Improved water retention measures needed to thwart floods

Flash floods that affected 418,000 people and left 23 dead and four missing this week in western Sri Lanka could have been avoided with proper water retention schemes, government irrigation engineers told IRIN.

Floods caused by the onset of the southwestern monsoon on 2 and 3 June affected more than 94,000 families in nine districts in the western lowlands, GM Gunewardena, assistant director at the National Disaster Relief Service Centre (NDRSC), told IRIN.

"The worst-hit area has been the Kalutara District, where over 150,000 people have been affected in some of the low-lying areas close to rivers," he said.

Deaths and disappearances

According to a joint situation report released by the government and the Inter Agency Standing Committee (IASC) on 4 June, 12 of the 23 deaths and three of the four flood-related disappearances were reported from southwestern Kalutara district.

Engineers at the Irrigation Department of Sri Lanka, which monitors floods, told IRIN the low-lying areas of Kalutara and other adjoining districts were submerged because they were in the flood basins of rivers that burst their banks after heavy rains.

"The rivers run down steep slopes in the hills, so water gains speed," BK Jayasundera, senior deputy director at the Irrigation Department in charge of flood protection, told IRIN. "On the low-lying areas there is less [of a] slope and when there are heavy rains the water rushes down," he said. "Unfortunately these areas have also become over-populated."

Photo: Amantha Perera/IRIN

Heavy rains in eastern Sri Lanka led to heavy flooding in late December 2007 and the temporary displacement of some 250,000 people

Other rivers pose threat

He warned that several other rivers flowing down the southern and southwestern slopes of the central hills posed the same threat to low-lying areas.
Jayasundera said the best option to reduce flooding in downstream areas was to build dams to retain the water upstream and release it gradually. "They could also help agriculture [irrigation] and power generation."

Two other flood protection schemes - the construction of pumping stations and of concrete walls along river banks - had been largely ineffective. "The pumping stations are very costly and when the waters swell, the walls are of little help," he said.

Officials at the Meteorological Department said these recent rainfall patterns were becoming more frequent. "This is what we predicted just before the monsoon set in," SH Kariyawasam, deputy director at the department told IRIN. "Between June and July the western slopes of the central hills get heavy rains."

Flash floods

Flash floods have become a regular occurrence in Sri Lanka, especially during the onset of the monsoons, and at least six have been recorded since April 2007, Irrigation Department officials said.

"It is a combination of natural causes and man-made factors that trigger these floods, and they are very hard to control in populated, urban areas," HP Somasiri, the director-general of the Irrigation Department, said.

Photo: UNDP

Destruction from a landslide following heavy rain in Wallapane Division, Nuwara Eliya District in July 2007

Floods in 2007 affected 488,000 people, killed 20 and damaged 9,800 homes, according to statistics maintained by the NDRSC.

Over Rs159 million (around US$1.4million) was spent on relief and reconstruction following the 2007 floods, the centre said.

Soon after flooding was reported this week, the Sri Lankan government released Rs29 million ($270,000) and appealed for assistance from UN agencies and other humanitarian agencies.

The World Food Programme (WFP) released 98 metric tonnes of rice, pulses and cooking oil, sufficient for 50,000 persons for a week, and the UN Children's Fund (UNICEF) contributed three tonnes of high protein biscuits, a joint statement by the Sri Lankan Government and ISAC said on 2 June.

"UNDP has hired a number of vehicles in the affected districts and UN Volunteers have been deployed to support efforts on the ground," the statement said. "The UN Office for the Coordination of Humanitarian Affairs is considering the release of an emergency cash grant for immediate non-food needs."

Officials at the Irrigation Department say such funds and resources should be readily available on a routine basis to support flood relief and reconstruction efforts, unless proper mitigation measures are taken.

"There are very few options open. You can try to move out hundreds of thousands of people from the downstream areas, which would not be very easy," Jayasundera said, "or you can think of retaining water upstream and releasing it gradually."

ap/bj/mw