Flooding occurs often across T&T as a result of several factors such as inadequate drainage infrastructure.
Floods across towns, villages and the capital Port-of-Spain and its environs are also exacerbated by rising tides, which can be particularly severe in low-lying areas close to the seafront.
The flooding events frequent occurrence is associated with sediment and debris movement from unplanned development in upstream areas.
The severity of these floods is worsened by hillside development which reduces natural vegetated covers (trees, plants, grasses) and increases impermeable surfaces thus a rapid movement of stormwater runoff downstream. This has led to erosion and landslides in hilly areas and flood events.
According to Dr Kiran Tota-Maharaj, Head of Civil and Environmental Engineering, Centre for Water, Communities and Resilience (CWCR) University of the West of England, Bristol (UWE Bristol), a solution to T&T’s flooding events can include a “sponge city initiative” which aims to capture and utilise stormwater runoff and rainwater harvesting.
Speaking with Guardian Media on Friday Tota-Maharaj said, “The principles of a “sponge city” approach, as the name implies are that towns or cities can absorb excess water when it rains and releases this water during drier periods or droughts.
“Sponge cities are designed to absorb large quantities of water and disperse it back into the environment in a slow manner. Like sponges, they are made of porous surfaces and spaces capable of keeping water.
“Basically, a town or city becomes equipped with engineered or artificial infrastructure such as green roofs, green walls and permeable ground surfaces, designed to interact with existing hydrosystems (lakes, rivers, wetlands) and landforms.
“Replacing tarmac roads and concrete pavements with wetlands, green rooftops and rain gardens means stormwater is absorbed back into the land, making water work for the towns and cities instead of against it.”
He said in 2014, the Chinese Government launched the Sponge City Programme in order to mitigate the impacts of water scarcity and urban flooding.
Tota-Maharaj said 30 Chinese towns and cities were selected as pilot cities for the programme and to this date, 50 per cent of the cities still suffer from significant floods.
He said this was very similar to the Sustainable Drainage Systems (SuDS) approaches in Ireland and the UK as well as Water Sensitive Urban Design (WSUD) in New Zealand and Australia respectively. Tota-Maharaj said by 2020, the Chinese Government wants 20 per cent of the built area of each pilot district to have sponge city functions, meaning at least 70 per cent of stormwater runoff should be captured, reused, recycled or absorbed by the ground. He said by 2030, a huge 80 per cent of each city should meet this requirement from the Chinese long-term strategic plan.
Tota-Maharaj said for some of these Chinese towns and cities within the sponge city programme, pavements were lined with trees, gardens and public parks were full of plant beds.
He said the programme had been piloting an ecologically friendly alternative to traditional flood defences and drainage systems in the coastal cities which also faced long-term risks from rising sea levels.
Tota-Maharaj said rapid concrete development across China had often blocked the natural movement and flow of water with hard impervious surfaces; to reverse this, the sponge city concept focused on green infrastructure, such as wetland areas, rooftop plants and rain gardens.
He said across natural environments, most precipitation (rainfall) was received by natural hydrosystems (surface water such as rivers, lakes) and/or infiltrated the ground.
Tota-Maharaj said however, this was disrupted when there were large-scale concrete and asphalt roads and pavements.
He said this caused only about 20 to 30 per cent of the rainfall infiltrating into the ground and urban areas, breaking the natural water circulation causing waterlogging and surface water pollution.
Tota-Maharaj said nonetheless, a sponge city was more than just its infrastructure, it was a town or city that made urban flood risk management central to its urban planning policies and designs.
He said there must be planning and legal frameworks and tools in place to implement, maintain, and adapt the infrastructure systems to collect, store, and purify excess rainwater.
Tota-Maharaj said the first thing with the sponge city approach was to try and preserve or restore natural waterways because that was the natural way to reduce the flooding risk.
He said for far too long, humans had taken the land away from the water, now they needed to give this land back.
Tota-Maharaj said sponge city infrastructure was beneficial because it was about changing the living environment, helping with pollution and creating a better quality of life in these areas.
He said the initial driver for sponge cities in China was the extreme flooding of urban areas, but the change in mindset, that development should have a more holistic, sustainable approach, was an extra benefit that was evolving during this project.
Tota-Maharaj said some challenges included the construction cost of sponge cities which had been enormously expensive.
Tota-Maharaj said however, cities were eager to join the programme as the subsidy, especially at this time of economic slowdown.
He said quite like what happens with a smart city, opportunities for innovation will give place to economic development.
Tota-Maharaj said a “sponge city initiative” required a holistic and sustained effort including effective environmental governance.
He said challenges for implementing such a scheme for T&T included the lack of expertise of Local Government to effectively coordinate and integrate a complex array of activities as well as financial constraints currently facing the Government.
Thus far Minister of Works and Transport Rohan Sinanan hailed the large automatic pump which is installed at South Quay, Port-of-Spain, as a success in mitigating flooding.
Sinanan said he was now hoping this success can be shared with the rest of the country as the government is facilitating discussions to install similar special pumps elsewhere.