The Environment Agency supervises and works with other organisations to manage the risk of flooding and coastal erosion in England. It also directly manages flood risk from main rivers, the sea and reservoirs. Much of the information below has been collected from Environment Agency resources:
Why is the coast changing?
Coastal change is a natural, ongoing process; shorelines constantly change due to waves and tides. The amount of physical change depends on many things, and happens over timescales from seconds to centuries.
As sea water meets cliffs and shores, it causes sediment or rocks to be broken down and washed out to sea. In some instances, this material may be moved to a different part of the coast and deposited in large quantities, causing ‘accretion’ – the opposite of erosion, where shorelines may advance or build up with sediment over time. In fact, the sand and shingle that makes our beaches is a product of erosion, and to remain in place they need a continual supply of material.
Erosion can happen under any conditions, but its rate tends to increase when waves are powerful and water levels are high – for instance during storms or in high winds.
The changing coastline has also been influenced by people’s actions throughout the years, particularly in attempts to stop the effect of erosion or flooding. In some cases, this has taken place without an appreciation of the effect these actions could have on other places up and down the coast.
How does erosion affect our coast?
The way erosion changes different parts of our coast depends largely on the type of rock – in other words, its geology.
Erosion of coasts with hard rocks tends to be slower, and can form dramatic rock formations over time, including tunnels, bridges, columns or pillars such as at Lulworth Cove in Dorset.
Where coastal geology is formed out of sedimentary deposits, such as on the soft cliffs around parts of the east coast, erosion can pose more of a risk for human settlements. Sedimentary rocks, such as sandstone and chalk, naturally erode more easily than hard rocks, so the coast recedes at a faster rate.
Coastal erosion and coastal flooding are often linked. One may lead to another, especially where an eroding shoreline separates the sea from flat, low-lying land.
How fast is the coast changing?
The tremendous diversity of our coast means that erosion rates vary significantly from area to area. Some parts of the coast are eroding faster than others.
To put things into context, across England and Wales, about 28 per cent of our coastline is subject to erosion of more than 10 centimetres per year, but rates vary according to location, sometimes reaching an average of as much as 1.8 metres per year.
In reality, coastal erosion is not always gradual, and can occur through events such as landslips where many metres of land may be lost once every five or ten years. Rates of erosion are expected to increase by the end of this century because of increasing storms and rising sea levels, brought about by climate change.
Predicting these rates as accurately as possible is extremely important – not only for the people living in coastal communities, but also for the Environment Agency’s management of the coast.
How is coastal erosion predicted?
It’s crucial that we understand and can predict large-scale, longer-term coastal changes, so that we can manage the risk to coastal settlements and the natural environment more effectively.
A range of advanced monitoring techniques are used to predict erosion, to assess its causes and ongoing impact. This includes aerial photographs, maps and surveys of coastal processes, which can then be analysed by teams of scientists. Records of historical rates of erosion on the coast also inform predictions of how the coast might evolve in the future.
This detailed information can then be used to:
- make predictions about the rate and impact of erosion;
- assess existing coastal management methods and how cost-effective they will remain over time;
- make informed decisions about future management, to ensure we tackle coastal erosion issues where the risk is greatest.
The Environment Agency uses the most up-to-date data on climate change, advanced modelling techniques and the best local survey information available to map coastal erosion predictions across England. These maps will be easily accessible to everyone from the Environment Agency’s website, so that all who live at, work on and manage the coast are better able to decide how to approach coastal change in their local area.
What is dredging and what effect does it have on erosion?
Dredging is the removal of sand and gravel from the coastline or seabed:
- to keep waterways navigable
- to produce material for construction projects
- to replace the materials lost from beaches as a result of erosion
It is sometimes claimed that dredging causes coastal erosion, or makes it worse, as it has in the past.
Various studies have been carried out to assess whether dredging makes surrounding areas more prone to erosion or not. Results, such as those from the Southern North Sea Sediment Transport Study, show that because dredging is now strictly controlled and carefully managed in UK waters, it no longer has an impact on coastal erosion.
A licence is required for dredging. Thorough assessments are carried out to ensure dredging will not have a negative impact on the coastline or the marine environment before a licence is granted.
Marine dredging licences are administered by the Marine Management Organisation.
What can be done to reduce the risk of coastal erosion?
There are many measures we can take to defend our coastline against erosion. This is often a combination of various defence structures and natural features. These measures can reduce the effects of coastal erosion upon communities and the natural environment.
Coastal management methods fall into two main categories:
- Hard engineering – man-made barriers such as sea walls and groynes, which reduced the impact of waves on the coast
- Soft engineering – techniques such as beach replenishment and saltmarsh creation which use natural materials, features and processes to absorb wave impact.
Many successful coastal management methods combine hard and soft techniques. In each case the effects upon coastal processes and the natural environment are fully explored before management decisions are made.
Where / what is chosen to be defended, and why?
The Environment Agency uses public money as effectively as possibly to reduce the risk to coastal communities, their property, infrastructure and the natural environment. Decisions on where to defend are based on risk assessment using a transparent, auditable and understandable process.
Factors we consider include:
- Number of households at risk.
- Number of deprived households at risk.
- Impact of our actions on agricultural land and the farming community.
- Impact of our actions on the environment and wildlife.
- Whether erosion affects local community infrastructure and transport.
- Cost of building and maintenance.
There are four possible outcomes:
- Hold the existing defence line – maintain existing coastal defence.
- Advance the existing defence line – new defences on seaward side.
- Managed re-alignment – shoreline adjusts position in a controlled way.
- No active intervention – no investment in coastal defence.
Coastal defences often protect against both coastal flooding and erosion. Inland flooding is also affected by how we manage coastal defences. Funding for coastal and flood defence is therefore linked. In each case, a set of agreed indicators called ‘outcome measures’ are employed to measure how effectively economic, social and environmental needs are met.
How is flood and coastal risk management funded?
Defra has overall national responsibility for policy on flood and coastal erosion risk management in England. The department provides funding for flood risk management through grants to the Environment Agency, local authorities and internal drainage boards.
In 2017/18, the Environment Agency spent a total of £856 million managing flood and coastal erosion risk across the UK, compared to £542 million* 10 years before (2007/08). The current five-year investment programme (2015-2021) budget runs at £2.6 billion.
Despite this large commitment, the scale of coastal erosion means the Environment Agency must prioritise projects to ensure the best possible results. Realistically, it is not possible to justify defending all locations to the same standard or in some cases at all.
* this figure doesn’t include the effects of inflation. In ‘real terms’ (at 2018 prices) the £542 million spent in 2007/08 equates to about £653 million.