Category: United Kingdom

Letting rivers run wild could reduce UK flooding – new research

Letting rivers run wild could reduce UK flooding – new research

By Neil Entwistle and George Heritage

The UK government currently spends £2.6 billion on flood defences in England, and that amount is set to double by 2026. Flooding in February 2020 showed how that’s likely to be a good investment, as climate change drives warmer and wetter weather each winter. But when it comes to managing rivers to prevent flooding in towns and cities downstream, we’re often our own worst enemy.

After the second world war, Britain embarked on a mission to reconstruct its rivers. Workers cut ditches to drain moorland, making it suitable for livestock farming. Looping rivers which once wound lazily through floodplains – flooding these areas once every two years or so – were straightened into rigid channels. River beds were dredged to deepen them and banks excavated to make them steeper, an unnatural situation that takes routine management to maintain.

The idea behind all of this was to reduce flooding by increasing the speed at which water moves downstream. But this also increased the power of rivers to move sediment. Gravels and cobbles dash along these modified and heavily managed rivers, accumulating where the water slows down, as it moves through towns and cities. Here, the river bed swells as sediment piles up, increasing local flood risk.

Flooding in Carlisle, December 2015. Environment Agency geomatics group, Author provided

Over 60% of the UK’s watercourses have been transformed in this way, changing the fundamental character of many British rivers – and the natural processes that would usually govern them – over just a few generations. In a new study, we found that doing nothing is often a better course of action for reducing flooding than these heavy handed attempts to mechanically alter rivers.

Going with the flow

We studied the River Caldew in Cumbria, which has caused three major floods in nearby Carlisle since 2010. Satellite data showed that straightening, deepening and embanking was common along the river between 2005 and 2016. Very little sediment was spotted in the river and across the floodplain, suggesting that almost all of it was being funnelled downstream towards Carlisle.

During this time, the channel through the city was widened in the hope that this would cause flood water to spread out and lose energy. But this only increased the problem of sediment building up within the river, creating a shallower channel through Carlisle that’s prone to overflowing.

A stretch of the Caldew near Mosedale in 2003. The channel is fairly rigid and surrounded by managed grassland. Google Earth, Author provided

Outside of the city, in parts where maintenance has been relaxed, the river has begun to return to a more natural state. Multiple “wandering” channels can now be seen alongside wide areas of deposited gravel. This is encouraging, as it suggests that the main river and its floodplain are reconnecting, allowing the sediment it transports to fall out of the channel and collect upstream.

We found that rivers which are allowed to behave more naturally are better at locking up sediment upstream, rather than letting it accumulate in unnaturally high quantities in flood-prone towns and cities. If more rivers are allowed to behave naturally and develop this way, it could help reduce future flooding.

The Caldew at Cummersdale in 2018. Note the variety of vegetation and increased gravel. Google Earth, Author provided

This hands-off approach to managing rivers is also much cheaper than hard engineering and brings a wealth of environmental benefits with it. The wandering channel system that’s evolving on the River Caldew has the greatest variety of features and habitats across the entire watercourse.

There are gravel bars, deep pools, floodplain wetlands, ponds and river cliffs. This diversity provides greater spawning habitat for fish, and cooler refuges for their fry. The open water habitats benefit amphibians, the trees and shrubs help kingfisher hunt and sand martins can nest in the river cliffs. Beetles and spiders scurry in the shingle, earning this wilder stretch of the Caldew a designation as a site of special scientific interest.

The last 75 years have seen many UK rivers change beyond recognition. The way we manage them in future must look very different. Relaxing our iron grip and allowing natural processes to flourish on rivers once more could be our best hope for reducing flooding, while reviving lost ecosystems rich in native wildlife.


This article was originally posted on The Conversation.

Cover photo from Wikimedia Commons.

Flash flooding is a serious threat in the UK – here’s how scientists are tackling its prediction

Flash flooding is a serious threat in the UK – here’s how scientists are tackling its prediction

By Christopher J White, Laura Kelly, and Linda Speight

It’s becoming a familiar scene on the news: sodden British people wading through streets up to their knees in flood water. From Stirling to Sheffield, many parts of the UK in 2019 felt the impact of severe surface water flooding – often referred to as flash flooding – that followed torrential rain. As the climate changes and the UK experiences more intense summer storms, this is becoming an increasingly important issue.

Surface water flooding is what happens in built-up areas when heavy rainfall has nowhere to go. Unable to enter a watercourse or drainage system, the water instead flows over the ground causing flash flooding. Increased development means more areas are paved over, leaving fewer places for rainfall to drain away. And more frequent heavy rains overload the sewer and drainage network, which makes flash flooding more likely.

James Bevan, chief executive of the England and Wales Environment Agencysaid this kind of flooding “threatens more people and properties than any other form of flood risk”. In 2016, the UK government included surface water flooding on the national risk register.

Unlike river and coastal flooding, which can be widespread (as was seen in November 2019 across parts of northern England), surface water flooding presents unique challenges because it’s difficult to predict the location, timing and impact of what are typically localised events.

As the climate changes and urban populations grow, the number of people at risk of surface water flooding increases. This risk is particularly high in Scotland with over 100,000 properties identified at risk from flash floods. And for many people, even if their home or business is not at risk, there’s a good chance the roads or railway lines they use are.

Flash flood forecasting in Scotland

Although Scotland’s river and coastal flooding warning systems are well established, surface water alerting is still in its infancy. To address this gap, the Scottish Environment Protection Agency (SEPA) is continually developing its flood forecasting service with the Flood Warning Development Framework for 2017-21, which aims to explore and test innovative ways to warn people about flash floods.

Developing an effective forecasting system requires hydrological models that represent surface run-off, inundation and water movement, showing how water travels via surface and urban sewerage and drainage networks. Prediction models are also needed to quantify uncertainty in forecasting the rainfall that causes surface water flooding.

The uncertain nature of intense storms means that heavy rainfall can happen without much warning. This coupled with the pressure that excess natural run-off puts on man-made drainage networks when there are fewer places for water to go, makes surface water flooding forecasting a real challenge.

It’s a particularly acute problem in Scotland where the climate and geography contribute to the high uncertainties around predicting the location and timing of flooding. A 2016 study found the most dangerous flash floods in the UK include those that resulted from rapidly developing thunderstorm systems. Such storms can result in sudden and dangerous flooding in urban areas – yet these are the most challenging weather systems for flood forecasters to predict.

In the past five years, there has been a rapid development of thunderstorm numerical weather prediction computer models and advances in what is called probabilistic ensemble forecasting. This means instead of making a single forecast of the most likely weather, a set (or ensemble) of forecasts is produced, giving an indication of the range of possible weather ahead. Combined with an increase in computing power and skill, it is now becoming feasible to develop flash flood forecasting systems for urban areas.

Innovative solutions

Earlier this year, we were commissioned by SEPA to review the state of the science behind surface water flood forecasting in Scotland. Based on an extensive review of published research and reports, coupled with discussions with industry experts, we show that recent advances in computing, thunderstorm models, ensemble forecasting and surface water modelling mean that it is possible for SEPA to explore and build on the accumulated global knowledge about flash flood forecasting.

The risk of surface water flooding in Scotland is communicated through SEPA’s Flood Guidance Statement and Flood Alerts, where assessment is based on predetermined rainfall amount and duration thresholds and local expert knowledge. This helped to provide the UK’s first surface water flood risk forecasts for each of the big sporting events at the 2014 Commonwealth Games in Glasgow.

This information is useful to emergency services and the public, but the ability to provide detailed information on the location and timing of flash flooding remains limited. SEPA’s review highlights the growing need to provide more focused forecasts to help those concerned make the right decisions. It also identifies opportunities to learn how other countries respond to similar flooding that could be applied to Scotland.

The review provides several examples of initiatives that could improve the monitoring of flash flood impacts, including better use of crowdsourced data, as happens in the Netherlands, and better weather forecast visualisation tools (such as 3-D interactive displays and animations) as demonstrated in Spain.

The future

It may never be possible to prevent flash flooding, but reliable and early forecasting can help improve the capacity to prepare, respond and recover. The recent introduction of thunderstorm models and ensemble forecasting has resulted in significant advances in forecasting rainfall. This means it may now be possible to forecast flash flooding in urban areas, as well as make forecasts and warnings more focused and easier to understand, which in turn will help people make better, more informed decisions.

Producing flood forecasts for any particular location is likely to remain challenging beyond a few hours in advance – there will always be limits to the predictability of extreme rainfall. But our capacity to predict extreme weather is constantly improving, which SEPA may be able to apply to surface water flood forecasting.

Solutions for communicating uncertainty of heavy rainfall forecasts continue to develop. Our work means that a step-change in flash flood forecasting that builds on the experience of SEPA, the rest of the UK and other countries, is now possible. Making the best use of all available data – including social media and crowdsourced data – will increase awareness of flash flooding and help communities prepare and respond more effectively.


This article was originally published on the Conversation.
Cover photo by Rainbow International on Flickr.
Technologies to manage climate change already exist – but UK needs to scale up efforts urgently

Technologies to manage climate change already exist – but UK needs to scale up efforts urgently

By Andreas Busch

When it comes to tackling climate change the UK is still taking baby steps. A lot more needs to be done – and fast – to hit the 2050 net zero carbon emission targets, which involves offsetting any emissions by absorbing an equivalent amount from the atmosphere.

While this process can build on future innovations, the technologies are actually already in place to make a real difference – technologies that, of all things, are based on the skills of the oil and gas industry.

The world is currently approaching an average global temperature increase of 1ºC compared to pre-industrial times, largely attributed to increasing atmospheric levels of carbon dioxide (CO2). Meanwhile, the BP Energy Outlook predicts a future increase in the use of fossil fuels.

The world population is growing and more people will be moving from low incomes to higher ones, resulting in a higher energy demand towards the end of the century. So achieving net zero carbon emissions by 2050 will be a tremendous challenge, requiring engineering solutions at mega-scale.

Effective solutions

The world already has effective engineering solutions to manage climate change and to limit global temperatures from rising above 1.5°C – a target set by the Intergovernmental Panel on Climate Change (IPCC). But there is a desperate lack of conviction from politicians and society to address the climate emergency.

Morgan Stanley estimated that meeting the 2050 targets requires an investment of US$50 trillion. Put into perspective, that’s about 50 times the company value of Apple.

The report states that investments need to be in electric cars, renewableshydrogencarbon capture and storage (CCS) and biofuels. Many of these technologies rely on the need to use the geological subsurface for producing heat in the form of geothermal energy, permanently storing carbon dioxide or for temporarily storing hydrogen. For CCS, CO2 is pumped into porous underground formations (such as water-bearing saline formations or depleted oil and gas reservoirs) at a depth of 1km or more, where a tight sealing layer prevents these fluids from leaking towards the surface.

In Australia, for example, oil and gas giant Chevron has started a large-scale CCS project where 3.4-4 million tons of CO2 will be stored beneath the seafloor annually, but this initiative is by no means unique. There are currently around 18 international CCS projects that are removing between 30 and 40 million tons of CO2 each year. While these figures may sound impressive, they only represent about 10% of emissions produced by the UK alone each year.

CCS is a technology that can be linked to large-scale fossil fuel combustion for decarbonising the energy sector. It can also be linked to direct CO2 capture from the air or CO2 produced from using biofuels, both having the potential to achieve net negative CO2 emissions.

According to the recent IPCC special report, CCS, when deployed globally, could amount to a reduction of hundreds of billions of tons of CO2 emissions by 2050. The scale of the problem is vast and existing global projects need to be scaled-up between 100 and 1,000 times their current size to be truly effective.

What lies beneath

Another energy solution – where size is not an issue – is harnessing the tremendous heat that lies beneath the Earth’s surface to generate electricity and heat. Investment in these geothermal energy projects is increasing, but not at the pace required.

Geothermal energy can provide decentralised, affordable and continuous energy to heat homes or produce electricity. While this energy is right beneath our feet, progress on adopting it is slow due to a lack of investment and political support compared to other renewable energies such as wind and solar.

While the operational cost of geothermal energy production is competitive with other renewable energies, the downside is that investment costs are high, especially when producing from a greater depth. As a consequence, installed capacity is less than 1% of the global electricity consumption.

The same is true of progressing towards a hydrogen economy. Hydrogen can be produced in many ways and used to heat homes, fuel cars or produce electricity. Hydrogen reacts with oxygen to form pure water. It can be produced from renewable energies or from natural gas in a refining process.

The drawback of a hydrogen economy is that it produces CO2 as a by-product, which must ultimately be integrated into the CCS chain. Hydrogen consumption is demand-driven while renewable energies produce energy independent of demand. Overproduction can temporarily be stored in geological formations, and back produced when demand is increasing.

Climate change campaigner Greta Thunberg. Shutterstock

All these technologies depend on using the subsurface either as a temporary or permanent solution. It requires the expertise of geoscientists and petroleum engineers – highly skilled specialists who have delivered a fossil fuel-based economy in the past, and who will contribute to providing energy in the future. But more than that, it calls for visionary political ideas and legislation. For many people it is a crucial issue in the December general election.

But given what is required, society has still not yet fully recognised the urgency required to combat climate change. An energy transition at this scale will change the way people live and work, but it will also require people to properly grasp the scale of the problem. Student activist group Fridays for Future and groundbreaking young campaigners like Greta Thunberg pave the way. But only political leadership, policies and funding can make it happen.


This article was originally published on The Conversation.
Cover photo by David Dibert on Unsplash