A nation’s struggle to overcome nature
As heavy showers descended, floods, strong winds and landslides reigned across the country during the last few days. The death toll thus far is 24 and more than 170,000 people have been affected in 20 districts.
Colombo is one of the most-affected districts and it has been so at an alarming frequency over the past few years. As the city expands in size, population and aspirations, it must address its susceptibility to flooding in order to provide better living standards for its residents.
There are several projects on the pipeline initiated by the Sri Lanka Land Reclamation and Development Corporation (SLLRDC) and the Colombo Municipal Council (CMC) Drainage and Water Supply Unit, with the objective of overcoming issues concerning floods in Colombo and its suburbs.
According to SLLRDC Chairman Roshan Gunawardena, Colombo would not face any floods once the flood-mitigation projects initiated are completed by 2020.
Rains to prevail
The Foundation for Environment, Climate and Technology (FECT) revealed that May was a month with high rainfall over Sri Lanka as a region of heavy cloud bands known as a Tropical Convergence Zone, passed from the South to the North. With such conditions, minor perturbations could lead to massive downpours.
FECT President Lareef Zubair said such perturbations could arise from certain atmospheric disturbances such as storms or changes in wind patterns.
“Historically, May is a month with high rainfall averages as well as variations. There is a condition known as Madden-Julian Oscillations (MJOs) which are currently augmenting this year’s rainfall. However, unlike the last two years, there have been no remote cyclones or cyclonic storms in the Bay of Bengal, augmenting mountain-induced rainfall by remote action as they give rise to unusual wind patterns,”
He further said the phenomenon could be attributed to climatic variability.
“Climate change is a phenomenon understood over longer periods such as decades and while there may be an influence, research does not positively attribute the heavy rains experienced this year to climate change,”
The Meteorology Department, in the meantime, highlighted that the South West Monsoons had been established over the country and several spells of showers would occur during afternoons in the South Western areas during the next few days.
The Department added that heavy falls above 50 mm could be expected at some places in the Sabaragamuwa, Western, Central and North Western provinces and also in the Galle and Matara districts. Increases in wind speeds are expected up to 50 kmph in inland areas and up to 70 kmph in coastal areas.
Consequences of calamity
According to research conducted by the Asia-Pacific Alliance for Disaster Management Sri Lanka (APAD SL), high-impact disaster events are a frequent occurrence in Sri Lanka since 2011, affecting an average of 1,000,000 people annually. During the period from 2005 to 2015, floods alone had affected 64 percent of the entire Sri Lankan population.
In May, 2016, a record-high rainfall affected 24 of the 25 districts across Sri Lanka. Four hundred and ninety-three thousand three hundred and nineteen people were affected by floods and landslides, causing 93 deaths and 117 reported missing (210 lives lost). The disaster claimed 58,925 houses and caused a income losses for over 1,000,000 people dependent on agriculture, trade and industries.
They further said that the Colombo and Gampaha districts, which are concentrated with more than 45 percent of Sri Lanka’s industries, were the most affected. Over 85 percent of the houses affected were from the said two districts.
The recorded total effect of the disaster was Rs. 105 billion. Private sector losses were Rs. 94.66 billion. May, 2017, witnessed repetitive heavy South West Monsoonal rains of over 600 mm within two days (May 25 and 26), triggering flash-floods and landslides, affecting 15 districts. The disaster affected 879, 778 people, causing 219 deaths and 74 reported missing (293 lives lost). Eight hundred thousand houses were damaged and livelihoods of over 342, 000 people, were affected.
According to APAD, an estimated 25 percent of businesses do not reopen following a major disaster and 80 percent of companies that do not recover within one month, post-disaster, were likely to go out of business.
Inefficiency of the CSS
In this background, it is important to look at what the future holds for the financial capital of the country. Colombo spans over a total land area of 37 square kilometres and approximately 80 percent of the area is presently covered by the Colombo Sewerage System (CSS), while the remaining 20 percent consists of 11 unsewered areas. Much of the Colombo Sewerage System was constructed between 1902 and 1925 and it could be divided into two major catchments; namely the Colombo North Catchment (CNC) and the Colombo South Catchment (CSC).
CMC Drainage and Water Supply Director Engineering M. I. M Saleem affirmed that the sewerage system was nearly 100 years old, with the wastewater line being over 50 years old. He added that the system could not cater to the present rainfall and flash-floods occurring in the country.
Saleem further said that the Colombo Municipal Council had commenced several flood-mitigation projects and that they had already witnessed positive changes in locations where the projects had been completed.
In addition, sewage from two adjoining municipalities, Dehiwala-Mt. Lavinia and Kolonnawa as well as from another 11 locations, including the Parliament Complex in Sri Jayawardenepura, was pumped into the Colombo Sewerage System. The CMC Drainage Division, which functions under the Municipal Engineers’ Department, was thus mainly responsible for operation and maintenance of the Colombo Sewerage System and the local storm-water network.
Flow from the Dehiwala-Mt. Lavinia Municipal Council (DMMC) area is received by the Wellawatta outfall and flow from the Kolonnawa Urban Council (KUC) area is received by the Mutwal outfall. These are transboundary flows to the CSS.
Saleem said the sewerage system was at present, inefficient and hence, experienced overflows.
He added that the recent, rapid development of the city required an upgrading of a number of sewers; several issues concerning the system had already been eradicated.
Although 80 percent of Colombo is served by the CSS, it is reported that up to 50 percent of the population is not connected, or has irregular connections. There are many cross-connections between the surface and foul water drainage systems. Sewers are purposely allowed to flow into storm-water systems to overcome capacity issues as well as diversions to overcome sewer blockages and collapses.
Saleem said that they had identified 45 places in Colombo where flash-floods occur even for smaller rains.
“We sought the support of the World Bank to initiate the project. Due to the limitation of funds, the project was implemented in just six places,”
The projected was implemented at Gregory Canal, Saunders Place, Devi Balika junction, Kynsey Road, Norris Canal and the Wijerama junction.
Saleem said work at the Devi Balika junction and Kynsey Road were currently in progress and added that the Norris Canal project was at its procurement stage.
He said there were other projects without funds as well; namely Green Lane, George R. de Silva Mawatha, the Rathnam playground area, High Level Road, Kirulapone junction, Robert Gunawardena Mawatha, Siridhamma Mawatha and its surrounding areas, Park Road, the Colombo Public Library junction, Braybrooke Place, Palm Grove Avenue, Serpentine Canal and the Baseline/Sri Saddharma Mawatha junction.
Saleem further said that two years ago, the Metro Colombo Urban Development Project (MCUDP) was initiated and among the six places, work at four places had already been completed with two more currently underway, adding that Rs. 3.2 billion was allocated for the project.
“Once all these projects are implemented, Colombo and its people need not worry about any floods,”
SLLRDC projects underway
SLLRDC Chairman Roshan Gunawardena said the rapid urbanisation taking place in Colombo and its surrounding suburbs had contributed to unplanned land-filling.
“During rainy seasons, massive floods occur and this problem is aggravated annually,”
Gunawardena said that the role of the SLLRDC was to ensure a flood-free habitat for the nation and added that rivers came under the purview of the Irrigation Department, while major canals were the responsibility of local governments.
He said that two projects were being implemented to mitigate floods in Colombo and its suburbs. They were the Weras Ganga Project and the Metro Colombo Urban Development Project.
The SLLRDC, with the assistance of the Japan International Cooperation Agency (JICA), had prepared a comprehensive Master Drainage Plan for the Colombo metropolitan region, while a feasibility study had revealed that the Weras ganga basin, a sub-catchment of the Bolgoda lake, required high-priority for flood-mitigation.
The Weras Ganga Storm-Water Drainage Development and Environmental-Improvement Project consists of the Nugegoda – Rattanapitiya basin, Boralesgamuwa North and South basins, Maha Ela basin, Bolgoda basin, aside from the Weras ganga itself. The said project was funded by the government through a loan from the National Savings Bank (NSB), with a treasury guarantee.
Gunawardena said the main objective of this project was to make the surrounding area a flood-free habitat.
SLLRDC Acting General Manager K. Rajapakse, explaining the activities that are being carried out under the project, said it included the widening of existing canal networks, protection of canal banks, preservation flood-retention areas, improvement of existing culverts and bridges, construction of new structures, re-cultivation of abandoned paddy fields, waterfront recreational activities and restoration of the Attidiya Bird Sanctuary.
According to the SLLRDC, renovation of the Nugegoda – Rattanapitiya canal which is 3.056 km in length, commenced in 2013 and is currently in progress with 95 percent of the work completed.
The Metro Colombo drainage basin is about 105 km long and covers areas such as Kotte, Battaramulla, Rajagiriya, Madiwela, Dehiwala and about 75 percent of the area falling under the Colombo Municipal Council’s jurisdiction. This basin has a number of sea outlets as well as river outlets. The 2010 November floods affected the said area the most.
“It has been identified that the present outfall capacity of the system is insufficient for such an event and infilling of the existing storage areas aggravate the condition,”
MCUDP Deputy Project Manager M. M. M. Moufer said.
He said that a number of outfalls were proposed under the MCUDP, while preserving the existing flood-retention areas.
Following feasibility studies, major interventions were identified to increase the outfall capacity of the system. They were the improvement of the Madiwela East diversion scheme, Madiwela South diversion scheme, St. Sebastian North lock gates and pumping station, the Torrington and New Mutuwal tunnels, the Ambatale pumping station, St. Sebastian South pumping station and the Kolonnawa canal diversion scheme.
In the meantime, Gunawardena said the SLLRDC focussed on the primary canal system and the overall drainage management in the basin, while the CMC was concerned with urban drainage management in the area.
The project was initiated in 2012 and according to Moufer, once completed, residents would have greater, direct protection from flooding and the entire city would benefit from the project’s quality of life investments.
“The Metro Colombo Urban Development Project is helping to reduce the risk and impact of flooding, while making the city more liveable and competitive through sound investments in public spaces, wetlands, and infrastructure,”
The project includes a component on flood and drainage management which involves complex, integrated works such as tunnels and pumping stations. This is in connection with the rehabilitation and management of street and drainage infrastructure, including canals and flood gates.
Moufer said that since 2013, the MCDUP had been supporting the government in reducing floods in the catchment of the Colombo water basin, while strengthening the capacity of local authorities to rehabilitate, improve and maintain infrastructure.
According to officials, the projects proposed by the SLLRDC and the CMC, were expected to make Colombo a flood-free habitat by 2020.