Recent incidents in Birmingham prove England must think differently about vulnerability to extreme rain as winter draws near.
The combination of extended dry spells, leading to drought conditions, followed by heavy downpours, is particularly problematic. As the ground hardens and soil loses moisture, the capacity for precipitation to be soaked up is reduced.
Cities and other built-up areas such as Birmingham — where flash flooding occurred over this year’s August Bank Holiday weekend — are highly susceptible to this phenomenon due to the ‘urban creep’, whereby brittle concrete and tarmac have taken over increasingly vast areas that were historically dominated by more porous natural landscapes.
According to ACO Water Management, local authorities and developers have a responsibility to prioritise rainfall interception when designing neighbourhoods and buildings, ensuring that the risk of flash flooding is cut through effective mitigation. The government should also bring Schedule 3 of the Flood & Water Management Act into law, which specifies sustainable drainage as a legal requirement of new developments.
Expanding pipework capacity should no longer be the go-to option, and instead solutions such as rain gardens, increasing the amount of permeable surfaces nearby, and attenuation systems capable of storing before slowly releasing water should be prioritised. The emphasis should be on stopping rainfall from accumulating long before it gets near to sewers, reducing pressure on the overall network. This approach can be applied to existing infrastructure, through retrofitting, too.
‘We keep trying to solve the urban flooding issue by upsizing pipes, but that is the most expensive and least effective solution,’ said Sam Hawkins, Head of Specification & Design at ACO Water Management. ‘The real answer revolves around using a range of hard and soft sustainable drainage systems (SuDS), such as rain gardens and attenuation systems, to reduce the volume of water that makes it to the sewer system. The challenge here is that SuDS uptake remains inconsistent.’
Image: Chris Gallagher / Unsplash
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