Decision Framework for Adaptive

Management at Pagham Harbour

Final Report

Reference number/code [Sector Code]

We are the Environment Agency. It's our job to look after your environment and make it a better place - for you, and for future generations.

Your environment is the air you breathe, the water you drink and the ground you walk on. Working with business, Government and society as a whole, we are making your environment cleaner and healthier.

The Environment Agency. Out there, making your environment a better place.

Published by:

Environment Agency Rio House

Waterside Drive, Aztec West Almondsbury, Bristol BS32 4UD Tel: 0870 8506506 Email: [email protected] www.environment-agency.gov.uk

© Environment Agency

All rights reserved. This document may be reproduced with prior permission of the Environment Agency.

E xecutive Summary

Introduction

Pagham Harbour has been the subject of a series of detailed geomorphological investigations and assessments over recent years. The complex nature of the harbour system and the large number of process interacting both within it and along the adjacent coastal frontage has meant that in the past managing flood risk has been reactive. This project aims to obtain a greater understanding of the geomorphology of Pagham Harbour and the adjacent coast to help development of management plans for the future. The project comprises three key stages:

Stage 1: development of an initial geomorphological conceptual model from existing information;
Stage 2: further assessments, which may include a variety of numerical modelling approaches, dependent on the outcomes of Stage 1; and
Stage 3: approaches and interventions for flood and coastal erosion risk management.

This report is the deliverable for Stage 3 and utilises the findings of the conceptual model to assess potential outline management options and strategies for Pagham Harbour.

The existing policy at Pagham Harbour is currently one of Adaptive Management in recognition of the complex interactions in and around the harbour. This document presents three potential future consequences of how the harbour may develop in the future naturally and explores the implications of those consequences and potential mitigation measures.

[Writer of foreword] [Writer’s job title]

Contents

Contents 1. Introduction 1 1.1. Project Objectives 1 1.2. Stage 3 Objectives 2 1.3. Location of Pagham Harbour 2 1.4. Strategic Policy 3 1.5 Report Structure 7 2. Defining the Issues 8 2.1. Coastal Erosion Risk 8 2.3. Flood Risk 13 2.4. Environmental Designations 18 2.5. Water Framework Directive Classification 19 3. Geomorphological Scenarios, Future Consequences and Effects 21 3.1. Do Nothing Effects of Future Consequence 1: Existing inlet channel remains open 24 3.2. Do Nothing Effects of Future Consequence 2: Inlet seals and Pagham Harbour closes 25 3.3. Do Nothing Effects of Future Consequence 3: Church Norton Spit breaches to create new inlet channel further south 27 4. Adaptive Management 29 4.1. Long List of Adaptive Management Options 32 4.2. Short List of Adaptive Management Options 32 5. Shortlist Options for Future Consequences 35 5.1. Future Consequence 1 Existing inlet channel remains open 35 5.2. Future Consequence 2 Natural closure of the existing inlet channel 35 5.3. Future Consequence 3 Natural opening of a new inlet channel to the south 37 6. Shortlist Options for Short-Term Effects 38 6.1 Effect 1: Erosion of Pagham Beach 38 6.2. Effect 2: Erosion of Existing Inlet Flood Embankments 41 6.3. Effect 3: Overtopping of Existing Inlet Flood Embankments 43 6.4. Effect 4: Impeded drainage into the inlet 45 7. Future Consequences Option Overview 47 7.1. Future Consequence 1: Existing inlet channel remains open 47 7.2. Future Consequence 2: Natural closure of the existing inlet channel 47 7.3. Future Consequence 3 Natural opening of a new inlet channel to the south 49 8. Consequence Effects Option Appraisal 51 8.1. Effect 1: Erosion of Pagham Beach 51

8.2. Effect 2: Erosion of Existing Inlet Flood Embankments 53 8.3. Effect 3: Overtopping of Existing Inlet Flood Embankments 55 8.4. Effect 4: Impeded Drainage into the Inlet 57 9. Long Term Preferred Options 60 9.1. Consequence 1: Existing inlet channel remains open 60 9.2. Consequence 2: Inlet seals and Pagham Harbour closes 60 9.3. Consequence 3: Church Norton Spit breaches to create new inlet channel further south 62 10. Selection of Short Term Preferred Option 62 10.1. Effect 1: Erosion of Pagham Beach 63 10.2 Effect 2: Erosion of Existing Inlet Flood Embankments 63 10.3 Effect 3: Overtopping of Existing Inlet Flood Embankments 64 10.4 Effect 4: Impeded drainage into the inlet 65 11 Monitoring Programme 66 11.1 Beach and Inlet Channel Morphology 67 11.2 Pagham Harbour Sedimentation 67 11.3 Condition Assessments of Flood Embankments and Training Arm 67 12 Conclusions 68 13 Recommendations 69 APPENDIX A 70 References 1

1. Introduction

1.1. Project Objectives In June 2010, the Environment Agency commissioned a team led by Royal Haskoning to develop a geomorphological model for Pagham Harbour. The objectives of the model are to determine the present and future geomorphological behaviour of Pagham Harbour and, using this information as a basis, develop a decision framework for adaptive management of flood and coastal erosion risk. To fulfil these two objectives, the project has been undertaken in three main stages:

° Stage 1: development of an initial geomorphological conceptual model from existing information (Environment Agency, 2010); ° Stage 2: further assessments including wave, tidal, sediment and beach modelling incorporated into an updated geomorphological conceptual model (Environment Agency, 2011); and ° Stage 3: a decision framework for adaptive approaches and interventions for flood and coastal erosion risk management (this report).

Figure 1-1 provides details of how the project has developed through the three main stages.

Figure 1-1 Methodology for development of management approaches and interventions

Stage 1- Collation of Information and Initial Geomorphological Model

Data Collection and Review

Assessment of processes Gap analysis

Initial Report Data requirements and further study identified Stage 2- Further Assessments

Numerical Modelling: Historic Trend Analysis Beach, Tidal and Wave

Updated geomorphological model, scenarios and consequences Technical understanding to be applied to options

Stage 3- Management Approaches and Intervention

Assessment of consequences and effects (including modelling)

Define management triggers

Develop long and short list of options

Review option suitability Final option report

1 Environment Agency

1.2. Stage 3 Objectives

The aim of this Stage 3 decision framework report is to provide recommendations for practical management interventions at Pagham Harbour, based on the results and predictions contained in the updated geomorphological model (provided as Appendix A). The key objectives are to:

° understand the consequences of potential future geomorphological scenarios on the functioning of Pagham Harbour tidal inlet; ° define what interventions could be carried out to protect the system against flood and coastal erosion risks; ° highlight key decisions to be taken by stakeholders on the future of Pagham Harbour, based on the long-term sustainability of the site; and ° recommend a monitoring programme to strengthen the basis for adaptive management decisions.

1.3. Location of Pagham Harbour

Pagham Harbour is situated approximately 2km northeast of Selsey in West Sussex (Figure 1-2). It is a tidal inlet fronted by a dynamic shingle beach, inlet channel and spit complex described in detail in the conceptual model (Appendix A). A number of local watercourses discharge into the inlet, including Pagham Rife, Bremere Rife and The Ferry/Broad Rife. In addition, the River Lavant Flood Alleviation Scheme (FAS) from Chichester (to the north) diverts flood water into the inlet during periods of high flow.

The mouth of the inlet lies between two dynamic shingle spits which have experienced large volume changes in recent history due to changes in natural processes. Historically, the mouth (inlet channel) has varied in location as a result of changes to the position of the spits, caused by fluctuations in the supply of shingle and longshore transport. Recent dramatic changes have been observed along the southern spit (Church Norton Spit), which has extended significantly to the northeast over the past six years (Appendix A). Migration of the northern spit (Pagham Beach) is prevented by an ageing training arm at its southwest end.

A number of settlements are situated close to the inlet including Sidlesham to the northwest, Pagham to the northeast and Selsey to the southwest (Figure 1-2). The existing series of clay embankments and revetments around the inlet perimeter currently provide flood protection to these settlements and surrounding low-lying agricultural areas.

2 Environment Agency

Figure 1-2. Regional location map of Pagham Harbour (Ordnance Survey 1986).

1.4. Strategic Policy

There are a number of current policy and guidance documents relating to Pagham Harbour, which are described in the following sections.

1.4.1. Selsey Bill to Beachy Head Shoreline Management Plan Review 2010 (South East Coastal Group)

Pagham Harbour and spits are located within Policy Unit 4d25 and Pagham to Selsey East Beach are covered by the Selsey Bill to Beachy Head Shoreline Management Plan (SMP) Review. The SMP recognised the need to move towards a “more naturally functioning coastal frontage, whilst also considering the way in which the coastline is currently managed”. The selected policy for all three epochs was Managed Realignment to achieve a more naturally functioning coastline. In the first epoch (0 -20 years) the training arm would be maintained, but the groynes along Church Norton Spit would be allowed to fail to promote rollback. If required, recycling was suggested to further encourage rollback by removing shingle from the front of the beach (and the surrounding shingle banks) and placing it to the rear of the spit. It was also recognised that existing inlet flood embankments would need to be maintained and upgraded to mitigate the impacts of sea-level rise.

In the second and third epochs (20-100 years) it was anticipated that realignment of the inlet defences would commence. However, the methodology to achieve this was not specified and was “to be determined through detailed study using robust analysis of past experience, data sets and research”. These policies are superseded by the Pagham to East Head Coastal Defence Strategy (PEHCDS) reviewed below which looks at the area in more detail.

3 Environment Agency

1.4.2. Pagham to East Head Coastal Defence Strategy 2009 (South East Coastal Group)

The Pagham to East Head Coastal Defence Strategy (PEHCDS), completed in 2009, identified that for a 1 in 200 year event (0.5% Annual Exceedence Probability (AEP)), occurring in 2008, 302 properties were at risk of flooding at Pagham Harbour (Environment Agency, 2009a). This number was predicted in the Strategy to rise to 1,303 properties by 2108, with 333 properties being written off over this period due to flooding and coastal erosion. Other assets identified as ‘at risk’ included the main access road to Selsey (B2145), Pagham Wastewater Treatment Works and a scheduled monument. The defences are predicted to currently offer a 2% Standard of Protection (SoP) and have a residual life of 20 years.

Given the level of uncertainty in this rapidly changing system (Appendix A), the preferred option selected for this frontage was Adaptive Management. “Specific actions in the short term would be to maintain Pagham Harbour as an intertidal system, develop a solution to the erosion of Pagham Beach, investigate opportunities for recycling material from the adjacent Aldwick Bay and to consider the need for new inner harbour flood defences to protect against rising sea levels”. In order to prevent a channel connecting between Medmerry and Pagham Harbour the strategy suggests the construction of five new bunds to provide a 1 in 200 year (0.5% AEP) SoP (Figure 1- 3). The options assessed in the PEHCDS are based on the tidal inlet remaining open.

4 Environment Agency

Figure 1-3 Key Plan 6 – Pagham Harbour Plan (Environment Agency, 2009a).

5 Environment Agency

1.4.3. Arun and Western Streams CFMP (2009)

Pagham Harbour is located within Policy Unit 13 Manhood Peninsula and rural Chichester Harbour covered by the Arun and Western Streams Catchment Flood Management Plan (CFMP) (Environment Agency, 2009b). A large part of this policy unit is characterised by low-lying coastal plains and artificial drainage channels. The CFMP identifies that the risk of flooding in these areas is moderate with 175 properties at risk, but likely to increase in the future to 205 properties. The CFMP does not consider coastal flooding or erosion; hence a lower number of properties are at risk than described in the PEHCDS.

An extensive network of ditches provides land drainage for this unit. The standard of protection provided by this system is highly variable; however it typically provides protection up to a 3% AEP flood event. A number of outfalls drain into Pagham Harbour, including the River Lavant Flood Alleviation Scheme (FAS). This scheme consists of bypass channels which direct excess flows into Pagham Rife and is designed to protect Chichester up to a 1.3% AEP flood event. These outfalls are gravity fed, with the exception of The Ferry, which is augmented by pumping. The key flood risk management approaches for the policy unit are:

° reduce or prevent an increase in flood risk to critical infrastructure, communication and transport links; ° sustain and improve the status of international and national designated conservation sites; ° sustain and increase the amount of priority habitats and species in the catchment in line with Biodiversity Action Plan (BAP) targets; ° enhance the character and leisure, recreation and amenity value of the landscape; ° reduce or prevent an increase in the economic damages from flooding to cities, towns and commercial property in the catchment; and ° reduce or prevent an increase in the economic losses from flooding to agricultural land in the catchment.

The CFMP preferred policy for this unit is:

Continue with existing or alternative actions to manage flood risk at the current level (accepting that flood risk will increase over time from this baseline).

1.4.4 South East River Basin Management Plan (2009) and the Water Framework Directive

The Water Framework Directive (2000/60/EC) (WFD) was adopted by the European Commission in December 2000 and established a common framework for the management of the water environment across all European Member States. The main aims of the Directive are to protect and enhance the aquatic ecosystem, promote sustainable water use, reduce pollution of the aquatic environment, and mitigate the effects of floods and droughts.

The WFD was transposed into law in England and Wales by the Water Environment (Water Framework Directive) (England and Wales) Regulations 2003. The regulations mean that the requirements of the WFD need to be considered at all stages of the planning and development process (including during the development of strategies and schemes). The WFD requires that environmental objectives are set for all surface and ground waters in each EU Member State. The default environmental objectives for surface waters are shown in Table 1.1.

6 Environment Agency

Table 1.1 Environmental objectives for surface waters in the WFD

Objectives (taken from Article 4 of the Directive) Reference Article Surface Water Member States shall implement the necessary measures to prevent deterioration of the status 4.1(a)(i) of all bodies of surface water Member States shall protect, enhance and restore all bodies of surface water, subject to the 4.1(a)(ii) application of subparagraph (iii) for artificial and heavily modified bodies of water, with the aim of achieving good surface water status by 2015. Heavily Modified and Artificial Water Bodies Member States shall protect and enhance all artificial and heavily modified bodies of water, 4.1(a)(iii) with the aim of achieving good ecological potential and good surface water chemical status by 2015. Progressively reduce pollution from priority substances and cease or phase out emissions, 4.1(a)(iv) discharges and losses of priority hazardous substances.

Specific mitigation measures are set for water bodies to achieve the environmental objectives of the WFD. Those that are applicable to Pagham Harbour and adjacent water bodies are listed within the Programme of Measures for the South East River Basin Management Plan (RBMP) (Environment Agency, 2009). These measures are intended to mitigate impacts that have been or are being caused by human activity, such as flood and coastal defence works, with the aim of enhancing and restoring the quality of the existing environment.

The RBMP includes a range of generic measures for application to water bodies in the River Basin District. Annex B also includes specific measures that have been identified as necessary to improve the ecological potential of Artificial or Heavily Modified Water Bodies (A/HMWBs). In addition, Annex D includes details of the measures that are required to maintain or improve Protected Areas such as the Pagham Harbour Special Protection Area (SPA) at Favourable Condition Status. Further details of specific measures identified for the water bodies within the Pagham area are provided in Section 2.4.

The WFD therefore needs to be considered from a compliance perspective, to ensure that any proposed actions do not cause deterioration in water body status, and as a potential mechanism for the delivery of measures to improve the water bodies and protected sites within and adjacent to Pagham Harbour.

1.5 Report Structure

This report comprises five sections of which this introduction is Section 1. Section 2 provides an overview of the potential flood and coastal erosion risks at Pagham Harbour. Section 3 outlines the suite of geomorphological scenarios initially discussed in the conceptual model (Appendix A), and their consequences on the position of the tidal inlet channel, and the effects these changes have on other parts of the system. Section 4 discusses adaptive management and monitoring at Pagham Harbour and recommends appropriate management interventions associated with the set of geomorphological states highlighted in Section 3. Section 5 presents a summary of the adaptive management process.

7 Environment Agency

2. Defining the Issues

At the outset of any project or planning initiative at Pagham Harbour it is important to have a clear understanding of the issues to be addressed. Three important steps need to be taken before adaptive management can be implemented:

• the temporal and spatial scales of the issues have to be determined; • the issues have to be placed into the legislative frameworks; and • the issues have to be defined within the framework of the conceptual model.

This section defines the current issues at Pagham Harbour within these contexts.

2.1. Coastal Erosion Risk

The conceptual model (Appendix A) highlights that the main short-term (0-10 years) risk is continued erosion and narrowing of Pagham Beach and flooding of Pagham Beach Estate. Two main causes were discussed:

• depletion of shingle along Pagham Beach is taking place along a sediment transport divide in front of Pagham Beach Estate in proximity to the groyne field. The transport divide is caused by a net southwest-directed longshore sediment transport along Pagham Beach in the lee of Church Norton Spit and a net northeast-directed longshore sediment transport east of the groyne field. The coastline at the divide is characterised by erosion because sediment is transported away in opposing directions resulting in a sediment deficit. The position and length of Church Norton Spit across the inlet mouth controls the position of the shingle transport divide; and • the rapid growth and extension of Church Norton Spit has deflected the inlet channel to flow parallel to and close to the beach in front of Pagham Beach Estate, inducing tidal current scour of the beach.

An analysis was carried out in the conceptual model (Appendix A) using a set of digital terrain models (DTMs) between 2003 and 2011. The aim was to determine the change in position of the crest of the beach relative to Pagham Beach Estate, identifying cross-shore beach migration rates over the past eight years. The analysis was carried out between the most southerly house and the northern limit of the 2003-2011 data at Pagham Yacht Club (Figure 2-1).

8 Environment Agency

Figure 2-1 Extent of digital terrain model analysis along Pagham Beach

The results indicate that between March 2003 and January 2009, the average back of beach width decreased by approximately 5.2m from 40.2m to 35.0m (equating to an average erosion rate of 0.9m/year). Between January 2009 and February 2011, the average beach width increased by approximately 3.4m from 35.0m to 38.4m (equating to an average accretion rate of 1.7m/year). The minimum width has shown a similar trend, decreasing by approximately 2.9m from 27.6m to 24.7m between March 2003 and December 2009, before increasing by approximately 1.5m from 24.7 to 26.2. These trends suggest that the beach narrowing may have been reversed in 2009 by the implementation of beach bypassing and nourishment activities.

An erosion rate of 0.9m/year has been assumed to predict when these triggers are likely to be reached, assuming the system reverses to an erosional trend again. Figure 2-2 indicates that if erosion continues at the historic rate of 0.9m/year the Warning trigger will be reached in six years with action being required in 12 years. This prediction is based on the current minimum berm width and is subject to fluctuations.

Environment Agency 9 Figure 2-2 Predicted erosion rate of minimum berm width assuming an average rate of

0.9m/year

Environment Agency 10 2.2. Drainage into Pagham Harbour

Figure 2-3 is a location plan detailing the structures that control drainage into Pagham Harbour and Table 2-1 provides details of the structures.

Figure 2-3 Location plan of drainage into Pagham Harbour

Environment Agency 11

Table 2-1 Description of existing inlet defences from NFCDD

Replacement Target Condition Actual Condition ID Asset Description Grid Reference Asset Location Cost (£K) Grade Grade

Asset_01 Flapvalve SZ8785897680 Little Welbourne 4000 3 3

Asset_02 Twin Flapvalve SZ8787497726 Little Welbourne 4000 3 3

Asset_03 Flapvalve SZ8742195427 East of Norton Priory N/A 3 3

Asset_04 Outfall and Concrete Headwall SZ8715197452 16500 3 3

Asset_05 Flapvalve SZ8699197645 Halsey's Farm 4000 3 3

Asset_06 Outfall and Concrete Headwall SZ8642997268 16500 3 3

Asset_07 Flapvalve SZ8634396489 N/A 3 3

Asset_08 Flapvalve SZ8636096500 800 metres east of Ferry outfall N/A 3 3

Asset_09 Twin Flapvalve SZ8608297271 Mill Lane, Sidlesham N/A 3 3

Asset_10 Ferry Pumphouse Outfall SZ8565696291 5000 3 3

12 Environment Agency

Pagham Harbour provides land drainage to the catchment via four main outfalls; Broad Rife, Bremere Rife, Keynor Rife and Pagham Rife, supplemented by runoff from the surrounding agricultural land. Flow along Broad Rife is pumped into the inlet by Ferry Pumping Station (Asset 10), as parts of the Rife have restricted capacity and become tidally locked. This has a potentially significant impact on flood risk to local assets due to the low-lying nature of the surrounding area. Bremere Rife flows from Mundham into Pagham Harbour, discharging via a gravity tidal flap gate outfall (Asset 05).

Historical evidence suggests that Pagham Rife was formerly the downstream reach of the River Lavant. The River Lavant was diverted through Chichester to provide a source of water for the town at some point prior to the early eighteenth century, and now drains into Chichester Harbour through the Fishbourne Channel upstream of Apuldram. Pagham Rife remains as the remnant of the original river, draining southwards from the southern edge of Chichester.

After large floods in 1994 and 2000, a scheme was implemented to divert high flows away from Chichester town centre through a bypass channel and into Pagham Harbour. This scheme known as the River Lavant Flood Alleviation Scheme starts at Westhampnett Mill, east of Chichester before flowing through a number of channels and discharging via a tidal flap gate outfall at Pagham Harbour (Asset 02). The scheme covers 13km of river and is designed to operate when river discharges are above 4.1m3s-1. Compared to the tidal prism of the harbour (3.3Mm3 on a mean spring tide; Appendix A), this is a negligible volume of water and therefore has little effect on the geomorphology of the inlet.

The conceptual model (Appendix A) concluded that sedimentation is occurring within the inlet at a rate of 4-8mm/year. It is possible that drainage may become impeded in future if Pagham Harbour continues its current trend of siltation as it may eventually be naturally filled. This may lead to closure of the inlet mouth, due to reduction of the tidal prism below is the level required to maintain a stable inlet. In addition, increased maintenance of gravity outfalls may be needed to prevent them from becoming blocked.

2.3. Flood Risk

The main medium (10-50 years) to long-term (50-100 years) risk at Pagham Harbour identified in the conceptual model (Appendix A) is flooding from the inlet. The conceptual model highlights two potential causes:

• risk related to a combination of continued siltation and raising of water levels due to climate change induced sea-level rise; and • catastrophic flooding induced by storm surge combined with sea-level rise.

The most significant potential source of flooding is likely to be from the sea (coastal/tidal) especially as sea levels rise. To ascertain flood risk, water levels from the tidal modelling of typical spring tide, sea-level rise and storm surge conditions were overlain on to LiDAR data to produce flood extents without defences (Figures 2-4 to 2-6) (Appendix A). The flood extents show the risk to Sidlesham and Pagham will increase in the future if defences are not raised.

13 Environment Agency

Figure 2-4. Potential flood extent without defences under typical spring tide conditions (2.66m ODN).

Figure 2 -5 Potential flood extent without defences under sea-level rise conditions (3.15m ODN).

Environment Agency 14 Figure 2-6 Potential flood extent without defences under sea level rise and storm surge conditions (3.91m ODN).

The inlet defences consist primarily of earth embankments, masonry walls and revetments and currently provide protection against a 1 in 20 year (5% AEP) event (Figure 2-7). Details of the defences from the National Flood and Coastal Defence Database (NFCDD) are provided in Table 2-3.

All the defences are currently meeting their target condition grade and providing the design SoP. However, Assets 09 and 10 will be overtopped under a surge condition and all defences are anticipated to be overtopped in the future due to climate change (Table 2-4).

Environment Agency 15 Figure 2-7 Location plan of existing inner harbour defences

Environment Agency 16

Table 2-3 Description of existing inlet defences from NFCDD Asset Actual Crest Effective Erosion Target Actual Design Grid ID Asset Description Length Standard Level Crest Level Rate Condition Condition Standard Reference (m) * (mOD) (mOD) (m/yr) Grade Grade** Asset_01 Foreshore & Rock Embankment 237.9 20 20 N/A 3.78 SZ8787197671 3 3 Asset_02 Foreshore & Rock Revetment 262.8 20 20 N/A 3.91 SZ8764097731 3 3 Asset_03 Foreshore & Concrete Armoflex 229.9 20 20 N/A 3.9 SZ8715097715 3 3 Asset_04 Foreshore & Rock Revetment 260.5 20 20 N/A 3.87 SZ8739097782 3 3 Asset_05 Earth embankment face and crest 1260.2 N/A N/A 3.89 N/A < 0.5 SZ8686396341 3 3 Asset_06 Foreshore & Rock Armour 93 20 20 N/A 3.65 SZ8591796610 3 3 Asset_07 Foreshore & Masonry Wall 25.5 20 20 N/A 3 SZ8618397267 3 3 Asset_08 Foreshore & Masonry Wall 125.4 20 20 N/A 3.15 SZ8630497234 3 3 Asset_09 Foreshore and Earth Embankment 187.2 20 20 N/A 3.5 SZ8648197288 3 3 Asset_10 Earth Embankment & Stone Revetment 143.7 20 20 N/A 3.28 SZ8707397297 3 3 Asset_11 Foreshore and Concrete Armoflex 38.3 20 N/A N/A N/A SZ8699497608 3 3 Asset_12 Foreshore & Masonry Wall 157 20 20 N/A 3.6 SZ8783397520 3 3 Asset_13 Shingle Ridge & Steel Sheet Piling 227.9 50 50 N/A 4.2 SZ8807596143 4 4

Note * Standard as of 01/03/2006 ** Standard as of 01/03/2006

A colour coded system has been used to indicate whether target conditions are reached as below.

Condition met Condition exceeded Not Applicable

17 Environment Agency

Table 2-4 Comparison of water levels from the tidal modelling with the effective crest height of existing inlet defences Spring Tide Sea-level Rise Sea-level Rise + Actual Effective Crest ID Water level Water level Storm Surge Water Standard* Level (mOD) (mOD) (mOD) level (mOD)

Asset_01 20 3.78 2.66 3.15 3.91

Asset_02 20 3.91 2.66 3.15 3.91

Asset_03 20 3.9 2.66 3.15 3.91

Asset_04 20 3.87 2.66 3.15 3.91

Asset_05 N/A N/A 2.66 3.15 3.91

Asset_06 20 3.65 2.66 3.15 3.91

Asset_07 20 3 2.66 3.15 3.91

Asset_08 20 3.15 2.66 3.15 3.91

Asset_09 20 3.5 2.66 3.15 3.91

Asset_10 20 3.28 2.66 3.15 3.91

Asset_11 N/A N/A 2.66 3.15 3.91

Asset_12 20 3.6 2.66 3.15 3.91

Asset_13 50 4.2 2.66 3.15 3.91 Note * Standard as of 01/03/2006

2.4. Environmental Designations

Pagham Harbour has international designations as a SPA and Ramsar site, which is nationally important for breeding bird populations and wintering wildfowl and waders (Bray and Cottle, 2003). The site is designated due to the important habitats it supports, including saltmarsh, intertidal mudflats, shingle, wet grassland, reed swamp, lagoons and open coastal water. The mudflats are particularly rich in invertebrates and algae, and therefore provide important feeding habitats for wading birds. The saltmarsh supports breeding populations of little tern (Sterna albifrons) in summer and wintering populations of pintail (Anas acuta) and ruff (Philomachus pugnax).

The shoreline, intertidal area and large areas of the inlet margins are within the Pagham Harbour Site of Special Scientific Interest (SSSI), which has been designated for a range of features including freshwater habitats, wet permanent grassland, open water, reed swamp, saline lagoons, vegetated shingle, saltmarsh and mudflats. In addition to ecological features, the SSSI has also been designated because of its geological and geomorphological importance. Pagham Harbour, and particularly Church Norton Spit, are considered to be key sites for coastal geomorphology and processes, due to the clearly demonstrated linkages between coastal nearshore and offshore forms, water circulation and sediment distribution. The shingle spits and beach fronting Pagham

18 Environment Agency

Harbour are also designated as a Geological Conservation Review (GCR) series site for their coastal landforms and exposures of fossil rich London Clay (which is also part of the SSSI).

The Pagham Harbour designations (SPA, Ramsar and SSSI) have a seaward boundary that follows mean low water and is described on maps as ‘liable to change’. This means that coastal landforms that accrete significantly (such as Church Norton Spit) will continue to be part of all three designations as mean low water migrates with the change in morphology. The biological and geomorphological interests of the site are considered to be of equal importance for conservation and would therefore need to be considered together to find an integrated solution that balances potential impacts and delivers maximum benefit for each interest.

Recent legislation, in the form of the Marine and Coastal Access Act (2009) has created a new type of Marine Protected Area (MPA), called a Marine Conservation Zone (MCZ). MCZs, together with other types of MPA (e.g. SACs, SPAs) will deliver the Government’s aim for an ecologically coherent network of MPAs. Pagham Harbour (dMCZ 25.1) is particularly important as the only place where Defolin’s lagoon snail (Caecum armoricum) occurs in the project area, and only one of three places where this species is found in the UK. It lives in salty water caught between shingle particles. It is possible that a recommendation will be made for the area of Pagham Harbour where Defolin’s lagoon snail is present to be designated as a reference area. The possibility of a reference area on Church Norton Spit will have to be considered in all the potential adaptive management options.

2.5. Water Framework Directive Classification

Pagham Harbour and the adjacent coastal waters and rivers are divided into six distinct water bodies in the South East RBMP (Table 2-5 and Figure 2-8). These water bodies have been extensively altered by anthropogenic activities, and have therefore generally been classified as Artificial or Heavily Modified Water Bodies (A/HMWBs). They are typically at Moderate Ecological Potential (MEP), with additional mitigation measures required to achieve Good Ecological Potential (GEP) after 2015.

Table 2-5 Key characteristics of water bodies in the Pagham Harbour area

Water Predicted Hydromorphological Current body Water body ID Type status/potential status status/potential name by 2015 Pagham GB670704700000 Coastal Artificial MEP MEP Harbour Sussex GB640704540003 Coastal Heavily Modified MEP MEP Pagham GB560704117300 Transitional Artificial MEP MEP Lagoon Pagham GB107041012880 River Heavily Modified MEP MEP Rife Moderate Moderate Bremere Not designated GB107041006610 River Ecological Ecological Rife A/HMWB Status Status Broad Not designated Bad Ecological Bad Ecological GB107041006580 River Rife A/HMWB Status Status

Environment Agency 19

Figure 2-8 Location of water bodies in the Pagham Harbour area

Pagham Harbour tidal inlet is an artificial coastal water body that is currently at MEP due to inappropriate drainage, pressures on macroalgae populations and high dissolved organic nitrogen concentrations. Annex D of the RBMP states that direct management is required to improve the site to Favourable Conservation Status, and suggests that this should be operational no later than 2012. This measure is also applicable to the other water bodies listed in Table 2-5.

Pagham Rife is at MEP due to pressures on fish and invertebrate populations and inappropriate dissolved oxygen and phosphate concentrations. In addition to the general measure listed in Annex D, Annex B of the RBMP lists three mitigation measures that are not yet in place, and therefore need to be implemented to achieve GEP:

• retain marginal aquatic and riparian habitats (channel alteration); • re-open existing culverts; and • increase in-channel morphological diversity.

Broad Rife is at MEP due to poor invertebrate populations and inappropriate ammonia, dissolved oxygen and phosphate concentrations. The adjacent Pagham Lagoon and Bremere Rife water bodies are also at MEP, although the RBMP does not provide a detailed justification for this classification. The RBMP does not include any specific mitigation measures for these water bodies, other than the direct management required for Pagham Harbour SPA as a whole.

The Sussex coastal water body is also at MEP, although the RMBP does not provide a detailed justification for this classification. Annex B of the RBMP lists a range of mitigation measures in addition to the general measure required for the SPA, none of which are yet in place:

• manage disturbance; • site selection (dredged material disposal) (e.g. avoid sensitive sites); • sediment management; • operational and structural changes to locks, sluices, weirs, beach control, etc;

Environment Agency 20 • preserve and where possible enhance ecological value of marginal aquatic habitat, banks and riparian zone; • managed realignment of flood defence; • bank rehabilitation/re-profiling; • preserve and, where possible, restore historic aquatic habitats; and • removal of hard bank reinforcement/revetment, or replacement with soft engineering solution.

3. Geomorphological Scenarios, Future Consequences and Effects

The conceptual model (Appendix A) describes a set of potential changes to the Pagham Harbour physical and sedimentary processes and the sensitivity of the potential responses of the system to those changes. Given that freshwater input to the inlet is low, changes in two parameters mainly control how the Pagham Harbour system functions; the rate of shingle supply and the volume of the inlet tidal prism. Potential future changes in these two parameters are used to build five future scenarios:

° Scenario 1: shingle inputs to Church Norton Spit decrease or cease; ° Scenario 2: shingle inputs to Church Norton Spit continue (or increase); ° Scenario 3: inlet tidal prism stays the same (approximates to siltation equalling sea-level rise); ° Scenario 4: reduced inlet tidal prism (siltation exceeds sea-level rise); and ° Scenario 5: increased inlet tidal prism (sea-level rise exceeds siltation).

The main component of the Pagham Harbour system that will change if one or more of these scenarios is applied is the position of the inlet channel. The configuration of the inlet channel has the greatest influence on the functioning of the inlet and its surroundings. The potential future consequences for the inlet channel of one or a combination of the five scenarios are:

1. Future Consequence 1: the existing inlet channel configuration is maintained; 2. Future Consequence 2: the existing inlet channel seals and Pagham Harbour closes to tidal inundation; and 3. Future Consequence 3: the existing inlet channel seals and Church Norton Spit breaches to form a new inlet channel further southwest (potentially at any location between Church Norton and the existing channel).

A flow chart detailing the potential relationships between the consequences and the geomorphological scenarios that could cause them, either on their own or in combination with other scenarios, is presented in Figure 3-1. Each potential future consequence will, in turn, set in motion a set of effects on different parts of the system that are important to flood and coastal erosion risk at Pagham Harbour. These include effects to Pagham Beach, the inlet flood embankments, drainage into the inlet, environmental considerations and Water Framework Directive (WFD) requirements. Table 3-1 describes the potential short-term (0-10 years) and long-term (50-100 years) effects on these components that could be brought about by each of the future consequences. Each of these effects relates directly to the conclusions drawn from the conceptual model (Appendix A).

Environment Agency 21 Figure 3-1 Relationships between the Future Consequences (left) and the geomorphological scenarios (right)

Environment Agency 22

Table 3-1 Potential short- and long-term effects of the future consequences on components of the Pagham Harbour system.

Pagham Beach Flood Embankments Drainage Environmental Characteristics WFD Compliance Future Consequence Short-term Long-term Long-term Short-term Long-term Short-term Long-term Long-term Short-term Effects Short-term Effects Effects Effects Effects Effects Effects Effects Effects Effects Continuing Unlikely to Siltation and Continuation Continuation of Reduced SoP. reduced SoP Siltation and Unlikely to cause cause further Existing inlet channel Eroding potential of tidal regime tidal regime with Instability Increased risk of and increased potential further deterioration deterioration in configuration and freshwater with mudflats, mudflats, continues overtopping with risk of freshwater in status. Will not status. Will not maintained unstable back-up saltmarsh and saltmarsh and sea-level rise overtopping with back-up help to deliver GEP help to deliver continues open water open water sea-level rise GEP Changes in Changes in the water body type hydromorphology Development of and Reduced risk Deferred risk and ecology of the Existing inlet channel freshwater characteristics Stable from siltation from siltation Creation of water body may seals and Pagham Stable and Reduced risk Reduced risk lagoon / marsh could and and increased and increased brackish cause deterioration Harbour closes to accreting (water levels) (water levels) (may be some potentially allow accreting risk from fresh risk from fresh lagoon in status. Will not tidal inundation brackish GEP to be water back-up water back-up deliver the direct influence) achieved over management longer measure timescales. Reduced SoP. Increased risk of Continuing Unlikely to Existing inlet channel Siltation and Continuation Continuation of overtopping with reduced SoP Siltation and Unlikely to cause cause further seals and Church Stable potential of tidal regime tidal regime with Becoming sea-level rise. and increased potential further deterioration deterioration in Norton Spit breaches and freshwater with mudflats, mudflats, less stable Local changes to risk of freshwater in status. Will not status. Will not to create a new inlet accreting back-up saltmarsh and saltmarsh and risk due to overtopping with back-up help to deliver GEP help to deliver further southwest continues open water open water channel re- sea-level rise GEP organisation A colour coded system has been used to indicate the degree of opportunity or constraints Positive impacts likely No change or little / unknown impact overall Negative impacts likely

23 Environment Agency

3.1. Do Nothing Effects of Future Consequence 1: Existing inlet channel remains open

3.1.1. Effects on Pagham Beach

The conceptual model (Appendix A) shows that over the past six years, Church Norton Spit has grown rapidly to the northeast causing the tidal inlet channel to curve and migrate northeast with the spit. The reasons for the increase in shingle supply to feed this growth have not been ascertained. The growth of the spit has exacerbated erosion along Pagham Beach due to the creation of a transport divide where shingle is moved away from a zone causing the beach to gradually recede (Figure 3-2). This focus of erosion has shifted northeast as the spit has migrated and is currently located in the vicinity of the suite of four groynes at the south end of Pagham Beach. Future elongation of the spit and maintenance of the tidal inlet channel will lead to continued short-term and long-term erosion and instability of Pagham Beach (although the focus of erosion may shift further to the northeast). The 2003-2009 trend of movement of the crest of the beach between the most southerly house of Pagham Beach Estate and Pagham Yacht Club has been landward at an average rate of 0.9m/year. Over the past couple of years the average trend has been seaward at a rate of 1.7m/year (probably in response to beach bypassing and recharge that took place in 2009 and 2010).

Figure 3-2 Physical processes of Future Consequence 1

3.1.2. Effects on Flood Embankments

Maintenance of the tidal inlet channel into the future will mean that Pagham Harbour will remain open to tidal inundation and will continue to respond to changes in marine physical forcing factors. The most important factor with respect to the standard of defence provided by the flood embankments will be future sea-level rise. UKCP09 predicted a long-term sea-level rise of 0.5m by 2095 (from a 1990 baseline), which will reduce the standard of protection from the 1 in 20 currently afforded by the embankments and increase the likelihood of overtopping or failure. As discussed in

24 Environment Agency

Section 2.3, as water levels rise due to climate change the embankments may fail resulting in overtopping and increased risk of breach (Table 2-4).

3.1.3 Effects on Drainage of Surrounding Area into the Inlet

The conceptual model (Appendix A) describes the rate of historic sedimentation in the inlet to be around 4-8mm/year over the 20th century, with the highest rates at the landward edges. If the inlet channel is maintained, this rate is likely to continue into the future resulting in exacerbation of back- up of freshwater through increased potential to block the tidal flaps gates at the downstream end of the rifes. This will be both a short-term and long-term phenomena.

3.1.4 Effects on Environmental Characteristics

An open tidal inlet channel will mean continuation of the natural shingle transport processes along Church Norton Spit, maintenance of the tidal regime within Pagham Harbour and continued accretion on the existing mudflats and saltmarshes. Changes in the short-term and long-term area of saltmarsh, mudflat and tidal channel habitats will depend on the rate of sedimentation compared to sea-level rise and the distribution of deposition across the inlet. Historical data suggests that sedimentation should be able to keep pace with future sea-level rise, resulting in general stability of intertidal habitat in the inlet.

3.1.5 Effects on WFD Compliance

The retention of the existing tidal inlet channel will maintain the current hydromorphological, ecological and hydrochemical conditions within the inlet and connected water bodies. This means that this consequence is unlikely to cause any further deterioration in water body status. However, the consequence does not offer any opportunities to improve water body status and does not deliver the direct management measure recommended in Annex D of the RBMP.

3.2. Do Nothing Effects of Future Consequence 2: Inlet seals and Pagham Harbour closes

3.2.1. Effects on Pagham Beach

Closure of the inlet channel would allow shingle from the remnant Church Norton Spit to be transported and accreted on to Pagham Beach. The sediment transport divide would cease to exist and alongshore and cross-shore sediment transport processes to the northeast would dominate to feed Pagham Beach and Aldwick Beach in both the short- and long-term (Figure 3-3). Pagham Harbour would be fronted by a barrier beach with transport connectivity from Selsey through to Aldwick. Shoreline evolution modelling as part of the conceptual model shows that a closed inlet channel has the potential to reduce recession of Pagham Beach by half in five years to the east of the groyne field (Appendix A). In the long-term, this rate of retreat is likely to reduce further until this part of the beach becomes stable / accretional. It is likely that along the beach closer to the distal end of the remnant spit, the reversion to accretion would be more rapid.

Environment Agency 25 Figure 3-3 Physical processes of Future Consequence 2

Wave and Tidal driven transport Wave driven transport Freshwater permeating shingle barrier h c a e B m a h g a P Pagham Harbour

h c a e B r ie rr a B

Relict barrier beach and ebb delta deposits associated with past inlet positions.

3.2.2. Effects on Flood Embankments

Closure of Pagham Harbour would disconnect the inlet from tidal inundation and sea-level rise. Hence, closing the inlet channel would reduce the short-term risk of coastal and tidal flooding of the areas behind the embankments. There would also be a reduced risk to the integrity of the flood embankments from marine physical processes. In the long-term, the risk may increase due to the potential for a breach of the shingle barrier beach because of future sea-level rise and increased storm frequency and intensity.

3.2.3. Effects on Drainage into the Inlet

There is currently a limited risk of river flooding from the watercourses that discharge into Pagham Harbour through outfalls. If the tidal inlet channel closes the risk may increase. Although the shingle barrier may be permeable initially, as sedimentation (from material transported into the lagoon from rivers) occurs in the longer term, permeability may be reduced leading to a pooling of flow in the inlet. If the pooling is not dissipated, the water could potentially overtop the current flood embankments and block the discharge of flow from outfalls into the inlet.

3.2.4 Effects on Environmental Characteristics

Closure of the inlet channel would lead to loss of tidal inundation of Pagham Harbour inducing major changes in habitats. In the short term (probably less than five years), saltmarsh and mudflat habitats would be replaced by a brackish lagoon as Pagham Harbour gradually becomes filled with freshwater from the rifes. A degree of saltwater may infiltrate the more seaward parts of the harbour because the shingle may be permeable. In the long-term, further transformation of habitat to freshwater lagoon and marsh would take place as the discharge from the rifes becomes dominant.

Environment Agency 26 3.2.4. Effects on WFD Compliance

Over shorter timescales, the closure of the tidal inlet is likely to cause considerable changes to the hydromorphology and ecology of the water body. This has the potential to cause deterioration in water body status, and will not deliver the direct management measure proposed in the RBMP. Over longer timescales, the hydromorphological changes may support different ecological communities (or the existing communities in differing proportions). This may present opportunities to achieve GEP.

3.3. Do Nothing Effects of Future Consequence 3: Church Norton Spit breaches to create new inlet channel further south

3.3.1. Effects on Pagham Beach

A breach of Church Norton Spit would create a new inlet channel further southwest with a more perpendicular alignment to the coast (Figure 3-4). The conceptual model suggests that the existing inlet channel would be cut off from the tidal flows that maintained it and the portion of the spit to the east of the new channel would be cut-off from its source of sediment (Appendix A). In the short- term the remnant spit would be reworked by waves in alongshore and cross-shore directions, infilling the existing channel with shingle. The sediment transport divide would dissipate and the net northeasterly transport of shingle would promote short-term accretion and stability of Pagham Beach (and Aldwick Beach). Assuming that the new inlet channel is maintained, Pagham Beach will become less stable in the long-term as the provision of shingle from the remnant spit is gradually depleted and transported to the northeast along Pagham Beach. Assuming a shingle volume of 325,000m3 (above the -1m ODN contour in February 2011) in Church Norton Spit, a transport rate of 30,000m3/year, it would take approximately eleven years to redistribute shingle along Pagham Beach. As shingle moves past Pagham Beach it will benefit frontages further downdrift (e.g. Aldwick).

Environment Agency 27 Figure 3-4 Physical processes of Future Consequence 3

3.3.2 Effects on Flood Embankments

The conceptual model shows that creation of a new inlet channel and closure of the existing channel will lead to a lowering of peak water levels by approximately 0.11-0.14m inside Pagham Harbour (Appendix A). The exposure of the flood embankments to sea-level rise would be slightly reduced compared to that for the existing inlet channel in place. There may also be local changes in risk associated with channel migration and re-organisation within the inlet due to the new position of the channel. There may be local impacts on the flood banks near to any new inlet channel.

3.3.3 Effects on Drainage of Surrounding Area into the Inlet

Unless the lowering of water levels induces major changes in the sedimentary processes within the inlet, the effects on drainage of the surrounding areas will be similar to those for the existing inlet channel in place (Section 3.1.3).

3.3.4 Effects on Environmental Characteristics

The opening of a new channel means that Pagham Harbour will continue to be inundated on high tides and drained on low tides. However, the lowering of peak water levels, up to 0.14m (approximately), could potentially affect the configuration of saltmarsh, mudflat and tidal channel areas. The natural geomorphological processes inherent to the designation of Pagham Harbour would only be upset if the breach was artificially induced. A breach caused by natural processes (e.g. a reduction in shingle supply) is considered a natural process and in line with the geological SSSI designation.

Environment Agency 28 3.3.4 Effects on WFD Compliance

The creation of a new tidal inlet channel may cause localised changes to the hydromorphology and ecology of the inlet, although the overriding conditions are likely to be maintained. This means that this option is unlikely to cause any further deterioration in water body status. However, the option does not offer any opportunities to improve water body status and does not deliver the direct management measure recommended in Annex D of the RBMP.

4. Adaptive Management

Adaptive management at Pagham Harbour considers the system as a series of future potential geomorphological ‘states’ in its sequential evolution and recommends appropriate management interventions associated with each state. Adaptive management is adopted because the Pagham Harbour system is extremely dynamic and a single long-term scheme to manage the inlet and its channel is not considered appropriate.

Adaptive management of Pagham Harbour is driven by geomorphological management triggers; points at which the system is potentially changing from one state to another. After the trigger is reached, the trajectory of change may lead to undesirable results and management intervention is appropriate. The determination of when a particular trigger is reached is based on monitoring; the triggers are set at a low threshold so that adaptive management will be implemented before adverse impacts occur. If assessment of monitoring results shows that no management trigger has been activated, then no management action is required.

The adaptive management process applies to the Pagham Harbour system as a whole, but management actions can be identified and implemented on individual elements of the system (e.g. Pagham Beach), as needed. The process is flexible as it allows for a wide range of management actions but it also imposes a structured approach as the need for intervention must derive from monitoring results.

In adaptive management at Pagham Harbour, each of the future consequences (geomorphological states) and their effects represent the policy decisions that need to be made; whether or not to intervene in order to allow, slow down, prevent or reverse them. A number of management triggers have been defined to indicate when the inlet is moving into a different geomorphological state (Table 4-1). Three trigger levels are defined:

• Level 3 Warning Trigger: appraise viable options and secure funding for works; • Level 2 Action Trigger: undertake works for preferred option; and • Level 1 Emergency Trigger: failure is imminent so undertake works immediately.

Environment Agency 29

Table 4-1 Geomorphological management triggers for Pagham Harbour

Warning Action Emergency Consequence/Effect Description Justification Monitoring Required Trigger Trigger Trigger The distance of re-curve at the distal end of Currently the inlet channel is between Geometries of Church Church Norton Spit from Pagham Beach at 95 and 155m wide at mean low water, 70m 50m 30m Norton Spit and inlet channel mean high water neap tide. increasing in width seaward (aerial photographs, beach Natural closure of the profiles and LiDAR) existing inlet channel The water depth on a mean low water neap Currently the water depth is around Condition assessments of tide at the seaward end of the inlet channel 1.6m 1.2m 0.8m 2.5m at mean low water neap existing training arm (survey shallows due to shingle build-up and visual observation)

The beach berm crest height at any point along Church Norton Spit between Church Predicted using beach profile Norton and the training arm lowers to the response modelling as part of the 5.3m AOD 5.1m AOD 4.9m AOD minimum height for a 200-year standard of conceptual model (Appendix A) Changes in geometry of Natural opening of a new protection (including sea-level rise) Church Norton Beach/Spit inlet channel to the south (aerial photographs, beach The beach berm crest width at any point profiles and LiDAR) along Church Norton Spit narrows to Predicted using beach profile minimum width for a 200-year standard of response modelling as part of the 14m 12m 10m protection (including sea-level rise) against conceptual model (Appendix A) breaching

The beach berm crest height at any point in Predicted using beach profile front of Pagham Beach Estate lowers to the response modelling as part of the 5.3m AOD 5.1m AOD 4.9m AOD minimum height for a 200-year standard of conceptual model (Appendix A) protection (including sea-level rise) Changes in geometry of Erosion of Pagham Beach Church Norton Beach/Spit (existing inlet channel The back of beach width (the distance from (aerial photographs, beach remains open) the beach berm crest to the most seaward Currently the minimum back of beach profiles and LiDAR) house) at any point in front of Pagham 20m 15m 10m Beach Estate width is approximately 25m

30 Environment Agency Warning Action Emergency Consequence/Effect Description Justification Monitoring Required Trigger Trigger Trigger Condition assessments of Erosion of existing inlet Structural integrity and condition of earth Condition Condition Condition the flood embankments N/A flood embankments embankment Grade 3 Grade 4 Grade 5 (survey and visual observation)

Topographic surveys of embankment crest heights and widths. Define Overtopping of existing The volume and frequency of overtopping N/A N/A* N/A* N/A* overtopping and freeboard inlet flood embankments using numerical modelling based on latest water level and sea-level rise estimates

Sediment accretion (or Projections based on accretion at the erosion) measurements local Drainage into the inlet is outfall suggests an unacceptable possibility to the outfalls N/A N/A** N/A** N/A** impeded (to be quantified) that drainage into the inlet (sedimentation-erosion will be prevented tables, plates, survey transects)

Notes

* The triggers to address overtopping of existing flood embankments have not been addressed as part of this study but should be considered for holistic future management of the system. ** The triggers have not been defined as part of this study as acceptable tolerances will vary between outfalls, however the outfalls should be maintain clear of sediment at all times

Environment Agency 31

4.1. Long List of Adaptive Management Options

The overall purpose of adaptive management at Pagham Harbour is to provide recommendations for management options that could be used in response to particular situations that might arise once a management trigger has been reached. Against each future consequence and effect a long list of potential management options has been identified including both structural and non-structural measures. Generally, these options seek to rectify direct or indirect adverse affects on flooding and/or erosion in both the short-term and long-term. The long list of potential management options is presented in a series of tables in Appendix B.

The opportunities and constraints of each option in the long list have been assessed against a set of appraisal criteria, which are used to eliminate management techniques that are not likely to be applicable at this location and select those that are viable for further analysis. The appraisal criteria for each option were:

° Engineering Issues: high level assessment of the required technical input, and key constraints associated with implementation; ° Environmental Issues: high level assessment of the key opportunities and constraints associated with implementation; ° Economic Issues: overview of factors affecting cost including consideration of the scale of maintenance required; and ° Selection Rationale: justification for selection or rejection of the option based on the factors listed above.

4.2. Short List of Adaptive Management Options

The management options from the long list which are potentially viable to reduce risks from erosion and flooding (taking environmental and other constraints into account) are taken forward as a short list for further assessment. The short-listed options are re-assessed at a higher level of detail using the following criteria:

• description: overview of potential works; • main advantages: key opportunities of this approach; • main disadvantages: key constraints of this approach; • potential applications: does the option provide a long-term or short-term measure; • implementation approach: indication of the type of works required for delivery (e.g. maintenance, capital works); and • further research: constraints to be considered prior to implementation.

The options are assessed according to their potential to provide a sustainable solution to the effects of each geomorphological scenario including:

• capital cost (all cost provided are indicative); • localised flood risk; • localised erosion risk; • future maintenance and operations frequency and cost; and • environmental enhancement opportunities.

A colour coded system has been used to indicate the degree of opportunity or constraints on each variable.

Positive impacts likely (£0 - £250k) No change or little / unknown impact overall (>£250k - £1000k) Negative impacts likely (>£1000k )

32 Environment Agency

Figure 4-1 describes the adaptive management process after a management trigger is reached for both future consequences and effects. Note that adaptive management of the inlet channel remaining open through natural processes (Future Consequence 1) is covered under its principal effect of erosion at Pagham Beach.

33 Environment Agency Title

Figure 4-1 Adaptive management summary for Pagham Harbour

34 Environment Agency

5. Shortlist Options for Future Consequences

This section provides a general description of the potential management options that could be implemented should a particular consequence arise. The decision to take forward any of the associated management options will have to be viewed within the high-level policies and legislation that are applicable to Pagham Harbour. The high level policy, relating to whether the inlet can be allowed to close, is the most important with respect to Future Consequences 1, 2 and 3 because the implementation of any particular management option will need to support this policy.

5.1. Future Consequence 1 Existing inlet channel remains open

Options for adaptive management if the existing channel remains open are described in Section 0 adaptive management options for erosion of Pagham Beach.

5.2. Future Consequence 2 Natural closure of the existing inlet channel

Five options for adaptive management are short-listed (Figure 4-1) if the present inlet channel reaches its management triggers (Table 4-1) after which it has the potential to seal through natural sedimentary processes.

5.2.1 Allow channel to close

The Do Nothing option would be to allow the inlet channel to close naturally. The impacts of allowing the tidal inlet channel to close (Future Consequence 2) are described in Section 3.2.

5.2.2 Excavate a new channel

Excavating a new low-water channel in a similar position to the previous channel would re-open the inlet to natural flood and ebb tidal movements, although it would be vulnerable to re-closure through shingle transport processes. The excavation of a new channel would have a modest impact on natural features and would incur relatively low implementation costs. If the decision is made to keep the channel open, repeat maintenance and/or additional structures (e.g. training arm) may be needed. Excavating a new channel is considered to be the best quick-response management option to avoid closure of the inlet channel. However, renewal of a channel behind Church Norton Spit would allow continuation of the coastal processes that cause Pagham Beach to erode.

This option would require considerable works within the SSSI, and could potentially adversely affect the geological SSSI (Church Norton Spit). However, the option would retain the overall functionality of the site and maintain the SPA and biological SSSI in their current condition. The timing of construction would need to be considered carefully to minimise the potential for disruption of breeding bird populations within the SPA.

The excavation of a new inlet channel is unlikely to significantly alter the hydromorphological or biological characteristics of the water bodies, and is therefore unlikely to lead to deterioration in status under the WFD. Furthermore, this option could potentially help to deliver the direct management measure identified for the SPA in the South East RBMP.

35 Environment Agency

5.2.3 Extend and/or renew the present training arm

The existing training arm was constructed in 1961 to stabilise the inlet channel. Since then it has effectively controlled the channel location and beach movements, focussing tidal flows which increase natural scour of the channel. The arm was reconstructed in the mid to late 1980s following a major collapse. If this is indicative of the life-span of the training arm then there is a possibility that it will fail again within the next ten years. Extension/renewal of the existing training arm at the end of its useful life will help to maintain an open channel adjacent to the structure. From an environmental perspective, the training arm is already a significant feature in the landscape. This option would have high mobilisation and capital costs and the new arm would likely need periodic refurbishments.

This option has the potential to alter the hydromorphological functionality of the system if the training arm is extended significantly. This could impact upon the biological quality elements and cause deterioration in water body status. The renewal of the existing structure is unlikely to cause significant changes to the existing hydrodynamics and is therefore unlikely to cause deterioration in status. However, this option is unlikely to contribute towards achieving Good Ecological Potential. The option could potentially help to deliver the direct management measure, but is unlikely to be considered as favourably as a more sustainable option.

5.2.4 Install a culvert between the inlet and the sea

Installation of a large-diameter culvert near low tide between the inlet and sea would allow entry of water into and exit of water from the inlet. Although culverts are proven in their ability to control tidal flows, the size of Pagham Harbour is likely to significantly restrict their volume. Hence the inlet may become a muted tidal system changing its habitat and environmental characteristics. This option is considered to be a potential compromise between an open channel and full closure of the inlet, and may be more appropriate in the long term. Installation of a pipe(s) would incur high mobilisation and capital costs and is expected to require ongoing maintenance.

This option would install a new artificial structure to the water body, which is likely to significantly alter the hydromorphological characteristics of the inlet. This could potentially lead to the loss or alteration of areas of SPA and SSSI habitats, and adversely affect the biological quality elements. This option is therefore likely to cause deterioration in water body status, and is therefore not compliant with the requirements of the WFD.

5.2.5 Realign the existing flood embankments

Realigning the existing flood defences around the inlet could potentially form part of a longer-term strategy for managing Pagham Harbour. Setting back the defences would increase the tidal prism of the inlet, increasing the velocity of the currents through the inlet channel, altering the balance between alongshore shingle transport and tidal flows. There is then the potential to increase the natural scour of the inlet channel, keeping it open (but also the potential for the scour to erode Pagham Beach if the spit remains in position).

Figure 1-3 shows the potential positions of set-back flood defence bunds (Environment Agency, 2009a). Using these bund positions, LiDAR data for areas behind the existing defences (average of 2009, 2010 and 2011 data to reduce errors) and the mean high water spring tide datum, the tidal prisms for various realignment scenarios have been calculated and compared to the tidal prism for the present Pagham Harbour configuration (Table 5-1). A potential 62% increase in tidal prism could be achieved if blanket realignment was undertaken in front of all the bunds. The majority of this increase would be due to realignment in front of bunds 2 and 3. This is a significant increase in tidal prism which would increase the stability of the inlet channel and provide a natural mechanism to keep it open.

36 Environment Agency Table 5-1 Comparison of tidal prisms for potential realignment of flood defences.

Realignment Scenario Tidal prism m3 x 106) % increase

No realignment (Pagham Harbour only) 3.29 N/A

Total realignment (all bunds) 5.32 62

Realignment using bunds 4 and 5 only 3.35 2

From an environmental perspective, realignment would cause major changes to land use, habitats and drainage into the inlet. Although the size and diversity of intertidal nature conservation interests would be increased, any scheme would also need to consider the potential impact of losing existing freshwater and wet grassland habitats. However, this option could potentially provide opportunities for the creation of new freshwater and wet grassland habitats and contribute towards the improvement of the SSSI and SPA.

The realignment of the flood embankments will allow natural processes to operate over a greater area, and as such is likely to have a beneficial impact on the hydromorphology of the water body. This will also provide improved conditions for the biological quality elements, and is therefore likely to contribute towards an improvement in the status of the water body. Embankment realignment is in accordance with the direct management measures included for the SPA in the RBMP, which could potentially provide a mechanism for implementing this option.

5.3. Future Consequence 3 Natural opening of a new inlet channel to the south

Five options are short-listed for adaptive management (Table 4-1) should Church Norton Beach/Spit reach its management trigger after which it is likely to breach and there is the potential for a new southern channel to open.

5.3.1 Allow the new southern channel to remain open

The Do Nothing option would be to allow the new southern inlet channel to open naturally. The impacts of allowing a new southern tidal inlet channel to open (Future Consequence 3) and stay open are described in Section 0. Allowing the new channel to open could potentially alter the hydromorphology of the water body by changing the configuration of the current inlet. However, this is unlikely to cause deterioration in water body status, providing there are no significant changes to the SPA and SSSI habitats and the biological quality elements they support. This option will therefore help maintain the status of the water body and could potentially be considered to be implementing the direct management measures identified for the SPA in the RBMP.

5.3.2 Construct training arms or terminal groyne

An option to maintain the opening (or encourage a breach to take place) would be to construct a terminal groyne on the updrift side of the new channel or by fixing a channel with training arms. Either of these options would provide barriers to alongshore sediment transport, encouraging the channel to remain open. In addition, training arms would focus tidal flows increasing the potential for scour of the channel. However, in the long-term these options may cause increased erosion downdrift as shingle supply from the southwest is reduced.

The construction of new training arms or a terminal groyne is likely to cause considerable changes to the hydromorphology of Pagham Harbour and disruption of natural geomorphological processes. This has the potential to cause deterioration in the hydromorphological quality elements and the biological quality elements they support, and is therefore unlikely to be compliant with the requirements of the WFD. Furthermore, this option has the potential to adversely affect the protected habitats within the SPA and SSSI.

37 Environment Agency 5.3.3 Recycle shingle into the potential breach

Shingle of sufficient volume from an area that is accumulating downdrift could be recycled, placed and profiled across the potential channel location in order to prevent a breach. The end result would be vulnerable to re-opening because alongshore transport will carry the placed shingle back towards the collection site, weakening the area that had temporarily been strengthened. In terms of the environment, the recycling process would disturb and deplete the extraction area. Hence, careful consideration would need to given to where shingle could be removed so as to minimize environmental damage. The recycling option would have low implementation costs, but may require regular repeat work and/or additional structures. Filling the potential new channel opening with recycled shingle is considered to be the best quick-response management option if the decision is made to keep it closed.

This option is likely to alter the hydromorphology of the inlet by altering the operation of natural processes and changing tidal flow and sediment transport patterns. The closure of the inlet to tidal currents is also likely to cause considerable changes to the SPA and SSSI habitats, and as such is likely to be detrimental for the biological quality elements. This option is therefore likely to cause deterioration in water body status under the WFD.

5.3.4 Place beach recharge shingle into the potential breach

Importing additional shingle from a licensed offshore source into the potential breach would have similar effects to beach shingle recycling. However, the recharge process avoids the need to excavate shingle from adjacent beaches (as recycling does). The recharge option could incur potentially high mobilisation costs. In the short-term, an option might be to implement beach recharge to complement beach recycling. This option is likely alter the hydromorphology of the inlet in the same way recycling shingle into the potential breach would do (Section 5.3.3).

5.3.5 Construct an armourstone sill across the potential breach

Rock armourstone from a licensed quarry could be placed across the potential breach to the high tide water level. The option provides a flexible approach; the armour can be rearranged and removed as required. Although there is high mobilisation and high initial capital costs associated with construction, these will be offset in the long term by low maintenance costs and durability of this option. The armourstone could be buried in existing beach shingle or used in combination with beach recharge to improve the aesthetics of the scheme. This option is likely alter the hydromorphology of the inlet in the same way as blocking the potential breach with shingle (Sections 5.3.3 and 5.3.4).

5.3.5 Realign the existing flood embankments

See Section 5.2.5 for further details

6. Shortlist Options for Short-Term Effects 6.1 Effect 1: Erosion of Pagham Beach

Seven options are short-listed for adaptive management should Pagham Beach reach its management trigger for failure, so that Pagham Beach Estate has the potential to flood. Erosion of Pagham Beach will continue if the existing channel remains open (Future Consequence 1, Section 3.1).

38 Environment Agency 6.1.1 Allow Pagham Beach to continue to erode

The Do Nothing option would be to allow the continued erosion of Pagham Beach. The impacts of allowing a reduction in beach volume are an increased risk of coastal flooding and the subsequent loss of properties along the frontage. Due to the increased risk of flooding this option is not acceptable. This option could lead to significant changes to the SPA and SSSI habitats currently supported in the inlet, particularly if wet grassland and other transitional habitats are lost. This option therefore has the potential to cause deterioration in the status of the water body, although this would occur as a result of natural processes. This option will not help to deliver the direct management measure listed for the SPA in the RBMP.

6.1.2 Bypass shingle across the inlet channel

Transferring beach shingle across the entrance to Pagham Harbour could potentially be used to stabilise the beaches in front of the Pagham Beach Estate. Bypassing operations were undertaken in November 2009 as a one-off short-term option using shingle collected from the ebb-tidal delta. A similar operation could be envisaged with extraction of shingle from areas that would have the least impact on geomorphological and biological processes. The conceptual model (Appendix A) suggests that the ebb-tidal delta is eroding and would be not be a suitable location for any future shingle extractions. This option would have low mobilisation costs, but may need regular repeat work. The operation is flexible with the quantities of shingle readily adjustable. This is considered a suitable short-term option for small scale works.

There are several environmental constraints of this technique as a coastal management/defence measure. These include the disturbance and depletion of shingle at the extraction site. The extraction also has the potential to damage vegetated shingle areas, although this could be avoided if only recently deposited, unvegetated shingle is targeted. For shingle beaches, bypassing operations are usually carried out using mechanical excavators and trucks. Hence, the transport of shingle to Pagham Beach could be problematic, whether by road or along the lower foreshore and across the tidal inlet channel.

This option may disrupt the operation of natural processes, and could potentially impact upon the condition of the geomorphological SSSI. There is also some potential for local degradation of the biological SSSI and SAC habitats. This option is therefore likely to adversely impact upon the hydromorphological and biological quality elements and could potentially cause deterioration in the status of the water body although effects are likely to be minor and temporary.

6.1.3 Recycle shingle from Aldwick Beach

Shingle from an area downdrift that is accumulating could be recycled and placed on Pagham Beach to restore the beach profile. The conceptual model (Appendix A) showed that beach volumes at Aldwick have increased recently, and there would be enough shingle in this location to supply a beach recycling operation for some years into the future. As the amount of shingle supplied to the beaches fronting Pagham and Aldwick from the west and offshore are likely to vary in future (as in the past), trying to manage the beach widths solely by recycling might require frequent and responsive operations. Beach sediment recycling is considered a suitable short-term option for small scale works.

This type of management operation needs to be carefully designed and monitored so that any detrimental impacts on beach usage, the environment and aesthetics are avoided or at least minimised. The recycling activities must be acceptable to those living on or close to the coast at Aldwick. Also, there is a need to maintain good access along the coastline for large mechanical excavators and trucks, requiring a promenade, tracking along the foreshore, or a beach crest wide enough to provide a haul route.

This option may disrupt the operation of natural processes at both Aldwick Beach and Pagham Harbour. In addition, there is also some potential for local degradation of the biological SSSI and SAC habitats. This option may impact upon the hydromorphological and biological quality elements and could potentially cause deterioration in the status of the water body, although effects are likely to be minor and temporary.

39 Environment Agency 6.1.4 Recharge beach with shingle from an offshore source

Recharging Pagham Beach would entail importing additional shingle, most likely from a licensed marine source, to restore the beach profile. The recharge volume should be sufficient that the artificially widened beach is able to accommodate subsequent short-term changes in its morphology, whilst providing the necessary standard of protection. As dredged material may have a higher proportion of fines they would need to be removed to function as a ‘normal’ beach. Beach recharge would not provide a solution to the beach erosion problem indefinitely, and operations may have to be repeated periodically to provide a satisfactory long-term beach management scheme. Beach recharge could be used alone, but the possibility of implementation alongside other forms of management such as beach recycling or groynes should be considered.

Future recharge of Pagham Beach is likely to require small quantities of shingle, which may make the option uneconomic because of high mobilisation costs. Therefore, beach recharge is considered a suitable short-term option, but only for large-scale works. Beach bypassing and recycling are considered more appropriate short-term techniques for mitigating the erosion of Pagham Beach.

This option could potentially disrupt the operation of natural processes, and could potentially impact upon the condition of the geological SSSI. There is also some potential for degradation of the biological SSSI and SAC habitats within Pagham Harbour. This option could potentially impact upon the hydromorphological and biological quality elements, and could potentially cause deterioration in the status of the water body (although effects are likely to be minor and temporary).

6.1.5 Construct additional groynes

Construction of additional groynes along Pagham Beach would act as a partial barrier to alongshore movement of shingle, and could potentially be implemented in combination with beach bypassing or recycling. The existing groynes at Pagham were not designed to control nearshore tidal currents, and have become less effective in retaining shingle as the channel has moved closer inshore. However, if the groynes are too long and high, and thus too effective, they will starve the downdrift (Aldwick) beaches of shingle.

The construction of groynes could potentially adversely impact upon the SSSI habitats supported on Pagham Beach, through direct disturbance during construction and as the result of longer term changes in beach morphology and habitats, caused by changing sediment dynamics. Groyne construction is likely to alter the hydromorphology of the water body, changing flow dynamics and sediment transport patterns. This option is therefore likely to adversely impact upon the hydromorphological and biological quality elements, and could potentially cause deterioration in the status of the water body. This option cannot, therefore, be considered to implement the direct management option included for the SPA in the RBMP.

6.1.6 Alternative tidal inlet channel to the south

If Church Norton Spit was breached artificially so that the tidal inlet channel was returned to its pre- 2001 alignment, there would be benefits to Pagham Beach. A similar sequence of events and impact on Pagham Beach to those following a natural breach in the south (Future Consequence 3) would take place (Section 3.3). Following a breach, the distal end of the present spit would become a ‘flying bar’. This feature would migrate east, in the direction of the net alongshore sediment transport, and onshore as waves transport sediment over its crest. Over time, these processes would restore the supply of sediment to the beaches fronting Pagham Beach Estate without having adverse effects to beaches further east (e.g. at Aldwick). The rate at which this morphological evolution might take place is uncertain and would depend on the subsequent wave conditions, especially the frequency and intensity of storm waves.

The main constraint to breaching the existing spit is that the outcome may be regarded as potentially detrimental to the geological interest of the SSSI, representing a disruption to the natural geomorphological processes, which are part of the site’s designation. The volumetric analysis in the conceptual model shows that the beaches between the Inner Owers and the tip of Church Norton Spit have gained substantial amounts of shingle over the last 5-6 years (Appendix A).

40 Environment Agency Hence, an artificial breach at this point would be contrary to the natural process of accretion taking place currently. However, if shingle supply becomes depleted in the future, the spine of the spit could become an area of erosion and a natural breach occurring at a point of weakness would be in line with natural processes.

This option would require considerable works within the SSSI and SPA and will significantly affect the condition of the geological SSSI and the geomorphological processes acting within it. However, the SPA and SSSI mudflats, salt marsh, wet grassland and open water habitats are likely to be retained in their current condition. The excavation of a new inlet channel is likely to significantly alter the overall hydromorphological and biological characteristics of the water body, by changing the flow and sediment dynamics and altering the position of saline intrusion. This could potentially cause deterioration in the status of the water body, although the retention of existing designated habitats (or regeneration after an initial period of adjustment) may minimise biological impacts. This option could potentially help to deliver the direct management measure identified for the SPA in the South East RBMP if the hydromorphological and biological adjustments do not cause deterioration in status.

6.1.7 Force closure of the tidal inlet channel

Many of the advantages to Pagham Beach of creating a new southern route for the inlet channel would also apply to a forced closure of the existing inlet channel. The width of the channel is small and would seem feasible to block. Closure would allow the longshore transport of shingle across the mouth of the inlet to be re-established. This would occur more directly and more rapidly than would be the case following the creation of a ‘flying bar’. This option would therefore achieve the same benefits for the beaches further east, but quicker than the excavation of a new inlet channel. The environmental and drainage impacts of forcibly closing the inlet channel are the same as those for Future Consequence 2 and are described in Section 0.

The closure of the tidal inlet is likely to cause considerable changes to the intertidal habitats supported within the SPA and SSSI. The sealing of the inlet is likely to cause a decrease in saline habitats in favour of an increase in freshwater habitats, as the ingress of sea water is stopped. This is likely to be highly detrimental to the SPA and SSSI interest features, although ongoing maintenance could potentially help to maintain non intertidal habitats.

Over short timescales, the forced closure of the tidal inlet is likely to cause considerable changes to the hydromorphology and ecology of the water body. This is likely to cause deterioration in water body status, and will therefore be contrary to the direct management measure proposed in the RBMP. Over longer timescales, the hydromorphological changes may support a new set of ecological communities (or the same communities in different proportions) which could potentially reach GEP.

6.2. Effect 2: Erosion of Existing Inlet Flood Embankments

There is potential for future erosion of the existing flood embankments if the inlet remains open to tidal influence under Future Consequences 1 and 3. Should the erosion of the flood embankments reach its management trigger, so that the integrity of the structures would be in doubt, then five options are short-listed as potential strategies to mitigate the erosion

6.2.1 Allow flood embankments to continue to erode

The Do Nothing option would be to allow the continued erosion of existing flood embankments. The impacts of allowing a reduction in structural integrity and crest width is an increased risk of breach leading to extensive flooding. Due to the increased risk of flooding this option is not acceptable.

The erosion of the flood embankments could potentially improve the hydromorphology of the site, allowing natural processes to operate unimpeded and establishing a more natural morphology. This hydromorphological change is likely to be beneficial to the biological quality elements. This

41 Environment Agency option is therefore unlikely to cause deterioration in water body status, and may help to improve status over longer timescales. This option could also be beneficial for the SPA and SSSI interest features by promoting the development of new habitats.

6.2.2 Construct armourstone revetment

A light-weight armourstone revetment could be constructed on the sloping face of existing embankments using material from a licensed site. The revetment would act as a barrier, dissipating and reflecting wave energy. Appropriate surveys would be required to identify where revetment is required to bolster the existing defences. This option has already been implemented at several locations on the existing embankments. This option would have low costs for both mobilisation and maintenance. This option is likely to be vulnerable to extreme events as the size of the armour required to withstand large return period events may not be appropriate at this location.

Construction of an armourstone revetment is likely to be detrimental to the geological SSSI by limiting natural processes. The main interest features of the SPA and biological SSSI are also likely to be adversely affected by the option, through direct disturbance during construction and potential loss of habitats adjacent to the existing embankments. However, the extent and severity of any impacts is likely to be dependent on the location of eroding embankment and their relationship to designated habitats.

This option is likely to alter the hydromorphology of the water body through direct physical modification and a reduction in natural processes. In addition, this option could potentially be detrimental to the biological quality elements through direct disturbance and loss of habitats. This option therefore has the potential to cause deterioration in water body status and is unlikely to be compliant with the requirements of the WFD.

6.2.3 Construct gabion mattress revetment

Rock filled wire mesh baskets placed on the sloping face the embankment would dissipate and reflect wave energy. Gabion boxes can be formed into complex shapes and maximise the opportunity for lower cost rock fill. The wire mesh gabion boxes are subject to corrosion which is likely to be a key issue in this saline inlet. Appropriate surveys would be required to identify where revetment is required. This option would have low mobilisation and maintenance costs.

Construction of a gabion mattress revetment is likely to be detrimental to the geological SSSI by limiting the operation of natural processes. The main interest features of the SPA and biological SSSI are also likely to be adversely affected by the option, through direct disturbance during construction and potential loss of habitats adjacent to the existing embankments. However, the extent and severity of any impacts is likely to be dependent on the location of eroding embankment and their relationship to designated habitats.

This option is likely to alter the hydromorphology of the water body through direct physical modification and a reduction in natural processes. In addition, this option could potentially be detrimental to the biological quality elements through direct disturbance and loss of habitats. This option therefore has the potential to cause deterioration in water body status and is unlikely to be compliant with the requirements of the WFD.

6.2.4 Construct concrete block revetment

This option would use interlinked pre-cast concrete blocks placed on the sloping face of the flood embankment to dissipate and reflect wave energy. This form of protection is predominantly used on exposed flood embankments in high energy environments. Surveys would be required to identify where this option is appropriate and compatible with existing embankments. This option would have high capital costs but low mobilisation costs.

Construction of a concrete block revetment is likely to be detrimental to the geological SSSI by limiting the operation of natural processes. The main interest features of the SPA and biological SSSI are also likely to be adversely affected by the option, through direct disturbance during construction and potential loss of habitats adjacent to the existing embankments. However, the

42 Environment Agency extent and severity of any impacts is likely to be dependent on the location of eroding embankment and their relationship to designated habitats.

This option is likely to alter the hydromorphology of the water body through direct physical modification and a reduction in natural processes. In addition, this option could potentially be detrimental to the biological quality elements through direct disturbance and loss of habitats. This option therefore has the potential to cause deterioration in water body status and is unlikely to be compliant with the requirements of the WFD.

6.2.5 Close channel by beach recycling

Recycling of shingle from Church Norton Spit to fill the existing inlet channel would close the inlet to tidal inundation and eliminate the pressure from waves and tides on the flood embankments. The closure of Pagham Harbour would have the same impacts as those associated with Future Consequence 2 and are described in Section 3.2.

The closure of the tidal inlet is likely to cause considerable changes to the habitats supported within the SPA and SSSI. The sealing of the inlet is likely to cause a decrease in saline habitats in favour of an increase in freshwater habitats, as the ingress of sea water is considerably reduced. This is likely to be highly detrimental to the SPA and SSSI interest features, although ongoing maintenance could potentially help to maintain these habitats. Furthermore, recycling sediment from Church Norton Spit to fill the existing inlet channel could potentially be highly detrimental to the geomorphology of the spit, which is designated as part of the SSSI for its geological interest.

Over short timescales, the forced closure of the tidal inlet is likely to cause considerable changes to the hydromorphology and ecology of the water body. This is likely to cause deterioration in water body status and will therefore be contrary to the direct management measure proposed in the RBMP. Over long timescales, the hydromorphological changes may support a new set of ecological communities (or the same communities in different proportions) which could potentially reach GEP.

6.2.5 Realign the existing flood embankments

See Section 5.2.5 for further details

6.3. Effect 3: Overtopping of Existing Inlet Flood Embankments

There is potential for future overtopping of the existing flood embankments if the inlet remains open to tidal influence under Future Consequences 1 and 3. If the overtopping management trigger is reached, five options are short-listed as potential strategies for mitigation.

6.3.1 Allow flood embankment to overtop

The Do Nothing option would be to allow increased overtopping of the existing flood embankments in time with sea-level rise. This could lead to ponding of water outside the inlet and would erode the embankments over time, increasing the risk of breach and therefore flood risk. Due to the increased risk of flooding this option is not acceptable.

The overtopping and eventual breach of the flood embankments could potentially improve the hydromorphology of the site, allowing natural processes to operate and establishing a more natural geomorphology. This hydromorphological change is likely to be beneficial to the biological quality elements. This option is therefore unlikely to cause deterioration in water body status and may help to improve status over longer timescales. This option could also be beneficial for the SPA and SSSI interest features by promoting the development of new habitats.

43 Environment Agency 6.3.2 Raise embankment using earth fill

To provide protection against overtopping the existing earth embankments could be raised by placing suitable fill material on their tops and, if required, on the sloping face to increase the footprint. This option would have relatively low costs for both mobilisation and maintenance.

An increase in the footprint of the existing embankments is likely to adversely affect the SPA and SSSI through encroachment and direct habitat loss. This option is unlikely to significantly alter the hydromorphology of the water body, although habitat loss could potentially cause changes to the biological quality elements and deterioration in water body status.

6.3.3 Construct a concrete gravity wall along the top of the embankment

The construction of a slender reinforced concrete vertical wall on a horizontal base embedded in the top of the embankment would reduce the probability of overtopping. However, this solution is unlikely to be in keeping with the current landscape and could reduce access to the inlet. One benefit of this approach is the ability to raise the wall in future as required for sea-level rise. This option would have high mobilisation costs.

The construction of a concrete gravity wall within the existing embankment footprint is unlikely to detrimentally affect the SPA and SSSI habitats in the long term, although there is a high likelihood of disturbance during construction. Restricting the works to within the existing footprint is likely to minimise the potential impacts on the hydromorphology of the water body. The biological quality elements are also unlikely to be affected, unless there is a significant disruption to designated habitats. The option is therefore unlikely to cause deterioration in water body status, but this cannot be ruled out completely.

6.3.4 Install steel sheet pile wall along the top of the embankment

The construction of a steel sheet pile wall embedded in to the embankment would reduce the probability of overtopping, whilst strengthening the existing embankments. This option has similar issues to those of a concrete gravity wall with respect to access and setting. This option would have high capital costs.

The construction of a steel sheet pile wall within the existing embankment footprint is unlikely to detrimentally affect the SPA and SSSI habitats in the long term, although there is a high likelihood of disturbance during construction. This could potentially be minimised by careful planning of construction works to avoid the most sensitive periods. Restricting the works to within the existing embankment footprint is likely to minimise the potential impacts on the hydromorphology of the water body. The biological quality elements are also unlikely to be affected, unless there is a significant disruption to designated habitats. The option is therefore unlikely to cause deterioration in water body status, but this cannot be ruled out completely.

6.3.5 Close channel by beach shingle recycling

Recycling of shingle from Church Norton Spit to fill the existing inlet channel would close the inlet to inundation on flood tides and significantly reduce the maximum water level at the flood embankments. The closure of Pagham Harbour would have the same impacts as those associated with Future Consequence 2 and are described in Section 3.2. Impacts on habitats and WFD are as mentioned in Section 6.2.5

5.3.5 Realign the existing flood embankments

See Section 5.2.5 for further details

44 Environment Agency 6.4. Effect 4: Impeded drainage into the inlet

Seven options are short-listed as potential strategies to mitigate the prevention of drainage into the inlet if the management trigger for drainage impedance is reached. The following single trigger that would require implementation of adaptive management interventions (Table 4-1) is identified:

• Projections based on accretion at the outfalls suggest an unacceptable possibility (to be quantified) that drainage into the inlet will be prevented.

6.4.1 Allow drainage impedance to continue

The Do Nothing option would be to allow blockage of existing gravity outfalls in the future due to natural processes. Due to ongoing sedimentation and sea-level rise, drainage would be impeded into the inlet. This could cause flooding upstream of the inlet. Due to the increased risk of flooding this option is not acceptable.

The natural blockage of the existing gravity outfalls is unlikely to adversely impact upon the SAC and SSSI interest features or the hydromorphological and biological quality elements over short timescales. However, continued sedimentation and projected sea level rise over longer timescales could potentially cause considerable changes to the types of habitats that are supported. This option could therefore be detrimental to the condition of the SPA and SSSI in the long term. In addition, these new hydromorphological conditions could cause deterioration in water body status, although they could also support a new set of ecological communities (or the same communities in different proportions) which could potentially reach GEP.

6.4.2 Fit duckbill check valves to the outfalls

Modifying existing gravity drainage outfalls and fitting duckbill valves would improve the drainage characteristics and potentially reduce maintenance. The valves can be selected to operate under defined flows discharging under pressure. When a threshold is reached the jet of water clears sediment around the outfall, reducing the cost of maintenance. This option would be relatively low cost.

The installation of check valves could potentially cause localised disruption to the SPA and SSSI during construction, but is unlikely to have a significant impact on the key interest features over longer timescales. This option could potential alter the hydromorphology of the water body and is likely to adversely impact on fish passage. This option therefore has the potential to cause deterioration in water body status.

6.4.3 Excavate inlet bed at outfalls

‘Natural’ channels could be excavated from the inlet bed to remove sediment build up and reduce the likelihood of the outfalls becoming blocked. Effects of increased water levels should be assessed and are not addressed in this option. These channels would need to be maintained as sediment is likely to accrete over time. This is a short-term maintenance solution with relatively low cost.

The excavation of the inlet bed is likely to cause considerable disturbance to the SPA and SSSI during construction and subsequent maintenance and may also have detrimental effects in the long term by reducing the extent of designated habitats. This option has the potential to adversely impact upon the hydromorphological and biological quality elements of the water body, and could potentially cause deterioration in water body status. However, the likelihood of deterioration increases with the footprint of the works and the frequency of maintenance and highly localised excavation, which requires infrequent maintenance, could potentially avoid deterioration.

45 Environment Agency 6.4.4 Extend outfalls into the inlet

Extending the existing drainage outfalls into the inlet would reduce the risk of future blockage of the outfalls due to sedimentation. The extended pipes could be placed on timber trestles to reduce the impact on the bed but would protrude into the inlet causing potential visual impacts and impacts to the sediment dynamics.

The extension of the outfalls into the inlet is likely to cause considerable disturbance to the SPA and SSSI during construction, and may also have detrimental effects in the long term by reducing the extent of habitats such as mudflats. This option has the potential to adversely impact upon the hydromorphological and biological quality elements, and could potentially cause deterioration in water body status. However, the likelihood of deterioration increases with the scale of the works, and small scale construction could potentially avoid deterioration.

6.4.5 Form temporary storage outside of harbour

Construction of a flood storage area upstream of the harbour would temporary delay conveyance of drainage water. This could be implemented by constructing bunded areas with control arrangements, reducing the risk of flooding due to high water level. When gravity outfalls are unable to operate flows would be diverted to the storage area until the issues can be resolved. The provision of storage upstream of the harbour will reduce impacts on environmentally designated areas. This is a proven solution but is relatively costly to implement.

This option is unlikely to affect the condition of the SPA and SSSI if all storage areas and associated infrastructure are located outside of the designated boundary. However, it is likely to have a considerable landscape impact and could potentially alter the way water is supplied to the wet grassland habitats. Despite this, this option offers the opportunity to deliver considerable environmental gain by creating new habitats within the flood storage areas, which could potentially be included within the SPA and SSSI over time.

This option is likely to have an impact upon the hydromorphology of the water bodies within Pagham Harbour by reducing river continuity and changing natural flow patterns. Furthermore, the option could potentially be detrimental to the biological quality elements by limiting fish passage. This option therefore has the potential to cause deterioration in the status of the water body. However, this risk can be minimised during the detailed design process, for example by addressing fish passage issues and avoiding the use of unnecessary structures. If combined with channel enhancement work this option could therefore potentially help to deliver the aims of the WFD for the freshwater bodies that drain into Pagham Harbour.

6.4.6 Pump drainage water into / out of the harbour

Installation of additional pumping facilities at key locations around harbour would ensure drainage into the harbour under high water levels, despite rising bed levels. Pumps already installed at Ferry Pool and Pagham Rife, however implementation will be costly with ongoing maintenance required.

The installation of additional pumps at strategic locations within Pagham Harbour is unlikely to have a significant effect on the condition of the SPA and SSSI, although construction will cause localised disturbance. The timing of pump operation will need to be considered carefully to avoid changes to the overall water balance at habitats adjacent to the pump inlets and outlets. This option is unlikely to cause significant hydromorphological or biological impacts, and is therefore unlikely to cause deterioration in water body status.

6.4.7 Close channel by beach recycling

Recycling of shingle from Church Norton Spit to fill the existing inlet channel would close the inlet to tidal inundation and hence siltation would not take place. The closure of Pagham Harbour would have the same impacts as those associated with Future Consequence 2 and are described in Section 3.2. Impacts on habitats and WFD are as detailed in Section 6.2.5.

46 Environment Agency 7. Future Consequences Option Overview

This section provides a general overview of the impacts and effects of potential management options that could be implemented should a particular consequence arise. The Do Nothing options are discussed in Section 3. A colour coded system has been used to indicate the degree of opportunity or constraints

Positive impacts likely No change or little / unknown impact overall Negative impacts likely

7.1. Future Consequence 1: Existing inlet channel remains open

Options for adaptive management if the existing channel remains open are described in Section 8.1.

7.2. Future Consequence 2: Natural closure of the existing inlet channel

Option Excavate a new channel Main Advantages Follows the existing arrangements Main Disadvantages Vulnerable to re-closure Potential Applications Initial quick response solution Implementation Approach Capital maintenance works Assuming the new channel is excavated to provide a similar cross-sectional area to the Flood Risk existing channel there will be no change in flood risk Assuming the new channel is excavated to provide a similar cross-sectional area and Erosion Risk on the same alignment to the existing channel there will be no change in erosion risk Capital Cost Medium Maintenance May need to be repeated as the channel starts to re-close Effect on Geological SSSI Requires repeated removal of shingle from the geological SSSI Effect on Habitats Existing habitats within the inlet would be sustained No deterioration in status if habitat is retained. Could potentially help to deliver the WFD direct management measure identified for the SPA in the South East RBMP Optimum methodology for excavation whilst minimising impacts on features to be Further Research determined

47 Environment Agency Option Extend and/or renew the present training arm Main Advantages Utilises existing wall Main Disadvantages Vulnerable to re-closure and significant feature within natural landscape Potential Applications Long term in conjunction with regular maintenance of the channel Initial major capital works scheme with ongoing maintenance and periodic Implementation Approach refurbishments Flood Risk The existing channel will be maintained resulting in no change in flood risk Erosion Risk The existing channel will be maintained resulting in no change in erosion risk Capital Cost Medium Maintenance May need to be repeated when new arm reaches the end of its useful life Effect on Geological SSSI May require removal of shingle from the geological SSSI. Existing habitats would be impacted by construction works in the short term but in the Effect on Habitats longer term they would be sustained Replacement unlikely to cause deterioration in status, although this is possible if the WFD structure is extended Further Research None required

Option Install a culvert between the inlet and the sea Drainage can be maintained under most conditions and culvert can control flow in and Main Advantages out of the inlet Main Disadvantages Impractical to achieve equivalent of open channel flows Potential Applications Long term Initial major capital works scheme with ongoing maintenance and periodic Implementation Approach refurbishments Whether a culvert has the capacity to drain the inlet without increasing flood risk is Flood Risk unknown The existing channel will be closed allowing shingle transport alongshore and providing Erosion Risk erosion protection to Pagham Beach Estate Capital Cost High Maintenance Minimal maintenance may be required Effect on Geological SSSI Culvert to be installed away from the spit allowing the spit to function naturally Effect on Habitats Existing habitats (saltmarsh and mudflats) altered due to reduced saline intrusion Potential for deterioration in status due to installation of a new artificial structure and WFD loss of saltmarsh and mudflat habitats Further Research Feasibility of culvert arrangement

Option Realign the existing flood embankments Main Advantages Naturally maintains tidal prism Main Disadvantages Major change to land use, landscape and habitats Potential Applications Long term Implementation Approach Initial major capital works scheme with ongoing maintenance Flood Risk Flood risk will be reduced due to the increased flood storage in and around the inlet Erosion Risk The existing channel will be maintained resulting in no change in erosion risk Capital Cost High Maintenance Minimal maintenance may be required to flood embankments The existing channel will be maintained by the increased tidal prism resulting in no Effect on Geological SSSI change to the geological SSSI Effect on Habitats Major changes to land use, landscape and habitats and drainage into inlet. Habitats are

48 Environment Agency likely to increase in area Beneficial effect on status if habitat area is increased – greater area for natural processes to operate in. Embankment realignment is in accordance with the direct WFD management measures included for the SPA in the RBMP, which could potentially provide a mechanism for implementing this option Optimum alignment of new embankments to maintain suitable tidal prism. Long term Further Research effectiveness of increased flows to maintain an open channel

7.3. Future Consequence 3 Natural opening of a new inlet channel to the south

Option Construct training arms or terminal groyne Main Advantages Well proven and robust Main Disadvantages Vulnerable to re-closure and significant feature within natural landscape Potential Applications Long term in conjunction with regular maintenance of the channel Initial major capital works scheme with ongoing maintenance and periodic Implementation Approach refurbishments Flood Risk The new channel will maintain tidal exchange resulting in no change to flood risk. The existing channel will close allowing shingle transport alongshore and providing Erosion Risk erosion protection to Pagham Beach Capital Cost Medium New channel will need to be maintained if it starts to re-close leading to repeat work Maintenance and costs. Structures will need to be maintained and replaced as and when required Effect on Geological SSSI Requires construction works on the SSSI and potentially repeated removal of shingle Forms a significant feature within the area. Existing habitats impacted by construction Effect on Habitats works in the short term but in the longer term would be sustained. Would require ongoing maintenance potentially impacting on the habitats within the inlet Potential for deterioration in status due to changes in natural hydromorphological WFD processes Further Research None required

Option Recycle shingle into the potential breach Main Advantages ‘Low-technology’ and flexible Main Disadvantages Vulnerable to re-opening Potential Applications Initial quick response option Implementation Approach Capital maintenance works Flood Risk Flood risk will not increase or decrease as long as the existing channel is maintained Erosion Risk Erosion risk will not increase or decrease as long as the existing channel is maintained Capital Cost Low Maintenance Repeat works required on a regular basis Effect on Geological SSSI Potential to change the geomorphology of the spit Existing habitats would be impacted by construction works in the short term but in the Effect on Habitats longer term they would be sustained Potential for deterioration in status due to changes in natural hydromorphological WFD processes Further Research None required

49 Environment Agency

Option Place beach recharge shingle into the potential breach Main Advantages Avoids the need to excavate from adjacent beaches Main Disadvantages Vulnerable to re-opening Potential Applications Short term to allow ongoing monitoring Implementation Approach Capital maintenance works Flood Risk Flood risk will not increase or decrease as long is existing channel is maintained Erosion Risk Erosion risk will not increase or decrease as long as the existing channel is maintained Capital Cost High Maintenance Repeat works required on a regular basis Effect on Geological SSSI Potential to change the geomorphology of the spit Existing habitats would be impacted by construction works in the short term but in the Effect on Habitats longer term they would be sustained Potential for deterioration in status due to changes in natural hydromorphological WFD processes Further Research Feasibility of delivery from the sea

Option Construct an armourstone sill across the potential breach Main Advantages Robust and flexible Main Disadvantages Possible re-opening alongside sill Potential Applications Long term in conjunction with shingle covering Implementation Approach Initial minor capital works scheme with ongoing shingle bank maintenance Flood Risk Flood risk will not increase or decrease as long is existing channel is maintained Erosion Risk Erosion risk will not increase or decrease as long as the existing channel is maintained Capital Cost High Maintenance Minimal maintenance required Short-term release of fines into the water column is expected whilst amourstone is Effect on Geological SSSI installed. Will interrupt natural processes impacting the SSSI spit Existing habitats would be impacted by construction works in the short term but in the Effect on Habitats longer term they would be sustained Potential for deterioration in status due to changes in natural hydromorphological WFD processes Further Research None Required

Option Realign the existing flood embankments Main Advantages Naturally maintains tidal prism Main Disadvantages Major change to land use, landscape and habitats Potential Applications Long term Initial major capital works scheme with ongoing maintenance. Potential to implement Implementation Approach staged localised realignment Flood Risk Flood risk will be reduced due to the increased flood storage in and around the inlet Additional intertidal habitat creating wider buffer to wave attack reducing erosion risk at Erosion Risk the embankments Capital Cost High Maintenance Minimal maintenance may be required to flood embankments Effect on Geological SSSI Capital works would impact Geological SSSI

50 Environment Agency Major changes to land use, landscape and habitats and drainage into inlet. Potential to Effect on Habitats increase area of intertidal habitat Beneficial effect on status if habitat area is increased – greater area for natural processes to operate in. Embankment realignment is in accordance with the direct WFD management measures included for the SPA in the RBMP, which could potentially provide a mechanism for implementing this option. Optimum alignment of new embankments to maintain suitable tidal prism. Long-term Further Research effectiveness of increased flows to maintain an open channel

8. Consequence Effects Option Appraisal

8.1. Effect 1: Erosion of Pagham Beach

Option Bypass shingle across the inlet channel Main Advantages Close to natural processes and readily adjustable to suit needs Needs to be repeated regularly Main Disadvantages Impacts of road haulage Mainly short term but could be long term if environmental impacts and costs are Potential Applications sustainable Implementation Approach Suitable for modest sized annual operation Flood Risk Short term reduction in risk of coastal flooding Erosion Risk Reduction in erosion risk Capital Cost Low Maintenance Will require repeat operations until source of erosion is addressed Repeated removal of shingle from the Geological SSSI. Potential to change the Effect on Geological SSSI geomorphology of the beach Effect on Habitats Potential loss of vegetated shingle. Disturbance of little tern breeding habitat Potential for deterioration in status due to changes in natural hydromorphological WFD processes Further Research Feasibility of road haulage or direct haulage across inlet channel

Option Recycle shingle from Aldwick Beach Main Advantages Close to natural processes and readily adjustable to suit needs Needs to be repeated regularly. Legal agreement to access Aldwick Beach source Main Disadvantages required. Impacts of haulage Potential Applications Mainly short term Implementation Approach Suitable for modest sized annual operation Flood Risk Short term reduction in risk of coastal flooding Erosion Risk Reduction in erosion risk Capital Cost Low Maintenance Will require repeat operations until source of erosion is addressed. Effect on Geological SSSI Potential to change the geomorphology of the beach Effect on Habitats Potential loss of vegetated shingle WFD Potential for deterioration in status due to changes in natural hydromorphological

51 Environment Agency processes Further Research Potential for contractual arrangements

Option Recharge beach with shingle from an offshore source Main Advantages Low impact on adjacent frontages Main Disadvantages Needs to be repeated regularly Mainly short term but could be long term if environmental impacts and costs are Potential Applications sustainable Implementation Approach Suitable for modest sized annual operation Flood Risk Short term reduction in risk of coastal flooding. Erosion Risk Reduction in erosion risk Capital Cost Medium Maintenance Will require repeat operations until source of erosion is addressed Effect on Geological SSSI Addition of new shingle could impact on the condition of the beach Effect on Habitats Existing habitats would be impacted by construction works in the short term Potential for deterioration in status due to changes in natural hydromorphological WFD processes (although this could be minimised during construction) Further Research Feasibility of delivery from the sea

Option Construct additional groynes Main Advantages Utilises existing groynes and is well proven Needs sufficient beach shingle and/or beach feed. Vulnerable to encroachment of Main Disadvantages shore-parallel channel Potential Applications Long term in conjunction with periodic beach bypassing, recycling or recharge Initial modest sized capital works scheme with ongoing maintenance and periodic Implementation Approach refurbishments Flood Risk Reduction in risk of coastal flooding Erosion Risk Reduction in erosion risk Capital Cost High Maintenance Minimal maintenance may be required Effect on Geological SSSI Natural processes interrupted impacting on SSSI Structure could potentially impact on habitats through direct disturbance and changes Effect on Habitats to beach morphology Potential for deterioration in status due to installation of a new artificial structure and WFD changes in natural hydromorphological processes Further Research None Required

Option Alternative tidal inlet channel to the south Would release significant natural beach feed. Anticipates potential natural breach to the Main Advantages south side of the inlet Major intervention in natural feature. Reliant on natural processes to feed Pagham Main Disadvantages Beach. May require further intervention to maintain channel open Medium term. However longer term there is potential for the new channel to behave as Potential Applications the present channel Implementation Approach Initial major capital works scheme with ongoing maintenance Flood Risk Reduction in risk of coastal flooding Erosion Risk Reduction in erosion risk

52 Environment Agency Capital Cost Low Maintenance Repeat works required on a regular basis to maintain breach. Effect on Geological SSSI Major initial and prolonged interventions to the SSSI and little tern habitat Likely to retain SPA habitats in existing condition (although potential for localised Effect on Habitats changes) Unlikely to cause deterioration in status. Could potentially help to deliver the direct WFD management measure identified for the SPA in the South East RBMP. Further Research Feasibility of breaching Church Norton Spit

Option Force closure of the tidal inlet channel Converts frontage to normal open coastline. Allows ongoing and uninterrupted beach Main Advantages feed onto Pagham Beach Main Disadvantages Major intervention in natural feature Potential Applications Long term with or without further intervention Implementation Approach Initial major capital works scheme with ongoing maintenance Further study will be required to understand the impacts of closing the harbour on the Flood Risk drainage of the peninsular. If the existing channel closes shingle transport alongshore will provide erosion Erosion Risk protection. Capital Cost Medium Maintenance Further works may be required to maintain closure Effect on Geological SSSI Major initial and prolonged interventions to the SSSI and little tern habitat Effect on Habitats Reduction in salinity potentially detrimental to habitats Potential for deterioration in status due to changes in natural hydromorphological WFD processes Further Research Effects of closure on drainage of the harbour

8.2. Effect 2: Erosion of Existing Inlet Flood Embankments

Option Construct armourstone revetment Main Advantages Configuration and rock size readily adjusted to suit needs. Rapid construction Main Disadvantages Vulnerable to extreme events Potential Applications Long term Implementation Approach Capital maintenance works Flood Risk Revetment will provide scour protection to embankments minimising risk of breach Erosion Risk Not Applicable Capital Cost Low Maintenance Minimal maintenance required Effect on Geological SSSI Potential to disrupt natural processes Effect on Habitats Potential loss of SPA and SSSI habitats Potential for deterioration in status due to changes in natural hydromorphological WFD processes and loss of habitats for biological quality elements Further Research None required

53 Environment Agency Option Construct gabion mattress revetment Gabion boxes can be formed into more complex shapes. Potential for lower cost rock Main Advantages fill Main Disadvantages Wire mesh subject to abrasion and corrosion Potential Applications Long term at special features, steeper slopes, etc Implementation Approach Capital maintenance works Flood Risk Gabions will provide scour protection to embankments minimising risk of breach Erosion Risk Not Applicable Capital Cost Low Maintenance Minimal maintenance required Effect on Geological SSSI Potential to disrupt natural processes Effect on Habitats Potential loss of SPA and SSSI habitats Potential for deterioration in status due to changes in natural hydromorphological WFD processes and loss of habitats for biological quality elements Further Research None required

Option Construct concrete block revetment Main Advantages Can withstand high energy situations Main Disadvantages Higher costs. Less in-keeping with surroundings Potential Applications Long term at more exposed or critical locations Implementation Approach Capital maintenance works Flood Risk Revetment will provide scour protection to embankments minimising risk of breach Erosion Risk Not Applicable Capital Cost Low Maintenance Minimal maintenance required Effect on Geological SSSI Potential to disrupt natural processes Effect on Habitats Potential loss of SPA and SSSI habitats Potential for deterioration in status due to changes in natural hydromorphological WFD processes and loss of habitats for biological quality elements Further Research None required

Option Close inlet channel by beach recycling Main Advantages Permanently curtails incident tidal and wave energy Main Disadvantages Major intervention in natural feature Potential Applications Long term with or without further intervention Implementation Approach Initial major capital works scheme with ongoing maintenance Further study will be required to understand the impacts of closing the harbour on the Flood Risk drainage of the peninsular. Erosion Risk Eliminates the pressure from waves and tides on the flood embankments Capital Cost Medium Maintenance Repeat works required on a regular basis to maintain closure Effect on Geological SSSI Major and prolonged interventions to the SSSI and little tern habitat Effect on Habitats Potential loss of SPA and SSSI habitats Potential for deterioration in status due to changes in natural hydromorphological WFD processes and loss of habitats for biological quality elements Further Research Effects of closure on drainage of the harbour

54 Environment Agency

Option Realign the existing flood embankments Main Advantages Naturally maintains tidal prism Main Disadvantages Major change to land use, landscape and habitats Potential Applications Long term Initial major capital works scheme with ongoing maintenance. Potential to implement Implementation Approach staged localised realignment Flood Risk Flood risk will be reduced due to the increased flood storage in and around the inlet Additional intertidal habitat creating wider buffer to wave attack reducing erosion risk at Erosion Risk the embankments Capital Cost High Maintenance Minimal maintenance may be required to flood embankments Effect on Geological SSSI Capital works would impact Geological SSSI Major changes to land use, landscape and habitats and drainage into inlet. Potential to Effect on Habitats increase area of intertidal habitat Beneficial effect on status if habitat area is increased – greater area for natural processes to operate in. Embankment realignment is in accordance with the direct WFD management measures included for the SPA in the RBMP, which could potentially provide a mechanism for implementing this option. Optimum alignment of new embankments to maintain suitable tidal prism. Long-term Further Research effectiveness of increased flows to maintain an open channel

8.3. Effect 3: Overtopping of Existing Inlet Flood Embankments

Option Raise embankment using earth fill Main Advantages ‘Low-technology’ and rapid construction. Compatible with existing embankments Main Disadvantages May need to widen the footprint of the embankment. May overload embankment Potential Applications Long term Implementation Approach Capital maintenance works Flood Risk Reduced risk of overtopping Erosion Risk Not Applicable Capital Cost High Maintenance Minimal maintenance required Effect on Geological SSSI None Effect on Habitats Potential loss of foreshore habitats due to increased footprint Potential for deterioration in water body status due to increased size of embankment WFD and resulting habitat loss Further Research Embankment critical freeboard heights

Option Construct a concrete gravity wall along the top of the embankment Main Advantages Compact / low surcharge loads Reduces accessibility along and across the embankment. Not in-keeping with Main Disadvantages surroundings Potential Applications Long term where a more compact solution necessary Implementation Approach Capital maintenance works Flood Risk Reduced risk of overtopping

55 Environment Agency Erosion Risk Not Applicable Capital Cost High Maintenance Minimal maintenance required Effect on Geological SSSI None Effect on Habitats Temporary disturbance during construction, but long term impacts unlikely Modification of the existing structure within its current footprint is unlikely to cause WFD deterioration in water body status Further Research Embankment critical freeboard heights

Option Install steel sheet pile wall along the top of the embankment Main Advantages Strengthens embankment Reduces accessibility along and across the embankment. Not in-keeping with Main Disadvantages surroundings Potential Applications Long term where embankment also needs strengthening Implementation Approach Capital maintenance works Flood Risk Reduced risk of overtopping and breach Erosion Risk Not Applicable Capital Cost High Maintenance Minimal maintenance required Effect on Geological SSSI None Effect on Habitats Temporary disturbance during construction, but long term impacts unlikely Modification of the existing structure within its current footprint is unlikely to cause WFD deterioration in water body status Further Research Embankment critical freeboard heights

Option Close inlet channel by beach recycling Main Advantages Permanently reduces maximum water levels Main Disadvantages Major intervention in natural feature Potential Applications Long term with or without further intervention Implementation Approach Initial major capital works scheme with ongoing maintenance Further study will be required to understand the impacts of closing the inlet on the Flood Risk drainage of the peninsular. Erosion Risk Eliminates the pressure from waves and tides on the flood embankments Capital Cost Medium Maintenance Repeat works required on a regular basis to maintain closure Effect on Geological SSSI Major and prolonged interventions to the SSSI and little tern habitat Effect on Habitats Potential loss of SPA and SSSI habitats Potential for deterioration in status due to changes in natural hydromorphological WFD processes and loss of habitats for biological quality elements Further Research Effects of closure on drainage of the harbour

56 Environment Agency Option Realign the existing flood embankments Main Advantages Naturally maintains tidal prism Main Disadvantages Major change to land use, landscape and habitats Potential Applications Long term Initial major capital works scheme with ongoing maintenance. Potential to implement Implementation Approach staged localised realignment Flood Risk Flood risk will be reduced due to the increased flood storage in and around the inlet Additional intertidal habitat creating wider buffer to wave attack reducing erosion risk at Erosion Risk the embankments Capital Cost High Maintenance Minimal maintenance may be required to flood embankments Effect on Geological SSSI Capital works would impact Geological SSSI Major changes to land use, landscape and habitats and drainage into inlet. Potential to Effect on Habitats increase area of intertidal habitat Beneficial effect on status if habitat area is increased – greater area for natural processes to operate in. Embankment realignment is in accordance with the direct WFD management measures included for the SPA in the RBMP, which could potentially provide a mechanism for implementing this option. Optimum alignment of new embankments to maintain suitable tidal prism. Long-term Further Research effectiveness of increased flows to maintain an open channel

8.4. Effect 4: Impeded Drainage into the Inlet

Option Fit duckbill check valves to the outfalls Main Advantages Low cost and unobtrusive Main Disadvantages Limited ability to cope with rising bed levels. Does not deal with rising water levels Potential Applications Initial quick response solution Implementation Approach Capital maintenance works Flood Risk Reduced risk of flooding due to blockages caused by sedimentation Erosion Risk Not Applicable Capital Cost Low Maintenance Minimal maintenance required Effect on Geological SSSI None Effect on Habitats Short term construction impact, but long term impacts unlikely Potential to alter hydromorphology and impede fish passage, causing deterioration in WFD status Further Research None required

57 Environment Agency Option Excavate inlet bed at outfalls Main Advantages Low cost and in-keeping with natural channels in the inlet bed Main Disadvantages Vulnerable to natural backfilling. Does not deal with rising water levels Potential Applications Short term maintenance operation Implementation Approach Capital maintenance works or annual maintenance operation Flood Risk Reduced risk of flooding due to blockages caused by sedimentation Erosion Risk Not Applicable Capital Cost Medium Maintenance Ongoing works required Effect on Geological SSSI None Effect on Habitats Regular disturbance of mudflat and saltmarsh habitats Small scale, localised excavation is unlikely to cause deterioration in status, although WFD extensive works could potentially have an impact Further Research None required

Option Extend outfalls into the inlet Main Advantages Avoids the need for bed excavation Main Disadvantages Potentially intrusive. Does not deal with rising water levels Potential Applications Short term capital works Implementation Approach Capital maintenance works Flood Risk Reduced risk of flooding due to blockages caused by sedimentation Erosion Risk Not Applicable Capital Cost High Maintenance Minimal maintenance required Effect on Geological SSSI None Effect on Habitats Visual impact on surrounding area and disturbance of mudflat and saltmarsh WFD The extension of the existing outfalls is unlikely to alter the status of the water body Further Research None required

58 Environment Agency Option Form temporary storage outside of harbour Main Advantages Avoids direct impact on inlet itself Potentially high cost. Significant changes to area around the inlet. Does not deal with Main Disadvantages rising bed levels Potential Applications Long term combined with wider management of land drainage around the inlet Implementation Approach Capital works schemes Flood Risk Reduced risk of flooding Erosion Risk Not Applicable Capital Cost High Maintenance Minimal maintenance required Effect on Geological SSSI None Unlikely to have adverse impacts if flood storage areas are located outside of the Effect on Habitats harbour. Offers opportunities for additional habitat creation and could potentially deliver environmental benefits Potential to cause deterioration in status by changing flows and impeding fish passage. WFD However, could deliver status improvements for freshwater bodies if combined with channel enhancement work Further Research None required

Option Pump drainage water into / out of the inlet Well proven and avoids disturbance of the inlet and surrounding area. Deals with both Main Advantages rising bed levels and rising water levels Main Disadvantages High maintenance and ongoing running costs Potential Applications Long term Implementation Approach Capital works scheme Flood Risk Reduced risk of flooding due to blockages caused by sedimentation and water levels Erosion Risk Not Applicable Capital Cost High Maintenance Ongoing maintenance and running costs are high Effect on Geological SSSI None Effect on Habitats None WFD The option is unlikely to alter the status of the water body Further Research Feasibility of system of pumps around the inlet

59 Environment Agency Option Close inlet channel by beach recycling Main Advantages Permanently stops rising bed levels and permanently reduces maximum water levels Main Disadvantages Major intervention in natural feature Potential Applications Long term with or without further intervention Implementation Approach Initial major capital works scheme with ongoing maintenance Further study will be required to understand the impacts of closing the harbour on the Flood Risk drainage of the peninsular Erosion Risk Not Applicable Capital Cost Medium Maintenance Repeat works required on a regular basis to maintain closure Effect on Geological SSSI Major and prolonged interventions to the SSSI and little tern habitat Effect on Habitats Potential loss of SPA and SSSI habitats Potential for deterioration in status due to changes in natural hydromorphological WFD processes and loss of habitats for biological quality elements Further Research Effects of closure on drainage of the harbour

9. Long Term Preferred Options

Due to the dynamic nature of the inlet there is currently no preferred option to provide sustainable management for the future. Alternative options need to be considered based on monitoring of the system until it reaches one or more defined geomorphological management triggers (as defined in Table 4-1). Once the Warning trigger is reached, then a variety of options are available to be implemented depending on the high-level policy and legislation drivers applicable at the time the trigger is reached. This section summarises the options that are available should a particular trigger be reached and the potential impacts of implementing a particular option. In the tables that follow, impacts are colour coded as green (positive impact), orange (no significant change) and red (negative).

9.1. Consequence 1: Existing inlet channel remains open

The options available should the existing channel remain open are discussed in Section 10.1 for erosion of Pagham Beach.

9.2. Consequence 2: Inlet seals and Pagham Harbour closes

Table 9-1 provides a summary of potential options should a management trigger be reached that indicates that the inlet channel will likely seal, leading to closure of Pagham Harbour.

60 Environment Agency Table 9-1 Summary of option appraisal

Effect on Flood Erosion Capital Effect on Option Maintenance Geological WFD Risk Risk Cost Habitats SSSI Do Nothing - allow the        channel to close Excavate a new        channel Extend and / or renew the present training        arm Install a culvert between the inlet and        the sea Realign the existing        flood embankments

The summary (Table 9-1) suggests that the preferred option to sustainably manage Pagham Harbour over the long term is likely to be realigning the existing flood embankments. Setting back the defences would reduce flood risk and have beneficial effects on habitats and WFD requirements. The main detrimental effect would be that erosion risk at Pagham Beach would continue. Also, this option is likely to require significant upfront investment which may render the option uneconomically viable.

Do Nothing and allow the channel to close should not be discounted as a preferred option. Further study will be required to understand the impact of allowing the channel to close on flood risk and drainage. Should further studies show that flood risk would not increase this option would be significantly more economically viable. From an environmental perspective there is the potential for loss of saltmarsh and mudflat habitats due to major changes in natural processes. However these habitats will be replaced by a brackish lagoon and the existing geological SSSI will be allowed to function naturally. Consultation with Natural England and other stakeholders will be required before any decision can be taken on allowing the inlet to close.

61 Environment Agency 9.3. Consequence 3: Church Norton Spit breaches to create new inlet channel further south

Table 9-2 provides a summary of potential options should a management trigger be reached that indicates that Church Norton Spit will likely breach to create a new inlet channel further south.

Table 9-2 Summary of option appraisal

Effect on Flood Erosion Capital Effect on Option Maintenance Geological WFD Risk Risk Cost Habitats SSSI Do Nothing - allow the new southern channel        to open Construct training arms or terminal        groyne Recycle shingle into        the potential breach Place beach recharge shingle into the        potential breach Construct an armourstone sill        across the potential breach Realign the existing        flood embankments

The summary (Table 9-2) suggests that the preferred option to sustainably manage a new inlet opening is to Do Nothing and allow the new southern channel to open. The opening of a new channel will mean that Pagham Harbour will continue to be tidally inundated. The cut-off piece of Church Norton Spit would be reworked and potentially meld on to Pagham Beach leading to short- term reduced erosion (or more likely accretion) in front of Pagham Beach Estate. From an environmental perspective the amounts of saltmarsh, mudflat and tidal channel area will remain effectively unaltered although their configuration would change. The natural geomorphological processes inherent to the designation of Pagham Harbour would only be upset if the breach was artificially induced. A breach caused by natural processes would be considered a natural process and in line with the geological SSSI designation. This option is economically viable with low initial capital costs and ongoing maintenance.

Realigning the existing flood embankments (see Section 9.2) should be considered in combination with maintaining the new channel to maintain the tidal prism and therefore keeping the channel open.

10. Selection of Short Term Preferred Option

If no long term solution is identified the options detailed below can be selected to address any immediate issues once a management trigger is reached.

62 Environment Agency 10.1. Effect 1: Erosion of Pagham Beach

Table 10-1 provides a summary of potential options should a management trigger for erosion of Pagham Beach be reached.

Table 10-1 Summary of option appraisal

Effect on Flood Erosion Capital Effect on Option Maintenance Geological WFD Risk Risk Cost Habitats SSSI Do Nothing - allow Pagham Beach to        continue to erode Bypass shingle across        the inlet channel Recycle shingle from        Aldwick Beach Recharge beach with shingle from an        offshore source Construct additional        groynes Alternative tidal inlet        channel to the south Force closure of the        tidal inlet channel

The preferred option is provide an Alternative inlet channel to the south. However, the environmental impacts on the spit and potential disturbance of little tern habitat need to be considered carefully. Realigning the existing flood embankments to maintain tidal prism may potentially complement this option. However if this option is not feasible, Recycle shingle from Aldwick Beach and Bypass shingle across the inlet channel would be viable alternatives that reduce risk but may impact on WFD status.

10.2 Effect 2: Erosion of Existing Inlet Flood Embankments

Table 10-2 provides a summary of potential options should a management trigger for erosion of the existing inlet flood embankments be reached.

63 Environment Agency Table 10-2 Summary of option appraisal

Effect on Flood Erosion Capital Maintenance Effect on Option Geological WFD Risk Risk Cost frequency Habitats SSSI Do Nothing - allow flood embankments to  N/A      continue to erode Construct armourstone  N/A      revetment Construct gabion  N/A      mattress revetment Construct concrete  N/A      block revetment Close inlet channel by        beach recycling Realign the existing        flood embankments

The overall preferred viable option is to Realign the existing flood embankments. However, this option may not be economically viable and would require a better understanding of the proposed realignment impacts on the inlet. Therefore, it is recommended that Construct armourstone revetment and Construct gabion mattress revetment should be considered with appropriate mitigation measures put in place to minimise any impacts on the landscape.

10.3 Effect 3: Overtopping of Existing Inlet Flood Embankments

Table 10-3 provides a summary of potential options should a management trigger for overtopping of the existing inlet flood embankments be reached.

Table 10-3 Summary of option appraisal

Effect on Flood Erosion Capital Maintenance Effect on Option Geological WFD Risk Risk Cost frequency Habitats SSSI Do Nothing - allow flood embankment to  N/A      overtop Raise embankment  N/A      using earth fill Construct a concrete gravity wall along the  N/A      top of the embankment Install steel sheet pile wall along the top of  N/A      the embankment Close channel by beach shingle        recycling

64 Environment Agency Realign the existing        flood embankments

The overall preferred viable option is to Realign the existing flood embankments. However, this may not be economically viable and would require a better understanding of the proposed realignments impacts on the harbour. Two options that should be considered to mitigate the effects of overtopping are Install steel sheet pile wall along the top of the embankment and Construct a concrete gravity wall along the top of the embankment.

10.4 Effect 4: Impeded drainage into the inlet

Table 10-4 provides a summary of potential options should a management trigger for impeded drainage into the inlet be reached.

Table 10-4 Summary of option appraisal

Flood Erosion Capital Maintenance Effect on Effect on Option WFD Risk Risk Cost frequency Geological SSSI Habitats

Do Nothing - allow drainage impedance  N/A      to continue Fit duckbill check       valves to the outfalls N/A Excavate inlet bed at       outfalls N/A Extend outfalls into       the inlet N/A Form temporary storage outside the  N/A      inlet Pump drainage water       into the inlet N/A Close channel by        beach recycling

The preferred option to address lack of drainage is not clear and should be properly explored during the PAR stage once the trigger is reached. The preferred option will depend on whether drainage is constrained by water levels and/or sedimentation, as well as the potential geomorphological state, and any specific environmental interests at the site of impedance.

65 Environment Agency

11 Monitoring Programme

Table 4-1 presented a series of geomorphological management triggers for adaptive management and the parameters that need to be monitored to ascertain when the trigger state has been reached. A monitoring strategy is developed here for each of the critical geomorphological components and their triggers; Church Norton Spit, Pagham Beach and the inlet. Table 11-1 describes the proposed monitoring parameters and their frequency of collection for the Pagham Harbour system.

Table 11-1. Monitoring parameters for the Pagham Harbour system.

Location Trigger Parameter Method and Frequency of Measurement

Position of Church Norton Spit re-curve relative to Pagham Beach

Church Norton Low water depth at the Beach/Spit seaward end of the inlet channel Beach profiles (cross sections) as provided by Regional Monitoring programme (three times Beach berm crest width a year in September, December and April, along Church Norton Spit although flexible to allow post-storm surveys)

Beach berm crest height LiDAR: as provided by Regional Monitoring along Pagham Beach programme Position of mean high water Pagham Beach Back of beach width (the distance from the beach berm crest to the most seaward house)

Accretion plates. Number, location and Sediment accretion/erosion frequency of measurement to be informed by local to the drainage outfalls previous work by University of Sussex Pagham Harbour Condition assessments of Survey and visual observation flood embankments Condition assessments of Survey and visual observation training arm

66 Environment Agency

11.1 Beach and Inlet Channel Morphology

Two methods are recommended to monitor changes in profile of Church Norton Beach/Spit, the inlet channel and Pagham Beach; beach profiling, aerial photographs and LiDAR.

11.1.1 Beach Profiles Beach morphology should be monitored using cross-shore profile data to assess changes in width, slope and volume, and to describe beach behaviour and its variability. These data can be used to identify trends and areas of high net change and high variability. The temporal and spatial frequency of profiles depends on the specific aim of the monitoring and in areas where more information is required the temporal and spatial frequency can be increased. Currently, the Strategic Regional Coastal Monitoring Programme collates and interprets beach profiles for the Pagham Harbour frontage every six months and this campaign should continue but some flexibility needs to be built in to future campaigns to be able to monitor extreme events. Beach profiling is particularly important within the inlet channel where other remote forms of monitoring are not effective because of a water covered bed.

11.1.2 LiDAR Airborne Laser Induced Direction and Range (LiDAR) is a remote sensing technique already extensively used at Pagham Harbour for the collection of topographic data. Worthing Borough Council and Strategic Regional Coastal Monitoring Programme have developed digital terrain models (DTMs) for the Pagham frontage between Selsey Bill and Dark Lane, Aldwick between March 2003 and February 2011. LiDAR data collected approximately every six months by the Environment Agency has been utilised in the DTMs. This data collection should be modified to monitor significant changes in morphology that may occur at random intervals.

11.2 Pagham Harbour Sedimentation

Medium-term accretion (or erosion) rates at the outfalls can be measured using perforated aluminium accretion plates buried at selected positions along a line perpendicular to the intertidal slope. The number of plates needed to achieve an appropriate representation of sedimentation will have to be assessed prior to deployment. The plates should be buried to a depth of approximately 10 cm and left to settle for 4-6 months before the initial baseline measurements are made. Measurements should be made every three months, by taking up to 15 readings from the sediment surface to each plate, using a fine metal ruler or graduated metal pin.

11.3 Condition Assessments of Flood Embankments and Training Arm

Visual inspection is the simplest, quickest and most cost effective form of inspection and should be undertaken by a competent person in line with the Environment Agency Condition Assessment Manual 2006.

67 Environment Agency

12 Conclusions

This Report has considered the environmental effects, flood and erosion risks due to the findings of the Geomorphological model and compared this with the potential options available to mitigate changes. The report has determined that currently the triggers to define a change in geomorphological consequence and effects have not been reached. However it is considered that the erosion of Pagham Beach trigger is likely to be the first reached if processes continue they have over the last 5 years with no intervention.

The following are key conclusions identified as part of this report:

° The study area comprises a tidal inlet fronted by a dynamic shingle beach and spit complex, approximately 2km north east of Selsey on the Manhood peninsular, in an area of key environmental importance; ° There are a number of settlements situated close to the inlet including Pagham, Selsey, Siddlesham and low lying agricultural areas which are currently protected but may in the future become vulnerable to flooding and erosion due to the evolution of the harbour. Additionally a number of local watercourses discharge into the harbour and any evolution of the harbour may affect a wider area including the Flood Alleviation Scheme at Chichester. ° The strategic policy for this dynamic area is Adaptive Management and advocates monitoring the existing system and taking action to address specific issues with the consideration of wider constraints. ° There is a short term risk of coastal erosion and flooding to Pagham Beach and Pagham estate due to a sediment divide and scour controlled by the position and length of Church Norton Spit. ° Between March 2003 and January 2009 Pagham beach eroded by 0.9m/year. However more recently January 2009 to February 2011 has accreted by 1.7m/ year due to the implementation of renourishment activities. ° Based on the historic erosion rate of 0.9m/year it is anticipated that the warning trigger will be reached within 6 years. ° All flood embankments currently provide the required Standard of Protection. Flood risk will increase to Pagham and Siddlesham long term due to predicted sea level rise under this scenario all but two flood defence structures will require upgrading. ° Drainage structures are currently of a required condition grade. The Geomorphological model suggests that if current processes continue sedimentation within the harbour will continue at a rate of 4-8mm/year and it is likely that clearance works will be required. ° There are 6 water bodies classified by as Artificial or Heavily Modified Water Bodies present in the area classified as Moderate Ecological Potential that must be improved to Good Ecological Potential by direct management after 2015. ° Three potential geomorphological consequences and four effects were identified and a number of options were reviewed to ascertain their potential for management. ° The harbour should be monitored to understand whether a geomorphological consequence or effect has been reached. Once the trigger is reached the decision to address the localised issue or to implement a wider response to the consequence should be taken by the Technical Advisory group.

68 Environment Agency ° Once the decision whether to mitigate the consequence or localised effect has been taken a PAR including any recommended studies should be undertaken to confirm the preferred option. ° It is recognised there are conflicts between maintaining the current configuration of habitats and protecting geological interests. In order to maintain achieve Good Potential after 2015 direct management will be required that is likely to impact on the geological SSSI. If the SSSI is allowed to function naturally it is anticipated that the requirements of the Water Framework Directive will not be reached.

13 Recommendations

The following are key recommendations as a result of the completion of this study:

° Monitor triggers outlined in Table 4-1; ° Undertake study to confirm the impact on flood risk / drainage on allowing the inlet to seal naturally or forcing closure. ° The appropriateness of preferred options should be confirmed through the Environment Agencies Project Appraisal process; ° Funding opportunities through the Water Framework Directive should be explored in further detail. ° It is recommended that the proposed flood risk management measures are discussed with the Technical Advisory Group at the earliest opportunity after the Warning trigger is reached to identify an approved way forward; ° Discussions should be held with Natural England to discuss the potential conflicting environmental interest and a clear response should be formed to facilitate a smooth implantation of works once a trigger reached.

69 Environment Agency APPENDIX A

70 Environment Agency References

BOVINGTON, J. 2011. Draft Beach Management Plan Report: Pagham Harbour 2010. Report BMP127, January 2011.

BRAMPTON, A. 2011. Pagham Harbour Geomorphological Model Coastal Defence Options. HR Wallingford Technical Note DDR4659-02, February 2011.

ENVIRONMENT AGENCY. 2009. Pagham to East Head Coastal Defence Strategy.

ENVIRONMENT AGENCY. 2009. Arun and Western Streams Catchment Flood Management Plan.

ENVIRONMENT AGENCY. 2009. South East River Basin Management Plan.

ROYAL HASKONING. 2011. Pagham Harbour Conceptual Model.

HALCROW. 2004. Beachy Head to Selsey Bill Shoreline Management Plan. Report to South East Coastal Group, (lead authority: Arun District Council).July 2004.

ROYAL HASKONING. 2009. Pagham Coastal Defence Study Geomorphological Assesment. Report to Arun District Council, February 2009

1 Environment Agency Title

Would you like to find out more about us, or about your environment?

Then call us on 08708 506 506* (Mon-Fri 8-6) email [email protected] or visit our website www.environment-agency.gov.uk incident hotline 0800 80 70 60 (24hrs) floodline 0845 988 1188

* Approximate calls costs: 8p plus 6p per minute (standard landline). Please note charges will vary across telephone providers

Environment first: This publication is printed on paper made from 100 per cent previously used waste. By-products from making the pulp and paper are used for composting and fertiliser, for making cement and for generating energy.

Environment Agency Title 2

3 Environment Agency Title