In the past few days several thousands were evacuated from low lying areas in the national capital after the water level of the river Yamuna touched 207.32 metre, just centimetres short of the maximum level during the infamous 1978 floods in Delhi. The level was well above the danger mark of 204.83 metre. While one child died, carried away by the strong current at Wazirabad in north-east Delhi, many others had to be evacuated from low-lying areas. The Yamuna spilled over its banks as unprecedented rainfall and the consequent discharge from the upper reaches inundated the Ring Road.
“Periodical floods of varying magnitudes are natural phenomena. The very concepts of 25-year flood, 50-year flood and 100-year flood show that this will happen from time to time; only we can't say when,” says Ramaswamy Iyer, former secretary of the ministry of water resources. Others have alluded to the odd timing of the rainfall and flood event given that this rise in water levels in mid June is unprecedented. “Similar rise is plausible, welcome and accepted in July and August,” says Manoj Misra, convenor of Yamuna Jiye Abhiyan, a campaign front in Delhi against the encroachment of rivers' floodplains. In fact, most of the high flood levels have historically been attained in the month of September (see graph).
Yamuna's peak flow
|Gush from Haryana
||Volume of water discharged by Haryana
(in cubic metre per second)
Sheila Dikshit, chief minister of Delhi, will be relieved as the India Meteorological Department announced that little or no rain is expected this weekend in the catchment, as water levels of the river receded somewhat to under the danger levels Friday. The army, however, remains on standby if the predictions turn out to be off the mark.
Pressure of construction, mining
“Flood plains are fertile areas and in a country where the population exerts a severe pressure on land resources, there is no logic in keeping vacant a vast area which the river may claim only for a few days in a year, and may not even claim every year,” says Chetan Pandit, former member of water policy, Central Water Commission, the technical wing of the ministry of water resources. “I am aware there is a lot of hue and cry against construction near Yamuna in Delhi. Any such construction has to be cleared by a committee which is chaired by the member (river management), Central Water Commission, adds Pandit.
Iyer argues that this is part of the problem. “If we obstruct the flows with structures, occupy the floodplain, and so on, and don't respect the space needed by the river, we have ourselves to blame when the floods become disastrous”. Given the intensity of rainfall we have seen over the past week, the rate of precipitation is such that often there is not enough time for water to percolate, which increases the rate of overland flow. The record flows have also led some to question the carrying capacity of the river. But there seems to be little direct evidence that the channel is losing its carrying capacity, other than in Delhi where the bed is shallower given the discharge of untreated sewage, physical dumping of idols, polythene, solid waste, all of which settles, and is not always washed away.
In other parts of the river there is rampant mining of sand, which is deleterious for base flows (groundwater feeding the river in the lean season), a result of which there is minimal ground water recharge, says Misra. This soil also holds water to reduce the intensity of the flood, but that would most likely be imperceptible in such events.
The impacts increase as there are further encroachments in the flood plains. The Yamuna is bound by the Noida link road on one side and the Ring Road on the other, and the river spilled its banks, implying that the width is far less than the required spread. There are several encroachments including Majnu Ka Tila resettlement colony, which are facing the brunt of this increasing water level and spill.
The Union Ministry of Environment and Forests has been attempting to notify a River Regulation Zone (RRZ) on the lines of the Coastal Regulation Zone notification since a decade. There has been little advancement in the matter, despite a draft proposal for the RRZ notification in 2002, which seeks to regulate construction activities within 500 metre from the boundary of the floodplain, or the highest flood level. It has, though, watered down the definition of the highest flood level, from the area that may get inundated once in 100 years to the area that gets flooded once in fifty years. The government defends its dithering on the grounds that it is a tricky issue requiring further study. But given that the notification will not be retrospective, it is important to quickly move towards a consensus on the issue as minimal construction in flood plains will serve to protect lives when rivers are in full spate.