Human miseries due to river erosion
Thursday, 19 July 2007
MASSIVE river erosion at the on-set of the monsoon has robbed the happiness of thousands of affected and threatened people in many areas along the banks of some of the major rivers including the Padma and the Jamuna. Every year thousands of people are rendered homeless and many thousands acres of land are lost to the rivers due to their erosion. According to recent reports, one entire village in an area has been already wiped off. The local protective embankment has collapsed and merged with the eroding river. The Water Development Board's engineers of the area expressed their helplessness about being of any assistance to the threatened people, as their office does not have sufficient funds for raising a new embankment as a protective shield to guard against erosion.
Repairing an embankment on developing cracks or breaches during the rainy season may be possible. But construction of a new embankment in this wet season is practically impossible. There can be at best some efforts at this time for river course management, which on a broad scale is called river training. But river training for containment of erosion during the rains is a dry season job if it involves only bank management. This work requires laying concrete slabs in a manner like raising the wall of a building. But course management as a whole needs periodic but regular dredging and also building groins at or ahead of points where a river has taken sudden or frequent turns.
The course management of rivers with groins in the alluvial soil of a deltaic belt, as is this country, is rather difficult. An overflowing turbulent river may on obstruction by a groin unpredictably corrode lands on its opposite bank in the immediate vicinity and significantly modify its course. Yet groin-like structures with tree-trunks, logs and other heavy materials are created on the beds of many rivers close to their banks in the rural areas by villagers and local fishermen in the rainy reason for harbouring fishes for netting in the winter. These obstructions shift the mid-stream of the rivers causing them to flow unpredictably and erode one side of their banks.
The artificial obstructions created through such practices also accentuate the silting process of the rivers maximising simultaneously the risks of erosion and floods during heavy monsoon. Want of awareness among the rural people of these cause-and-effect relations is one of the reasons behind massive river erosions in the countryside. Occasional floods in Dhaka due to encroachment on the Buriganga and the Turag and the same in Chittagong due to encroachment on the Karnaphuli and the Chaktai canal also expose the hazards created by obstructions to normal flows of rivers.
Clearly, river course management for safety of the people and their possessions -- land and other valuables, and for controlling, if not precluding, floods is not easy for this country. The need for river training should be minimised to as far as possible by keeping the river course clear of artificial obstructions and pre-empting encroachment in any manner. While groins may be constructed wherever required to modify a river's course, protective shields with large concrete slabs may be raised, instead of earth, where necessary to avoid repetitive commitment of funds. However, the misery unleashed to many people in areas affected by river erosion in this monsoon should not go unattended. These people should receive immediate support from the government. The eroding rivers in their areas may also be tamed with temporary arrangements pending enduring measures in the next dry season.
Repairing an embankment on developing cracks or breaches during the rainy season may be possible. But construction of a new embankment in this wet season is practically impossible. There can be at best some efforts at this time for river course management, which on a broad scale is called river training. But river training for containment of erosion during the rains is a dry season job if it involves only bank management. This work requires laying concrete slabs in a manner like raising the wall of a building. But course management as a whole needs periodic but regular dredging and also building groins at or ahead of points where a river has taken sudden or frequent turns.
The course management of rivers with groins in the alluvial soil of a deltaic belt, as is this country, is rather difficult. An overflowing turbulent river may on obstruction by a groin unpredictably corrode lands on its opposite bank in the immediate vicinity and significantly modify its course. Yet groin-like structures with tree-trunks, logs and other heavy materials are created on the beds of many rivers close to their banks in the rural areas by villagers and local fishermen in the rainy reason for harbouring fishes for netting in the winter. These obstructions shift the mid-stream of the rivers causing them to flow unpredictably and erode one side of their banks.
The artificial obstructions created through such practices also accentuate the silting process of the rivers maximising simultaneously the risks of erosion and floods during heavy monsoon. Want of awareness among the rural people of these cause-and-effect relations is one of the reasons behind massive river erosions in the countryside. Occasional floods in Dhaka due to encroachment on the Buriganga and the Turag and the same in Chittagong due to encroachment on the Karnaphuli and the Chaktai canal also expose the hazards created by obstructions to normal flows of rivers.
Clearly, river course management for safety of the people and their possessions -- land and other valuables, and for controlling, if not precluding, floods is not easy for this country. The need for river training should be minimised to as far as possible by keeping the river course clear of artificial obstructions and pre-empting encroachment in any manner. While groins may be constructed wherever required to modify a river's course, protective shields with large concrete slabs may be raised, instead of earth, where necessary to avoid repetitive commitment of funds. However, the misery unleashed to many people in areas affected by river erosion in this monsoon should not go unattended. These people should receive immediate support from the government. The eroding rivers in their areas may also be tamed with temporary arrangements pending enduring measures in the next dry season.