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Coastal Management Issues

Management Issues

Coastal Management encompasses all activities and interest groups that occur in and around the coast. Through consultation, better communication and understanding, coastal management attempts to balance these often conflicting issues and still deliver effective defences.

Saltmarsh Erosion

Prior to the Strategy study there was significant concern for the condition and long-term existence of the local saltmarshes and mudflats that provide an effective, natural method of flood protection to 10km of coastline, between Keyhaven and Sowley. They are an integral part of the coastal defence system within the Western Solent, absorbing the energy, and reducing the damaging effects of storm waves. Monitoring by NFDC has shown that the seaward edges of the saltmarshes are eroding on average at 3m per year. Our research indicates that with no intervention to reduce or halt the saltmarsh erosion rates, the saltmarshes will provide a decreasing amount of protection to the harbours and seawalls for perhaps another 40 years, and will have completely disappeared by the end of this century, if not sooner.

There are a number of factors that are likely to contribute to saltmarsh decline. Within the Solent tides are much stronger on the ebb than on the flood. So when saltmarshes erode, the sediment is taken offshore and not deposited within the estuaries. Therefore there is not enough sediment to feed the saltmarshes. With sea level rise the saltmarshes are inundated at high water for longer and more often. This alters the soil composition and affects the root systems. Once the vegetation begins to decline their ability to bind the sediment is reduced and therefore are more prone to further erosion. Ideally, as sea levels increase, saltmarsh would erode but the sediment would be deposited further inland. In this way the saltmarsh 'migrates' inland to keep pace with changes to water levels. Coastal squeeze is the term for when saltmarshes are prevented from migrating inland due to the presence of fixed seawalls. This is happening in the Solent and in most UK estuaries.

Performance of Coastal and Flood Defences

Along the shoreline is a mixture of local authority and privately owned defences. There are wooden groynes and walls, rock and concrete revetments all of which vary in age and condition. Each defence has a finite life of effectiveness. If they are in poor condition or not maintained etc they may be more susceptible to overtopping and failure. The performance of these defences will be investigated in the study. The costs and implications of removing, maintaining, improving or adding defences will be assessed.

Climate Change Factors

There are a number of factors associated with climate change. At the coast the affects of increased sea levels, more storms, higher waves and stronger tidal currents will directly impact on the shoreline. Increased rainfall inland during winter months will affect the levels of the rivers which feed into the Solent. If there are changes in temperature the type and extent of plant species at the coast and inland may also change. This may alter the drainage behaviour within the river catchment which would directly affect water levels within the estuaries. The potential for flooding is therefore higher, especially at times when high rainfall coincides with high tides and storm surge events.

Economics

The local economy is largely dependent on marine activities. Taking Lymington as an example, there are two major marinas, 3 boatyards and 5 sailing clubs within the Lymington River alone. Ship and boat traffic is concentrated in the Lymington River, and recreational activities which have become increasingly popular in the Solent, occur in some of the inter-tidal creek channels. These activities and the Lymington to Yarmouth ferry service, are crucial elements to the economy of the region, particularly in terms of tourism and commercial trade.

Number and Location of Moorings

As the saltmarshes erode the rivers and harbours are subject to larger waves reaching further into the estuaries. This has already affected the number and position of yacht moorings in both Lymington and Keyhaven Rivers. If the saltmarshes continue to disappear even more moorings in the outer reaches of the river would be lost as exposure to storm waves increases. Safety within the harbour and marinas would also be affected. This would have major economic impacts for the region, affecting commercial interests and tourism. The vibrancy and prosperity of the region would be threatened if appropriate action to save the saltmarshes is not taken. The loss of saltmarsh and mudflats would also seriously damage the wildlife habitats, which in turn would adversely affect the character of the area.

Nature Conservation

The north-west Solent coastline is host to a wide variety of plants, wildlife and habitats, many of which are considered to be of European importance to nature conservation. These areas are protected by a number of national and European legislation. The designation of most of the coastal area within the West Solent has implications for the future management of the coastal defences. There is a need to meet the obligations of European legislation relating to protecting the extent and condition of sites and the favourable conservation status of species and habitats. Currently, there is no clear guidance on how to implement this legislation in the context of evolving coastal systems within which habitats are being created and lost as a result of natural processes.

Summary of the nature conservation designations in the West Solent :

European / International Designations

Birds Directive - Special Protected Areas SPAs

Habitats Directive - Special Areas of Conservation SACs

Wetland sites - Ramsar

Solent European Marine Site

National Designations

Sites Special Sites of Scientific Interest SSSIs

Local Sites of Interest for Nature Conservation SINCs

National Nature Reserves NNRs

Landscape Designations

South Hampshire Coast Area of Outstanding Natural Beauty AONB

New Forest Heritage Area

Scheduled Ancient Monument

Keyhaven and Lymington Seawall

The existing coastal and flood defences between Keyhaven and Lymington were designed on the basis of a saltmarsh fronting them. If there were no saltmarshes in front of the coastal defences, the standards of protection these walls provide would be reduced. Enormous financial costs would also be incurred in maintaining the existing sea defences. New and alternative means of protecting the towns from severe flooding may need to be designed and trialled.

The seawall is also a boundary between different nature conservation sites with a Special Area of Conservation on the seaward side of the wall and a Special Protected Area on both sides of wall. If works are done to upgrade the wall the scheme may conform to one set of legislation but conflict with another. This poses a serious nature conservation dilemma and the government is looking at this type of conflict at a national scale.

Useful links

adobe icon Coastal Management Issues. [2Mb],

adobe icon Lymington-Keyhaven Saltmarshes [3Mb],

adobe icon West Solent Strategy Leaflet [1Mb]

Updated: 12 Mar 2015
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