As rain clouds gather overhead and the monsoon season looms, Colombo finds itself at a critical juncture, grappling with the dual challenges of blocked waterways and impending floods. Against the backdrop of invasive vegetation clogging drains and streams, concerns mount regarding the city’s preparedness to withstand the deluge.
The activation of the monsoon season in the country serves as a serious reminder of the urgent need to address the state of Colombo’s infrastructure. With waterways choked by Salvinia and water hyacinth, and once-clear pathways now obscured, doubts emerge about the city’s resilience in the face of impending rainfall. The Meteorology Department’s forecast for above-normal rainfalls from 10-30 May only adds to the sense of urgency.
Sri Lanka experiences two distinct monsoon seasons, both often characterised by heavy rainfall leading to flooding. The southwest monsoon, occurring from May to September, predominantly affects the southern provinces. In contrast, the northeast monsoon, spanning from December to February, primarily impacts the Eastern, Northern, and North Central Provinces.
During the southwest monsoon, rainfall occurs unpredictably throughout the day and night, particularly in the southwestern region of the country. Rainfall amounts vary widely during this season, ranging from approximately 100-3,000 mm. The highest rainfall is typically observed in the mid-elevations of the western slopes, such as Ginigathhena, Watawala, and Norton, where it can exceed 3,000 mm.
As elevation increases, rainfall diminishes rapidly, with areas like Nuwara Eliya experiencing much lower rainfall, dropping to around 853 mm. However, along the southwestern coastal belt, the decrease in rainfall is less abrupt, with precipitation ranging from 1,000-1,600 mm during the five-month-long southwest monsoon period. The lowest rainfall figures are recorded in the northern and southeastern regions of the country.
Results of land filling
Elaborating on the flood risks in Colombo and its suburbs, Centre for Environmental Justice (CEJ) Executive Director Hemantha Withanage stressed: “Most of the wetlands in Colombo and its suburbs are already polluted and some of the wetlands are refilled illegally. As a result, the water in drains and streams does not flow properly.
“Most of these streams and drains have been blocked and when heavy rains come, the water gets stuck and starts flooding. During the dry season, nobody cares about these wetlands, and when flood risks loom, people start talking about the importance of wetlands.”
According to the final report on the Colombo Wetland Management Strategy of the Metro Colombo Urban Development Project, wetlands currently cover around 19 square kilometres, constituting approximately 15.4% of the total area of 121.5 square kilometres, including densely urban, peri-urban, and rural environments. However, their historical extent was much larger.
Freshwater wetlands dominate, making up nearly 85% of all wetlands, with herb-dominated areas, including active and abandoned paddy lands, comprising almost two-fifths of the total. About a third of wetland areas consist of mosaics of woodlands, tall and short herbs, and open water habitats, while open water wetlands like tanks, lakes, and canals cover just over 20%.
The report also notes that wetlands within the Colombo Metropolitan Region (CMR) have faced progressive degradation, infilling, and loss since the days of the Kingdom of Kotte, with much of this damage considered irreversible. The rates and extent of wetland loss vary across the CMR, with some estimates indicating reductions of up to 65% in wetlands like the Kolonnawa Marsh since the 1980s.
Similarly, as much as 60% of paddy lands across CMR wetlands may have been converted to non-wetland use during a similar period. Other estimates suggest a lower figure of around 22% across the city, but this still signifies a significant loss. Regardless of type, wetlands continue to face degradation and loss across the CMR.
Withanage emphasised that only about 2,000 hectares of wetlands remained in Colombo today. He highlighted that over 75% of Colombo’s land was once covered by wetlands, but extensive development activities had led to a gradual reduction in wetland cover.
He further noted that areas from Muthurajawela through Kotte to Bolgoda were previously enveloped in wetlands, while alleging that much of the land filling of these areas was carried out by the Government, including for the construction of the Central Environment Authority (CEA) and Parliament, which are situated in wetland areas.
According to Withanage, one of the main reasons for unregulated filling is the lack of coordination among relevant authorities responsible for approving such activities. He pointed out that approvals had to be obtained from multiple institutions, including the Department of Wildlife, CEA, Irrigation Department, and Sri Lanka Land Development Corporation (SLLDC). However, due to the absence of a single controlling body, there was a lack of proper coordination between these departments.
According to the Disaster Information and Management System (DIMS) in Sri Lanka, flooding follows a cyclical pattern, with peaks in May and October to January, likely due to monsoons. Floods have been most frequent in recent years, with 2006 seeing the highest occurrence.
May and December are peak months for flooding. The most-affected districts include Jaffna, Kalutara, Ratnapura, Gampaha, and Ampara. Although deaths from floods are low, 2003 saw nearly 180 casualties. Damage to houses, buildings, and paddy fields follow similar patterns, with Ratnapura, Ampara, Batticaloa, Polonnaruwa, and Jaffna most affected.
Drain cleaning delayed
Kaduwela Municipal Council Municipal Engineer K.P.S. Wijesiri acknowledged that the council had undertaken cleaning of blocked drainage. However, he pointed out that the management of water streams in the area fell under the jurisdiction of the Irrigation Department.
Wijesiri emphasised that main drains along the roadsides should be overseen by the Road Development Authority (RDA).
In the meantime, Disaster Management Centre (DMC) Director General Major General (Retd) Udaya Herath stated that district-level monsoon meetings were currently underway to address preparedness and mitigation strategies for floods and other disasters during the upcoming monsoon season.
“The Meteorology Department has officially announced the activation of the monsoon season. As a result, we are discussing potential disaster risks and methods to prevent and mitigate these disasters,” he emphasised.
“All stakeholders are actively participating in these disaster meetings. We are advising authorities on keeping drains and streams unblocked and recommending actions to prevent flooding. We also discuss necessary mitigation efforts,” he explained.
Explaining flood mitigation efforts in the Colombo Municipal area, Colombo Municipal Commission Badhrani Jayawardena stated that they had identified 27 critical points for flood mitigation in the Colombo Municipal area.
“There is a natural gravitational pull towards the sea. Water from higher elevations cascades down, leading to high water flow in areas near the coast as it accumulates from upper levels. Hence, mitigating floods in Colombo requires more than just the city’s tax money,” she stressed.
Under the Metro-Colombo Development Project funded by the World Bank, a comprehensive survey has been conducted to identify flood risk areas and allocate funds for their mitigation. Consequently, 27 locations have been earmarked as critical points for flood mitigation. However, implementation has been hindered in some areas due to various issues such as opposition from residents and ongoing construction projects.
Nevertheless, the Commissioner emphasised that flood mitigation efforts would persist.
When contacted, Irrigation Department Director General Engineer Ajith Gunesekera stated that the inlets in Kaduwela near the Kelani River and near Panadura had already been unblocked. “There are some areas where blockages occurred due to actions taken by the respective municipalities. However, aside from those specific areas, all other inlets have been cleared,” he added.