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We are holding back the flood

Written by Science

As storms Ciara & Dennis ripped apart the country and caused horrendous flooding, particularly in the North – the city of Carlisle stayed dry. That wasn’t left to chance.

Carlisle is just one of many cities which have been dealing with flooding for the last couple of decades. In January 2005, the city was underwater and later in December 2015, Storm Desmond led to a repeat. The Carlisle Flood Action Group believe that if it wasn’t for the flood protections put in place after these disasters, Ciara would’ve once again led to flooding.

The defences have been praised as the “best outside of London” and cost upwards of £25m and involves the raising of flood walls, land levels and increasing the speed of river flow.

Flood walls are large concrete barriers built to, literally, prevent the river from flowing above it. They’re ideal where space is scarce, such as when a river runs through an urban area. Often, cheaper temporary barriers made of metal or glass are used instead of concrete.

Natural methods of preventing flooding have also been used. These consist of methods such as diverting rivers in to large, open fields which are designed to flood – lowering the force of floodwater. In 2016, the government considered a plan to pay farmers to allow their fields to be flooded. Trees can also prevent flooding, as they reduce the amount of rainfall hitting the ground.

Built-up urban areas are particularly at risk of flooding, due to impermeable ground terrain leading to the drainage systems becoming overwhelmed. Replacing these impermeable surfaces (e.g. concrete) with permeable surfaces that allow water to seep through would increase the amount of water needed to overwhelm drainage systems.

One lady on BBC Question Time blamed the European Union for the flooding caused by Storm Ciara & Dennis, claiming that they “they stopped dredging all the rivers across the country”. Dredging is a particularly controversial method of preventing floods, as the impact it has isn’t fully known and it can be detrimental to habitats, as well as costly. It involves removing silt from the riverbed by vacuum pumps to allow for the river to hold more water. It’s worth noting that the dredging of rivers is the responsibility of the UK Environment Agency, not the European Union.

Last modified: 2nd March 2020

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