Real-time flood monitoring in Sri Lanka
By Dimithri Wijesinghe and Chenelle Fernando
The Centre for Urban Water Sri Lanka of the Metro Colombo Urban Development Project (MCUDP) has a system underway to monitor floods in real time.
According to engineer and Project Director Thushari Andra Hannadige, the real-time warning system has already been implemented through a pilot project. She said: “The project will reach full completion by June, 2020, with the completion of other factorial interventions.” These, according her, include the construction of pumping stations, tunnels, and floodgates.
We spoke to the Team Leader of the MCUDP Prof. Sri Kantha Herath about the real-time monitoring system for floods and other projects underway in order to make Colombo a sustainable city, resistant to flooding.
According to Herath, Colombo city often falls victim to urban flooding caused by excessive rains, resulting in the available drainage systems being insufficient.
“Currently, the system includes four drainage ways, three into the sea, and one to the river (Kelani River). However, in the past 30 years, we’ve had eight major floods and that’s been due to the Kelani River overflowing, thereby being unable to contain the excess being drained from the city.”
Urban flooding is often caused due to a lack of drainage in an urban area, and as there is little open soil that can be used for water storage, nearly all the precipitation needs to be transported to surface water or the sewage system.
High intensity rainfall can cause flooding when the city sewage system and draining canals do not have the necessary capacity to drain away the amounts of rain that are falling. Water may even enter the sewage system in one place and then get deposited somewhere else in the city.
Herath discussed other cities which have undergone severe urban flooding disasters, such as Beijing in China, which is a city that has a high land value and therefore, construction of drainage is near impossible and so the city finds it extremely difficult to drain water.
There’s also Tokyo, which has an underground river; the same has been adopted by Bangkok, Malaysia, and Singapore by building underground tunnels. However, these are very expensive alternatives – expenses that are overwhelming for a country like ours, and we are, thankfully, not at a level where we require such extreme measures; that is if we utilise our available resources.
For this issue, there have been various steps undertaken under the purview of the Ministry of Megapolis and Western Development. One such solution includes the implementation of two strategic micro tunnels, one of which is situated in Torrington and was very recently executed.
The Irrigation department too has a World Bank project in place, looking into alternative options to contain water in the Kelani River to prevent it from overflowing.
There are further steps taken and implemented by the Colombo municipality with regard to building and planning, which requires all establishments coming up to satisfy a certain requirement of water retention. Then, there is the utilising of Colombo’s wetlands, which are a natural resource – an ideal solution to urban flooding; there is a system underway to optimise the utilising of wetlands.
As for the monitoring system, its main job remains to forecast rain level in the city in order to estimate the best operational system. Referring to such a system for the purpose of creating such a database, which is able to forecast accurately, Herath said: “We need a dense network of monitoring systems, and we should be able to couple them with the rain level and other information. We need to read this data quickly, and so we do it in real time via an internet of pings; it is also very cost effective.”
Herath added that currently, additional rain gauges (30 currently) are being installed as a final measure, including other gauges to measure humidity. The data acquired will be transmitted to their computer model which is not inclusive of a human interface and the data collected is an open source and will be available to everyone. He said: “The system is largely done now, and with the installation of output measures, we can calibrate.”