin goals of — nirmalta (purity) and aviralta (free flow). Oversilting comes in the way of achieving the second goal of ecological flow of the river.
An engineering solution to the problem would be to undertake large-scale desilting by dredging. It’s a costly option and not ecologically sustainable. It also goes against the notion that silt in Indian rivers is an integral part of the rivers themselves. The Chitale committee set up last year to keep an eye on the desiltation of Ganga has acknowledged this in its recent report.
“Rivers should be provided with sufficient floodplains without any hindrance to the flow. Instead of ‘keeping the silt away’, a strategy to ‘give the silt way’ should be adopted,” the panel has observed. Erosion of banks as well as movement and deposition of sediment are natural regulating functions of any river and ‘sediment equilibrium’ of the river should be maintained, it has said.
This means that dredging may not be a solution. The natural paths of rivers and their tributaries get constricted because of reservoirs, dams and barrages being built. These structures are important contributors to silting of rivers. Reservoirs on the Ganga and its tributaries in the upper reaches, the committee has observed, should be operated in a manner that allows first floods that carry a silt load to pass through without storage. River flows in later phases of the monsoon only should be stored for use during non-monsoon season. This would call for scientific management of reservoirs and all associated decision-making systems.
A good example of the silting problem is the Farakka barrage where the annual silt accumulation is estimated to be over 320 million tonnes. This has massive repercussions for both upstream and downstream areas. Desilting such huge piles of silt through degrading would be impractical and cost a huge sum of money. Perhaps it would be prudent to follow what the expert panel has recommended — letting the river flow with the silt in the early monsoon days. In addition to river control structures, several other factors like soil and water conservation measures, tree cover and riparian land-use decide sediment loads in rivers.
Instead of looking at piecemeal solutions, the need of the hour is a comprehensive national silt policy based on scientific evidence and data. If needed, tough decisions like decommissioning of heavily silted barrages should be taken. Politics should have no role to play in keeping our rivers clean and ecologically safe.
(Courtesy: Mail Today)