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Being more spongey 

Dr Louise Walker, Senior Research Manager at CIRIA considers the implications of the recently published National Infrastructure Commission report Reducing the risk of surface water flooding.

I live in Ribchester, a small village in Lancashire, at one time an important hub for Roman soldiers. Within the Roman remains, carefully constructed drainage channels still exist. Built in about 100AD the Romans knew how to quickly drain away excess water to the nearby river.

As our settlements have grown we have got used to installing drainage to take surface water away as quickly as possible. This worked well for small settlements and was successfully adapted, mostly within systems of buried pipes, for large cities as they grew. 

Times have changed though, and we need to adapt again. Heavy, unpredictable rainstorms cause localised flooding, particularly in built up areas. Drainage systems can reach capacity and be overwhelmed. Paradoxically we can suffer from the effects of drought and flood simultaneously. 

The water cycle is one of the first natural systems we learn about in school. Thinking about this big picture, it makes sense to follow it - to capture the rainfall close to where it falls, to let it sink into the ground, to replenish our stocks and irrigate plant life, creating habitats for our rapidly decreasing biodiversity.

There are many pressures on society and perhaps drainage doesn’t seem so important, but water is. As much needed new housing continues to be constructed, more hard surfaces appear and more surface water is drained away. 

The concept of ‘sponge cities’, originating in China, has been around for a while now, and is an evocative way to describe what CIRIA has been promoting for many years: slowing the flow of surface water by increasing blue and green space. Thinking about surface water as a resource, making space to capture and filter it, and encouraging the use of green space wherever possible in new developments - and within existing settlements, makes them nicer places to be.

Rethinking the management of surface water presents opportunities to reduce pollution, reduce flooding, increase biodiversity and provide beautiful green spaces. The NIC report includes some stark figures on the number of homes at risk of surface water flooding and the likely increase in this figure if these opportunities are not taken, and it outlines practical, joined-up ways to do this. 

Flooding isn’t always about damage to property; nuisance flooding can be inconvenient, blocking roads, walking and cycling routes. We can’t prevent all flooding but we can be more prepared for changing weather patterns.

The Romans might have been surprised at the quantity of rainfall in Lancashire (I know I am sometimes), they had to adapt to new conditions. 1,922 years later, it’s time for us to take all the opportunities we can, to adapt and to be more spongey.

CIRIA welcomes the publication of the National Infrastructure Commission’s assessment of how responsible bodies in England can better manage and mitigate surface water flooding. We were most grateful to have been able to input to the work in preparation of the report ‘Reducing the risk of surface water flooding’ published on 29th November.