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Written by Hamish Hall

So far the start of this year has seen nearly the entire country spared from the disastrous scenes of last year's flooding crisis. There have been pockets of small incidents, but rolling coverage of people travelling in dinghys from their newly moated houses have thankfully not been filling our newsfeeds.

However, floods on the scale we saw last year could potentially happen again. This isn't scaremongering; floods are the most common and widespread natural disaster in the UK, which is the seventh most economically exposed country to flooding in the world. Climate change is happening: Increasing temperatures and sea levels combined with changing rainfall patterns mean that we need to increase our understanding of our exposure to flooding and also develop successful strategies to live with and adapt to a heightened risk of flooding.

As with many problems of this nature there is unfortunately no technical silver bullet to preventing floods, but there are a variety of ways to appropriately cope with floods. Each flood is different - last year different solutions were required for three of the worst hit areas, Cornwall's coast, the Somerset Levels, and the Thames.

Recently I have been working with communities in tropical Africa's west coast. In one new community in particular there is an area that is subject to regular and severe flooding and so needs to be planned with that in mind.

What was immediately apparent was that using modern "western" techniques such as piped systems just weren't suitable, not least because of a lack of local expertise to properly install and maintain it. Instead we implemented a plan that maximised the existing assets such as flood plains and water channels, but also used the roads systems for conveyance so that in times of severe flood the roads can literally become rivers, guiding excess water directly to the sea. Using roads over pipes provided infrastructure that was cheaper to build and maintain whilst creating a better ecology for the region.

The trick is therefore not to follow a formulaic response. If there should be one consistency it is collaboration, which is perhaps an overused term, but from my experience the most successful projects are those where the authorities, communities and industry work together.

For example, on one project to protect a section of a rail line on the south coast of England WSP is working with charities, NGOs, government departments, contractors, rail firms, marinas and the local population. This is the singular most important factor in ensuring the right solution is found.

In the tight-budget, urbanising times that we operate in it is also important to understand how even small changes can make a big impact. A classic example is lining streets with trees, which help drain rain water and slow its flow.

On houses we can create larger eaves (the part of the roof that overhangs the building) that still allow for sunlight whilst slowing the flow of water and easing run off. This also means there is no need for clogged up gutters.

A further positive knock-on effect for communities with larger eaves and more trees would be an increase in bird wildlife habitation as there will be more nesting opportunities, increasing an area's biodiversity and liveability.

It is also, of course, more cost effective to prepare for flooding now then having to deal with it after the event. There are schemes that could be implemented in England such as lazy rivers, which hold back water in upper catchments first, throttling flow and controlling it in times of high flow. Although not usually called reservoirs, that is what they are functioning as.

Dredging, a highly debated topic in last year's media, is also worth revisiting. Dredging does increase conveyance in the river, meaning that waters will travel downstream faster towards the sea/ocean however, this can lead to "passing the buck" from one community to the next downstream, affecting established ecologies and putting pressure on ageing assets.

In some places such as Somerset we may need to look at using fields that do not currently suffer from flooding to act as flood storage areas for the benefit of the wider community. A recent National Trust experiment near Minehead has involved farmers allowing their land to be flooded once river levels rise to reduce the amount of water passing downstream. This would be controversial without government subsidy to farmers, but is a debate worth having.

Advances in technology are also beginning to positively impact how we manage water levels across catchment levels.

A new 'smart' system developed by PyTerra with WSP and Imperial College London can automatically catch, store and release rainwater throughout the year using a computerised network of water control devices which respond to weather forecasts. A series of underground pipes would connect the various ponds, streams and wetlands in a catchment or sub-catchment and hydraulic devices, such as a valve, would control the flow.

Small transmitters in the field would receive signals sent from the central system, and open or close the valves as needed. Such systems use weather forecast data as well as real-time 'big data' from hi-tech water sensors and satellites to work out where and when capacity is needed.

Whatever the strategy implemented, the best outcomes are achieved when tangible benefits can be demonstrated and therefore become the end goal. In all instances not suffering from flooding is outcome number one. After that resilience can be rewarded in many ways.

For example, a seaside town that properly protects itself can benefit from increased tourism, which means investment, economic stability and improved prospects for the town. This in turn can lead to an increase in house prices, employment and ultimately make the town a better place to live. The next problem will be to then maintain good practice as our population continues to grow.

Returning to the start, we have not suffered last year's fate yet. But there is plenty to be done now to create better, safer and more sustainable and resilient communities. There is no time to be complacent.

Hamish Hall is senior technical director at WSP

 

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