Tackling flooding along coastlines

Flooding in Cornwall cpt Marie Preece

The tidal surge that occurred along the eastern coast of England in early December 2013 was the most serious in over 60 years. Subsequent storms and floods in 2014 have caused severe damage.

Recent tidal surges and storms have resulted in thousands of damaged properties and record sea levels, which in places were higher than those seen during the devastating storms of January 1953.

The subsequent breach of sea defences caused by the storms in January and February 2014 has caused more flooding and has had a big impact on our coasts across large areas of England and Wales. 

The scheme has also created wildlife benefits, creating a haven for breeding birds and unusual flora

Coastal habitats are, by their very nature, dynamic environments.  Changes in sea level and erosion are amongst the many variables responsible for the formation of many of the UK’s most interesting coastal landscapes and most valued habitats.

The problem is that coastal habitats need space to adjust to the changes which storms and high tides bring.  In a period of sea level rise, the natural response of beaches, dunes, mudflats and saltmarshes would be to migrate inland.  But almost everywhere around the lowland UK coast, the intertidal area is increasingly being squeezed between rising sea levels and inflexible artificial defences and building development.  This is known as ‘coastal squeeze.’ Coastal squeeze threatens the inherent value of our coastal habitats; habitats that function to reduce the force of tidal surges elsewhere along the coast. The problems are worst in south-east England, where it is estimated that 20% of saltmarshes were lost through coastal squeeze between 1973 and 1988. If current trends continue, a further 13,000 ha of intertidal flats and saltmarsh could be lost in the next 20 years through rising sea level.  Without positive intervention, we face losing on a massive scale unique habitat, vital natural sea defence and buffer mechanisms, with serious economic, pollution and wildlife implications.

The Yorkshire, Lincolnshire, Norfolk and Suffolk coasts were badly affected by the high coastal surge in December, damaging property, businesses and wildlife.  Whilst in some areas nature can be left to take its course, there are many internationally important nature reserves along the eastern coast that support special habitats and species that, in addition to their biodiversity value, deliver economic and social benefits. In some cases these will need to be defended against further damage and loss. Many of these sites attract tens of thousands of people to visit each year and have a deep historic and cultural importance. They also provide a critical function in absorbing the power of the sea and protecting communities and properties.  Hence, a policy of “abandonment” to natural processes is not always the best course of action for some of the special sites.  In some cases, where these important habitats are lost or at risk of being lost, compensatory habitat may need to be found inland, because these habitats cannot be “rolled back” gradually due to a lack of space (extreme coastal squeeze).

Because of changes to the management of the coastal flood defences on the north Norfolk coast at Norfolk Wildlife Trust’s Cley Marshes nature reserve over the past few years, it is predicted that the site’s vital reedbed habitat will be lost due to an increased influx of saline water into freshwater areas. This will gradually change the area’s characteristics, reduce reedbed habitat and make it unsuitable for breeding bittern. Norfolk Wildlife Trust has been working with the Environment Agency at Hilgay to create alternative reedbed habitat inland. You can read more about the Hilgay Project here.

At some sites, repairs need to be urgently undertaken. At Cley National Nature Reserve in Norfolk, for example, unless repaired quickly, the breaching of a shingle bank will expose this special place to ongoing flooding during most tides.

Thus, while The Wildlife Trusts generally advocate a “natural processes” approach to tackling flooding, there are instances where the value of these special sites along our coastline is such that protecting them from further damage is necessary and justifiable.

How we are helping

The Wildlife Trusts believe that we need to work with, rather than against, the natural evolution of the shoreline.  

Managed realignment and habitat restoration is an economically viable, environmentally acceptable solution to compensate for past and future coastal habitat losses.

The scheme has also created wildlife benefits, creating a haven for breeding birds and unusual flora

At Abbotts Hall Farm (pictured), Essex Wildlife Trust has led the way in ‘managed realignment’ schemes.  Eleven years ago, and with partners' support, it broke the seawall in several places, to allow tidal water naturally to recreate traditional Essex marshes.  There is now a natural incline, which acts as a flood defence.  

Though the tidal surge of 2013 was very high it did not reach the site’s arable areas, which in the past were next to the seawall and may well have been flooded.  

These kind of approaches can only work in certain places – they cannot be considered in places where people live next to the sea, but this scheme has proved very successful in an area where there is with very little habitation. The scheme has also created wildlife benefits, creating a haven for breeding birds and unusual flora.

Along the Fylde Coast in Lancashire there has been some major erosion of sand dunes during recent storms, exposing some of the work that Lancashire Wildlife Trust had done to shore up and create new dunes.  The work included planting posts and old Christmas trees - these hold up shifting sands helping them to form dunes and allow plants to grow, strengthening the structures. The difference that this work made was evident after storms. Where there was no protection the sea dramatically removed 8-10 metres of dunes. Yet where work had been done to strengthen the dunes naturally, the sands were held more securely. The worst damage occured where the sand dunes' vegetation - marram, lime and couch grasses - had been damaged by people in the past.

 

This work has proved to be very worthwhile because, without it, properties would have been open to the ravages of the stormy seas.

Northumberland Wildlife Trust is managing their sites along Druridge Bay with coastal change in mind and a slow but steady retreat. They are just in the process of buying 5ha of additional land at our Hauxley reserve, for people to enjoy and to create additional habitat.

See our Impacts on Wildlife page for coastal and wildlife news from Wildlife Trusts around the country.

Natural England reports surge and flood impacts on designated sites 2013/2014


• The coastal flooding of December, 2013, and early January, 2014, has affected at least 48 Sites of Special Scientific Interest (SSSIs), including 22 National Nature Reserves (NNRs). Natural England estimate that, a maximum of c.4,500 ha of designated coastal nature conservation sites in England were flooded.
• In most cases this flooding rresulted from waves overtopping seawalls and shingle/dune ridges, but in a few cases significant breaches of seawalls occurred.
• The sites affected mostly comprise coastal grazing marsh (grasslands with wet ditches), saline lagoons and reedbed. All of these sites are of national importance (SSSIs) and 37 of the 48 are also of international importance (SPA/SAC/Ramsar).
• Seawalls protecting at least 8 conservation sites were breached in Norfolk, Suffolk, Kent and the Tees estuary. In some locations, mainly Norfolk, there are multiple breaches to seawalls. NE is assessing the situation but it is possible that the existing conservation interest of the North Norfolk SPA may be comprised by the extent of habitat change.
• Three large seal colonies were inundated by flood water: Donna Nook in Lincolnshire, and Blakeney Point and Winterton to Horsey Dunes in Norfolk. This is the pupping season and young seal pups have been washed away. Losses are being assessed but at least 170 pups were lost at Winterton.
• There is damage to infrastructure on many sites, including visitor centres, bird-watching hides, footpaths and  fencing.
• The conservation interest and ecology of most coastal sites means that they are able to recover from periodic winter inundation.  However, on a small number of sites, the Environment Agency and Internal Drainage Boards have been pumping to evacuate saline water from freshwater sites to aid recovery.
• There has clearly been significant erosion in North-West England, The Severn Estuary and along the Channel coast as a result of the flooding 3rd to 6th January – but impacts are still being assessed.

Natural England priority sites

At some coastal sites the impacts are so severe that restoration may be challenging in terms of resources required, technical feasibility or long-term sustainability.

The list below indicates those SSSIs, as of 10th January, 2014, that Natural England believes fall into this ‘priority site’ category. Additional sites may be identified as priorities in due course as our assessment of impacts is completed.
The Humber and Lincolnshire
• Humber Estuary SSSI – Overwashing and major change to the spit at Spurn NNR. HelpYorkshire Wildlife Trust at Spurn - see events here.
• Saltfleetby-Theddlethorpe Dunes SSSI and NNR – Freshwater marsh inundated and Natterjack Toad dune breeding ponds damaged.
• Gibraltar Point SSSI and NNR – Breaches of seawalls and significant tidal inundation of freshwater marsh. See Lincolnshire Wildlife Trust's coastal flood appeal here.
Norfolk
• North Norfolk Coast SSSI – Titchwell Marshes. Dunes reduced in height and West Bank overtopped. East Bank may be structurally compromised. Saline inundation to freshwater marsh and fen meadow.
• North Norfolk Coast SSSI – Brancaster West Marsh. Seawall breaches and freshwater marsh inundated with sea water. Possible implications for Titchwell.
• North Norfolk Coast SSSI – Burnham Deepdale/Norton Marshes. Significant breaches to seawalls. Grazing marsh inundated.
• North Norfolk Coast SSSI – Blakeney Freshes (part of Blakeney NNR).  Significant breaches and inundation. Potential medium-term managed realignment in the North Norfolk SMP.
• North Norfolk Coast SSSI – Cley-Salthouse Marshes. Overtopping and significant breaches to shingle ridge and seawall (the latter now repaired). See Norfolk Wildlife Trust info and appeals here.
• The Wash SSSI and NNR – Snettisham.  Shingle bank breached and saline lagoons flooded.
• Winterton-Horsey Dunes SSSI and Winterton NNR – Dune losses and breaches. 
Suffolk
• Alde-Ore Estuary SSSI – Severe, multiple breaches to seawalls. Extensive inundation. Also seawall breaches and impacts on Havergate Island (an RSPB reserve).
• Minsmere-Walberswick Heaths and Marshes SSSI – Shingle ridges breached or overtopped. Significant freshwater habitat inundation. Insecure wall on Blythe Estuary. Dingle Marshes shingle bank breached (though likely to self-heal). Area between Dunwich and Walberswick open to tide.
• Pakefield to Easton Bavents SSSI and Benacre NNR – Easton Broad (part of NNR) shingle ridge breached. Freshwater reedbeds and saline lagoons inundated. Shingle ridge needs assessing. For news of Suffolk Wildlife Trust's coastal reserves including Hazelwood marshes see here.

Sussex
• Pagham Harbour SSSI – Flood defence failures and possible remedial measures may affect SSSI/SPA interests.