Cornwall Beach & Dune Management Plans – Porthcothan

REPORT ( FINAL)

Prepared for Cornwall Council

October 2016

CH2M Ash House Falcon Road Sowton, Exeter EX2 7LB

Contents

Section Page Executive Summary ...... v Introduction ...... 1 1.1 Project Background ...... 1 1.2 Project Aims ...... 3 1.3 Dune Management Plan ...... 3 1.4 Key Contacts ...... 3 Site Description ...... 5 2.1 Location...... 5 2.2 Setting ...... 7 2.3 Key Characteristics ...... 7 2.3.1 Present Site ...... 7 2.4 Natural and Historic Environment ...... 8 2.4.1 Ecology ...... 10 2.4.2 Designated Geological Conservation Sites ...... 14 2.4.3 Landscape Setting ...... 14 2.4.4 Archaeology and Cultural Heritage ...... 15 2.5 Land Use ...... 15 2.6 Value of the Dunes ...... 15 2.7 Key Problems Experienced...... 15 2.8 Other Studies ...... 16 2.8.1 Shoreline Management Plan (SMP) Policy ...... 16 Factors Affecting the Beach Dune System ...... 17 3.1 Wind, Wave Climate and Tides ...... 17 3.1.1 Wave Climate ...... 17 3.1.2 Storm Waves ...... 18 3.1.3 Tides ...... 19 3.1.4 Climate Change and Sea Level Rise ...... 20 3.2 Sediment Budget and Linkages ...... 21 3.3 Historical Changes ...... 22 3.3.1 General Description ...... 22 3.3.2 Long Term Evolution ...... 22 3.4 Summary of Site Influences ...... 28 3.5 Future Changes ...... 29 Beach & Dune Management Plan ...... 30 4.1 Key Issues ...... 30 4.2 Management Techniques to Apply at Porthcothan...... 30 4.3 Plan of Action ...... 31 4.4 Monitoring and Response ...... 35 4.4.1 Survey Requirements ...... 35 4.4.2 Trigger Conditions ...... 36 References ...... 39

Appendices Appendix A Sand Dune Management Techniques & Preliminary Decision Support Tool v2.0

III CONTENTS

Section Page Appendix B An Overview of Coastal Sand Dunes Appendix C Baseline (Interim) Report Appendix D Site Actions Summary Map Appendix E Summary Leaflet

Document history This document has been issued and amended as follows:

Version Date Description Created by Verified by Approved by

0.1 06-09-16 Draft for CC comment AF, SB, EH JR JR

1.0 07-10-16 Final AF, SB, EH JR JR

IV EXECUTIVE SUMMARY Executive Summary

This Beach & Dune Management Plan (BDMP) for Porthcothan has been produced as part of the Cornwall Beach & Sand Dune Management Project commissioned by Cornwall Council in 2015. The BDMP has two purposes: 1. Identify the best management approach; in terms of monitoring and intervention (when trigger levels are reached) requirements for the beach and dune system at Porthcothan; based upon the best practice framework developed as part of the Cornwall Sand Dune and Beach Management Strategy produced by Halcrow in 2009, and updated as part of developing the new BDMPs by CH2M in 2015 (see Appendix A). 2. Provide a long-term (50 year) approach to beach and dune management at Porthcothan that is based upon an up-to-date understanding of the beach-dune system and coastal processes at the site, as well as predictions of future coastal evolution. For background information, Appendix B provides an overview of how beach-dune systems work. This BDMP report provides: • An introduction to the project and BDMP (Section 1); • A summary of the characteristics (Section 2) and coastal process drivers at Porthcothan (Section 3); and • Discussion and definition of suitable management techniques to apply at Porthcothan, including a plan of action and the recommended monitoring and response programme (Section 4). The key issue to be addressed by beach and dune management activities at Porthcothan Bay is the periodic relocation of the stream channel along the toe of the dunes and consequent perception that erosion of the dunes as a result of this is detrimental to the dune system, habitats and to public safety / access onto the beach. Porthcothan Bay, including the beach, dunes and stream, is a naturally functioning system, where periodically the dunes are eroded during storms, material is drawn down from the dunes and beach to the offshore. Periodically when conditions are conducive, the stream channel relocates along the dune toe. Evidence presented in Section 3 has shown that over time, material is returned to the beach and dune system and the stream channel relocates back to its position in the north of the bay. Even when the stream channel has been artificially relocated to a straight position, the channel tends to find its own equilibrium position, forming meanders again over time. This is a process that will repeat itself in the future. In the future, as sea levels rise, the risk of erosion of the bridge and road and resulting increases in flood risk upstream will be an issue. Artificial relocation of the channel to a straight position in the north will only exacerbate this risk, as storm waves will be funnelled up the channel and towards the bridge. However, the natural channel meanders down the beach and a berm of sand in the northern meander provides a line of defence by dissipating wave energy. It is therefore recommended that the beach, dune and stream system to the north of the bay should be left to behave naturally. There is little benefit to any intervention in this system from a flood and erosion risk management or environmental management point of view. The implication of this approach in the long-term for the road and bridge will need to be considered by the Highways Authority at a later date. If as a result of allowing natural processes to occur, safe access to the beach from either of the two current footpaths is an issue, then the following can likely be done by local groups, subject to obtaining any consents that may be required from the local planning authority (planning

V SECTION 1 – INTRODUCTION permission), Natural England and the Marine Management Organisation (given the proximity of the MCZ to Porthcothan): • Re-profile the dune face at the access point when required (i.e. become over-steep for safe access). • Install temporary/removable (and relocatable) access measures such as steps, a bridge or stepping stone across the stream. • Relocate access paths through the dunes away from historic routes and undertake grass planting (such as marram grass or lyme grass) along the redundant path to help stabilise the dunes. If during the summer period the channel cuts into the dune toe such that the dune is eroded back to the trigger point (approximately 30m of erosion back from the lifeguard hut – see Figure e4.1), posing a significant amenity and health and safety access issue, then intervention could take place with limited works to relocate the stream by local groups, subject to obtaining any consents as outlined above. If such works are undertaken then the following conditions will apply: • The berm north of the stream should not be cut through and should be retained. • When relocating the stream within the zone indicated on Figure 4.1, incorporate meanders around the berm (also shown on Figure 4.1). Any sediment extracted to create the channel that is not used to aid channel realignment, should be placed along the dune front shown on Figure 4.1, with priority being areas of erosion. The cost for these measures would need to be funded from non-Flood and Coastal Grant in Aid, i.e. from local funding sources, as it falls outside the scope of that funding source. In addition, if to be implemented, any consents required should be obtained beforehand.

VI SECTION 1 – INTRODUCTION

Introduction 1.1 Project Background Many of the sand dunes and beaches around Cornwall’s coast are currently experiencing erosion and sediment loss. This is a pressing concern as these sand dunes and their associated sandy beaches are one of the most important resources in Cornwall due to: 1. Their role in providing protection against the risk of coastal flooding due to the dynamic nature of beach-dune interactions and their sheer size preventing the sea from impacting upon the hinterland behind the dune systems. 2. Their role in providing important biologically diverse habitats that cannot be easily recreated elsewhere if it were to be lost to coastal erosion or inappropriate development. 3. Their role in providing access to the sea for residents and visitors alike, which is vital to the holiday industry upon which a significant proportion of Cornwall’s economy depends. It is vital therefore that the sand dunes and beaches around Cornwall’s coast, that represent some 15% of the total sand dune habitat in Britain, are managed in a holistic, sustainable way over the long-term that balances the needs of each of the three distinct functions of sand dunes and beaches that combined make up the beach-dune system. To ensure that these vital resources are managed in such a way, in 2009 the Cornwall Sand Dune and Beach Management Strategy was developed by Halcrow (now CH2M) for the Cornwall & Isles of Scilly Coastal Group. The main focus of the strategy is the management of flood and coastal erosion, although the habitat and tourism value of the dunes will also be considered. This project delivered an Inventory of Beaches and Dunes; a Best Practice Management Guide and two pilot Beach and Dune Management Plans (BDMPs) for Fistral Beach and Harvey’s Towans (Hayle). To build on this previous work, Cornwall Council commissioned CH2M to work with them and local communities to (a) produce seven new BDMPs for locations at Constantine Bay, Porthcothan, Porthtowan, Par Sands, Praa Sands, Summerleaze and Widemouth Bay; and (b) review and update the two pilot BDMPs for Harvey’s Towans and Fistral Beach produced in 2009. Figure 1.1 shows each of these locations. This document is the BDMP for Porthcothan and sets out sustainable management practices for the sand dunes and beach in this area. It should be reviewed every 5-10 years unless significant, rapid changes occur that warrant an earlier review.

1 SECTION 1 – INTRODUCTION

Figure 1.1 BDMP locations around Cornwall

2 SECTION 1 – INTRODUCTION

1.2 Project Aims Beaches and Sand Dunes have many uses and functions. These include amenity, recreation, commercial and community uses, and coast defence, habitat and earth science functions; all of which have social, environmental and economic value. In this case, the main focus of the BDMP is the management of the dunes and beach to ensure they fulfil their flood and coastal defence function to help protect communities around the coast of Cornwall from coastal flooding and erosion by the sea; whilst also considering the needs for management of habitat and amenity use in the area. BDMPs are a non-statutory method of providing a coastal defence plan for managing a beach and dune system at a local level that takes into account and, where possible, promotes or enhances the other uses and functions of a beach. BDMPs provide a framework for more cohesive management of a beach and dune system that may be regulated and used by different parties, all with their own agendas. They establish a means to control the physical form of beaches and sand dunes and the general beach and dune environment, and to promote good practice within the environment. BDMP production is often led by Local Authorities with support from the Environment Agency and is usually done in collaboration with relevant stakeholders, as will be the case here. Assistance is available to the authorities to undertake appropriate management and to maintain the coastal defence function provided by the beach and dune system and any associated hard defence structures, as well as other requirements both now and in the future. Given this, the aim of this BDMP is to provide a new long-term strategic BDMP for Porthcothan. This will be achieved by delivering the following objectives: 1. Identify the best management approach; in terms of monitoring and intervention (when trigger levels are reached) requirements for the beach and dune system at Porthcothan; based upon the best practice framework developed as part of the Cornwall Sand Dune and Beach Management Strategy produced by Halcrow in 2009, and updated as part of developing the new BDMPs by CH2M in 2015 (see Appendix A). 2. Provide a long-term (50 year) approach to beach and dune management at Porthcothan that is based upon an up-to-date understanding of the beach-dune system and coastal processes at the site, as well as predictions of future coastal evolution. For background information, Appendix B provides an overview of how beach-dune systems work. 1.3 Dune Management Plan To achieve the aim and objectives defined in Section 1.2, the BDMP for Porthcothan is structured as follows: • Section 1 – Introduction (this section). • Section 2 – Site Description. • Section 3 – Factors Affecting the Beach Dune System. • Section 4 – Beach & Dune Management Plan. 1.4 Key Contacts The BDMP and its implementation is led by Cornwall Council. The key contact for this work is: Name: Mr Martin Clemo Job Title: Flood and Drainage Team Leader, Contracts and Commissioning Service Postal Address: South Building, Central Group Centre, Castle Canyke Road, Bodmin, Cornwall, PL31 1DZ.

Telephone: 01209 614383 Email: [email protected]

Site Description 2.1 Location Porthcothan is located on the north coast of Cornwall, between Trevose Head and Park Head, south of Treyarnon Bay (refer to Figure 2.1).

5 SECTION 2 – SITE DESCRIPTION

Figure 2.1 Map showing the Porthcothan BDMP location and extent (red outline).

6 SECTION 2 – SITE DESCRIPTION

2.2 Setting Porthcothan Bay is a westerly facing bay on the north coast of Cornwall that is exposed to dominant Atlantic waves and weather systems. The bay is bounded by two rocky headlands – Trevose Head and Park Head. The beach and dune system here, which is located seaward of the B3276 coastal road, formed after the second world war when fences were placed at the back of the beach. Sand accumulated and the dunes have grown considerably over recent decades, more than doubling in height over the last twenty years. Photographic and anecdotal evidence suggests that the dune system continues landward of the road and that the houses built before the war along the road formed a barrier to dune movement and helped encourage the build-up of sand seaward (Appendix C provides further details). The dunes are tall, stable and extensively vegetated with grasses as well as brambles. One of two public access routes is through the dunes and there are erosion pressures along this route, particularly where it drops down on to the beach and is subject to dune cliffing. The other access route is to the north of the beach leading from the road bridge onto the beach. A stream flows onto the beach, meandering along the north of the beach but periodically diverting to run along the toe of the dunes causing erosion during such periods which in turn poses access issues for beach users, which is a concern particularly in summer season when there are many more visitors to the site. The beach (up to the high tide water mark) is part of the nationally designated Padstow Bay and Surrounds Marine Conservation Zone (MCZ) designated to conserve the diversity of nationally rare, threatened and representative habitats and species in the area. The MCZ includes the tidal stream channel up to the bridge and road. 2.3 Key Characteristics 2.3.1 Present Site The principal characteristics of the present beach system are as follows: • The beach at Porthcothan Bay is west facing and exposed to the predominant westerly wave regime. • Beach profile analysis suggests that over the longer-term (2007 to 2014) the beach to the north and centre of the bay is eroding, and the beach to the south is accreting. • The bay is situated between two rocky headlands to the north and south that prevent sediment movement outside of the bay. Consequently, Porthcothan Bay is a closed sediment system. • Sediment transport within the bay is dominated by on/offshore movement of sediment between the dune and beach areas. • The high tide beach is relatively narrow, although at low tide the beach is very wide. • A small stream discharges onto the beach in the north east. The stream channel is known to meander naturally and on occasion run along the toe of the dunes for periods, posing erosion and access issues at those times. The principal characteristics of the dune system are: • An area of well-established fringing dune along the backshore of the bay • The dune face is steep with notable cliffing, consequently the lifeguard station has been moved from within the dunes, onto the beach.

• There is estimated to be 1ha of active dune and 0ha of inactive dune at Porthcothan Bay (Halcrow, 2009a). 2.4 Natural and Historic Environment The Study Area contains, or is in the vicinity of, the following nature conservation designations. These are central in the consideration of options for the beach and dune management plan: • Padstow Bay and Surrounds Marine Conservation Zone (MCZ). • The Cornwall Area of Outstanding Natural Beauty (AONB). • Bedruthan Steps and Park Head SSSI (biological and geological). • Bristol Channel Approaches pSAC. • Archaeological and Cultural Heritage designated features. These features are shown on Figure 2.2 and discussed in further detail below.

8 SECTION 2 – SITE DESCRIPTION

Figure 2.2 Environmental designation features in the vicinity of the Porthcothan Bay BDMP area.

9 SECTION 2 – SITE DESCRIPTION

2.4.1 Ecology 2.4.1.1 Designated Nature Conservation Sites The following nature conservation designations and their qualifying interest features are all within or lie in close proximity to the Study Area and will require consideration during the development of the BDMP (see Figure 2.2 above): • Padstow Bay and Surrounds Marine Conservation Zone includes Porthcothan Beach up to the high tide water mark and includes the stream channel outlet that runs onto the beach from under the road bridge on the northern side. The MCZ is designated for protection of exposed cliffs, rocky shores, sandy wave-exposed bays, rocky outcrops and reefs that support rich underwater habitats and benthic communities. An MCZ assessment may be required dependant on the proposed actions of the BDMP. The MCZ protects seven types of seabed habitat and two marine species as listed in Table 2.1. Table 2.1 Padstow Bay and Surrounds Marine Conservation Zone features.

Padstow Bay and Surrounds General management Present within MCZ features approach Porthcothan BDMP boundary Intertidal coarse sediment Maintain in favourable  condition Intertidal sand and muddy sand Maintain in favourable  condition Moderate energy intertidal rock Maintain in favourable No records condition Moderate energy infra-littoral; Maintain in favourable No records rock condition High energy intertidal rock Maintain in favourable  condition High energy infra-littoral rock Maintain in favourable No records condition High energy circa-littoral rock Maintain in favourable No records condition Pink sea-fan (eunicella Maintain in favourable No records. verrucosa) condition Potential to be present below MLW adjacent to site

Spiny Lobster (Palinurus Recover to favourable No records. elephas) condition Potential to be present during high tide and below MLW adjacent to site

• Bristol Channel Approaches possible Special Area of Conservation (pSAC) is located from mean low water at Porthcothan. The large geographical area of the SAC is proposed to be designated for protection and management of the wide-ranging highly mobile Annex II species harbour porpoise (Phocoena phocoena) and its habitat. A Habitats Regulations Assessment may be required depending on the nature of any proposed actions defined in the BDMP. • Bedruthan Steps and Park Head SSSI is located approximately 0.6km south of Porthcothan and designated for biological and geological interests. Biologically the site supports features of important maritime cliff species Armeria maritima - Cerastium diffusum ssp. diffusum

maritime therophyte community, grassland species Festuca rubra, Armeria maritima, Festuca rubra and Holcus lanatus, and lowland heath (calluna vulgaris, Scilla verna and Ulex gallii). The geological interests are described in Section 2.4.2 below. The following designated sites have been identified and considered or discounted for bird-habitat connectivity between the protected area and the site (see Figure 2.3 below): • Falmouth Bay to St Austell Bay pSPA is approximately 28km from Porthcothan at its nearest point. The proposed SPA (pSPA) supports rare wintering birds and diving birds that are proposed for designation under the Birds Directive (2009/147/EC). The pSPA is a large area, and encompasses the Fal and Helford SAC within the pSPAs north western section. This site is designated under article 4 (4) of the Habitats Directive (92/43/EEC) for the following Annex 1 habitats: Sandbanks which are slightly covered by sea water all the time; Mudflats and sandflats not covered by seawater at low tide; Large shallow inlets and bays that include low tidal sandbanks and Atlantic salt meadows (Glauco-Puccinellietalia maritimae). Other Annex I habitats that are present as a qualifying feature of the SAC but not the primary reason for selection include Estuaries and Reefs and includes the Annex II plant species Shore dock Rumex rupestris. Connectivity with Porthcothan Bay and the SAC/pSPA is possible. Habitat, as described in the MCZ that surrounds Porthcothan Bay (as mentioned above) may support seabirds and diving birds, and consideration may be required. • Tamar Estuaries complex SPA is approximately 51km northeast from Porthcothan at its nearest point. The estuary system is a large marine inlet on the English Channel coast comprising the estuaries of the Rivers Tamar, Lynher and Tavy. Habitats include extensive tidal mud-flats bordered by saltmarsh communities. The mud-flats contain extensive and varied infaunal communities rich in bivalves and other invertebrates, and feeding grounds for waterbirds in numbers of European importance. Saltmarshes provide important feeding and roosting areas for large numbers of wintering and passage waterbirds. This site qualifies under Article 4.1 of the Directive (79/409/EEC) by supporting populations of Little Egret Egretta garzetta (on passage, and a population over winter) and Avocet Recurvirostra avosetta (over winter). Connectivity is possible but likely low due to a lack of estuarine mudflat and saltmarsh habitat at Porthcothan. • Marizion Marsh SPA/SSSI is approximately 52km south of Porthcothan from its nearest point. The marsh is at the mouth of a wide coastal valley, separated from the sea by a shingle bar with fringing sand dunes. The marsh is important for passage and wintering birds associated in particular with the extensive reedbed. The site qualifies under Article 4.1 of the Directive (79/409/EEC) by supporting populations of Annex I species Aquatic Warbler Acrocephalus paludicola (in passage) and Bittern Botaurus stellaris (over winter). Connectivity between the SPA/SSSI and Porthcothan Bay is unlikely due the absence of similar freshwater habitat. • Isles of Scilly SPA is approximately 106km from Porthcothan at its closest point. The SPA qualifies for its seabird assemblage of international importance and breeding seabird assemblage of European importance. The isolated nature of the islands and rocks, together with their low levels of disturbance and predation, makes them particularly suitable for nesting seabirds. This site qualifies under Article 4.1 of the Directive (79/409/EEC) by supporting populations of European importance of the following Annex I species Storm Petrel Hydrobates pelagicus and Lesser Black-backed Gull Larus fuscus. The site also qualifies under Article 4.2 of the Directive (79/409/EEC) for regularly supporting a seabird assemblage of international importance of at least 20,000 seabirds. The SPA boundary only encompasses those areas used for nesting. The vast majority of the feeding areas used by the seabirds are marine waters outside the SPA. Connectivity with feeding areas seaward around Porthcothan is feasible. • The Exe Estuary SPA (approximately 109km from Porthcothan Bay at its nearest point) is a complex of coastal habitats waters, foreshore, low-lying land, three saltmarshes and an

unusual double spit across the mouth of the estuary, and the sand dunes of Dawlish Warren. The mud and sandflats support Eelgrass Zostera spp. and Enteromorpha beds, and contain an abundance of invertebrates including extensive Mussel Mytilus edulis beds, which together provide rich feeding habitats for wintering waders and wildfowl. Site qualifies under Article 4.1 of the Directive (79/409/EEC) by supporting populations of Annex I species Avocet Recurvirostra avosetta and Slavonian Grebe Podiceps auritus (over winter) and qualifies under Article 4.2 of the Directive (79/409/EEC) as a wetland of international importance for regularly supporting at least 20,000 waterfowl. Connectivity is likely low due to a lack of estuarine habitat present at Porthcothan Bay to support the associated species.

12 SECTION 2 – SITE DESCRIPTION

Figure 2.3 Potential bird-habitat connectivity between the protected area and the BDMP site.

2.4.1.2 Biodiversity Action Plan (BAP) Habitats The following are listed as UK priority BAP habitats and are either represented in the Study Area or are within 1km. The following habitats have been identified from http://webarchive.nationalarchives.gov.uk/20140605090108/http:/www.naturalengland.org.uk/our work/conservation/biodiversity/protectandmanage/habsandspeciesimportance.aspx (go to ‘list of habitats’) as being likely to be found around the site: • Coastal Sand Dunes. • Maritime cliff and slope. • Spiny lobster (Palinurus elephas). There are no formal records identified at Porthcothan, but as a designated feature of the MCZ, spiny lobster has potential to be present within the intertidal zone (during high tide) and within inshore waters adjacent to the BMP area. Spiny lobster needs to be considered by any potential BMP works. • Pink sea-fan (eunicella verrucosa). There are no formal records identified at Porthcothan, but as a designated feature of the MCZ, pink sea fan has potential to be present within inshore waters adjacent to the BMP area and needs to be considered by any potential BMP works. • Harbour porpoise (Phocoena phocoena). European protected species and designated feature of the pSAC. Harbour porpoise are highly mobile species and have potential to be present within the intertidal area adjacent to the BMP area. Any proposed works needs to consider harbour porpoise and harbour porpoise habitat. Note, no baseline habitat assessment report has been undertaken by Cornwall Council for Porthcothan to date, therefore priority BAP habitat has been identified using records described in the online environmental mapping tool MAGIC in combination with the citation descriptions of habitat as described for the designated sites. Only habitats that are considered relevant to the Study Area, i.e. they are likely to be impacted upon or are likely to have an influence on beach management options, have been described. Firm confirmation of priority BAP habitat would require an ecological assessment. 2.4.2 Designated Geological Conservation Sites There are no designated sites for earth sciences at Porthcothan, however the following nationally and regionally important designations are located nearby: • Bedruthan Steps and Park Head SSSI is located approximately 0.6km south of Porthcothan. The SSSI is designated for biological (as noted above in Section 2.4.4.1) and geological interests. Geologically the cliffs are of importance for rich fossil fauna, within extensive exposures of grey Devonian slates indicating an Eifelian Age. It is the best site of this type in Cornwall. • Bedruthan Steps Geological Conservation Review site is recognised for its source of rare fish fossils representing possibly a late and large pteraspid. The specimens are rare elsewhere in north Cornwall, and may be some of the last recorded pteraspids, and so considered of great importance. 2.4.3 Landscape Setting The importance of landscape to the Porthcothan Bay area is recognised by the following nationally and regionally important designations (see Figure 2.2 above): • The Cornwall Area of Outstanding Natural Beauty (Trevose Head to Stepper Point) has an extremely varied coastal scenery but can be characterised by sandy bays giving way to sand dunes and small hamlets /holiday villages (of which Porthcothan is one), small coves, high

cliffs and stacks and a gently rolling plateau rising to higher ground inland with panoramic views. 2.4.4 Archaeology and Cultural Heritage A number of historic sites and monuments and listed buildings are located within the area (see Figure 2.2 above). 2.5 Land Use The dunes are backed by the B3276 coastal road which is a key access route for the area, as well as properties and a car park that is used by visitors to the beach and dune system. 2.6 Value of the Dunes The management of the dunes needs to acknowledge the benefit of the sand dunes for their aesthetic value, and thus attractiveness to local residents and visitors, as well as acknowledging the coastal defence function of the dunes. The specific values of the dunes at Porthcothan Bay include: • Coastal flood and erosion buffer for properties, key access road and local infrastructure behind the sand dunes. • Local recreational value. • Providing a store of sand that can naturally feed the beach to compensate for seasonal erosion. • To form an aesthetically attractive backdrop to the beach, providing sheltered areas and viewing points for beach users. • Significant environmental habitat value. 2.7 Key Problems Experienced The key issue at Porthcothan Bay is that when the dunes erode as a result of movement of the stream channel, the erosion that results along the dune front causes issues for public safety and access onto the beach. It is also considered to be potentially detrimental to the dune system and habitats. During storm events waves reach the dune toe. Dunes and beach are eroded and sediment is redistributed or moved offshore. When combined with heavy rainfall events, where the stream deposits more sediment onto the beach, a berm has formed and the stream has tended to divert, changing course southwards along the toe of the dunes. The stream channel itself erodes the frontal dunes and allows the sea to reach the dune toe, resulting in exacerbated erosion. This creates the following issues of concern: • Safety hazard with regards to accessing the beach due to cliffing of the dune face. • The stream erodes and damages the dune system. • Erosion of the dune system resulting in habitat loss. During the winter of 2014/15, high rainfall resulted in large volumes of sediment from the stream being deposited on the beach. Incoming tides moved sediment up the beach resulting in the formation of a bank in the north-east of the bay. The bank effectively formed a barrier which diverted the stream south along the toe of the dunes, causing significant erosion of the frontal dunes. In January 2015, intervention took place without consent of statutory bodies (i.e. MMO, Natural England etc.). This intervention involved digging a new straight channel to move the stream back along the north of the beach. Reinstatement of the stream towards the north of the beach had an immediate effect of reducing the dune erosion.

During the winter of 2015/16, the stream again relocated along the dune toe, resulting in erosion of the dunes. However, during this time the stream was allowed to meander and move position naturally and subsequently, over time, the stream has moved again back to a more natural alignment to the north. The greatest potential risk at Porthcothan is of surge waves during storm events up and under the B3276 Road Bridge which could result in structural damage or failure. Therefore, it is the bridge and road that is most at risk. The natural channel meanders down the beach and a berm of sand in the northern meander provides a line of defence by dissipating wave energy. Relocating the channel straight along the north of the beach will exacerbate this risk under storm conditions, as the channel would allow waves to easily reach the bridge. Further details of this issue are provided in Appendix C. 2.8 Other Studies 2.8.1 Shoreline Management Plan (SMP) Policy Porthcothan Bay lies within Policy Unit 33.6 (Porthcothan Beach) of the Cornwall & Isles of Scilly Shoreline Management Plan Review (SMP2), adopted in 2011 (Royal Haskoning, 2011b). The policy for flood and coastal erosion risk management defined in the SMP2 for this area over the next 100 years is: • Short term (to 2025) = No Active Intervention (with localised Hold the Line). • Medium term (to 2055) = No Active Intervention (with localised Hold the Line). • Long term (to 2105) = No Active Intervention (with localised Hold the Line). The intent of this policy is to apply “a non-interventional approach to best manage the dune area but it would be acceptable to HTL along short section of road adjacent to the rear of the beach.” The SMP2 provides the following rationale for this policy: “A non-interventional approach is considered best to manage the dune and beach area at Porthcothan and to allow the shoreline to respond naturally to sea level rise and adjust its form and profile accordingly. It is considered justifiable however to hold the line along a short section of defences (around 120m) which front the B3276 road adjacent to the rear of the beach. This may be satisfactory over all epochs but possible realignment routes for the road appear feasible and may prove more sustainable in the long term.”

Factors Affecting the Beach Dune System 3.1 Wind, Wave Climate and Tides 3.1.1 Wave Climate The coastline at Porthcothan is orientated north-south, with the beach facing west and dunes approximately north-west. The predominant wave direction along the north coast of Cornwall is reported (Royal Haskoning, 2011b) to be from the west to north-west (approaching from 270o – 315o), however, large swell waves from the south to southwest will refract around the Lands End Peninsula and reach the most westerly facing beaches, (with reduced energy) (Royal Haskoning, 2011b), such as Porthcothan Bay. The Perranporth Directional Waverider Buoy, operated as part of the South West Regional Coastal Monitoring Programme (SWRCMP), is the nearest wave buoy to Porthcothan Bay, and has been reviewed for this study. The wave buoy is located approximately 20 miles south-west from Porthcothan Bay, and provides a record of wave height for a seven year period between 18th December 2006 and 30th June 2014. A plot of wave height in Figure 3.1 shows that the predominant wave direction in this area is from the west. The data set also indicates significant wave heights frequently exceed 5m during the winter months and that wave periods of 15 seconds (i.e. powerful swell waves generated by storms offshore) and higher are not uncommon (Royal Haskoning, 2011b).

Figure 3.1 Offshore wave height recorded by the Perranporth Directional Waverider Buoy between 18th December 2006 and 30th June 2014 (PCO, 2014a).

3.1.2 Storm Waves Storm analysis undertaken by Plymouth Coastal Observatory (PCO) (2014b) provides an overview of the storm conditions recorded by the Perranporth Directional Waverider Buoy since 2007. For each wave buoy in the SWRCMP, an individual storm threshold is set. A storm event is defined when significant wave heights equivalent to the 0.25 year return period (i.e. the threshold wave height (Hs) for 2 to 4 storms in an average year) occurs for a set period of time (i.e. 16 hours). The significant wave height is calculated when a 5-year time series of data becomes available for the wave buoy and is then reset each year. Prior to that, the height is based on an educated conservative guess from looking at the wave data available. The reason that the 0.25 year return period is used is because the SWRCMP have found that in general there are 3 to 4 storms in any one year that result in the movement of significant amounts of sediment. For their reporting, PCO produce a storm calendar. The calendar includes a graph, where each dot represents a storm (i.e. where the Hs exceeds the storm threshold) and shows the Hs for that particular storm. PCO plot the significant wave height for the 1 year return period for that particular buoy on the graph (calculated in the same way as significant wave height for the 0.25 year return period) as a red line. Where storms plot above the red line they are considered to be more severe/extreme and are listed in a separate table. The storm calendar and table for the Perranporth Directional Waverider Buoy are presented in Figure 3.2 and Table 3.1 respectively. The storm calendar shows that eight severe/extreme storms have exceeded the 1 year Return Period since 2007; three of those storms (38 %) occurred between October 2013 and February 2014. The impact of these storms on beach change is described in Section 3.3.

Figure 3.2 Storm calendar for Perranporth (source: PCO, 2014b).

Table 3.1 Storms exceeding 1 year Return Period at Perranporth since deployment in 2007. Those occurring during the storm season October 2013 to February 2014 are shaded pink (source: PC0, 2014b).

Date Wave Height (m) Return Period

01/02/2014 7.28 Greater than 1 in 20 years

02/11/2013 7.06 1 in 10 years

27/12/2013 6.81 1 in 5 years

15/12/2011 6.75 1 in 5 years

12/03/2008 6.53 1 in 3 years

10/03/2008 6.37 1 in 2 years

11/11/2010 6.3 1 in 1 year

31/03/2010 6.25 1 in 1 year

3.1.3 Tides Tidal levels have been extracted from the current Admiralty Tide Tables (UKHO, 2013) for the closest location with the best available data, in this case Newquay, and converted to Ordnance Datum (mOD). The tide levels for Newquay are presented in Table 3.2 and illustrated in relation to a typical beach-dune profile at Porthcothan in Figure 3.3.

Table 3.2 Tide levels (in mOD) for Newquay, adjusted from standard port Milford Haven.

Tidal Condition Tide Level (mOD)

Highest Astronomical Tide (HAT) 4.20

Mean High Water Spring (MHWS) 3.40

Mean High Water Neap (MHWN) 2.00

Mean Sea Level (MSL) 0.38

Mean Low Water Neap (MLWN) -1.10

Mean Low Water Spring (MLWS) -3.00

Lowest Astronomical Tide (HAT) Data not available

Figure 3.3 Tide levels in relation to typical beach-dune profile at Porthcothan (based on SWRCMP monitoring data).

3.1.4 Climate Change and Sea Level Rise Information on the impacts of climate change is available from ‘Advice for Flood and Coastal Erosion Risk Management Authorities’ (Environment Agency, 2011). This guidance highlights that the main risk of climate change in relation to beach management is from sea level rise. The guidance (Environment Agency, 2011) suggests that predictions of the future rate of sea level rise for the UK coastline should be taken from UKCP09. Data downloaded from UKCP09 provides sea level rise from 1990. Anticipated rates of relative sea level rise and surge estimates over three time periods are presented in Table 3.3. The following estimates are presented in the table: • Lower End Estimate: this is the low emissions scenario, 50% frequency, taken from the UKCP09 User Interface. • Change Factor: this is the medium emissions scenario, 95% frequency, taken from the UKCP09 User Interface. • Upper End Estimate: these are generic values of sea level rise provided in the climate change guidance; they are 4mm (up to 2025), 7mm (2026 to 2050), 11mm (2051 to 2080), and 15mm (2081 to 2115). • H++ Scenario: these are generic values of sea level rise provided in the climate change guidance; they are 6mm (up to 2025), 12.5mm (2026 to 2050), 24mm (2051 to 2080), and 33mm (2081 to 2115). • Upper End Estimate + Surge Estimate: This is the upper end estimate plus the upper end surge estimate. The surge estimate are generic values provided in the climate change guidance; they are 20cm (up to the year 2020’s), 35cm (up to the year 2050’s), and 70cm (up to the year 2080’s). With regard to the surge increase, the uncertainty with surge increase is even greater than for sea level rise.

The climate change guidance (Environment Agency, 2011) recommends that in planning future coastal management options, the Change Factor (medium 95% frequency scenario) be used as the preferred scenario. All other scenarios are included to demonstrate the sensitivity of decision making through time, and can be used to refine the options to prepare for a wider range of future change. Table 3.3 Relative sea level rise estimates for Porthcothan (see text above for explanation of terms used in this table).

Time period Various estimates of relative sea level rise and surge (mm/year)

Lower End Change Upper End H++ Upper End Estimate Factor Estimate Scenario Estimate + Surge Estimate

2015 to 2025 0.03 0.06 0.04 0.24 0.06

2015 to 2055 0.15 0.26 0.27 0.62 0.49

2015 to 2115 0.44 0.77 0.92 1.62 1.92

3.2 Sediment Budget and Linkages Sediment transport at Porthcothan Bay is dominated by the on/offshore movement of material between the beach and dunes (Halcrow, 1999a; Halcrow, 2009b). In winter, storm waves erode the dune front releasing sediment onto the beach and redistributes the material to the small rocky coves (Figure 3.4) that can be seen when the tide is out, and to the offshore, such as occurred in the 2013/2014 storms. In calmer conditions, this material is returned to the dunes through wave action and wind-blown transport.

Figure 3.4 Sand accumulating in rocky embayments within Porthcothan Bay.

The rock headlands which bound the bay to the north and south, and Trescore Islands to the west prevent sediment movement outside of the bay. Consequently, Porthcothan Bay is a closed sediment cell with no significant alongshore exchange of material (Halcrow, 2009b). The main contemporary beach sediment source is from offshore carbonate shell material (Halcrow, 2002), with limited sediments supplied from cliffs adjacent to the beach. The stream is also unlikely to provide a significant sediment input to the system. 3.3 Historical Changes 3.3.1 General Description Porthcothan Bay is located on the north coast of Cornwall, between Trevose Head and Park Head, south of Treyarnon Bay. The westerly facing bay is exposed to dominant Atlantic waves and weather systems. Futurecoast (Halcrow, 2002) suggests that there is no interaction between the beaches along this coast in terms of sediment exchange. This is probably true given the deeply incised nature of this section of coast and its swash aligned tendencies. The bay is situated between two rocky headlands of hard resistant Devonian slates (Royal Haskoning, 2011b) to the north and south. At low tide Porthcothan Bay is long and narrow compared to at high tide where the remaining beach reduces in size considerably. An area of well-established fringing dune line the backshore of the bay, along with a small stream which discharges onto the beach in the north east. Porthcothan dunes are high, hummocky and well vegetated with grasses and brambles. The dune face is steep with notable cliffing, consequently the lifeguard station has been moved from within the dunes, onto the beach. However, analysis of historical maps indicates a healthy, stable dune system. The dune system formed after the war when fences were placed at the back of the beach. Sand accumulated and the dunes have grown considerably over recent decades. A stream flows onto the beach, meandering along the north of the beach. An accumulation of sand can be seen to the north of the meander, where beach levels are higher. During storm events waves reach the dune toe. The dunes and beach are eroded and sediment is moved offshore. When combined with heavy rainfall the stream deposits more sediment on the beach, specifically on the berm, which forms a barrier. As a result, the stream has periodically diverted course, relocating southwards along the toe of the dunes. When the dunes erode as a result of channel movement the erosion is detrimental to the safety of the public and access onto the beach; it is also considered to be potentially detrimental to the dune system and habitats. Two years ago, following relocation of the stream along the toe of the dunes and consequent erosion, intervention without appropriate consent being granted by the MMO and other statutory bodies took place whereby a new straight channel was dug, moving the stream back along the north of the beach. Subsequently, over time, the stream has moved again back to a more natural alignment. Appendix C provides further details. 3.3.2 Long Term Evolution A number of photographs and postcards of Porthcothan Bay from St Eval Parish archive, dated between 1908 and 1936, are included in Appendix C. The images show a much smaller extent of dunes compared to that observed today, suggesting a growth of the dunes of approximately 60m seaward over the last 80 years. Aerial photographs in Figure 3.5 (2001), Figure 3.6 (2005) and Figure 3.7 (2009) show little change in dune position, but clearly show how the position of the stream flowing through the beach has changed over time. The dunes to the south of the stream, where it discharges onto the beach, have receded slightly as a result of natural channel movement. Figure 3.6 shows evidence of two channels, where the channel has relocated along the dune toe, but then is slowly re-orientating to its previous equilibrium position.

lifeguard station There is also evidence of frontal dune erosion which has resulted in the (blue circle) being moved onto the beach (Figures 3.6 and 3.7) from its location on the dunes (Figure 3.5). During the winter of 2014/15, rapid relocation of the stream along the dune toe, combined with exceptional tides, resulted in a significant loss of the dunes through erosion, causing unprecedented changes to the beach and dune profiles (Figure 3.8). Anecdotal evidence suggests that continual erosion of the dunes by the stream in November 2014 over a number of days resulted in between 6m and 10m of frontal dune erosion (Figure 3.9). Further erosion of the dune system occurred in the winter of 2015/16, when the stream again relocated along the dune toe. Direct erosion of the dunes by the sea occurs infrequently, predominantly when high spring tides and storms coincide.

Stream channel (2001)

Location of lifeguard station

Figure 3.5 Porthcothan dunes and stream, 2001 (source: Google Earth 2016).

Stream channel (2005)

Previous channel route

Location of lifeguard station

Figure 3.6 Porthcothan dunes and stream, 2005 (source: Google Earth 2016).

Stream channel (2009)

Location of lifeguard station

Figure 3.7 Porthcothan dunes and stream, 2009 (source: Google Earth 2016).

Figure 3.8 Relocation of the stream along the front of the dune system, November 2014 (source: Andrew Marriott)

Figure 3.9 Frontal dune erosion, November 2014. (source: Andrew Marriott)

3.3.2.1 Beach Profile Analysis Beach profile monitoring undertaken by Plymouth Coastal Observatory (PCO) for the South West Regional Coastal Monitoring Programme (SWRCMP), provides recent data and analysis for the beach at Porthcothan Bay. A summary of the findings from the latest annual survey report (PCO, 2014a) are presented in this section and provide an overview of beach profile change in the year, between Spring 2013 and Spring 2014, and over the longer-term from the baseline survey in 2007 to the most recent survey in Spring 2014. It should be noted that the assessment of cross-sectional area (CSA) for the profiles at Porthcothan Bay exclude the dunes, covering only beach change. • Between Spring 2013 and Spring 2014 (refer to Figure 3.10), the northern and central profiles have lost material, with the northern profile, 7a02034, losing >30m2, equating to 34% in CSA. • Over the longer term, between 2007 and Spring 2014 (refer to Figure 3.11), the trend is for erosion in the north and central areas of the bay, profile 7a02034 (CSA reduction of 8%) and profile 7a02031 (CSA reduction of 4%) and slight accretion to the south of the bay, profile 7a02028 (CSA change of 3%). • Mapping of the Mean High Water contour (refer to Figure 3.12) shows that the upper beach position has fluctuated over the survey period, with no clear trend. • Observations made during the site visit on the 12th March 2015 found the dunes to be overall stable but with a steep cliffed face. As part of the SWRCMP, PCO have also prepared two reports (PCO, 2014b and 2014c), which examine the change to a selection of the beaches along the south-west coast, with a view to identify how beach change occurring as a result of the 2013/2014 winter storms compares to the longer- term behaviour of the beach. However, analysis of beach volume change and a topographic difference model has not been completed for Porthcothan Bay.

Figure 3.10 Beach profile change at Porthcothan Bay Spring 2013 to Spring 2014 (source: PCO, 2014a).

Figure 3.11 Beach profile change at Porthcothan Bay baseline 2007 to Spring 2014 (source: PCO, 2014a).

Figure 3.12 MHW contour change at Porthcothan Bay (source: PCO, 2014a). 3.4 Summary of Site Influences The beach at Porthcothan Bay is west facing and exposed to the predominant westerly wave regime. As a result alongshore transport is limited. Sediment transport is therefore dominated by an onshore-offshore movement of material. An area of well-established fringing dune lines is located at the backshore of the bay, along with a small stream which discharges onto the beach in the north east. The dune system formed after the war when fences were placed at the back of the beach. Sand accumulated and the dunes have grown considerably over recent decades. Today the high, hummocky, vegetated dunes are considered stable. As the dunes erode during storms, material is moved offshore. Increase in the size of the berm to the north, due to deposit of fluvial material during high rain events, has at times diverted the stream southwards along the dune toe, resulting in erosion of the fronting dunes for periods of time. Beach profile analysis suggests that over the longer-term (2007 to 2014) the beach to the north and centre of the bay is eroding and the beach to the south is accreting. These trends are generally mirrored by on-the-ground observations, as material is lost from the beach temporarily and returned over time. Dune erosion occurs during storm events and the dunes suffered significant erosion during the 2014/15 storms, exacerbated by the stream channel changing course. In January 2014, intervention by a group of active residents moved the stream back towards the north and erosion was considerably reduced. In the winter of 2015/16 the stream relocated again along the dune toe and resulted in dune erosion, however this time no intervention took place and the channel moved back towards the north naturally over time. Aerial photographs between 2005 and 2009 show evidence of channel movement from its position in the north part of the bay, to relocating along the dune toe, to repositioning back along the northern shore. This is a process that will repeat itself in the future.

3.5 Future Changes The pocket beach at Porthcothan is likely to maintain its overall form in the future. Marine carbonate sources will continue to feed a supply of sand. The resistant cliffs will continue to erode slowly. Flood risk to the low-lying backshore area will increase as sea levels rise. There is a potential for some narrowing of the foreshore and dune erosion as sea levels rise and during storm events, however, the Shoreline Management Plan (SMP) states that the dunes are not expected to erode significantly and should recover as sediment exchange will continue freely between the beach and dune system (Royal Haskoning 2011a). With climate change and increased storm events, the combination of high intensity rainfall events and storms could result in further instances where the channel is diverted south along the dune frontage. There is therefore potential for accelerated dune loss episodes in the future as a result. Figure 3.13 highlights the predicted erosion risk to the hinterland stated in the SMP2 (Royal Haskoning, 2011a). Under a no active intervention scenario, the SMP predicts that if the dune system is lost then there is risk to the bridge, road and houses over the 100-year appraisal period.

Figure 3.13 Porthcothan flood and erosion risk (Source: Royal Haskoning, 2011a).

Beach & Dune Management Plan

This section covers the development of the Beach & Dune Management Plan and is divided into three sections: 1. Key Issues. 2. Management techniques to apply at Porthcothan. 3. Plan of Action. 4.1 Key Issues The key issue to be addressed by beach and dune management activities at Porthcothan Bay is the periodic relocation of the stream channel along the toe of the dunes and consequent perception that erosion of the dunes as a result of this is detrimental to the dune system, habitats and to public safety / access onto the beach. Porthcothan Bay, including the beach, dunes and stream, is a naturally functioning system, where periodically the dunes are eroded during storms, material is drawn down from the dunes and beach to the offshore. Periodically when conditions are conducive, the stream channel relocates along the dune toe. Evidence presented in Section 3 has shown that over time, material is returned to the beach and dune system and the stream channel relocates back to its position in the north of the bay. Even when the stream channel has been artificially relocated to a straight position, the channel tends to find its own equilibrium position, forming meanders again over time. This is a process that will repeat itself in the future. In the future, as sea levels rise, the risk of erosion of the bridge and road and resulting increases in flood risk upstream will be an issue. Artificial relocation of the channel to a straight position in the north will only exacerbate this risk, as storm waves will be funnelled up the channel and towards the bridge. However, the natural channel meanders down the beach and a berm of sand in the northern meander provides a line of defence by dissipating wave energy. 4.2 Management Techniques to Apply at Porthcothan It is recommended that the beach, dune and stream system to the north of the bay should be left to behave naturally. There is little benefit to any intervention in this system from a flood and erosion risk management or environmental management point of view. The implication of this approach in the long-term for the road and bridge will need to be considered by the Highways Authority at a later date. If as a result of allowing natural processes to occur, safe access to the beach from either of the two current footpaths is an issue, then the following can likely be done by local groups, subject to obtaining any consents that may be required from the local planning authority (planning permission), Natural England and the Marine Management Organisation (given the proximity of the MCZ to Porthcothan): • Re-profile the dune face at the access point when required (i.e. become over-steep for safe access). • Install temporary/removable (and relocatable) access measures such as steps, a bridge or stepping stone across the stream. • Relocate access paths through the dunes away from historic routes and undertake grass planting (such as marram grass or lyme grass) along the redundant path to help stabilise the dunes. If during the summer period the channel cuts into the dune toe such that the dune is eroded back to the trigger point (approximately 30m of erosion back from the lifeguard hut – see Figure 4.1 below

and/or Appendix D), posing a significant amenity and health and safety access issue, then intervention could take place with limited works to relocate the stream by local groups, subject to obtaining any consents as outlined above. If such works are undertaken then the following conditions will apply: • The berm north of the stream should not be cut through and should be retained. • When relocating the stream within the zone indicated on Figure 4.1, incorporate meanders around the berm (also shown on Figure 4.1). Any sediment extracted to create the channel that is not used to aid channel realignment, should be placed along the dune front shown on Figure 4.1, with priority being areas of erosion. The cost for these measures would need to be funded from non-Flood and Coastal Grant in Aid, i.e. from local funding sources, as it falls outside the scope of that funding source. In addition, if to be implemented, any consents required should be obtained beforehand. In addition to the above, from a dunes BAP habitat perspective, monitoring of the dunes could also be undertaken by the local community in order to keep a record of any habitat changes over time; for example, anthropogenic impacts and extent of invasive/non-native dune vegetation species. This could be taken forward in discussion with local environmental organisations. 4.3 Plan of Action Table 4.1 provides a summary of the recommended actions at Porthcothan discussed in Section 4.2 that could be undertaken by local groups subject to obtaining any necessary consents. Reference should also be made to the site actions summary map (Figure 4.1 or Appendix D) that indicates where on the site specific actions relate to.

31 Table 4.1 Recommended actions for Porthcothan

Issue Recommended Timing Who Should Risk Identification When by? Reference: Management Action Action Risk Mitigation Links all correct when accessed on 29th July 2016

Erosion of beaches and • Construct • Establish safe access Local • Unsafe access reduces • Monitor and maintain safe Ongoing BOARDWALKS / WALKWAYS – dunes by natural boardwalks/steps at key points and monitor Community, usability of beach and and defined access points. from 2016 http://www.mass.gov/eea/agencies/czm/program- processes, causing in discussion areas/communications/cz-tips/cz-tip-boardwalks.html erosion focus points or and maintain. increases risk of injury to the • Monitor dune extent in cliffing along dune with MMO, over the stream if • Intervention to public. relation to trigger line (see front and safe access Natural http://lizardandpenrose.blogspot.co.uk/2012/03/under- required. address erosion if • If erosion of dunes not Figure 4.1) and intervene if issues. England and boardwalk.html • Intervene to realign trigger level reached addressed if trigger line is trigger reached, subject to Cornwall stream channel and/or to be based on reached, increases risk of obtaining necessary consents Council. recover dunes only if ongoing monitoring. erosion and flooding to road before works occur. erosion caused reaches • Planting in Spring – and property behind the • Select robust species. Plant trigger line (see Figure prior to peak tourist dunes. when conditions are most 4.1), subject to obtaining season. In general favourable (early Spring). necessary consents planting tends to be before works occur. most successful in • Where public access early March. safety is compromised, fence off vulnerable areas and re- route path. • Where bare sand areas do not re-establish on old paths undertake planting to stabilise vulnerable areas. Lack of information / • Implement monitoring • Post storm Local • Requirement for post storm • Identify threshold storm Ongoing SOUTH WEST REGIONAL COASTAL MONITORING SCHEME - data relating to beach scheme and response inspections/surveys community in survey not identified soon conditions to initiate post from 2016 http://www.channelcoast.org and dune levels and regime. to occur within one conjunction enough and beach profile storm surveys. BAP habitats. with • Coastal processes to or two tidal cycles of has readjusted. • Work with SWRCMP to Plymouth continue to be storm event. • Lack of appropriate data to ensure capture required Coastal monitored as part of • Coastal processes make informed decisions to coastal processes data. Observatory / SWRCMP, ideally monitoring to be as manage coastal risk. other • Liaise with Plymouth Coastal incorporating additional per SWRCMP environmenta Observatory to ensure requirements identified programme (refer to l groups. Porthcothan Bay is a key site (refer to Section 4.4.1.1). Section 4.4.1.1). for post storm surveys. • Asset condition to be • Walkover inspections • Ensure summary reports are assessed by regular at least each spring produced after each visual walkover visual and autumn and walkover inspection and that inspections, supported after notable storm these document actions to by fixed aspect events, with report be taken. photography and produced after each reporting (refer to inspection (refer to Section 4.4.1.2). Section 4.4.1.2).

Dune habitat • Develop and implement • Medium term. Local • Potential for ecological gains • Develop and implement a Ongoing management, including a wider dune Community in limited if not managing wider dune management from 2016 control of any non- management plan to conjunction habitat of whole dune plan. native invasive species guide all aspects of with Natural system is a planned way. within dune vegetation. managing dune habitat England and for ecological gain. other environmenta • Remove non-native l groups. species by hand or mechanically and treat with a biodegradable herbicide. • Monitor dune vegetation

Issue Recommended Timing Who Should Risk Identification When by? Reference: Management Action Action Risk Mitigation Links all correct when accessed on 29th July 2016

Limited funding to • Community to take • Short, medium and Local • If funding is not available to • Assess potential beneficiaries Ongoing FCERM FUNDING GUIDANCE – undertake measures to raise funds long-term. Community undertake management and develop a partnership from 2016 https://www.gov.uk/guidance/flood-and-coastal-defence-funding- management works. for any management activities when and how it is funding strategy to guide submit-a-project activities required. best to do so, then there is a discussions with potential risk that no works will occur, funding partners. Partnership funding and collaborative delivery of local flood risk management: a practical resource for LLFAs – increasing risk of erosion as a • Seek funding commitments http://sciencesearch.defra.gov.uk/Default.aspx?Menu=Menu&Modul result. from partners. e=More&Location=None&Completed=0&ProjectID=17085

Figure 4.1 Site Actions Summary Map for Porthcothan (copy also provided in Appendix D).

34 SECTION 4 – BEACH & DUNE MANAGEMENT PLAN

4.4 Monitoring and Response 4.4.1 Survey Requirements 4.4.1.1 Coastal processes monitoring Monitoring of coastal processes is to continue to be undertaken until at least 2021 by the South West Regional Coastal Monitoring Programme (SWRCMP). The SWRCMP survey schedule for Porthcothan Bay is shown below in Table 4.2. Table 4.2 SWRCMP survey schedule for Porthcothan (from http://www.channelcoast.org/southwest/survey_programme_schedule/).

Figure 4.2 shows the location of the baseline and interim beach profiles measured at Porthcothan.

Figure 4.2 Location of beach profiles currently measured by the South West Regional Coastal Monitoring Programme at Porthcothan (Source: Plymouth Coastal Observatory).

The work of the SWRCMP is to continue to be the primary means of monitoring the physical processes at Porthcothan.

4.4.1.2 Asset condition monitoring In addition to the coastal processes monitoring data collected by the SWRCMP described in Section 4.4.1.1, it is recommended that the land owner/responsible operator (possibly working with the Local Community) should undertake regular walkover surveys to monitor the issues identified in this report, and the success of any management measures implemented. This should include a visual assessment of aspects such as: • Erosion along access routes. • Position / course of the stream. • Vegetation coverage and condition. • Consideration of whether or not trigger levels, as defined in Section 4.4.2, have been reached. These visual condition inspections should be undertaken at least each spring and autumn, and following notable storm events. These visual inspections should also include fixed aspect photography at key problem areas including access routes subject to erosion and also bare sand areas (i.e. take photos at the same location of the same view on each inspection). Regular monitoring of any implemented management techniques should be carried out in the future. Dunes are dynamic systems and the effectiveness of management techniques may not be consistent. Through monitoring, the dune management techniques in place can be regularly assessed and adapted to improve effectiveness and prevent the continuation of unsuccessful techniques that do not benefit the dune system. A brief inspection report, including photos and summary of findings and actions to be taken, should be produced after each inspection and copies retained alongside this BDMP. 4.4.2 Trigger Conditions Trigger conditions enable a quick assessment of whether intervention is required to maintain the existing dune system. The actions required when the trigger conditions are reached should be considered in light of the conditions immediately prior to, during and predicted to follow the assessment. The beach and dunes will be inspected following a storm event. However, the dune system will typically experience erosion during a storm event and usually recover to near the pre-storm level following a period of calmer conditions. It is therefore recommended that unless further storm conditions are predicted, the dunes should be allowed a period to recover after a storm event before remedial action is taken (e.g. re-routing the stream channel). Similarly, erosion of access points may be more significant in summer when visitor numbers are high, but show some recovery during the quieter seasons if conditions allow. Action and Emergency trigger states have been developed for the dunes based on assessment of the data available, the dune characteristics and engineering judgement. These trigger levels are to be reviewed and refined when the BDMP is next reviewed, taking into account the greater amount of monitoring data that is expected to be available by that point (assuming that the monitoring needs defined in Section 4.4.1 are implemented). 4.4.2.1 Action conditions and response The Action State is defined as the beach/dune level at which intervention may be required. At Porthcothan Bay this is defined as the point at which erosion of the dune system reaches a stage whereby public access is considered dangerous and safe access cannot be resumed without intervention.

Table 4.3 outlines the key indicators for action conditions and the criteria for assessing whether action conditions have been reached. Refer also to the site actions summary map in Figure 4.1 above. When Action Conditions are observed, the specific problem should first be assessed to identify the appropriate response. Responses to Action Condition Indicators are suggested in Table 4.3. Table 4.3 Action conditions and responses

Criteria Likely consequence Response Access Points eroded to a level at which they cause a health and safety risk.

• Access points eroded to form a • Access is eroded at start of the • Re-profile the dune slope at high steep slope which is not safe peak season and is likely to be the access point. for pedestrians and is at high risk worsened by high foot traffic • Consider re-routing pathways of causing injury. throughout the peak season. away from the eroded area • Access point has been eroded to where possible. Fence off and form a steep cliffed slope for more stabilise the eroded access than one season. route through planting to enable it to recover. • Erosion is continuing and access is becoming more difficult and/or a • Introduce temporary access greater health and safety risk. infrastructure to provide safe access at key points.

4.4.2.2 Emergency conditions and response The Emergency State is defined as the beach/dune state at which emergency remedial action should be considered as soon as practicable. At Porthcothan Bay the Emergency State may be reached following a very severe storm event combined with re-location of the stream along the dune toe. Table 4.4 outlines the key indicators for Emergency Conditions and the criteria for assessing whether emergency conditions have been reached. If emergency conditions are reached, recycling of sediment in the local system and re-profiling of the beach and dunes will only be considered to reduce the risk of erosion and flooding to the road, bridge and properties behind the dunes. Otherwise, if emergency conditions are reached, but without risk to the road, bridge or properties, then local intervention to re-route the steam could be considered, subject to consents be obtained. Responses to Emergency Condition Indicators are suggested in Table 4.4. Table 4.4 Emergency conditions and responses

Criteria Likely consequence Response Erosion of the dune front back to the trigger line

• Stream has relocated along the • Safety hazard with regards to • Re-route stream channel along dune toe resulting in erosion of beach access. the northern edge (refer to the dunes back to the trigger Figure 4.1). • point, approximately 30m of Significant damage to the dune system. • Re-profile slope at access points. erosion back from the lifeguard hut. • Habitat loss within the dune • Re-route access pathways to system. avoid eroded areas using • Steep cliffing of the dune front fencing and signage. Fence off leads to unstable dune front, • Further storm conditions eroded areas to enable recovery possible with an overhang, predicted which are likely to which causes a health and with planting and dune cause further erosion of the stabilisation methods applied as safety issue. dune front and increased cliffing, necessary. and potentially pose risk of loss of assets to erosion. • Ensure monitoring of dune front is carried out to provide information on trends in the dune front position and to

Criteria Likely consequence Response monitor whether cliffing worsens to emergency state.

Erosion of the dune front or berm resulting in immediate risk to the road, bridge or properties

• Dunes erode back to a point • Beach/ dune users could fall and • Re-distribute sediment on the where cliffing is becoming be injured in the immediate beach to reinstall the berm to steeper and higher as erosion future. the north. continues with no sign of • Loss of road, bridge and • If assets are deemed to be at recovery and increasing risk of loss of assets (bridge, road, properties. imminent risk of loss, implement coastal adaptation properties) landwards of the • Increased flood risk upstream. dunes. measures (to be defined in CCMA that Cornwall Council is • Erosion of the berm with to produce). subsequent imminent risk of loss of the bridge and road. • Re-profile slope at access points.

References

• Environment Agency (2011). Adapting to Climate Change: Advice for Flood and Coastal Erosion Risk Management Authorities. Report by the Environment Agency, 2011, pp. 29. • DCLG (2012). National Planning Policy Framework. Available online: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/6077/211695 0.pdf • Halcrow (2015). Coastal Change Adaptation Planning Guidance for England (CCAPG). Available online: http://lgacoastalsig.com/resources/coastal-guidance-and-manuals/. • Halcrow (2009a). Cornwall Sand Dune and Beach Management Strategy. Report produced by Halcrow Group Limited for the Cornwall and Isles of Scilly Coastal Advisory Group, September 2009. • Halcrow (2009b). Sand Dune Inventory. Cornwall Sand Dune and Beach Management Strategy. Report produced by Halcrow Group Limited for the Cornwall and Isles of Scilly Coastal Advisory Group, September 2009. • Halcrow (2009c). Sediment Budget Report. Cornwall Sand Dune and Beach Management Strategy. Report produced by Halcrow Group Limited for the Cornwall and Isles of Scilly Coastal Advisory Group, September 2009. • Halcrow (2002). Futurecoast CD. Produced by Halcrow Group Ltd for Defra. • Halcrow (1999). Land’s End to Hartland Point Shoreline Management Plan. Volumes 1 to 4. Report produced by Halcrow Group Limited for Cornwall and Isles of Scilly Coastal Group. • Plymouth Coastal Observatory (PCO) (2014a). Annual Survey Report. Land’s End to Hartland Point. Report Number AR43. Report produced for the South West Regional Monitoring Programme, September 2014. • Plymouth Coastal Observatory (PCO) (2014b). Review of South West Coast Beach Response to Wave Conditions During the Winter of 2013-2014. Report Number SW SR01. Report produced for the South West Regional Monitoring Programme, June 2014. • Royal Haskoning (2011a). Cornwall and Isles of Scilly Shoreline Management Plan Review (SMP2). Report for the Cornwall and Isles of Scilly Coastal Group. February 2011. • Royal Haskoning (2011b). Cornwall and Isles of Scilly SMP2. Main Report, Final. Report produced by Royal Haskoning for the Cornwall and Isles of Scilly Coastal Advisory Group, February 2011. • Royal Haskoning (2011c). Cornwall and Isles of Scilly SMP2. Appendix C, Review of Coastal Processes and Geomorphology, Final Report. Report produced by Royal Haskoning for the Cornwall and Isles of Scilly Coastal Advisory Group, February 2011. Report reference 9T8801. • United Kingdom Hydrographic Office, UKHO (2013). Admiralty Tide Tables. Volume 1. United Kingdom and Ireland. Reference NP201-13.

Appendix A Sand Dune Management Techniques & Preliminary Decision Support Tool v2.0

Appendix B An Overview of Coastal Sand Dunes

Appendix C Baseline (Interim) Report

Appendix D Site Actions Summary Map

Appendix E Summary Leaflet