The Coastal Climate Change Challenge

It’s a mouthful isn’t it? But the impact of climate change on our coasts is one of the biggest challenges that we face today. It’s not surprising that so many people want to live by the coast, but it is here that the impact of climate change may be felt most strongly and we need to think carefully about how we are going to adapt to it.

I’m Mike Williams and I’m part of the Environment Agency’s team leading on the PACCo project. I am delighted to have been asked, together with our French partner lead Régis Leymarie, to write one of the first blogs to launch this exciting initiative. Just getting to this point has required a huge amount of work by many people, but now we are at the point of starting work on the ground and it’s really exciting. In the next few pages I hope to explain why.

I have been working on habitat restoration for the Environment Agency for over twenty years now and have delivered a number of relatively small scale projects across Devon – on the Exe, Clyst, Avon, Axe and Torridge. At the same time, I’ve been part of a wider, national network working on similar projects and have had the opportunity to visit some of the large scale sites that have delivered so much elsewhere – Alkborough on the Humber, Porlock and Steart in Somerset, Medmerry in Sussex and Wallasea in Essex – and learnt a lot from them and the people involved. It always felt that we could play our part in Devon when we found the right site.

About ten years ago I was asked to get involved in thinking about how the Otter Estuary could be managed in a more sustainable way in the face of a rapidly changing climate. It was a site that I had known for a long time and always thought had a lot of potential that was not being fully realised. Ten years ago a general recognition of the need to adapt to climate change, particularly sea level rise, was just emerging. The Environment Agency has been close to the forefront of this thinking, acknowledging that we must prioritise where and what we are able to defend – and that there are real benefits to adapting wisely.

Increasingly, the reality of climate change becomes clearer and more widely understood. Our forecasts of the impacts are constantly being reviewed and revised. Government policies are changing in an effort to slow the trend. The evidence is pretty compelling. We are already seeing the changes in weather patterns, and the distribution of habitats and species. Human activities are estimated to have caused approximately 1.0°C of global warming above pre-industrial levels, and is likely to reach 1.5°C between 2030 and 2052 if it continues to increase at the current rate. In the UK the sea level has risen 16 cm since 1900. This trend is set to continue with current forecasts for sea level rise of between 1.0m and 1.35m by 2115. At the same time we expect peak river flows to increase by up to 85%. These impacts will combine in our estuaries.

Our coastlines have evolved continuously over time. During the last ice age (about 18,000 years ago), sea levels were 127 metres lower than today. When the hunter-gatherers were mending their flint tools on the high ground overlooking the Otter estuary some 10,000 years ago, the mouth of the estuary was way out in what is now the English Channel. Even in the recent past, the coast continues to change, with cliffs eroding and sediments shifting from one place to another. The Otter estuary extended at least as far inland as Otterton and the shingle bar only grew in the mid-16th century to partially close what had previously been an estuary fully open to the sea. But it is the hand of man that has caused the greatest changes over the last thousand years or so; the rate of change has increased dramatically in the last 250 years.

Settlements and embankments have been built, wetlands drained and reclaimed for agriculture and infrastructure. Roads and railways, sewage treatment works and refuse tips, even houses and recreational facilities have been constructed in areas which were once subject to natural fluvial or tidal flooding. These actions have had, in many instances, benefits for society. But they have also had an environmental cost that has not been so immediately obvious. In the UK, for example, over 65% of seagrass/wetland habitat has been destroyed, with over 90% of formerly important inter-tidal species significantly reduced in number. Ongoing saltmarsh loss is estimated at 100ha/year in the UK. Around the world less than half of its original wetlands remain. These are facts. They are reflected in the Otter valley that we see today.

Although beautiful and much-loved by both those who live close by and those who visit from far and wide, the environment of the River Otter and its estuary – like many others in Devon – is far from natural. The same is true of our sister site – the Saâne Valley in Normandy; the list goes on and on. In the early 19th century in the Otter valley embankments were built to claim land for agriculture. About three-quarters of the original extent of the estuary, known as the Runnie and described by engineer James Green as “a piece of mudland”, was enclosed by the banks, turning natural intertidal habitats from mudflat and saltmarsh into land that could be used for agriculture.

Unfortunately, we don’t have records from that period, but we can safely assume that, in the absence of fertilisers and pesticides and with flows unaffected by abstraction, the river and estuary would have had healthy populations of invertebrates and fish and that the mudflats, illustrated on James Green’s drawings of 1809, would have been home to large numbers of wading birds and wildfowl. That drawing also shows the course of the main estuary channel as it meandered across the valley floor between the river cliffs. That channel was also straightened and placed into a new cut, disconnected from its floodplain and constrained by reinforcements. The old channel scars remain visible in the valley floor today.

These fundamental changes to the estuary were to enable a whole series of further modifications to the lower valley with the construction of a road and bridge over the river (c 1850), the railway (1897), an aqueduct (c 1920) a refuse tip (1928) and, of course, a cricket club (1930). In addition, the marshes were progressively drained, first with the excavation of the Trunk Drain and the creation of the outfall into the sea and later with a more sophisticated pump drainage scheme. Such changes were quite typical of how estuaries were managed for the short-term benefit of society without the recognition of the adverse impact or the difficulty of sustaining these changes in the longer term.

The impact of the changes soon became apparent. Just a few years after the original embankments were built, James Green was called back to build another bank (Big Bank), as the farmer at Pulhayes Farm found that his land was wetter than it had been. Over the years, there have been failures, repairs and additions. At one point Lord Rolle even said he “wished he’d never been bothered by the project”. The massive reduction in the volume of water entering and leaving the estuary on each tide meant that the estuary has accreted more quickly than it would have done naturally. The straightening of the river and disconnection from its floodplain means that flood flows can no longer pass downstream and instead must back up in the floodplain until the water overtops the banks and fills the marshes behind. Once there, where it floods the road and the cricket club, the water cannot drain effectively and prolonged deep flooding occurs. The outfall into the sea is frequently blocked by shingle and has to be constantly cleared and even then is often tide-locked.

Many of these effects are also found in the Saâne valley, where a road runs along the coast behind the beach and the river is constrained by embankments which have allowed development to take place in what should be natural floodplain. Here a campsite is the victim of flooding, instead of a cricket club.

The once-natural biodiversity of the Otter has also been reduced. The remnant estuary has no extensive mudflats as it once did. There is little lower saltmarsh and much of the intertidal habitat in the estuary is only inundated on the biggest tides. As for the freshwater marshes, it is the areas where scrapes have been created that hold the largest concentrations of birds. And the Budleigh Brook, once a fine trout stream, has declined in quality as a result of its extensive modification.

Although our coastlines and coastal communities have always been subject to change, our changing climate has accelerated both its speed and scale. Protecting homes and businesses within coastal communities will continue to play an important role in supporting society into the future. However, building and maintaining sea defences comes at significant long-term financial and environmental cost. Ultimately, for some locations, holding the line may not be a sustainable response.

An alternative approach is, rather than trying to fight change, to plan ahead and find sustainable ways to enable society and the coastline to adapt in the face of a rapidly changing climate. Such a response would mean allowing some coastal areas to realign through natural processes. This approach of accepting the realities of climate change and sea level rise, adapting to it early and working with nature rather than against it will likely provide a more affordable and sustainable management approach for some communities. It is also likely to help us protect those locations where it’s most important to do so.

This is the approach we are showcasing through the PACCo initiative. By delivering early adaptation at two real life example sites in Devon (Otter Valley) and Normandy (Saâne Valley) we want to show that it is possible for society to adapt successfully to climate change and deliver a range of benefits for people and the environment.

These valleys are just two examples of as many as 70 heavily modified estuaries in the area covered by the France Channel England programme. Over 200 sections of the English coast between the Wash and the Severn Estuary have managed realignment as the recommended option over the next 50 years. The PACCo project will create a model to help organisations and communities to find the best way of responding to the challenge of climate change and, where adaptation is considered the solution, provide guidance on how to enable it to happen with the support and endorsement of everyone involved.

The project team know that good communication is a vitally important part of what we are doing. I am passionate about the environment, the coast and estuaries, climate change and how we as humans affect those things. I am proud to be involved with this project together with our varied partners. Through what we achieve on the ground, our PACCo website, face-to-face discussions, the use of social media, the PACCo model and this blog we hope we can inspire others to accompany on us on our journey and perhaps begin theirs. Over the next couple of years please do look out for further postings where a range of different voices involved with the scheme will highlight aspects of climate change adaptation of significance. And, of course, please do visit our websites to find out what progress we have made.

Mike Williams