Urban Flooding

Urban Flooding in India

By: C Ramachandraiah
Of late, flooding in urban areas has increased due to changes in land use and recurrent extreme event episodes. Although advances in forecasting and relief operations have minimised the loss of lives, yet the damage to property continues to be severe.
Disaster Events

Urban flooding is a rising phenomenon in recent times. Whether coastal or inland, flooding in an urban centre can cause grave damage owing to the high population density involved.

Moreover, the capacity of Indian cities to withstand heavy rains has also weakened owing to land use changes and interference with natural watersheds. Thus, notwithstanding the improved accuracy of forecasts and communications, as also the administrative efficiency in tackling floods, cities have ended up becoming more vulnerable to floods. The unprecedented floods that left Mumbai, Hyderabad, Surat and Bangalore reeling in recent times only prove this true. Rainfall variations and extreme event episodes have only succeeded in making things worse.

The authorities have prioritised cities for economic growth and employment generation, but without any focus on protection of water bodies and water channels. Reclaiming large tracts of land for building has left many cities bereft of wetlands and water bodies that can absorb urban outflows during the monsoon. Consequently, recurring urban floods are an annual occurrence today.

In an urban setting, flooding results in large scale disruption of power, transport, water supply, sanitation and other basic utilities. This in turn can pose additional problems, resulting in a crisis that is unmanageable owing to its sheer volume and intensity. With the capacity of the administration stretched to its limits, the affected people end up the worst sufferers, as pointed out by R Chigurupati 2008 paper ‘Urban growth, loss of water bodies and flooding in Indian cities: The case of Hyderabad’, in J Feyen, et. al. edited, Water and Urban Development Paradigms: Towards an Integration of Engineering, Design and Management Approaches, published by CRC Press/Balkema and Taylor & Francis Group, London.

Such extreme events are estimated to increasingly occur, especially owing to heavier precipitation resulting in an increase in frequency and proportion of heavy rainfall episodes. According to D Dutta and S Herath’s undated article, ‘Trend of floods in Asia and flood risk management with integrated river basin approach’, flood frequency is increasing in all Asian countries owing to climate and land use changes. Whenever a flood occurs, the poor and low-income groups are four times as likely to suffer or die. Given that, floods are by far the most frequent and devastating of natural disasters in Asia, it has sizably increased the vulnerability of the urban poor of late.

In recent times, the most well documented case of flooding in a mega city has been that experienced by Mumbai in July 2005 when 94.4 cm of rain received in a span of 14 hours causing a deluge of hitherto unimaginable proportions. One of the major causes behind the flooding was the blocking of the 14 km long Mithi river, and reducing it into one third its size, to create acres of office space in the posh Bandra- Kurla complex. The city paid its price when several went missing and died in the deluge that flooded the city, and rendered it immobile for days without power and water.

The floods in the first week of August, 2006 displaced lakhs of people in Surat, Vadodara, Broach and several other cities and towns in Gujarat, when more than 0.25 million had to be evacuated to safer places. With 70 per cent of Surat under 8-10 feet of water, people were issued an advisory to move to places that were at least 20 feet higher than the ground level.

Bangalore, the ‘Silicon Valley of India’, has been experiencing frequent floods for the last several years. The reason for this is not far to seek. The city had about 262 lakes until 30 years ago; the number had come down to 81, as revealed by the Central Pollution Control Board in its 1999-2000 Annual Report. At present, media reports claim the presence of 60 lakes, the health of most being questionable.

Renowned for its undulating topography and its scenic lakes, Hyderabad has lost many of its water bodies in the last few decades due to encroachments. Environmentalists feel that a repeat of the August 2000 floods that paralysed Hyderabad for days could be ten times worse today. This is because dozens of housing colonies have sprung up in and around the city’s lakes, blocking inflows into water bodies.

Kurnool town, on the right bank of the river Tungabhadra, experienced one of its worst floods in October, 2009. The rainfall was estimated to be the highest in about 100 years. Several areas were submerged in more than 30 feet water, and it took more than three days for the water to recede completely. There were heavy inflows into the three rivers, which merge into each other in and outside Kurnool town. A number of tanks were breached and the Sunkesula Barrage across Tungabhadra, upstream from Kurnool, was washed away. These rivers received inflows far in excess of their carrying capacities resulting in inundation of the town. During the same time there was a rare phenomenon of synchronisation of peak inflows from the three rivers into the Srisailam reservoir. An unprecedented inflow of 26 lakh cusecs, described as the ‘maximum probable flood’ in the Krishna basin flowed into the Srisailam reservoir. This saw the top of the Srisailam dam tilt towards the downstream side by 8.8 mm. About 11.56 sq km or 30 per cent of Kurnool town was submerged, with 3.36 sq km of that area experiencing upto 13 m (42.5 ft) of submergence.

Incidentally, the worst inundation took place in a low lying area sandwiched between the Tungabhadra and Hundri rivers. Luckily, since the flooding occurred during the day, the loss of lives was negligible. Massive relief operation involving personnel and machinery from several urban local bodies in Andhra Pradesh reined in the disaster, and limited the damage. However, it is important to note that this heavy flooding occurred in Kurnool after the district had been declared drought-affected due to scanty rainfall, in September 2009. Even otherwise, Kurnool lies in the zone of scanty rainfall receiving 500–750 mm per annum. At the time of the flood, all dams in Karnataka, that is, the upper riparian State were full and the Srisailam reservoir, downstream of Kurnool, was also nearly full. Yet, the Nagarjunasagar reservoir, further downstream of Srisailam, was nearly
half empty.

Experts attribute the backwater effect of the Srisailam reservoir (which extends upto Kurnool town) for aggravating the intensity of the floods. However, the Kurnool floods threw up several issues in water management pertaining to river basins that cover different states. For instance, it has been argued that matters could have been possibly controlled by releasing a good amount of water from Srisailam into Nagarjunasagar.

On October 12, 2014, Visakhapatnam was hit by a very severe cyclonic storm, Hudhud. The cyclone caused extensive damage to the city and the neighbouring districts of Vizianagaram and Srikakulam. At the time of impact, the wind force was estimated to be 200 km/hour, and the height of the waves reached up to 3 m. This was the first time in more than a hundred years that a city had been hit by a cyclone in full force.

Endnote

The importance of cities as vehicles of economic growth and development are well realized by the authorities. Yet, changing land use patterns in utter disregard of the natural channels and water-bodies that have controlled urban outflows for centuries is costing everyone dear. Unless we revamp our theories of urban planning and give due importance to watersheds, the erratic weather patterns and rainfall characteristic of climate change will throw up frequent natural disasters in our urban centres that will be difficult to manage, given population densities, which multiply every problem several times over.

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