Changing the dynamic

02 October 2012

Iris Möller, Deputy Director of the University of Cambridge's Coastal Research Unit, asks if the challenges affecting the UK's coastal areas are beyond the grasp of policy…

How to manage our coastal environments without sacrificing the benefits they bring us from both an economic and social perspective is one of the key challenges of the 21st Century. Never before have population densities in areas at risk from flood and coastal erosion been as high as they are now, and never, since humans have inhabited the southern British Isles, have sea levels in this region risen at the rate at which they are doing. Add to this the prospect of the increased likelihood of extreme weather events as a result of climate change, and the £2.17bn that the UK government is expecting to spend on flooding and coastal erosion over the next four years (via Defra) comes as no surprise.

Human settlements have historically been (and still are) focused on the coast, as the coast provided access to resources (food), transport routes and trade. As global populations are rising, population densities in coastal regions are rising faster (the Centre for Climate Systems Research at Columbia University predicts the number of people living within 60 miles of the coast will increase by 35% between 1995-2025). In the UK, major coastal conurbations (London, Hull, Southampton, Liverpool and others) have resulted from this affinity to the coast. Even in the case of smaller towns, net in-migration has been significant: the working age population of the UK's 43 principal seaside towns rose by more than 20% between 1971 and 2001.¹ A significant proportion of the British population, infrastructure and industry is thus directly (and in many more cases indirectly) affected in some way by the coast, and this proportion is likely to rise. With this rise comes an increased economic, social and political responsibility for getting the management of coastal environments 'right'.

In addition to being heavily populated, coasts are one of the most naturally dynamic environments on Earth. Tides and the weather change water levels and waves hourly. Those in turn redistribute sand and gravel continuously, with several truckloads of sand moving along some UK beaches in a matter of days. This movement affects the growth of dune and wetland vegetation over months to years, and both the growth and erosion of beaches, dunes and wetlands results, at rates of up to several metres per year.

Unlike most terrestrial environments in which change in the landscape as forced by nature itself is slower and often only perceptible/measurable over decades, such change is an inherent characteristic of the coastal landscape. Indeed, most organisms that inhabit the coast depend on change for their existence (as exemplified by the accelerated growth of Marram Grass on dunes where sand accumulation occurs). Thanks to an increasing research effort in the field of coastal and marine science over the last half century, we now also know that the forces that cause landform change at the coast cannot simply be 'controlled'. The transport of sediment is determined by energy thresholds (a grain of sand only moves when the stress it is exposed to is great enough). It is thus the frequency and magnitude of certain types of weather/tide events – rather than the average – that explain change.

Such events, however, are controlled by the weather, and meteorological conditions are largely unpredictable over more than a few days. Moreover, the degree to which an individual event can cause change depends on the shape of the coast prior to that event – and that again depends on previous weather/tide conditions. The shape of the coast that results without human intervention and under a repeated sequence of meteorological conditions can thus become increasingly 'resilient' to change, as sediment is transported from high energy to low energy regions until the coastal shape itself reduces energy without any further change to its shape (by friction with the seabed or by reflecting the energy back out to sea).

The construction of a seawall, however, can alter the shape of the coast artificially, thus altering the way in which energy is distributed and causing sediment to be eroded where energy levels were previously too low to do so – often immediately in front of the seawall, as wave energy is reflected and interacts with incoming waves to create higher energy conditions. Getting the management of coastal environments 'right' requires: a recognition of coastal change as a form of 'resilience' that has to be accommodated rather than fought; and a sound understanding of this dynamism – not only the forces that drive change, but also the ways (and the locations) in which change is most likely to occur.

Arguably, the vast majority of coastal management challenges facing communities in the UK today result not from the forces that drive landform change at the coast, but from a prolonged historical failure to recognise that coastal change itself is a form of natural resilience that has to be accommodated and cannot be fought against. The large-scale construction of hard sea defences in the aftermath of the 1953 North Sea storm surge exemplifies what might be called the 'old fashioned' approach towards coastal management.

Although the hard defence solution towards coastal erosion and flood risk reduction is now less commonly adopted, the construction of such defences in the past has, in many locations, led to: several decades of industrial and residential growth in areas seemingly 'protected' by these hard structures; and a reconfiguration of tidal/wave currents and sediment transport pathways seaward of them, frequently putting those locations at an increased risk from flooding and erosion. Thus, we are now no longer faced with the management of a 'natural' system with its inbuilt dynamism and resilience, but with the management of a system that is (and has for many decades been) a human artefact.

So what should our current priorities be in the field of coastal management? Clearly, where people's health and wellbeing is directly at risk, coastal management should aim to reduce flood and erosion risk to a minimum. In many locations, however, the reason why this exposure to flood and erosion risk has arisen in the first place is due to a failure to regulate the movement of people and infrastructure into areas that we now know are at risk.

We now understand the intrinsic dynamic nature of the coastal zone better than ever before, and that this dynamism must be preserved if we are to preserve the coast's natural resilience to environmental change. Out of this knowledge, one key management priority emerges that, arguably, sits above all others: the need to restore a natural coastal 'buffer' zone, free from permanent human occupation and compatible with the 'inbuilt' ability of the coast to respond dynamically to environmental change, such as sea level rise or more frequent storms. Clearly, this must be achieved without sacrificing the economic benefits provided by the coast. It is, however, becoming increasingly obvious that we have been ignoring many of the benefits provided by a dynamic coast. Hard defences are expensive and doomed to fail (or incur ever increasing-costs) in the context of their own impact on coastal processes, a changing climate and accelerated sea level rise.

But hard defence cost savings achieved through the 'dynamic coast model' of management are only one benefit. Many more 'ecosystem services' are being recognised as having economic and social value – biodiversity, recreation, environmental education, grazing and carbon storage, to name but a few. The government's current Shoreline Management Plans recognise these values and the need for the restoration of a dynamic coast. Their non-statutory nature and the government's reluctance to adopt a centralised strategic approach towards the management of our coasts, however, means that any attempts at putting these ideas into practice remain reliant upon local initiative. The restoration of the coast towards a naturally dynamic state only occurs where individual stakeholders (councils, land-owners, conservation organisations, etc.) go out of their way to do so (rarely with adequate financial recognition for the benefits provided by the conversion of the use of their land to this new purpose).

Over the past decade, much progress has been made in channelling resources towards the better monitoring and understanding of coastal change, but resources are still small, given the urgency of this issue. Of the £2.17bn the government is expecting to spend on flooding and coastal erosion over the next four years, £1.04bn is capital spending. This figure includes river flooding and is in some contrast with the much lower government spending per year of circa £40-50m (via Defra and the Research Councils) on what might be called targeted, proactive, objective research in fields such as 'coastal sediment systems', 'biodiversity and ecosystem services sustainability', and 'flood risk from extreme events'.

A clear mismatch exists between, on one hand, funding for local capital flood and erosion risk reduction projects, and on the other, an improved understanding of coastal dynamics so that strategic monitoring systems can be put in place, to identify and learn from the dynamic behaviour of the coast, and ensure that areas most likely to be affected by change can be safely used. If we are to adopt truly economically (ecologically and socially) sustainable coastal management practices without escalating costs into the future, the government must continue to address this mismatch.

1 Seaside Economy Report, 2003