Sand Dune Management Techniques & Preliminary Decision Support Tool

Appendix A Sand Dune Management Techniques & Preliminary Decision Support Tool v2.0 (NB: See accompanying CD to access the tool, which is only provided in digital format) REPORT Sand Dune Management Techniques & Preliminary Decision Support Tool v2.0 Prepared for Cornwall Council November 2015 Halcrow Group Limited, a CH2M HILL Company Ash House, Falcon Road, Sowton, Exeter, Devon, EX2 7LB UK +44 1392 444 252 +44 1392 444 301 Contents Section Page 1 Introduction ....................................................................................................................... 1 1.1 Background and context ............................................................................................... 1 1.2 About this report .......................................................................................................... 2 2 Management Techniques ................................................................................................... 3 3 Dune Management Preliminary Decision Assistance Tool User Guide ............................... 22 3.1 Introduction ................................................................................................................ 22 3.2 Using the tool .............................................................................................................. 22 References ................................................................................................................................... 28 Appendices Appendix A Dune Management Preliminary Decision Assistance Tool III 1 Introduction 1.1 Background and context Cornish dune sites are subject to high visitor numbers and the development of tourist amenities both within and behind the dune system. Sites are also subject to significant natural pressures, and storm wave conditions often result from a long fetch across the Atlantic and the relatively steep near‐shore bathymetry at many sites which produces high levels of wave energy at the coast. Climate change and sea level rise provide further pressures on Cornish dunes whose transgression landwards in response to sea level rise is limited by the surrounding tourism development and rising land levels. As a result of these pressures, dune management is required to maintain the flood and coastal defence properties of the dunes, while also enabling the important tourism economy to thrive. The various uses of the dunes often conflict, with stable fixed dunes being preferred for flood management schemes, dynamic dunes preferred with slacks and blow outs for habitat value, and higher visitor numbers required for the tourist economy. Conflicts between recreation and conservation are typical of the Cornish dune sites. Dune management can provide a number of benefits to the dunes including (CIRIA, 2010): Increased aesthetic value of the beach and dunes; A reduction in the need for fixed flood defence structures. This, however, can also increase the requirement for: Regular monitoring and interference with natural processes; Labour and time intensive management schemes; Increased public awareness leading to concern over storm impacts; Limited public access to part of or the entire site. The first aspect for consideration in dune management is whether the site actually requires management. Preliminary surveys and site monitoring should be carried out to assess the condition of the site. The BTCV (2005) suggest a list of questions to clarify management requirements. They suggest it is important to distinguish between natural and human or human related impacts and, where possible, only the human influenced problems should be managed. Techniques that interfere with the natural dynamics of the dunes should only be employed as a last resort. Over‐management of dunes should be avoided where possible (Carter, 1988). A diverse dune system with features such as blow outs and slacks is thought to be more able to react to changing conditions than a system in which all blown sand is trapped and covered with uniform planted vegetation. Management should therefore work with the natural system where possible, rather than preventing all dynamic natural processes. Once the dune site has been evaluated and it is clear what the problems are and what the underlying cause for these is, the relevant dune management techniques can be identified. There are a large variety of techniques that are applicable to the wide variety of dune sites and problems across the world. 1 1.2 About this report To aid coastal managers in identifying appropriate management approaches, as part of the Cornwall Sand Dunes & Beach Management Strategy completed in 2009, a review of available literature was carried out to produce a summary of national and international techniques for sand dune management (Halcrow, 2009). That work has been reviewed in 2015 as part of the Cornwall Beach & Dune Management Plans project and additional techniques have been identified. Section 2 of this report provides a summary of the dune management techniques practised worldwide to manage dunes for flood and coastal defence purposes first identified in 2009, and updated in 2015. In order to create a sustainable and long term management scheme a combination of these techniques may be required. A nourishment scheme for example may require planting, binding and fencing to stabilise the sand surface following the nourishment, and groynes may be required to retain the new beach material. This information is presented in Section 2 as a summary table of management techniques and can be used by sand dune managers as a reference for the planning of dune management schemes. The information, along with further details, is also included in a ‘Preliminary Decision Assistance Tool’ which can be used by site managers as a first indication of what techniques would be appropriate for the problems encountered at their site. It is presented as a Microsoft Excel document in Appendix A of this report. Section 3 of this report provides an overview and user guide as to the contents of the tool. 2 2 Management Techniques A review of available literature was carried out to produce a summary of national and international techniques for sand dune management in 2009 (Halcrow, 2009) and this has been reviewed as part of this current project. Table 2‐1 provides a description of the management technique along with: a reference given for further information on that technique (where applicable); an indication of when the technique is appropriate; and the associated benefits and problems associated with the technique. Where possible, an example of a sand dune site in Cornwall is provided where the technique is in use. The methods listed can be used in combination to produce the most appropriate management approach for a specific sand dune site. Adaptive management involves the application of dune management alongside detailed monitoring of the site. Through assessment of the results of ongoing monitoring, management techniques can be modified and refined. Through ongoing monitoring, management and adaptation, a successful and sustainable management approach can be developed. The categories of management identified in Table 2‐1, in alphabetical order, are: Access management; Adaptation of backshore management/uses; Cease existing management; Ecological modification; Funding; Hard protection methods; Manual maintenance; Monitoring; Morphological modification; Public awareness; Sediment modification; and Stabilisation. 3 Table 2‐1 Summary of Sand Dune Management Techniques Technique When Appropriate Benefits Problems Example Site ACCESS MANAGEMENT Zoning Tourist sites where erosion is Natural processes can Amenities such as picnic Cornwall Planning of the site to reduce or spread the taking place due to visitor continue. areas may attract further Gwithian to Mexico Towans. impact of visitors. Tactics are employed in site numbers. Eroded areas are able visitors. Perranporth (Penhale Sands). planning which encourage visitors to less to recover. Potential vandalism of sensitive zones and discourage them from signs and fencing. These sites are managed by sensitive areas. This includes consideration of rangers to limit damage to aspects such as: the sensitive habitats. Location of amenities. Other Location and size of car parks. Sefton Coast Dunes England. Location of campsites. Kennemerduinen National Fencing, boardwalks and planting to Park, west central Holland. discourage visitors from straying into sensitive areas (see below) Ability to rotate visitor attractions such as picnic areas. Limit/ prevent vehicle access. Fees such as car park tickets set at a rate to limit visitor numbers. (Carter, 1988) Boardwalks Sites with high visitor numbers Limits trampling and Expensive to construct Cornwall Generally constructed on fore dunes to where pedestrian traffic is erosion along main and require Hayle Towans (Part of Mexico prevent lowering of dune and development of concentrated along access routes. maintenance. to Gwithian Towans). blowouts when pedestrian traffic is routes causing erosion and dune Encourages visitors to May impact upon natural Sennen Cove. concentrated along access paths. lowering. keep to designated dune processes. paths. Other (BTCV, 2005) Morfa Dyffryn, North Wales. 4 Technique When Appropriate Benefits Problems Example Site If not designed correctly La Dune de Bouctouche, can increase wind along the Northumberland erosion. Strait near Bouctouche, Vandalism may be a Canada. problem. Sefton Coast Dunes, England.

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