Planting to Prevent Flooding

At the time of writing this, there are currently 40 Flood warnings in affect across the UK, "Flooding is expected - immediate action required". And if that wasn't enough, the 95 Flood Alerts, "Flooding possible - be prepared." Has it always been this bad? I don't remember it flooding this much whan I was younger so what's changed?...

Well it isn’t just one thing, unfortunately, and there isn’t really one neat answer that will solve everything. Here are some of the main causes:

• Poor maintenance of sewers, drainage networks and inadequate maintenance of watercourse.

• The removal of peat, heather moorland and deciduous woodland, combined with the addition of improved drainage on farmland, means that instead of the water being held in the uplands, it shoots downhill and in to the river.

• Straightening of rivers and draining of traditional flood land gives the water a clear path to rush down, find the weakest point and flood!

• Inappropriate development in flood plains… Pretty obvious what’s going to happen when you build houses on a flood plain, but developers don’t seem to care.

• Building roads and car parks in such a way that it is impermeable to water. The water has nowhere to go so it ends up in the drainage system and then the rivers.

• Flood defences either don’t work or are badly managed.

• All these factors combined with an increase in rainfall has led to the flooding we are seeing today.

According to the UK Met Office, February 2020 has been the 5th wettest month in series, since records begun in 1862, beaten by October 1903, December 2015, November 2009 and December 1929. There is huge scientific debate about the effect of environmental climate change on the amount of rainfall we are seeing in the UK. In March 2020 and we’ve already seen the devastating effects of flooding following Storm Ciara, Storm Dennis and Storm Jorge.

Unfortunately, putting in flood defences doesn’t always solve the problem. Often the problem is just moved downstream to cause flooding elsewhere. The story of devastation in the village of Fishlake, Doncaster, in 2019 highlights just such a problem. Severe flooding in Sheffield, 2007 forced hundreds of people to be evacuated. Afterwards they spent £83m on 60 flood prevention measures along a 5 mile stretch of the river Don, running through Sheffield. And it worked! The flood risk in Sheffield has decreased dramatically.

However, 12 years later, this poorly planned flood defence pushed the problem downstream to Doncaster. In November 2019, despite only having flooded once before, the small town of Fishlake practically got swept away. Local residents blame local authority flood defence and poor flood management. Under these circumstances it seem madness to continue to build on flood plains. An estimated 4.6 millions homes will be on floodplain by 2070. The pressure for an effective solution for flood defence has never been more important.

Hope for the future of flood prevention

In 2016, while the rest of the north of England was being partially submerged, Pickering stood out with its head above the water. This was strange at the time because Pickering has a reputation for being hit hard by flooding.

So why didn’t Pickering flood when everywhere else did?

A group of academics from Oxford, Newcastle and Durham Universities have come up with a very innovative and sustainable system for dealing with flooding. And it works. By looking closely at the real causes of flooding and consequently using natural flood defences, they have managed to reduce the flood risk in Pickering dramatically.

Here’s what they came up with:

They created 19 ha of riparian (banks of the river) and floodplain woodland.

This woodland is designed to slow the movement of river water when flooding is at its peak and to “potentially increase upstream flood storage.” In other words, the trees suck up the water. A healthy, 100ft tree can drink 11000 gallons of water from the soil every growing season. That’s a lot of water! Imagine what 19 ha of woodland can do?!

They restored large woody debris (LWD) dams.

These dams are common place along woodland streams. It’s where debris, like branches or fallen trees, get stuck during their trip down stream and form a natural dam. Previously woodland debris was being removed by forest management companies, due to fears that it would become dislodged, wash down stream and end up blocking bridges. These dams aren’t water tight by any means but they slow down the progression of water towards the river, and in doing so reduce the amount of water that in the river. 129 LWD dams were installed around Pickering.

Planting trees in targeted areas on farmland around Pickering.

Deforestation and overgrazing of the grassland around Pickering has caused large amounts of rain run-off. This is a big problem in the UK and is a big contributor to flooding every year. Strategic tree planting stopped the water in its tracks.

They targeted moorland drainage streams.

By putting bales of heather into moorland streams they slowed the progression of water to hold it in upland areas. This works in a similar way to the LWD dams. By slowing the water flow, the amount of water reaching the river in one go is reduced.

All in all, they planted 40,000 trees, 129 LWD dams and have reduced the amount of water hitting the river during floods by up 20%. The Environment Agency have said that these measures have not only slowed the progression of water during flooding, but also improved water quality. All that for only £500,000… Which might seem a lot, but in comparison to the £20 million concrete block, they were going to drop into the middle of Pickering, it’s amazing!!!

For more information on this and other project see forestresearch.gov.

For all the information about flooding in the UK visit the goverment flood warnings website

If your garden is water logged or has poor drainage you might be interest in our Bog Plants Blog! Our top suggestion for plants that love getting their feet wet!

Flood defences for your home

SHOP HERE

If you’ve liked this and you want to learn more then you might like to check out some of our other blogs and please share this one!