Cornwall Coastal Flood Risk Modelling: Scoping Study

Summary Report

April 2011

South West Region Sir John Moore House Victoria Square PL31 1EB

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JBA Office

South Barn Broughton Hall Skipton North Yorkshire BD23 3AE JBA Project Manager

Dr Mark Lawless Revision History

Revision Ref / Date Issued Amendments Issued to 11 April 2011 - Gregg Kerry

Contract

This report describes work commissioned by Environment Agency under contract SW055. The Environment Agency’s representative for the contract was Gregg Kerry. Mark Lawless, Olga Kirton, Matt Hird and Chris Nickerson of JBA Consulting carried out the work.

Prepared by ...... Mark Lawless BSc MSc PhD CSci CEnv CWEM MCIWEM

Reviewed by ...... Simon Waller CEng BEng MICE Director Purpose

This document has been prepared as a Summary Report for the Environment Agency. JBA Consulting accepts no responsibility or liability for any use that is made of this document other than by the Environment Agency for the purposes for which it was originally commissioned and prepared. JBA Consulting has no liability regarding the use of this report except to the Environment Agency.

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Acknowledgments

JBA would like to extend our thanks to Gregg Kerry, Alice Howard and Richard Clements of the Environment Agency for their assistance in the preparation of this work. We would also like to all those that contributed to our consultation process. Copyright

© Jeremy Benn Associates Limited 2011 Carbon Footprint

294g

A printed copy of the main text in this document will result in a carbon footprint of 231g if 100% post-consumer recycled paper is used and 294g if primary-source paper is used. These figures assume the report is printed in black and white on A4 paper and in duplex. JBA is a carbon neutral company and the carbon emissions from our activities are offset.

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Executive Summary

This Scoping Study was commissioned by the Environment Agency’s South West Region, as part of its Flood Risk and Hazard Mapping Strategy. The principal objectives of the Scoping Study were as follows: To develop an innovative scope for a multi-faceted coastal flood risk modelling study; To update the methods and approaches traditionally used for standard coastal flood risk modelling studies to suit the unique mix of Flood Risk Drivers in the Environment Agency's Cornwall region (including the estuary); To engage with all relevant arms of the Environment Agency and its key partners to ensure that the Scope of Works developed will result in outputs providing maximum benefit to the region; To enhance the Environment Agency’s understanding of its exposure to coastal flood risk and to provide outputs that will help the Agency to prepare for and mitigate against these risks. Approach To achieve the above objectives, a Site Risk Assessment was carried out for 169 communities considered to have some level of coastal flood risk in the study area. This assessment culminated in the development of detailed Site Risk Assessment Sheets and Maps, supplied separately to this report. As part of this assessment, the communities were ranked in terms of priority for future investment in flood risk modelling and mapping. This ranking took account of the level of risk in each community and the complexity of the local Flood Risk Drivers. A range of methodologies, designed to formally evaluate flood risk as part of subsequent studies, have also been recommended. Given the wide range of Flood Risk Drivers that affect sites in the study area, and the varying degrees of risk, a one size fits all approach was not considered appropriate. Rather, it was considered more appropriate to outline a suite of methods that can be selected from to suit a site's prioritisation value and other local factors. Under this general approach, complex and costly methods will generally be reserved for higher priority sites, whilst simpler methods will be applied to lower priority sites. This risk based approach is in line with the Environment Agency's new Flood and Coastal Risk Management Risk and Modelling Strategies. It is intended that this Scoping Study will be followed by a Pilot Study and a Main Assessment Phase. The key objective of the Pilot Study will be to evaluate the methods proposed for a pilot region. This will help to further refine the methods proposed before commencement of the Main Assessment Phase. The objective of the Main Assessment Phase will be to produce new coastal flood risk information for the whole of the Cornwall region and potentially the . In addition to standard Flood Map products, it is anticipated that the Pilot Study and Main Assessment Phases will result in a range of additional datasets and deliverables, which will maximise the outcomes of the study for the region. Recommendations Pilot Study The key objective of the Pilot Study will be to test and refine the methods proposed to update these recommendations for the Main Assessment Phase accordingly. It will therefore be important to test and compare both the simplified methods and the advanced methods proposed so that the costs, strengths and limitations associated with both are better known. The Mount's Bay region, extending between and , has been chosen for the Pilot Study based on the following: (1) it includes a large number of properties potentially at risk of coastal flooding; (2) the region is subject to a wide variety of Flood Risk Drivers. In particular, there is a wide range of wave related risks; (3) given the nature of the bay, the communities in the region have varying exposure radii; (4) the region is very rich in terms of available data; (5) the opportunities for testing and comparing both simple and complex methods for evaluating risk are excellent; (6) the scale of the region is considered appropriate for a Pilot Study; (7) there are good opportunities for breakwater failure modelling in the

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region given the various ports, and; (8) there are good opportunities for forecasting improvements given the vulnerability to wave related risks and the varying exposures. A detailed Scope of Works has been provided for the Pilot Study, including a breakdown of all of the tasks required, the outputs that will be delivered and the associated costs. The Pilot Study represents an innovative and ambitious project, including the adoption of ensemble modelling techniques and advanced joint probability analysis; methods which are in keeping with the Environment Agency's new Flood and Coastal Risk Management Risk and Modelling Strategies. Whilst a number of event simulations and outputs are recommended, these recommendations are based on our current understanding of your requirements, gathered through the consultation process, rather than an as yet agreed set of simulations and deliverables. It will therefore be necessary to more formally agree a set of event simulations and deliverables at the start of the Pilot Study. This process may affect the cost estimates provided. Main Assessment Phase The objective of the Main Assessment Phase will be to produce new coastal flood risk information for the whole of Cornwall and potentially the Isles of Scilly. In practise, the Main Assessment Phase may consist of a series of projects, rather than one large project. The Site Summary Sheets and additional tables presented in this report provide good insight into the scale of work, where priorities should lie, and the methods required for the Main Assessment Phase. The Pilot Study will also provide further insight in this respect. Data This study included an assessment of the data requirements for the Pilot Study and Main Assessment Phase, set against the methods recommended for the evaluation of flood risk for each community. Whilst these data assessment was reasonably comprehensive, it has not been possible to fully check all data availability and/or quality. It will therefore be necessary to include a data collection and review phase for all subsequent stages of the project, informed by the details provided in the Site Risk Assessment Sheets and Maps. In particular, it is not known whether there is a complete coverage of reliable defence crest levels available, although it is expected that a near complete dataset is. Furthermore, it is expected that a reasonable amount of defence cross-section surveying will be required as part of any subsequent study involving wave overtopping analysis. Some inner harbour bathymetry data is also required. It is expected that these data will be available from the Port Authorities. Recommendations are provided with respect to the deployment of temporary wave buoys and water level gauges. Deployment of these devices would provide useful new data to aid in the calibration and validation of the modelling proposed. However, the deployment of these devices may be overly expensive. It is therefore recommended that the issue of device deployment is discussed further following the Pilot Study. We note that the Environment Agency owns two wave buoys that are currently not in operation. We would recommend that these buoys are deployed strategically before the winter season in order to obtain new data to aid in future phases of the project. This should be discussed further as part of the Pilot Study.

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Contents

Executive Summary ...... iii 1. Introduction ...... 1 1.1 Introduction ...... 1 1.2 Study Approach ...... 1 1.3 Chapter Summary ...... 2 2. Outcomes of Consultation Process ...... 3 2.1 Introduction ...... 3 2.2 Flood Risk Drivers ...... 3 2.3 Site Risk Assessment and Prioritisation ...... 5 2.4 Modelling Scenarios and Outputs Required ...... 5 2.5 Data Requirements and Availability ...... 6 3. Site Assessment Methodology ...... 9 3.1 Introduction ...... 9 3.2 Site Risk Assessment Sheet Content ...... 9 3.3 General ...... 9 4. Summary of Site Assessment Results ...... 17 4.1 Introduction ...... 17 4.2 Summary of Prioritisation Results ...... 18 4.3 Implications for Pilot Stage ...... 21 4.4 Implication for Main Assessment Phase ...... 25 5. Methodology ...... 26 5.1 Introduction ...... 26 5.2 Derivation of Boundary Conditions ...... 26 5.3 Wave Transformation Modelling ...... 28 5.4 Wave Overtopping and Run-up Modelling...... 30 5.5 Flood Inundation Modelling ...... 31 6. Scope for Pilot Study ...... 35 6.1 Introduction ...... 35 6.2 Task 1: Data Collection and Analysis ...... 35 6.3 Task 2: Wave Transformation and Overtopping Modelling ...... 36 6.4 Task 3: Flood Inundation Modelling ...... 38 6.5 Task 4: Reporting and Recommendations ...... 39 6.6 Project Meetings and Site Visits ...... 40 6.7 Pilot Study Costs and Programme ...... 40 7. Summary, Conclusions and Recommendations ...... 41 7.1 Summary ...... 41 7.2 Conclusions and Recommendations ...... 41 A. Site Summary Master Tables ...... I

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List of Figures

Figure 1: Flood Risk Drivers ...... 5 Figure 2: Schematic Representation of Modified Projection Modelling ...... 32 List of Tables

Table 1: Data Types and Sources ...... 7 Table 2: Site Assessment Summary Sheet Information ...... 17 Table 3: North Coast Summary Statistics ...... 19 Table 4: South Coast Summary Statistics ...... 20 Table 5: Potential Pilot Study Locations and Statistics ...... 22

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1. Introduction

1.1 Introduction This Scoping Study was commissioned by the Environment Agency’s South West Region, as part of its Flood Risk and Hazard Mapping Strategy. The principal objectives of the Scoping Study were as follows: To develop an innovative scope for a multi-faceted coastal flood risk modelling study; To update the methods and approaches traditionally used for standard coastal flood risk modelling studies to suit the unique mix of Flood Risk Drivers in the Environment Agency's Cornwall region (Including the River Tamar estuary); To engage with all relevant arms of the Environment Agency and its key partners to ensure that the Scope of Works developed will result in outputs providing maximum benefit to the region; To enhance the Environment Agency’s understanding of its exposure to coastal flood risk and to provide outputs that will help the Agency to prepare for and mitigate against these. It is intended that this Scoping Study will form part of a suite of studies, which will principally include a Pilot Study and a Main Assessment Phase, but may also include additional pieces of work. The key objective of the Pilot Study will be to evaluate the methods proposed herein for a pilot region. This will help to further refine the methods proposed before commencement of the Main Assessment Phase. The objective of the Main Assessment Phase will be to produce new coastal flood risk information for the whole of the Cornwall region and potentially the Isles of Scilly. In addition to standard Flood Map products, it is anticipated that the Pilot Study and Main Assessment Phases will result in a range of additional datasets and deliverables, which will maximise the outcomes of the study.

1.2 Study Approach Following from the objectives above, the Scoping Study involved 6 key tasks, as summarised below: Task 1 (Consultation). This task involved two stages of consultation designed to aid in the development of the Scope of Works for the subsequent stages of the project and to discuss project expectations, flood scenarios and outputs required, and data availability. Task 2 (Site Assessment). This task involved a site by site evaluation of the nature of the flood risk for the 169 communities identified as potentially vulnerable to flooding from the sea. This evaluation culminated in the development of Site Risk Assessment Sheets and Maps. Task 3 (Prioritisation). This task involved a prioritisation exercise designed to provide direction in terms of how to best direct funds for the Pilot Study and Main Assessment Phases. Task 4 (Method Assessment). This task involved an assessment of how to best evaluate flood risk for each Flood Risk Site, accounting for the overall objectives of the study and the outcomes of Tasks 1-3. Task 5 (Review of Data Availability). This task involved a review of the data available for the region, set against the methods proposed in Task 4. Where data gaps exist, these have been identified as best possible. Task 6 (Scope Development for the Pilot Study). This task involved the development of a scope of works for the Pilot Study.

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1.3 Chapter Summary In addition to this chapter, this report includes the following 6 chapters: Chapter 1 (Introduction) introduces the report and its context. Chapter 2 (Consultation Meeting) summarises the outcomes of the consultation process in a manner that puts the remainder of the report into context. Chapter 3 (Site Risk Assessment Methodology) outlines the methods undertaken to assess flood risk for the 169 communities potentially at risk of flooding from the sea and introduces the associated Site Risk Assessment Sheets and Maps. This chapter also summarises the approaches taken to prioritise the coastal communities in terms of future investment in flood modelling and mapping. Finally, the chapter provides background in terms of the methods available for coastal flood risk modelling and assesses which methods are best suited to each coastal community. Chapter 4 (Summary of the Site Assessment Results) summarises the findings of the Site Risk Assessment exercise and discusses the implications of these results in terms of the Pilot Study and Main Assessment Phase. Chapter 5 (Methodology) outlines the analysis and modelling approaches recommended for the Pilot Study and Main Assessment Phase. Chapter 6 (Scope for Pilot Study) outlines the proposed Scope of Works for the Pilot Study. Chapter 7 (Conclusions and Recommendations) provides final conclusions and recommendations for the study. Appendix A (Site Summary Master Tables) includes two tables which summarise the key results from the Site Risk Assessment and Prioritisation exercise.

Two additional detailed reports accompany this Summary Report. These include the following: Cornwall Site Risk Assessment Sheets (North Coast). Report produced by JBA on behalf of the Environment Agency, April 2011. Cornwall Site Risk Assessment Sheets (South Coast). Report produced by JBA on behalf of the Environment Agency, April 2011. These reports include all of the individual Site Risk Assessment Sheets, as introduced further in Chapter 2.

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2. Outcomes of Consultation Process

2.1 Introduction One of the key objectives of this Scoping Study was to engage with all relevant arms of the Environment Agency and its partners. This helped to ensure that the Scope of Works developed for the Pilot Study and Main Assessment Phase will result in outputs providing maximum benefit to the region and will fully account for the nature of coastal flood risk in the region. To ensure that this is the case, two separate stages of consultation were held. The first stage was held on 18 August 2010 and was attended by members of the Environment Agency, , Plymouth City Council and the Channel Coastal Observatory (CCO). This meeting provided important initial direction for the study in terms of expectations, requirements, previous and ongoing work and data availability. The second stage of consultation was held on the 24 March 2011 and was attended by key members of the Environment Agency. At this consultation meeting, the results of the Scoping Study were discussed and final agreement was reached on its key outcomes, conclusions and recommendations. Rather than report the minutes from each of the meetings directly, this chapter summarises the outcomes of the consultation process in a manner that puts the remainder of the report into context. To do so, a number of key topics addressed as part of the consultation process are discussed below, including: (1) Flood Risk Drivers; (2) Site Risk Assessment and Prioritisation; (3) Modelling scenarios and outputs required, and; (4) Data requirements and availability.

2.2 Flood Risk Drivers The geography of the Cornwall study area is such that it is vulnerable to a wide range of coastal Flood Risk Drivers. The key drivers of risk discussed at the consultation meetings that require consideration as part of the Pilot and Main Assessment Studies are as followings: Extreme still water flooding. The term still water sea-level refers to the level that the sea reaches as a function of the underlying astronomical tide and the passage of a large-scale storm surge (Figure 1a). Many of the communities in the study area are protected from still water flooding due to the presence of flood defences or because they are situated on higher ground. However, there remains a risk from still water flooding for many communities on the tidal rivers and estuaries in the study area, where there are "No Defences" or the defence standards are low. Furthermore, vulnerability to still water flood risk will increase in the future due to sea-level rise. Wave overtopping. Wave overtopping is the process by which waves impact and overtop flood defences, leading to flooding behind them (Figure 1a). For sites exposed to significant wave action, wave overtopping is the principal Flood Risk Driver in the region. Wave run-up. Wave run-up is the oscillating elevation of sea-levels associated with the advance and retreat of individual waves (Figure 1b). In areas exposed to significant wave action, the elevation that each individual wave reaches can far exceed the still water sea-level, increasing local vulnerability to coastal flooding. Wave run-up is a key risk in the study area where raised flood defences are not present to disrupt wave run-up (e.g. natural beaches, slipways).

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Wave set-up. Waves transport not just energy, but also momentum. This momentum transport is equivalent to a stress which acts as a 'push' on the sea surface, similar to wind. The consequence of this force is that waves, like wind, can tilt the sea surface towards land (Figure 1a). This 'tilting' effectively raises the still water sea-level in the nearshore zone, thereby exacerbating flood risk. A recent study undertaken by Royal Haskoning1, on behalf of the Environment Agency, investigated the consequences of wave set-up in the Cornwall region and indicated that set-up values of the order of 0.2-0.3m, and perhaps as high as 0.9m, have occurred. The locations of greatest vulnerability are those with an exposure to significant wave action. , , and the region between and are particular communities highlighted as at risk to wave set-up in the Royal Haskoning report. However, it is expected that the vulnerability to this Flood Risk Driver is more widespread. Wave surge. Under particular combinations of conditions, an additional wave related risk is also known to occur in the study area. This phenomenon, referred to as wave surge herein, occurs when breaking waves coalesce in the nearshore region, resulting in incoming masses of water which exhibit a wave-like leading edge. The effect of this phenomenon, which has been captured in a variety of videos in the study area, can lead to transient, but dramatic rises in sea-level. Wind set-up. In estuaries and tidal rivers, strong local winds can also increase sea- levels as the wind pushes the water into narrowing channels and/or constricting coves and inlets. As the water enters these areas, it elevates as it backs up. This set-up is similar to a large-scale storm surge. However, it is a local phenomenon generated by local winds. Large-scale storm surges, on the other hand, generate deep in the Atlantic and are regional in scale.

The impacts of all of the above Flood Risk Drivers, during a particular storm, for a particular community, are heavily dependent upon the directional characteristics of the storm (i.e. the trajectory of the surge, wave direction, wind direction) and the exposure radius of the community. The term exposure radius refers to the range of directions that a community is exposed to in terms of wave and wind impacts. The communities in the study area for this project exhibit a wide range of exposure radii. This means that one community may be flooded significantly during a storm event, whilst a community nearby but with a different exposure radius, may receive no flooding at all. During the consultation phase, it was agreed that the effects of exposure and storm direction should be a key element of the analysis undertaken as part of the Pilot Study and Main Assessment Phase. In addition to the above parameters, coastal flood risk in the study area can be exacerbated by the following additional drivers: Fluvial flooding Pluvial flooding Defence failure Breakwater failure Sea-level rise Whilst most of the above parameters do not require definition, it is worth discussing breakwater failure. Breakwater failure was highlighted as a key Flood Risk Driver that should be evaluated as part of the Pilot Study and Main Assessment Phase. Breakwaters are often overlooked in terms of their importance as a flood defences. If breakwaters fail, larger waves will penetrate into harbour areas and exacerbate flood risk. There are a large number of breakwaters in the study area providing flood protection for a significant population. Some of these structures are in a bad state of repair. Consequently, there is a desire on the part of the Environment Agency to produce evidence to highlight the importance of breakwaters as flood defences. This may help secure funding for breakwater improvements.

1 Pilot Study into the Influence of Storm Conditions on Extreme Tide Levels. Report by Royal Haskoning on behalf of the Environment Agency, February 2009.

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Wave Overtopping Wave Set-Up

Waves Surge Still-water level Tide

Wave Run-Up

Figure 1: Flood Risk Drivers

2.3 Site Risk Assessment and Prioritisation It was recognised at the consultation meetings that the relevance and impact of the above Flood Risk Drivers varies substantially from one community to another. Some sites are subject to a wide range of Flood Risk Drivers and the assessment of flood risk required for these sites as part of the Pilot Study and Main Assessment Phase will therefore be relatively complex. Some sites, on the other hand, are only subject to a limited number of Flood Risk Drivers and will be much simpler to assess in terms of flood risk. Furthermore, the level of risk in terms of receptors varies substantially from one community to another, meaning that complex and expensive methods may not be justified for all communities. Recognition of the above during the consultation process highlighted a desire to undertake a prioritisation exercise as part of the Scoping Study. The goal of this exercise was to provide guidance in terms of locations where relatively complex and expensive modelling is required and justified and where simpler, cheaper techniques could be employed. It was agreed that the best way to undertake this prioritisation exercise was to develop Site Risk Assessment sheets for each community. These Site Risk Assessment sheets would quantify each site in terms of its complexity (i.e. the number of Flood Risk Drivers acting locally) and its risks (i.e. the number of properties at risk). The complexity and risk factors would then be used to prioritise all of the sites as low, medium or high priority in terms of future investment. This risk-based approach is in keeping with the Environment Agency's Flood and Coastal Risk Management Risk and Modelling Strategies. Following from the first consultation meeting, a methodology for the Site Risk Assessment and Prioritisation exercise was developed and undertaken, as discussed in the following two chapters.

2.4 Modelling Scenarios and Outputs Required A key element of the consultation process involved identification of the requirements of the Pilot Study and Main Assessment Phase in terms of modelling scenarios and outputs. As discussed in Chapter 1, one of the key goals of the study was to develop a Scope of Works that will provide maximum benefit to the region. The modelling scenarios identified as required were as follows: Standard Flood Map Scenarios (i.e. Flood Zone 2 and 3, and Areas Benefiting from Defences). Whilst it was agreed that these standard modelling scenarios are required, it was also agreed that the approaches taken to model them should be

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adapted from national standards to suit the unique nature of flood risk in study area. For instance, it was agreed that a number of the key Flood Risk Drivers identified above, which are not currently recognised in national guidance, require inclusion in the modelling processes. These include the effects of Wave Run-up, Wave Set-up and Wind Set-up as well as modelling which better accounts for the importance of the joint probability of sea-level and wave properties and the effects of storm direction and exposure. It was agreed that the outputs should be based on worst-case combinations of these variables. Additional Return Period Simulations. In addition to the standard Flood Map outputs, modelling the flooding associated with lesser return period events was also highlighted as a key objective for Flood Forecasting Improvements. These scenarios are required to be "With Defences" in nature and designed to account for realistic combinations of sea-level, wave properties and storm direction. Climate Change Scenarios. Climate change scenarios based on a range of time horizons are required. Breach Scenarios. It was agreed that the development of continuous breach simulations are a requirement of the Pilot Study and Main Assessment Phase for higher priority sites; these outputs will help to improve development control and flood forecasting. For this type of modelling, breaches are modelled in the defences at regular intervals, perhaps of the order of one per 500m of defence. This approach will provide a complete set of breach-based flood outlines. Furthermore, it could be argued that producing a composite maximum flood outline based on the combination of all the individual breach outlines provides a more realistic, and in some cases conservative, representation of the worst-case flood outlines than is achieve by standard "No Defences" modelling. The breach modelling should account for worst case combinations of sea-level, wave properties and storm direction. Ensemble/probabilistic modelling. Undertaking the above modelling will require a large number of simulations to be undertaken and detailed evaluation of joint probabilities. Collectively, the requirements of these outputs point towards modelling that is ensemble, or probabilistic in nature; an approach that is part of the Environment Agency's future strategy for Flood Risk Modelling and Mapping. It was therefore agreed that a probabilistic type approach should be taken for the Pilot Study and Main Assessment Phase. Breakwater failure modelling. In addition to standard breach type simulations, the simulation of the impacts of breakwater failure modelling, as discussed above, was a key modelling scenarios identified at the consultation meeting.

For each of the above scenarios, a number of deliverables were highlighted as required. Whilst not all deliverables will be required for all scenarios, as a collective, the types of deliverables that were identified as required are as follows: Flood outlines (individual and composite) Flood depth, velocity and hazard grids Animations of flooding Onset of Flooding grids It was agreed that the Pilot Study will provide the opportunity to further evaluate the exact nature of the outputs required. This issue is discussed in further detail in Chapter 5 and 6.

2.5 Data Requirements and Availability A wide variety of data requirements were discussed as part of the consultation process. A summary of the key data types, the nature of the application of these data and potential sources of data are outlined in Table 1. A more detailed site by site assessment of the availability of data is provided in Site Assessment Sheets introduced in Chapter 4.

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Table 1: Data Types and Sources Data Type Requirement Data Source Bathymetry Data Required to represent the Data is available from the CCO for a sea-bed in wave significant proportion of the study area. transformation models and This includes single beam data (cross- flood inundation models sections that extend 0.5 to 1km out to sea) and SWATH bathymetry data. Key areas where CCO data does not exist includes the estuaries and tidal rivers. These data may be available from the Ministry of Defence for the River Tamar estuary and SeaZone for some other locations. LiDAR data will also provide a representation of bathymetry in some shallow water locations given that it is generally flown at low tide. Plymouth University is also likely to hold bathymetry data. LiDAR Data Required to represent the terrain The principal source of LiDAR data is the for flood inundation models. High Geomatics Group, who hold a near resolution data may also provide a complete coverage of 1m and 2m LiDAR representation of defence crest data for all coastal areas, as well as 0.5m levels and profiles in some LiDAR for some urban areas. The CCO locations. also holds 0.5m LiDAR data for the Isles of Scilly. Finally, at the time of the first consultation meeting, the CCO were in the process of collecting new LiDAR data for the whole of the Cornish coastline. Defence Crest Levels Required to represent flood Data is available from NFCDD as well as defences in the "With Defences" recent local surveys. It is expected that models and for wave overtopping there is a near complete coverage of calculations. crest level data. However, it is not clear if these data have all been incorporated into NFCDD. As discussed further in the forthcoming chapters, it is likely that some defence surveying will be required for the Pilot and Main Assessment Studies. Defence Cross Sections Required for wave overtopping There is no purpose built source of data on calculation. flood defence cross-sections. However, as discussed below, the CCO collect beach profiles on a regular basis. Where defences are present on the beaches these are normally surveyed. As discussed further in the forthcoming chapters, it is likely that some defence surveying will be required for the Pilot and Main Assessment Studies.

Beach Profiles Required for wave overtopping The CCO hold beach profile data for most and wave run-up calculation. areas where there are accumulations of sediment. These data include annual profiles as well as post storm event profiles.

Tide Gauge Data Required to calibrate and validate Recorded water level data with a tidal flood inundation models and for signature is available for a number of sites joint probability analysis in the study area. Whilst not an exhaustive list, some of the key sites are: , Port Issac (step gauge), , , Sladesbridge, , St Ives, , Falmouth, , Pentewan, Par, , Plymouth (Devonport).

Wave Buoy Data Required to calibrate and validate Wave buoy data is available from the wave transformation models and CCO for Penzance, , Seven for extremes and joint probability Stones, Looe and Bideford Bay. It is also analysis. expected that wave buoy data will be available from the MOD for the River Tamar estuary. Hindcast wave buoy data are also available from the Met Office's UK Waters Wave Model as part of a

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licence agreement with the EA. Meteorological Data Wind data required for extremes Hindcast wind data are available from the and joint probability analysis for Met Office's UK Waters Wave Model as wave transformation modelling. discussed above. Recorded wind data is also available from the Met Office. However, these data are very expensive. Channel cross-section data Required to represent narrow Will be available only for studies where channels in flood inundation previous detailed fluvial modelling has models. been undertaken. As discussed further in the forthcoming chapters, it is likely that some channel surveying will be required for the Pilot and Main Assessment Studies.

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3. Site Assessment Methodology

3.1 Introduction Chapter 2 summarises the results of the consultation process that provided the principal direction for the Scoping Study. As outlined in Chapter 2, a key objective that came out of the consultation process was a desire to base the scope of works for the Pilot Study and Main Assessment Phase on a risk-based or prioritisation-based approach. The methodology developed to achieve this objective involved a step by step appraisal of the nature of risk for each of 169 communities in the study area deemed to have some degree of coastal/tidal flood risk. This appraisal is detailed for each community in a series of Site Risk Assessment Sheets, supplied separately to this Summary Report. These Site Risk Assessment Sheets achieve the following for each community: Identify the risk receptors in each community; Identify the key Flood Risk Drivers for each community; Classify each community as low, medium or high priority in terms of the future investment in flood risk mapping and modelling; Recommend an approach for evaluating flood risk at each site based on its risk receptors, Flood Risk Drivers and priority assessment; Identify the data required for the proposed evaluation method for each site and outline any likely data gaps. The Site Assessment Sheets contain nine sections for each community. A general description of the information contained in each of these sections is provided below.

3.2 Site Risk Assessment Sheet Content

3.3 General FRS Reference: Unique Flood Risk Site (FRS) reference number given to each site. A community may have more than one Flood Risk Site. This reflects the fact that different parts of a community may be vulnerable to different mechanisms of flooding. FRS Name: Flood Risk Site Name FRS Description: General description of the Flood Risk Site.

3.3.1 Risk Receptors (Related to Coastal Flooding) Indicative number of properties at risk: This is an indicative estimate of the number of properties that may be at risk of coastal flooding. This number has been estimated using simple projection modelling techniques to identify properties below a particular threshold level, termed the Indicative Extreme Sea-level. This assessment has been undertaken using a simple GIS approach and available LiDAR data. The property numbers have been tabulated using the National Property Dataset and professional judgement. The nature of the Indicative Extreme Sea-level estimate used varies somewhat from site to site. For all sites this level principally includes a 0.5% Annual Exceedance Probability (AEP) extreme still water sea-level estimate, as provided by the new Coastal Flood Boundary Data Project (SC060064). An allowance for 100 years of climate change (sea-level rise) has been added to these extreme still water sea-level estimates. This means that the property estimates represent properties considered to be at risk now, or over the next century.

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For sites which are expected to be exposed to significant wave action, the Indicative Extreme Sea-level estimate also includes a Wave Impacts Allowance based on a significant wave height and wave set-up estimate. The significant wave heights used for this allowance are generally those derived by Royal Haskoning as part of the 2006 Areas Benefiting from Defences study. However, for some sites no previous estimates were available and an indicative value was used for the analysis. The wave set- up values are based on a rule of thumb approach, where wave set-up is considered to be of the order of 10% of the wave height2.

Once the Indicative Extreme Sea-level estimates were derived for each site, a flood outline was produced based on this level; the property numbers within each outline was then estimated. The Site Assessment Maps that accompany this report illustrate the outlines produced using this method for both present day climate conditions (2010) and climate conditions in the year 2115.

It is important to recognise that simply projecting the extreme still-water sea-level estimate plus a wave height and set-up allowance by no means accounts for the complexity of wave overtopping, wave set-up and wave run-up processes. Nevertheless, in a region like Cornwall, where floodplains are generally narrow due to steep topography, this simple approach is suitable for the purposes of the general assessment carried out for this study. Clearly, more sophisticated wave modelling will be required as part of the Pilot and Main Assessment Phases. Furthermore, the assessment does not take account of defences and therefore represents the undefended floodplain.

The outlines produced for this general assessment are not a replacement for the current Flood Map. In some areas, the maps produced will represent an overestimate of the actual floodplain and in some areas the outlines produced will represent an underestimate. However, the outlines provide a useful tool by which to compare the scale of risk between different sites. General description of properties: General description of property at risk (i.e. residential, commercial, industrial, caravans, beach huts, etc). Key infrastructure at risk: Any key infrastructure at risk (generally roads and transport networks) Historical evidence of flooding: Key dates of known flood events.

3.3.2 Flood Defences Coastal defence types: General description of defences present. Coastal defence heights: Summary of crest levels if known. Breakwaters: General description of breakwaters present. Breakwater heights: Summary of breakwater level if known. Fluvial defence types: General description of defences present. Fluvial defence heights: Summary of crest levels if known.

2 Random Seas and Design of Maritime Structures, Advanced Series on Ocean Engineering Volume 15, Y Goda, 2000.

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3.3.3 Photos This section includes key photographs taken during the site visits. It should be noted that only some sites were visited as part of this study. The sites visited were those that are considered to be high risk in terms of coastal flooding and where there is an interface with the open sea (i.e. where complex wave related processes are expected to occur during a storm). It will be necessary to carry out additional site visits as part of the Pilot Study and Main Assessment studies. 3.3.4 Flood Risk Drivers Flood Risk Sources This section provides an assessment of the vulnerability of each site to each of the key flood risk sources outlined in the table below. Variable Relevant Comments Still water flooding Yes/No Is the site at risk of flooding from still water sea-levels alone? Wave overtopping Yes/No Is the site at risk of flooding from wave overtopping? This is only the case if there is a defence or natural barrier to overtop. Wave set-up Yes/No Is the site at risk of flooding from wave set-up? This will only be the case if the site is expected to be exposed to persistent, significant wave action (i.e. sites with an open sea exposure). Wave run-up Yes/No Is the site at risk of flooding from wave run-up? This will be the case for instance where waves can run up a beach or onto a road and affect adjacent properties. This will generally be the case for a site where there are "No Defences" present to interrupt wave run-up. Wind set-up Yes/No Is the site at risk of flooding from wind set-up? Wind set up, which is in addition to storm surge, is known to increase water levels in estuaries and tidal rivers (above the predicted extreme still water sea-level) if the winds are in the direction of surge propagation and are persistent. Defence failure Yes/No Is the site at risk of flooding from defence failure? This will only be the case if raised flood defences are present and if there is property behind these defences. No account has been made of the impacts of the failure of rip rap on a non raised coastal defence. Furthermore, no account of the condition of defences has been taken. Breakwater failure Yes/No Is the site at risk of flooding from breakwater failure? This will only be the case if a breakwater is present and if the failure of this breakwater would result in the penetration of large waves into a flood risk area, thereby increasing flood risk. Fluvial flooding Yes/No Is the site at risk of flooding from fluvial sources? This assessment is based simply on whether or not a fluvial watercourse is present and whether a combined fluvial/tidal event is expected to exacerbate flood risk. No account of the joint probability of this occurrence has been accounted for. Sea-level rise Yes/No Is the site vulnerable to sea-level rise? This is the case if the Year 2115 flood outlines include more property than the Year 2010 flood outlines. This is normally the case.

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Indicative Extreme Values In this section, key information is included on relevant sea-level and wave components. This includes the following: Extreme sea-level estimates for the site based on the Coastal Flood Boundary Data project. These are presented in both numerical form and graphic form. The reference number from the Coastal Flood Boundary Project is also provided (CEE Ref). A wave exposure radius plot, which illustrates the directions for which the site is exposed to wave action. Sites that are sheltered from significant wave action do not include an exposure graph. An indicative significant wave height estimate. These are generally based on the estimates derived by Royal Haskoning as part of the 2006 Areas Benefiting from Defences project. Some professional judgement has also been used where previous estimates do not exist. An indication of wave set-up. This value represents 10% of the indicative significant wave height. The significant wave height and wave set-up values have also been summed to derive a Wave Impacts Allowance. As discussed above, this indicative Wave Impacts Allowance was added to the still water sea-level for each site to produce an Indicative Extreme Sea-level estimate for a 200 year return period event now and in the year 2115. These values were used to produce the indicative flood outlines. They are also illustrated on the extreme sea-level plots in the Site Assessment Sheets, as shown below (termed Indicative wave height in the legend). These extreme sea-level plots also include a line that indicates the approximate threshold level of the lowest property in the flood risk area. Comparison of the different lines on the extreme sea-level plots therefore provides a general indication of whether the site is vulnerable to still water flooding and/or wave impacts now or in the future.

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Figure 1: Representation of extreme sea-levels, wave allowances and wave exposure radius

Still-Water Sea-Level (2010) 10 Still Water Sea-Level (2115) Minimum crest height 9 Indicative wave height (2010) Indicative wave height (2115) 8 N (0o)

7 level (mAOD) - 6 wave

Sea exposure W (270o) E (90o) 5

4 1 10 100 1000 10000 S (180o) Return Period (years) Variable Source Data Extreme sea CEE Ref: 86 AEP (%) ESWL (2010) ESWL (2115) levels 100.00 4.72 5.8 50.00 4.79 5.87 20.00 4.88 5.96 10.00 4.95 6.03 5.00 5.01 6.09 4.00 5.02 6.1 2.00 5.08 6.16 1.33 5.11 6.19 1.00 5.13 6.21 0.67 5.16 6.24 0.50 5.18 6.26 0.40 5.19 6.27 0.33 5.2 6.28 0.20 5.22 6.3 0.10 5.24 6.32 0.01 5.26 6.34 Indicative 2006 ABD e.g. Depth limited wave height: 2.39m. nearshore wave heights Wave exposure e.g. Winds from 185 to 355 degrees. Strongest winds radius from 240-330. Wave set-up e.g. of the order of 0.24m.

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3.3.5 Prioritisation Factor Prioritisation Ranking A prioritisation exercise was carried out to provide guidance in terms of how to best direct funds for the Main Assessment Phase (for instance, where should advanced modelling techniques be applied to evaluate flood risk and where can money be saved by using simple methods?). This prioritisation was based on a Risk Factor, related to the number of properties at risk of flooding and a Complexity Factor, based on the number of Flood Risk Drivers acting at the site (as identified in Section 3.3.4 above). Clearly, if a site is vulnerable to a multitude of Flood Risk Drivers, the modelling required to simulate flood risk will be more complicated than a site vulnerable to less drivers. The key factors used to evaluate the Prioritisation Factor are further discussed below. Risk Factor (RF): The Risk Factor is based on the number of properties identified as potentially at risk of coastal flooding. Flood Risk Sites with no properties considered to be at risk of coastal flooding have been assigned a Risk Factor of 0. Flood Risk Sites with 1-10 properties considered to be at risk of coastal flooding have been assigned a Risk Factor of 1. Flood Risk Sites with 11-100 properties considered to be at risk of coastal flooding have been assigned a Risk Factor of 2. Flood Risk Sites with more than 100 properties considered to be at risk of coastal flooding have been assigned a Risk Factor of 3. Complexity Factor (CF): The Complexity Factor was evaluated by summing up the total number of Flood Risk Drivers acting at each site based on the table given in Section 3.3.4 above. A total of 9 drivers have been used in the assessment. Sites with 3 or less Flood Risk Drivers have been assigned a Complexity Factor of 1. Sites with between 3 and 6 drivers have been assigned a Complexity Factor of 2. Sites with greater than 6 drivers have been assigned a Complexity Factor of 3. Prioritisation Factor (PF): Evaluation of the Prioritisation Factor involved two steps. Firstly, the Risk Factor (RF) and Complexity Factor (CF) were combined in the following way to evaluate a Prioritisation Score (PS):

PS=(2*RF)×(CF)

The double weighting of the Risk Factor was done to ensure that the risk, in terms of people and property, was the key factor used in the prioritisation exercise. Once the Prioritisation Score was computed, the Prioritisation Factor was evaluated based on the following categories:

PF= Low for PS between 0 and 4 PF = Medium for PS between 5 and 8 PF = High for PS greater than 8

It is important to recognise that whilst the Prioritisation Factor was evaluated in a systematic and objective manner, it is not based on any nationally recognised method or guidance. The method was designed for the purposes of this study only. It was schematised based on professional judgement and our understanding of the Environment Agency's objectives. The assessment should be considered with this in mind. Indeed, there may be other factors that will affect the Environment Agency's opinion on prioritisation that have not been considered in this objective assessment (e.g. political, proposed schemes, etc).

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Proposed Methodology Assessment The Site Assessment Sheets also include a consideration of the most suitable method of evaluating flood risk at each site based on the Flood Risk Drivers acting locally and the Prioritisation Factors evaluated. Additional information on the methods considered for each site is given below. Variable Required Comments Wave transformation modelling Yes/No Does the site require wave transformation modelling to fully evaluate flood risk and are the costs associated with this complex modelling justified by the Prioritisation Factor? Wave overtopping Yes/No Does the site require wave calculations to fully evaluate flood risk and are the costs associated with this analysis justified by the Prioritisation Factor? Wave set-up analysis Yes/No Does the site require wave set-up analysis to fully evaluate flood risk? Given the Prioritisation Factor, should this assessment be based on simple methods or complex methods? Wave run-up analysis Yes/No Does the site require wave run-up calculations to fully evaluate flood risk and are the costs associated with this analysis justified by the Prioritisation Factor? Wind set-up analysis Yes/No Does the site require wind set-up analysis to fully evaluate flood risk? Given the Prioritisation Factor, should this assessment be based on simple methods or complex methods? Defence failure modelling Yes/No Should defence failure modelling be undertaken for the site and is this justified by the Prioritisation Factor? Breakwater failure modelling Yes/No Should breakwater failure modelling be undertaken for the site and is this complex modelling justified by the Prioritisation Factor? This type of modelling would require the construction of a wave transformation model. Projection modelling Yes/No Can simple projection modelling be used to evaluate flood risk and is the use of this method justified by the Prioritisation Factor? Hydrodynamic flood modelling Yes/No Does the site require the construction of a (2D, 1D/2D) hydrodynamic model to fully evaluate flood risk and are the costs associated with this complex modelling justified by the Prioritisation Factor? Combined tidal/fluvial Yes/No Does the site require the consideration of combined fluvial/tidal modelling to fully evaluate flood risk and are the costs associated with this complex modelling and analysis justified by the Prioritisation Factor? Summary of proposed In this section a summary of the modelling approach approach: recommended is provided.

3.3.6 Data Requirements A general review of the data available for each site, set against the methods proposed to evaluate flood risk was also undertaken. Where data gaps exist, these have been evaluated as best possible. However, it is important to recognise that given the scale of the assessment undertaken, it was not possible to exhaustively evaluate whether all of the data required is currently available for each site. This is particularly the case for crest level information, where it was not possible to assess whether crest levels are available for every defence component. In addition to the Site Assessment Sheets, key elements of data available are also illustrated

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on the Site Assessment Maps. This includes bathymetry and beach profile data obtained from the Channel Coastal Observatory and NFCDD data. The assessment undertaken provides a general evaluation of whether the data required is available. A more detailed evaluation will be required for each site as part of the Main Assessment Phase.

Data Type Available Required? Data gaps Bathymetry Single beam Yes/No Is bathymetry data Are there any data Swath Yes/No available for the site gaps? and is these data required? What is the source of these data? Channel cross- Yes/No Is channel cross- Are there any data section data section available for gaps? the site and is these data required. Defence crest Yes/No Is crest level data Are there any data levels available for the gaps? defences present? What is the source of these data? Defence profiles Yes/No Is flood defences Are there any data data available for the gaps? defences present? What is the source of these data? Beach profiles Yes/No Is beach profile data Are there any data available for the site? gaps? What is the source of these data? LiDAR data 0.5m Yes/No Is 0.5m LiDAR Are there any data available for the site? gaps? 1m Yes/No Is 1m LiDAR Are there any data available for the site? gaps?

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4. Summary of Site Assessment Results

4.1 Introduction The Site Summary Sheets and Maps discussed in Chapter 3 provide a site by site assessment of the risks, drivers and prioritisation results for the 169 flood risk sites evaluated as part of this study. This chapter summarises the results of the Site Assessment exercise and provides insight into the implications of this assessment for the Pilot Study and Main Assessment Phase. The results are presented within a number of tables and discussion sections. Two master summary tables are also presented in Appendix A. These tables summarise all of the key information from the Site Summary Sheets. A description of what is included in these two tables is provided in Table 2 below. In the sections below, subsamples of data from the two master tables are presented for discussion purposes.

Table 2: Site Assessment Summary Sheet Information FRS Reference: Flood Risk Site (FRS) reference number FRS Name: Flood Risk Site Name Estuary/River Group: The estuary or tidal river group that the site is within River: The river that the site is within Indicative number of properties Estimate of the number of properties at risk of coastal flooding at risk: Risk Factor: Risk Factor for the site (0=none, 1=low, 2=medium, 3=high) Complexity Factor: Complexity Factor for the site (1=low, 2=medium, 3=high) Prioritisation Factor: Prioritisation Ranking for the site (1=low, 2=medium, 3=high) Flood Risk Mechanisms Still water flooding: Is the site at risk of flooding from still water sea-levels alone? Wave overtopping: Is the site at risk of flooding from wave overtopping? Wave set-up: Is the site at risk of flooding from wave set-up? Wave run-up: Is the site at risk of flooding from wave run-up? Wind set-up: Is the site at risk of flooding from wind set-up? Defence failure: Is the site at risk of flooding from defence failure? Breakwater failure: Is the site at risk of flooding from breakwater failure? Fluvial flooding: Is the site at risk of flooding from fluvial sources? Climate Change: Is the site vulnerable to sea-level rise? Recommended method: Summary of the recommended method of assessment Data requirements: Summary of the data requirements

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4.2 Summary of Prioritisation Results Table 3 and Table 4 summarise the indicative estimates of the number of properties identified as potentially at risk of coastal flooding for the north and south coasts, respectively. Again, it is important to stress that the simple projection modelling technique used to obtain these estimates by no means accounts for the complexity of wave overtopping, wave set-up, wind set-up and wave run-up processes acting in the study area. Furthermore, the estimates are effectively based on future climate conditions and are therefore likely to be conservative. Nevertheless, the estimates provide an indication of the scale of risk in the study area as well as a means by which to evaluate the relative level of risk for different communities and groupings of communities. The numbers provided in Table 3 and Table 4 are provided in terms of absolute numbers as well as percentages relative to the total number of properties at risk on each coast and as a whole in the study area. Some of the key messages to draw from these tables are as follows: Approximately 26% of the risk is on the north coast and 74% of the risk is on the south coast; The top 15 communities at risk are as follows: o (221 properties) o (320) o (346) o Bude (400) o Newlyn (405) o East Looe (411) o St Ives (452) o Perranporth (500) o Falmouth (521) o Truro (610) o Par (619) o Penzance (645) o Wadebridge (692) o (726) o Greater Plymouth (4,227); The greater Plymouth area represents, by far, the greatest overall risk (29%); As discussed in the Site Assessment Sheets, the modelling of risk for some sites will be best achieved by building regional or estuary models. This represents the best overall approach in terms of: hydrodynamics; value for money, and; prospects in terms of the use of the modelling for purposes beyond flood risk mapping (i.e. flood warning, breakwater failure, etc). The regional models proposed are as shown in Table 3 and Table 4. These tables also highlight the cumulative number of properties in each grouping. The top three estuary groups are as follows: Mount's Bay (1,188) Fal Estuary and tributaries (1,850) Tamar Estuary and tributaries (4,888) Of these groups, the Tamar Estuary, which includes Plymouth is associated with the largest risk (33%).

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Table 3: North Coast Summary Statistics General Total Percentage of Percentage of Total Total (North) (Study Area) Total number of properties: 3,787 100.0% 25.7% Number of properties in low priority 160 4.2% 1.1% category: Number of properties in medium priority 264 7.0% 1.8% category: Number of properties in high priority 3,363 88.8% 22.8% category:

High Priority Sites Porth 13 0.3% 0.1% Camel Estuary South Shore 18 0.5% 0.1% Flexbury 113 3.0% 0.8% Padstow 201 5.3% 1.4% Portreath 320 8.4% 2.2% Bude 400 10.6% 2.7% St Ives 452 11.9% 3.1% Perranporth 500 13.2% 3.4% Wadebridge 692 18.3% 4.7% Hayle 726 19.2% 4.9%

Summary for Estuary Groups Proposed and tributaries 961 25.4% 6.5% and tributaries 864 22.8% 5.9%

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Table 4: South Coast Summary Statistics General Total Percentage of Percentage of Total Total (North) (Study Area) Total number of properties: 10,970 100.0% 74.3% Number of properties in low priority 197 1.8% 1.3% category: Number of properties in medium priority 1,679 15.3% 11.4% category: Number of properties in high priority 9,094 82.9% 61.6% category:

High Priority Sites 26 0.2% 0.2% 64 0.6% 0.4% Marazion 101 0.9% 0.7% Looe Beach 101 0.9% 0.7% Rosehill and Victoria 132 1.2% 0.9% West Looe 134 1.2% 0.9% 155 1.4% 1.1% Flushing 157 1.4% 1.1% 177 1.6% 1.2% Penryn 205 1.9% 1.4% Fowey 209 1.9% 1.4% Millbrook 212 1.9% 1.4% Polperro 221 2.0% 1.5% Mevagissey 346 3.2% 2.3% Newlyn 405 3.7% 2.7% East Looe 411 3.7% 2.8% Falmouth 521 4.7% 3.5% Truro 610 5.6% 4.1% Par 619 5.6% 4.2% Penzance 645 5.9% 4.4% Greater Plymouth 4,227 38.5% 28.6%

Summary for Estuary Groups Proposed and tributaries 77 2.0% 0.5% River Foy and tributaries 492 13.0% 3.3% Looe River and tributaries 652 17.2% 4.4% Mount's Bay 1,188 10.8% 0.08% Fal Estuary and tributaries 1,850 48.9% 12.5% Tamar Estuary and tributaries 4,888 129.1% 33.1%

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4.3 Implications for Pilot Stage This Scoping Study will be followed by a Pilot Study. The purpose of the Pilot Study will be to evaluate the methods proposed herein for a variety of sites with varying Flood Risk Drivers. This will help to further refine the methods proposed before commencement of the Main Assessment Phase. Accordingly, an objective of this study is to make recommendations in terms of where the Pilot Study should be conducted. The following criteria were considered in this assessment: High Level of Risk. The region chosen should, as a whole, represent an area with a high level of coastal flood risk. Variety of Flood Risk Drivers. The region chosen should include a variety of sites with different Flood Risk Drivers. This will ensure that a range of techniques, both simple and complex, can be evaluated as part of the Pilot Study. The evaluation of the various wave related risk drivers (wave overtopping, run-up and set-up) is of principal interest. Range of Exposures. Given the variability of exposures within the study area, coastal flood risk is heavily dependent upon the trajectory of a storm. As discussed further in the next chapter, a key objective of the Pilot Study will therefore be to evaluate the impact of storm trajectory on flood risk. Choosing a Pilot Study area that includes a range of sites with varying exposure radii is therefore advantageous. Availability of Data. It will be advantageous if the region chosen has a good availability of data. This will ensure that costs and delays associated with data collection are minimised. In particular, the availability of local wave data is of particular importance. Scale. Given that a variety of methods will be developed and tested as part of the Pilot Study, it is important to ensure that the scale of the study is appropriate. A Pilot Study that is too small may suffer from a lack of variety in terms of Flood Risk Drivers and assessment techniques. A Pilot Study that is too large may be difficult to manage given the R&D nature of the study. It will be important to choose a region that strikes a good balance in terms of scale. Breakwater Failure Modelling. Modelling the impacts of breakwater failure is a secondary objective raised at the consultation meeting. Accordingly, choice of a site where breakwater failure would increase risk and is of concern would be advantageous. Forecasting Improvements. In order to maximise the benefits of the work, it will be sensible to choose a Pilot Study area where there is a potential for flood forecasting improvements. Previous or Proposed Modelling. The selection of a Pilot Study area where there is a possibility of re-cycling previously constructed models or where there are plans to commence such studies is sensible. Finally, there will be political or funding related issues that will influence the selection of the Pilot Study area. These issues have not been considered as part of the assessment. Following from the above logic, three areas are considered to be suitable for consideration as a Pilot Study location. These areas, which include Mount's Bay, the Fal Estuary and the River Tamar Estuary, and the associated communities at risk and statistics are presented in Table 5.

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Table 5: Potential Pilot Study Locations and Statistics Area Sites Population at Risk Mount's Bay Mousehole 24 Newlyn 405 Penzance 645 Marazion Marshes 13 Marazion 101 Total: 1,188 Fal Estuary and tributaries Falmouth 521 Penryn 205 Flushing 157 16 39 Restronguet 17 17 43 Penpol/Point 31 Feock 1 Creek 10 Creek 16 Truro 610 Malpas 36 32 St. Just-in Roseland 1 St. Mawes 155 Total: 1,907 Tamar Estuary and tributaries 16 Empacombe 2 Millbrook 212 St. John 4 Torpoint 177 10 Polbathic 14 St. Germans 10 Tideford 7 Notter Bridge 9 Forder 22 Saltash 64 South Pill 2 3 Cargreen 26 Salter Mill 2 Halton Quay 4 2 28 14 Morwellham 2 Heron's-Reach 12 Bere Ferrers 17 Greater Plymouth 4,227 Total: 4,886

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The key advantages and disadvantages associated with undertaking the Pilot Study for each of the potential candidate areas are detailed below: 4.3.1 Mount's Bay This region occupies Mount's Bay from Mousehole to Marazion, comprising a total of approximately 1,190 properties at risk. The potential advantages of choosing this region for the Pilot Study are as follow: This region includes a large number of properties potentially at risk of coastal flooding. The region is subject to a wide variety of Flood Risk Drivers. In particular, there is a wide range of wave related risks. Given the nature of the bay, the communities in the region have varying exposure radii. The region is very rich in terms of available data, including: o Wave data: A wave buoy is located in Mount's Bay from which historic data dating back to 2007 is available. This buoy is located in approximately 10m of depth making it ideal for the validation of a wave transformation model. Full validation of the wave transformation model will ideally also involve deployment of a second wave buoy in the nearshore environment. However, this is not considered essential. o Bathymetry: There is an excellent coverage of bathymetry and beach profile data. Some harbour bathymetry data will be required. o Terrain data: There is a full coverage of 1m LiDAR data. The opportunities for testing and comparing both simple and complex methods for evaluating risk are excellent. The scale of the region is considered appropriate for a Pilot Study. There are good opportunities for breakwater failure modelling in the region given the various ports. There are good opportunities for forecasting improvements given the vulnerability to wave related risks and the varying exposures. There are good links with proposed modelling of the 4 primary fluvial rivers in this area. The potential disadvantages of choosing this region for the Pilot Study are as follow: The two other regions score higher in terms of population at risk. The opportunities for testing wind set-up are limited. Wind set-up is not a particular issue in this region.

4.3.2 Fal Estuary and Tributaries This region occupies the Fal estuary, including communities such as Falmouth, Penryn, Truro and St Mawes. The total number of properties considered to be at risk is of the order of 1,900. The potential advantages of choosing this region for the Pilot Study are as follow: This region includes a large number of properties potentially at risk of coastal flooding. The region is subject to a reasonable variety of Flood Risk Drivers. In particular, there is vulnerability to wind set-up. Data: o There is a full coverage of 1m LiDAR data. The scale of the region is considered appropriate for a Pilot Study.

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There are reasonable opportunities for forecasting improvements given the vulnerability to wave and wind set-up risks. There are good links with previous modelling in Truro. The potential disadvantages of choosing this region for the Pilot Study are as follow: The River Tamar estuary scores higher in terms of population at risk. The region is not as rich in terms of available data as St Mount's Bay: o Wave data: There are no wave buoys in the region. Ideally, wave buoy data would be available from a deep water location and a nearshore location. Consequently costs to obtain wave data will be higher than St Mount's Bay and will stall the modelling process. o Bathymetry: CCO bathymetry data does not exist for the estuary. Consequently, these data would need to be sourced from SeaZone or otherwise. The opportunities for testing and comparing both simple and complex methods for evaluating risk are considered lower than St Mount's Bay and the Tamar Estuary. The opportunities for breakwater failure modelling in the region are limited.

4.3.3 River Tamar estuary and Tributaries This region occupies the River Tamar estuary and its tributaries, including communities such as Millbrook, Torpoint and Plymouth. The total number of properties considered to be at risk is of the order of 4,886. The potential advantages of choosing this region for the Pilot Study are as follow: This region includes the largest number of properties potentially at risk of coastal flooding. The region is subject to a wide variety of Flood Risk Drivers. In particular, there is a wide range of wave related risks as well as wind set-up risk. Given the nature of the estuary, the communities in the region have varying exposure radii. Data: o The region has a near complete coverage of 1m LiDAR data (the exceptions to this are Gunnislake and Morwellham. o It is likely that wave buoy data would be available from the MOD although this has not been confirmed. The opportunities for testing and comparing both simple and complex methods for evaluating risk are excellent. There are good opportunities for breakwater failure modelling in the region given the principal estuary breakwater as well as secondary breakwaters. There are good opportunities for forecasting improvements given the vulnerability to wave related risks, wind set-up and the varying exposures. There are good links with previously constructed models (Plym and Plympton). A number of previous wave modelling studies have also been undertaken. The potential disadvantages of choosing this region for the Pilot Study are as follow: The region is not as rich in terms of available data as St Mount's Bay: o Bathymetry: CCO bathymetry data does not exist for the estuary. Consequently, these data would need to be sourced from SeaZone or the MOD. The scale of the study is considered to possibly be too large for a Pilot Study.

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Following from the above, and additional consultation with the Environment Agency, it is considered that the best option for the Pilot Study is Mount's Bay.

4.4 Implication for Main Assessment Phase The objective of the Main Assessment Phase will be to produce new coastal flood risk information for the whole of Cornwall and potentially the Isles of Scilly. In practise, the Main Assessment Phase may consist of a series of projects, rather than one large project. The Site Summary Sheets and additional tables presented in this chapter provide good insight into the scale of work, where priorities should lie, and the methods required for the Main Assessment Phase. The Pilot Study will also provide further insight in this respect.

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5. Methodology

5.1 Introduction A key objective of this study was to investigate and recommend methods that could be used to formally evaluate flood risk for each community as part of the Main Assessment Phase. Given the wide range of Flood Risk Drivers that affect sites in the study area, and the varying degrees of risk, a one size fits all approach is not considered appropriate. Rather, it is considered more appropriate to outline a suite of methods that can be selected from to suit a site's prioritisation value and other local factors. Under this general approach, complex and costly methods will generally be reserved for higher priority sites, whilst simpler methods will be applied to lower priority sites. The principal components of analysis and modelling that will be required to evaluate a site's flood risk include the following, in order of application: Derivation of boundary conditions (sea-level, waves, wind); Wave transformation modelling; Wave overtopping and run-up modelling, and; Flood inundation modelling. In the sections below, methods are proposed for each of the above components. Where appropriate, both simple and complex alternatives of analysis and modelling are outlined. An initial recommendation is also provided in terms of which methods should be applied to which types of sites. As discussed further in the next chapter, a key element of the Pilot Study will be to test and refine all of the different methods outlined herein and to provide further guidance on how and where they should be applied as part of the Main Assessment Phase.

5.2 Derivation of Boundary Conditions The first step of analysis required for all sites will be the derivation of model boundary conditions (extreme sea-levels, waves, wind and flow). These boundaries effectively represent the storm conditions that will be simulated as part of the modelling. The exact nature of the boundary conditions required for a site will vary dependent upon the overall approach taken to evaluate flood risk for that site and other local factors. However, the key elements of boundary data required, and recommendations for how these variables should be derived, is outlined below. 5.2.1 Extreme still water sea-level estimates Extreme still water sea-level estimates are required for all of the subsequent steps of analysis and modelling, including wave overtopping and run-up analysis, wave transformation modelling and flood inundation modelling. It will not be necessary to calculate new extreme sea-level estimates as part of the Pilot Study or Main Assessment Phase given the recent release of the Coastal Flood Boundary Data study. The values from this study, which are available along a 2km chainage line, will be used directly for all of the analysis and modelling required for the subsequent stages of the project. The manner in which this will be done is explained in the relevant sections below. 5.2.2 Deep water extreme wave heights and periods Extreme wave property estimates are not available with the same ease as extreme still water sea-level estimates. Consequently, it will be necessary to derive extreme wave height and period estimates for a variety of return periods as part of the subsequent phases of the study. Whilst in practice what is required is extreme wave height and period estimates in the very nearshore region, at the toe of defences and beaches, no recorded or modelled wave data are available for this region that could be analysed to evaluate extreme conditions. It will therefore be necessary to derive extreme wave properties for deeper water locations, where data do exist, and then to transform these estimates into the nearshore region separately.

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The manner in which the wave transformation work will be undertaken is descried is Section 5.3 below. To estimate the required extreme wave height and period estimates for deep water locations, it is recommended that the methods developed as part of the Coastal Flood Boundary Data Study are adapted to suit the evaluation of wind waves. At present they only account for Swell Waves. We have contacted Professor Jonathan Tawn of Lancaster University, who developed this method, and confirmed that it is indeed adaptable for wind waves. Following the update to the wave analysis code, extreme wave height properties can be estimated for wind waves based on deep water wave buoy data, where these exist, or hindcast wave model data available as part of a licence agreement between the Environment Agency and the Met Office (these are the data used as part of the Coastal Flood Boundary Data Study). These hindcast data, which cover the period August 2000 to December 2008. are based on the Met Office's UK Waters Wave Model, which has a spatial resolution of approximately 12km and a temporal resolution of 3 hours. The outputs from this model include: wind wave, swell and resultant (wind waves and swell combined) significant wave height; mean zero crossing wave period, and; wave direction. As part of the Pilot Study, extreme wave property data will be estimated for the Pilot Study region using the above approach. Recommendations for how the methods should be applied for subsequent stages of the study will also be provided. 5.2.3 Extreme wind speeds and directions As discussed below, it will also be necessary to include wind boundaries in the wave transformation models and some of the flood inundation models developed for the study. As for waves, these estimates can be derived based on either recorded data or hindcast model data. Our experience is that recorded wind speed data, available from the Met Office, is costly (of the order of £8,000 for a site record). A cheaper alternative will be to use hindcast wind data currently available to the Environment Agency as part of the hindcast wave dataset discussed above. To estimate the required extreme wind properties, these data can be analysed using a standard Peaks Over Threshold based technique. To account for wind direction, which is very important in terms of risk in this study, this extremes analysis will be undertaken using a directional sector-based approach. 5.2.4 Fluvial flows In some instances, fluvial flow boundaries will be required as additional inputs to the flood inundation models developed for the subsequent stages of the study. Where this is the case, flow estimates should be based on the most appropriate methodology outlined in the latest Environment Agency Flood Estimation Guidelines4. The exact methodology used will depend on the modelling undertaken and the availability of local data. 5.2.5 Joint Probability and Event Set Derivation The sections above outline the methods required to estimate the individual extreme probabilities of the different boundary conditions required. It will also be important to consider how these variables may combine during an event, creating the composite storm conditions that lead to flooding. Whilst for low and medium priority sites it may be sufficient to simply choose pragmatic combinations of variables for modelling purposes, for higher priority sites, it will be important to consider more formally how the different variables are expected to occur simultaneously, based on their respective joint probabilities. This type of analysis is particularly relevant for the study area given the importance of variations is exposure radius, as discussed as part of the consultation process (Chapter 2). Following from the consultation process, and mindful of the importance of storm direction and exposure radius, one of the key recommendations of this study is to undertake ensemble modelling for high priority regions. Under this approach, many iterations of a model are simulated, with each simulation or ensemble member representing some variation in terms of the composite storm conditions. The individual outputs from this type of the modelling can be

4 Environment Agency (2009). 197_08 Flood Estimation Guidelines.

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used for a variety of purposes, including the development of a composite worst-case flood outlines as well as storm condition-based flood outlines for forecasting purposes. Undertaking this type of ensemble modelling will require the development 'event sets' for each return period modelled. These event sets effectively represent lists of different potential composite storm characteristics for each return period, where each storm has an equal probability of occurrence but different combinations of the driving variables. For instance, one storm in the event set may represent a 0.5% AEP storm composed of moderate sea-levels and extreme waves and winds approaching from the south west, whilst another may represent a storm with the same overall probability but with extreme sea-levels and only moderate waves and winds approaching from the south east. These two different events, whilst representing the same overall probability of occurrence, may have significantly different impacts in terms of flooding. The manner in which the event sets will be used in the different modelling elements is discussed further below. To develop the event sets themselves, it is recommended that two key methods are evaluated for potential use as part of the Pilot Study. These include: JOIN-SEA Heffernan and Tawn5 Following the evaluation of the above methods, one will be chosen and developed as part of the Pilot Study. Regardless of which approach is taken, the output will initially take the form of multi-dimensional matrices describing realistic combinations of sea-level, wave height and wind speed. These matrices will then been drawn from to developed the 'event set' for a given overall return period. The matrices will be developed for different sectors of wave and wind direction to account for the directional elements of these variables.

5.3 Wave Transformation Modelling (WTM) As discussed above, extreme wave heights and periods will initially be derived for deep water conditions. It will then be necessary to transform these estimates to the nearshore region so that they represent the wave properties expected at the toe of beaches and flood defences. These nearshore estimates are what is required for the wave overtopping and wave run-up analysis components of the study. Two methods for undertaking the required wave transformation modelling are presented below; a simplified approach and a complex approach. 5.3.1 WTM Method 1: Simplified Approach For most low and medium priority sites, it will not be justified to develop complex, costly models to transform deep water wave heights and periods to the nearshore region. As an alternative, several analytical approaches are available. These approaches generally take as input a deep water wave height estimate and an estimate of the foreshore slope. Two widely used methods that are outlined in both the European Wave Overtopping Manual and the CIRIA Rock Manual are Goda6 and Van Der Meer7. It is important to stress that these simplified methods are generally only recommended for simple, gentle sloping foreshores and are known to overestimate shallow water wave heights in many cases. It will therefore be important to test the validity of these approaches as part of the Pilot Study by comparing their outputs with more sophisticated modelling approaches (as outlined below). Assuming that they are reasonably valid, the recommendation would be to use these methods for low and medium priority sites. The input data required would be the deep water wave height estimates described above and beach and bathymetry data available from the CCO or surveyed as part of the study.

5 Heffernan J. E. and Tawn J. A. (2004) A conditional approach for multivariate extreme values (with discussion), J. R. Statist. Soc. B, 66 497-546. 6 Goda, Y (2000). Random seas and design of maritime structures. In: P L-F Liu (ed) Advanced Series on Ocean Engineering, vol 15, World Scientific, Singapore, 444pp. 7 Van Der Meer, J W (1990). Extreme shallow water wave conditions. Report H198, Delft Hydraulics, Delft.

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Given that the simplified wave transformation methods would probably only be applied to low and medium priority sites, it is unlikely that they would be used as part of any ensemble modelling. Rather, for pragmatic purposes, an approach based on the combination of a 1 year significant wave height and a 0.5% AEP still water sea-level will probably be acceptable; this is in keeping with the ABD guidelines. However, it will be sensible to assess whether an alternative combination of sea-level and wave height is more appropriate for the study area as part of the Pilot Study. 5.3.2 WTM Method 2: Wave Transformation Modelling For high priority sites and some low and medium priority sites that are within the domain of a regional model (see Chapter 4), it will be desirable to construct a nearshore wave transformation model to transform the deepwater wave height estimates to the nearshore region. This approach will, in theory, provide more reliable estimates of nearshore wave heights and periods than the analytical methods described above. It will also provide the potential for undertaking the type of ensemble modelling recommended for high priority sites. The goal of the ensemble modelling will be to model a range of scenarios (i.e. different combinations of sea-level, wave and wind properties) for each model domain in order to deduce which scenario will result in the worst-case conditions for each flood defence within the model domain. These worst-case conditions, which may be different for each defence, can then be modelled in terms of flood inundation (as discussed in the sections below), giving a truer picture of risk than the traditional deterministic modelling normally undertaken for Environment Agency coastal flood modelling. The general steps required as part of this type of modelling are detailed below: Construct and validate a phase-averaging nearshore wave transformation model for the regional domain under consideration. Several models are available for this type of modelling, including SWAN and Mike21. The calibration and validation of the nearshore wave transformation models will ideally be undertaken using recorded wave buoy data for both deep water (near the models offshore boundary) and inter-tidal locations. In reality, very little wave buoy data are available in the region. The only wave buoys that are operating are in Penzance, Perranporth and Looe and these buoys are neither in particularly deep water or the inter-tidal zone (they are generally in 10m depth). Furthermore, of these three locations, only the Penzance buoy falls within a location where wave transformation modelling is recommended. The other regions for which wave transformation modelling are recommended have no wave buoys. The hindcast wave model data described above provides a reasonable alternative to recorded data for deepwater locations, comprising of approximately 8 years for data. For the nearshore region, the Penzance buoy will probably suffice to calibrate and validate the nearshore wave model for this region with reasonable confidence. However, for this region and other regions where wave transformation modelling is recommended, it would be preferable to survey additional wave data in the inter-tidal zone. We have received a quotation for this type of surveying from Titon Surveys Ltd. The cost to deploy a wave buoy in the inter-tidal zone would be of the order of £18,000 for a six month survey covering the winter storm period. Select an event set to model. Once the wave transformation models have been calibrated and validated, the ensemble modelling will be undertaken. The methods outlined above for generating an event set will, in practice, result in hundreds or thousands of potential composite storm conditions. Clearly, it will not be practical to simulate all of the events as part of the study. It will therefore be necessary to choose a subset from the event set to model. This subset will be chosen to account for realistic ranges in the underlying variables. Developing guidance in terms of how to choose these ranges will be a key element of the Pilot Study. Simulate wave transformation for each ensemble. The final step in the wave transformation modelling process will be to simulate the outcomes of each ensemble member of the selected event set. For each simulation, it will be necessary to output the relevant wave properties for each flood defence in the model domain. These

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wave properties will then be used in the wave overtopping and run-up calculation step, as described below. Where breakwater failure modelling is required, this should be undertaken by removing the breakwaters from the wave transformation model and simulating the impacts. It is expected that this modelling would be undertaken for only a few selected events.

5.4 Wave Overtopping (WOM) and Run-up Modelling Following the derivation of boundary conditions and the wave transformation modelling, the next step in the flood modelling process will be wave overtopping and wave run-up modelling. Wave overtopping modelling is required where a raised flood defence, which is subject to wave impact and overtopping, is present. Wave run-up modelling is required for beaches and frontages where no raised defence exists, but where waves may intermittently run up the beach and exacerbate local flood risk. It is also recommended that wave run-up modelling is undertaken for "No Defences" modelling for the Flood Map, where raised defences are removed from the terrain data. Recommendations in terms of how the wave overtopping and run-up modelling should be undertaken as part of subsequent studies is discussed below. This modelling will be required for most low, medium and high priority sites where there is a risk of wave impacts. However, it is considered that an ensemble based approach is only required for high priority sites or low and medium priority sites that are within the domain of a regional wave transformation model. For all other sites, a pragmatic combination of sea-level and significant wave height will be suitable. Appropriate combinations of these variables will be evaluated as part of the Pilot Study. 5.4.1 WOM Method 1: Wave Overtopping Modelling (Raised Defences) The steps required to undertake the wave overtopping modelling for raised defences are outlined below. Undertake any required surveying. Wave overtopping modelling requires flood defence profiles for each defence. As discussed in the Site Assessment Sheets, a large body of beach and defence profile data is available from the CCO. However, it may be necessary to undertake additional surveying to ensure that the necessary data are available. A detailed assessment of survey requirements should be undertaken at the beginning of any subsequent studies. Determine the most appropriate wave overtopping model to use. A variety of wave overtopping models are available. Generally speaking, the models outlined in the EurOtop manual are the industry standard approach and should be used as part of any subsequent studies. However, it will still be necessary to evaluate which of the models contained in the EurOtop manual (i.e. Empirical, PC Overtopping or Neural Network) is best suited to each defence profile under consideration. Each model has different application recommendations and constraints. Schematise wave overtopping models for each defence section. Once a wave overtopping model is chosen, the defence under consideration requires schematisation according to the modelling approach. Calculate wave overtopping discharges for each defence. As discussed above, this modelling should be based on ensemble approaches where justified and pragmatic combinations of sea-level and wave height elsewhere.

5.4.2 WOM Method 2: Wave Run-up Modelling (None Raised Defences) The steps required to undertake the wave run-up modelling for None Raised defence situations (e.g. beaches and for "No Defences" modelling) are outlined below. Undertake any required surveying. As discussed above.

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Remove any raised defence sections from the defence/beach profile for "No Defences" modelling. If the wave run-up calculations are being undertaken for the purposes of "No Defences" modelling for the Flood Map, it will be necessary to remove any raised defence sections from the defence/beach profiles before modelling. Determine the most appropriate wave run-up model to use. As discussed above. It is worth noting that a different choice of wave overtopping model may be required for "With Defences" and "No Defences" models for the same defence. This stems from the application recommendations and constraints associated with each model. The PC overtopping tool will probably be the norm for None Raised defence wave run-up modelling. Schematise wave run-up models for each defence section. Once a wave run-up model is chosen, the defence under consideration requires schematisation according to the modelling approach. Calculate wave run-up elevations for each defence. As discussed above, this modelling should be based on ensemble approaches where justified and pragmatic combinations of sea-level and wave height elsewhere. 5.4.3 Note on Wave Set-up One of the key Flood Risk Drivers highlighted for the study area is the impact of wave set-up. As part of this project, the developers of the European Wave Overtopping Manual at HR Wallingford were contacted in order to better understand how this variable is dealt with in the wave overtopping models contained in EurOtop. HR Wallingford confirmed that because the models were developed based on laboratory and field experiments, they inherently account for wave set-up and additional allowances for this variable would not normally be required. The exception to this is a type of site-specific wave set-up caused by a particular peculiarity in the local bathymetry, or for instance when long-shore currents are blocked, or a number of low-tide bars trap returning flows. In such cases, HR suggest that it might be necessary to account for an additional local contribution to wave set-up in the assessment of flood risk. It is expected that this type of additional wave set-up is what has been observed at some sites in Cornwall and is described as Wave Surge in Chapter 2. This issue should be addressed further as part of the Pilot Study.

5.5 Flood Inundation Modelling (FIM) The final step in the modelling process will involve simulating flood inundation based on the composite storm conditions and wave overtopping modelling results. As with the tasks discussed above, the method applied to undertake the flood inundation model will vary dependent upon the prioritisation factor of a site, its proximity to other sites and the Flood Risk Drivers acting locally. Four general approaches are discussed below. 5.5.1 FIM Method 1: Projection Modelling Many of the sites with an exposure to the open coast are of low and medium priority, are distant to any other sites and are reasonably steep in terms of topography. For these sites, it is not considered required or justifiable to construct costly hydrodynamic models to evaluate flood risk and a more simplified approach is recommended. In reality, for some of these sites a simplified approach may indeed provide as good an answer as more costly methods. The two methods recommended herein are based on adaptations of the traditional projection modelling technique often applied in coastal flood modelling. These methods, which are schematised in Figure 2 and discussed below, have been adapted to better account for the impacts of waves.

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“With Defences” flood

Waves Surge

Tide

Waves “No Defences” flood Surge

Tide

Figure 2: Schematic Representation of Modified Projection Modelling

FIM Method 1A: "With Defences" Modelling Traditionally, projection modelling has largely been undertaken based on extreme still water sea-level estimates alone and wave overtopping and wave set-up has not been accounted for. In some cases, this approach will significantly underestimate flood risk (i.e. where the only risk of flooding comes from wave action) and in some locations this approach will significantly overestimate flood risk (i.e. where the flood outline will be limited by the volume of wave water rather than sea-levels). As an alternative to this approach, a type of projection modelling based on the accumulative volume of flood water associated with wave overtopping is recommended for "With Defences" modelling. These accumulative volumes will be integrated based on sensible storm durations and the relevant lengths of defences. The flood outline associated with the accumulated volumes will then be projected by filling the DTM using a GIS routine. In practice, significant professional judgement will also be required to produce a final flood outline using this method. However, the costs associated with this approach will be a small proportion of the equivalent hydrodynamic model approach. As with all of the simplified approaches recommended in this chapter, it will be important to test and refine this method during the Pilot Study through a comparison with more sophisticated approaches. FIM Method 1B: "No Defences" Modelling For "No Defences" Modelling, or where raised defences do not exist, it is also considered important to consider the impacts of waves. In this case, the impacts are associated with wave set-up and wave run-up. To do so, wave run-up elevations, which inherently account for wave set-up, will be evaluated for each flood defence (as discussed above). These elevations will then be plotted on a DTM. An enhanced version of a connect the dots type approach will then be used to evaluate the overall flood outline, accounting for the individual elevations calculated and the topography between them. As with Method 1A, in practice, this method will need to be tested and refined in the Pilot Study and a significant amount of professional judgement will be required even after this refinement. In practice, it may also be necessary to combine the flood outlines associated with Method 1A and 1B in some locations to ensure that the "With Defences" outlines does not extend beyond the "No Defences" outline. This is in keeping with ABD guidelines.

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5.5.2 FIM Method 2: Hydrodynamic modelling For high priority sites and some low and medium priority sites that are within the domain of a regional model (Chapter 4), the projection modelling techniques described above are not considered appropriate for evaluating flood risk. For these areas, more complex hydrodynamic models will be required. These models will provide a better evaluation of flood risk as well as important additional deliverables required for higher risk sites (e.g. breach modelling, hazard rating grids, onset of flooding grids and animations of flood wave progression). The use of hydrodynamic modelling will also allow for ensemble modelling to be undertaken using the outputs discussed above. For the purposes of this section, hydrodynamic flood inundation modelling is subdivided into two types: Open Coast Modelling and Tidal River/Estuary Modelling. This division reflects the fact that the Flood Risk Drivers in these two environments necessitate different approaches. FIM Method 2A: Open Coast Modelling For open coastal regions, such as Mount's Bay, the principal Flood Risk Drivers that require accounting for in the modelling include wave impacts (wave set-up, run-up and overtopping) and still water flooding. The effects of wind set-up and fluvial flooding are generally considered insignificant in comparison to these processes. For these regions, it is recommended that 2D hydrodynamic models are developed using software such as TUFLOW. Where important, 1D/2D model sections could be incorporated into these models to better account for important channels that represent conduits for saltwater penetration inland or where tidal/fluvial interaction modelling is considered appropriate. It is expected that this will not normally be the case. The hydrodynamic models should be validated and calibrated as best possible using available data and standard approaches. It would also be helpful to install temporary sea- level gauges in strategic locations to aid in the calibration process. However, this is considered more important for the modelling of estuaries and tidal rivers where it is expected that there will be greater spatial variations in sea-levels during an event. Once the models have been constructed, they can be forced with any one of the composite storm conditions contained in the event set (and associated wave overtopping estimates). Exactly which simulations should be run will need to be agreed with the Environment Agency at the start of the project in consultation with representatives from the Flood Mapping, Forecasting and Development Control Teams (and perhaps the local councils). Insights into the expected requirements, following from the consultation stage, are given in Section 2.4. In terms of the standard Flood Map components, it is recommended that the ensemble methods are at least used to derive Flood Zone 3 and the Areas Benefiting from Defences (Flood Zone 2 may also be a sensible scenario to model). To do so, it will be necessary to determine, for each defence section, which event from the 0.5% AEP event set represents the worst-case condition for that defence. Each of these worst-case events should then be simulated using the model, outputting the relevant grids and outlines. These simulations will be required to be done twice; once in a "No Defences" mode and once in a "With Defences" mode. To construct overall worst-case flood grids for the "With Defences" scenario, the individual "With Defences" flood grids will be combined to create composite flood grids. In doing so, these composite grids do not represent an individual event that could realistically happen, but rather the sum of all of the worst case events that could happen considering expected variations in the driving variables. To construct the worst-case flood grids for the "No Defences" scenario, the individual "No Defences" flood grids will be combined in the same manner as above. The only additional step required will be to check whether any of the wave run-up elevations exceed the outlines in either the "With Defences" or "No Defences" composite grids. If this is the case, some manual modifications may be required to increase the extent of the "No Defences" outline before generation of the ABDs. The extent to which this will be required will become clearer after the Pilot Study.

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FIM Method 2B: Tidal River and Estuary Modelling For estuaries and tidal river groups (see Chapter 4, e.g. Camel, Hayle, Helford, Foy, Looe, Tamar and Fal), the principal Flood Risk Drivers that require accounting for in the modelling include still water flooding and wind set-up. Some exposed locations will also require wave overtopping and run-up analysis, although this will be limited. If wave overtopping modelling is required, this should be carried out using one of the methods outlined above (and as outlined in the Site Assessment Sheets). This may or may not involve wave transformation modelling. The River Tamar is probably the only estuary where this is necessary. The hydrodynamic modelling required for the tidal river and estuary groups will involve the construction of a 2D model. Where important, 1D/2D model sections should be incorporated into these models to better account for important channels that represent significant conduits for saltwater penetration inland or where tidal/fluvial interaction modelling is considered appropriate. An additional element to the modelling for tidal rivers and estuaries is the inclusion of wind set-up affects. TUFLOW is now capable of including wind set-up in flood simulations and this approach should be used. To do so, ensemble modelling should be undertaken in a manner similar to that discussed above for wave impacts, but where the defining variable is variations in wind speed and direction, as drawn from the event sets. The hydrodynamic models developed should be validated and calibrated as best possible using available data and standard approaches. It may be helpful to install temporary sea- level gauges in strategic locations to aid in the calibration process. This would need to be determined in the initial stages of the project. We have received a quotation for this type of surveying from Titon Surveying. The cost to deploy a water level gauge would be of the order of £17,000 for a six month survey covering the winter storm period. As with FIM Method 2A, the exact simulations that will be required for the tidal river and estuary groups will need to be agreed with the Environment Agency at the start of the project in consultation with representatives from the Flood Mapping, Forecasting and Development Control Teams (and perhaps the local councils). Insights into the expected requirements, following from the consultation stage, are given in Section 2.4. In terms of the standard Flood Map components, it is recommended that the ensemble methods are at least used to derive Flood Zone 3 and the Areas Benefiting from Defences (Flood Zone 2 may also be a sensible scenario to model). To do so, it will be necessary to determine, for each community, which event from the 0.5% AEP event set represents the worst-case condition for that community8. Each of these worst-case events should then be simulated using the model, outputting the relevant grids and outlines. These simulations will be required to be done twice; once in a "No Defences" mode and once in a "With Defences" mode. Form these two outputs the Flood Zone 3 and the ABDs can be generated using standard approaches. Breach Modelling As discussed with respect to the consultation outcomes (Chapter 2), it was agreed that continuous breach modelling is a requirement of the Pilot Study and Main Assessment Phase for higher priority sites; these outputs will help to improve development control and flood forecasting. The hydrodynamic modelling techniques outlined can be used to undertake this type of modelling. To do so, it is recommended that breaches are modelled in the defences at regular intervals, perhaps of the order of one per 500m of defence. This approach will provide a complete set of breach-based flood outlines for high priority areas. Furthermore, it could be argued that producing a composite maximum flood outline based on the combination of all the individual breach outlines provides a more realistic, and in some cases conservative, representation of the worst-case flood outlines than will be achieved using the "No Defences" approach outlined above. This issue will be explored as part of the Pilot Study.

8 It will not be necessary to do the ensemble modelling at the resolution of individual defences given that wind set-up effects are more regional than variations in wave properties.

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6. Scope for Pilot Study

6.1 Introduction The key objective of the Pilot Study will be to test and refine the methods proposed in Chapter 5 for a Pilot Study region and to update the recommendations for the Main Assessment Phase studies accordingly. It will therefore be important to test and compare both the simplified methods and the advanced methods so that the costs, strengths and limitations associated with both are better known. Following from the discussion in Section 4.3 and the Consultation Phase, Mount's Bay has been chosen as the Pilot Study region, extending from Mousehole to Marazion. In the sections below a scope is outlined for the Pilot Study. To avoid unnecessary repetition, where appropriate reference is made to the methods outlined in Chapter 5. The work proposed for the Pilot Study is broken down into 4 key tasks. The associated cost estimate for the study is supplied in a separate Activity Schedule.

6.2 Task 1: Data Collection and Analysis 6.2.1 Data collection Whilst the Scoping Study has involved the collection and review of a wide range of data, as outlined in the Site Summary Sheets, it will be necessary to more fully review the data requirements and quality as part of the Pilot Study. The key data sources that will require review include wind, wave, sea-level, bathymetry, ground level, beach, defence, channel and land-use. Details on the source of these data are provided in Chapter 5 and in the Site Summary Sheets. 6.2.2 Data review and preparation of model grids It will be necessary to create a seamless terrain and bathymetry grid for the study region for use in both the development of a wave transformation model and a hydrodynamic flood inundation model. As discussed in Chapter 5, there is a good coverage of 1m LiDAR data, Swath bathymetry data and beach profile data available for the region. It is not expected that any new surveying of terrain or bathymetry will be required. It will be necessary to create two versions of the seamless terrain/bathymetry grid; a "With Defences" version and a "No Defences" version. It is recommended that the issue of defacto defences is discussed further at the start-up of the Pilot Study. 6.2.3 Data review and preparation for extremes analysis and event set generation As outlined in Chapter 5, it will be necessary to collect, review and prepare a wide range of wind, wave and sea-level data for use in the extremes analysis and event set generation elements of the study. 6.2.4 Data review and preparation for wave overtopping modelling The flood inundation modelling and wave overtopping and run-up modelling proposed for the Pilot Study requires detailed information on defence locations, crest levels and profiles. It is expected that most of these data are already available. However, it has not been possible to confirm this assumption at the level of detail required for the Pilot Study. It will therefore be necessary to collect and review all available data at the start of the Pilot Study and where necessary recommend any additional surveying. No allowance for surveying has been made in the cost estimates for the Pilot Study. In addition to the review of data availability and quality, it will also be necessary to analyse and prepare defence profiles for the wave overtopping and run-up work. This will involve the following steps:

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Analyse the beach profile data for each defence and produce a characteristic profile that represents a conservative winter storm profile. The analysis associated with this task is significant given the number of defence sections involved and the wealth of beach profile data available from the CCO. Where necessary modify each defence profile to create a "With Defences" and "No Defences" version, as discussed in Section 5.4. 6.2.5 Detailed site visits A detailed site visit will be required in the initial phase of the project. This site visit is expected to involve several days and include the following objectives: Confirm data completeness and identify any surveying requirements; Identify where overtopping calculations are required and photograph as necessary; Identify the location and nature of relevant control structures, breakwaters, and river channels; Confirm overall system understanding, and; Identify logical choices in terms of breach locations. 6.2.6 Extremes Analysis It will be necessary to evaluate extremes in terms of waves and wind for a variety of return periods and directions as outlined in Section 5.2. The key data sources available for this analysis include recorded wave buoy data at Penzance and hindcast wind and wave data available for deep water locations. As discussed in Chapter 5, it should not be necessary to undertake any extreme sea-level analysis as new values are available as part of Coastal Flood Boundary Data Study. 6.2.7 Derivation of Event Sets Following the derivation of extremes in each of the above variables, it will be necessary to develop the event matrices described in Section 5.2.5. These event matrices will have important use in terms of flood forecasting and will be drawn from to develop event sets for the ensemble modelling discussed below. 6.2.8 Outputs from Task 1 The key outputs from Task 1 will include the following: Combined bathymetry and ground level grids ("With Defences" and "No Defences" versions) for the wave transformation and flood inundation modelling; A complete set of defence crest levels and profiles for the flood inundation modelling and wave overtopping modelling; Extreme wave and wind speed estimates, based on directional sectors, and; Event set matrices.

6.3 Task 2: Wave Transformation and Overtopping Modelling 6.3.1 Construction, validation and calibration of wave transformation model A phase-averaging nearshore wave transformation model will be constructed, calibrated and validated using SWAN according to the methods outlined in Chapter 5 (Note, it has been assumed that it will be possible to obtain bathymetry data for Newlyn and Penzance Harbour from the Harbour Authorities). Whilst the study area location for the flood modelling work will only extend from Mousehole to Marazion, it is sensible to extend the domain for the wave transformation model from Head to The to aid in future studies and forecasting improvements and to tie in with model forecast points available from the Met Office for there operations Wave Watch III model. Whilst it would be ideal to deploy a wave buoy in the inter-tidal region for calibration purposes, this is not considered essential. The

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costs for this deployment have therefore not been accounted for in this proposal. However, it is recommended that this issue is discussed again at the start-up of the Pilot Study. 6.3.2 Ensemble design runs Once the wave transformation models have been calibrated and validated, ensemble modelling will be undertaken first for a 0.5% AEP scenario according to the methods outlined in Chapter 5. Wave properties will be output for each ensemble, for each defence section. As discussed in Chapter 5, it will be necessary to choose a subset from the event sets to model. This subset will be chosen to account for realistic ranges in the underlying variables during a 0.5% AEP event. The total number of events to model for the 0.5% AEP event will need to be considered carefully following the generation of the event matrices. However, for the purposes of cost estimates, it is assumed that the number of events modelled will not exceed 100. As discussed in Section 2.4, a range of additional return period events are required for modelling purposes. These include a 0.1% AEP event (used for Flood Zone 2), lesser return period events (used for flood forecasting and development control purposes), and climate change events. For each of these events, it is proposed that a limited ensemble modelling should undertaken, informed by the work carried out for a 0.5% AEP event. It will be necessary to agree the nature and number of scenarios with the Environment Agency at the appropriate stage. However, for the purposes of cost estimates, it is assumed that the number of events modelled for these scenarios will not exceed an additional 100 simulations in total. 6.3.3 Calculation of wave transformation based on simplified approaches To test and refine the simplified methods for evaluating wave transformation discussed in Chapter 5, wave transformation between the location of the Penzance wave buoy and nearshore locations will be undertaken using the simplified methods for a range of composite storm conditions. These calculations will be undertaken for a total of around 30 events. 6.3.4 Comparison of simplified and advanced wave transformation techniques The outputs from the simplified wave transformations will be compared to the outputs from the more detailed wave transformation modelling approach. These comparisons will be detailed in the study report and associated recommendations will be provided with respect to the Main Assessment Phase. 6.3.5 Schematise defence/beach profiles for defended and undefended wave overtopping / run-up calculations Each of the defence/breach profiles derived as part of step 6.2.4 will need to be schematised in terms of the required wave overtopping and run-up calculations for both "With Defences" and "No Defences" scenarios, as discussed in Section 5.4. 6.3.6 Ensemble wave overtopping and run-up modelling Once the wave overtopping/run-up models have been constructed, calculations will be undertaken based on the ensemble storm conditions from step 6.3.2. From this analysis it will be possible to determine which composite storm condition is the worst-case scenario for each defence section. The wave overtopping discharges from these worst-case conditions will then be used in the flood inundation modelling described below. 6.3.7 Breakwater failure modelling Breakwater failure modelling will also be carried out for Newlyn and Penzance Harbour. The breakwaters will be removed from the bathymetry/terrain grid in order to evaluate the magnitude of waves that could penetrate the harbour following such a failure. This work will only be undertaken for the 0.5% AEP event that represents the worst-case composite storm conditions for each harbour, as deduced from the analysis carried out for step 6.3.6. Wave

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overtopping calculations will be carried out for these scenarios so that the impacts in terms of flood inundation can be evaluated, as discussed below. 6.3.8 Outputs from Task 2 The key outputs from Task 2 will include the following: Calibrated and validated SWAN wave transformation model for Mount's Bay; Ensemble wave transformation data based on modelling; Wave transformation data based on simplified techniques; Comparison of wave transformation approaches; Ensemble wave overtopping data with worst-case conditions highlighted for each defence section; Breakwater failure modelling wave data.

6.4 Task 3: Flood Inundation Modelling 6.4.1 Construction, validation and calibration of flood inundation model A 2D hydrodynamic flood inundation model, built using TUFLOW will be constructed for the region between Mousehole and Marazion according to the methods outlined in Chapter 5. The resolution of the model will be of the order of 5m, or the highest achievable resolution given the size of the overall domain and run-time constraints. "With Defences" and "No Defences" models will be constructed. 6.4.2 Worst-case design runs for a 0.5% AEP event (defended and undefended) Worst-case design runs will be simulated for "With Defences" and "No Defences" simulations based on the outputs from the wave overtopping and run-up modelling and according to the methods outlined in Chapter 5. 6.4.3 Construction of worst-case "With Defences" and "No Defences" grids and outlines for the 0.5% AEP event Worst-case flood grids and outlines will be constructed for the 0.5% AEP event for both "With Defences" and "No Defences" conditions according to the methods outlined in Chapter 5. These outputs that will be generated include: Flood outlines and ABDs; Depth, velocity and flood hazard rating grids; Onset of flooding grids; Animations. 6.4.4 Design runs for other events A number of additional events will be simulated in terms of flood inundation. The exact events to be modelled will be agreed with the Environment Agency at the start of the Pilot Study. For the purposes of cost estimates, the following have events have been assumed to be required: A 0.1% AEP event based on present day sea-levels. This will be a "No Defences" event based on a particular event simulation rather than a worst-case event as described above for a 0.5% AEP event; 0.5% and 0.1% AEP "No Defences" events for two climate change horizons based on a particular event simulation. 0.5% AEP "With Defences" event for one climate change horizon based on a worst- case event approach. 10 additional event simulations for the purposes of Flood Warning improvements.

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It is assumed that the outputs required for these additional runs will include the following: Flood outlines; Depth, velocity and flood hazard rating grids; Onset of flooding grids; Animations. 6.4.5 Continuous breach modelling In addition to the above, continuous breach modelling will be undertaken for a 0.5% AEP event according to the methods outlined in Chapter 5. The outputs for each simulation will include the following: Flood outlines; Depth, velocity and flood hazard rating grids; Onset of flooding grids; Animations. 6.4.6 Breakwater failure modelling Breakwater failure flood scenarios will also be carried out for a 0.5% AEP event based on the wave overtopping outputs from step 6.3.7. The outputs for each simulation will include the following: Flood outlines; Depth, velocity and flood hazard rating grids; Animations. 6.4.7 Testing of simplified methods of flood modelling for defended and undefended modelling Two locations will be chosen at the start of the project where flood outlines and depth grids will be developed for a 0.5% AEP event based on the simplified approaches outlined in Section 5.5.1. These outlines and depth grids will then be compared to those based on the hydrodynamic model. The comparisons will be detailed in the study report and associated recommendations will be provided with respect to the Main Assessment Phase. 6.4.8 Outputs from Task 3 The outputs from task 3 are generally outlined in the relevant sections above. In addition to these outputs, the hydrodynamic model itself will be supplied as an output from the study.

6.5 Task 4: Reporting and Recommendations In addition to the digital deliverables outlined above a study report will be issued. This report will outline the following: Study approach, methodology and results; Conclusions and recommendations with respect to flood risk in the study area; Conclusion and recommendations with respect to the Main Assessment Phase, including: o Updates and refinements to the methods and recommendations outlined in this Scoping Study; o An evaluation and comparison of simplified and complex approaches; o Guidance on appropriate combinations of sea-level and wave heights to be used for low and medium priority sites; Recommendations with respect to forecasting improvements.

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6.6 Project Meetings and Site Visits Following discussions with the Environment Agency, a healthy budget allowance has been made for project meetings and site visits, including the following: Three project meetings (Project start-up, 2 mid project progress meetings and a project close meetings) Two site visits (both taking place over a 3 day period)

6.7 Pilot Study Costs and Programme The costs for the Pilot Study, and a programme, have been supplied separately to this report. The costs provided represent all staff costs and expenses but do not include any data costs or VAT. As discussed above, and in the Site Summary Sheets, it is expected that some minor defence surveying may be required for the study area. It is expected that this surveying could be carried out by the Environment Agency's in-house surveyors minimising additional costs. It will also be necessary to obtained bathymetry data from Penzance and Newlyn inner harbours. It is expected that these data will be supplied free of charge but this had not been confirmed.

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7. Summary, Conclusions and Recommendations

7.1 Summary The principal objectives of this Scoping Study were as follows: To develop an innovative scope for a multi-faceted coastal flood risk modelling study; To update the methods and approaches traditionally used for standard coastal flood risk modelling studies to suit the unique mix of Flood Risk Drivers in the Environment Agency's Cornwall region (including the River Tamar estuary); To engage with all relevant arms of the Environment Agency and its key partners to ensure that the Scope of Works developed will result in outputs providing maximum benefit to the region; To enhance the Environment Agency’s understanding of its exposure to coastal flood risk and to provide outputs that will help the Agency to prepare for and mitigate against these risks. To achieve these objectives, a Site Risk Assessment was carried out for 169 communities considered to have some level of coastal flood risk in the study area. This assessment culminated in the development of detailed Site Risk Assessment Sheets and Maps, supplied separately to this report. As part of this assessment, the communities were ranked in terms of priority for future investment in flood risk modelling and mapping. This ranking took account of the level of risk in each community and the complexity of the local Flood Risk Drivers. A range of methodologies, designed to formally evaluate flood risk as part of subsequent studies, have also been recommended. Given the wide range of Flood Risk Drivers that affect sites in the study area, and the varying degrees of risk, a one size fits all approach was not considered appropriate. Rather, it was considered more appropriate to outline a suite of methods that can be selected from to suit a site's prioritisation value and other local factors. Under this general approach, complex and costly methods will generally be reserved for higher priority sites, whilst simpler methods will be applied to lower priority sites. This risk based approach is in line with the Environment Agency's new Flood and Coastal Risk Management Risk and Modelling Strategies. It is intended that this Scoping Study will be followed by a Pilot Study and a Main Assessment Phase. The key objective of the Pilot Study will be to evaluate the methods proposed herein for a pilot region. This will help to further refine the methods proposed before commencement of the Main Assessment Phase. The objective of the Main Assessment Phase will be to produce new coastal flood risk information for the whole of the Cornwall region and potentially the Isles of Scilly. In addition to standard Flood Map products, it is anticipated that the Pilot Study and Main Assessment Phases will result in a range of additional datasets and deliverables, which will maximise the outcomes of the study for the region.

7.2 Conclusions and Recommendations 7.2.1 Pilot Study The key objective of the Pilot Study will be to test and refine the methods proposed and to update these recommendations for the Main Assessment Phase accordingly. It will therefore be important to test and compare both the simplified methods and the advanced methods proposed so that the costs, strengths and limitations associated with both are better known. The Mount's Bay region, extending between Mousehole and Marazion, has been chosen for the Pilot Study based on the following: (1) it includes a large number of properties potentially at risk of coastal flooding; (2) the region is subject to a wide variety of Flood Risk Drivers. In particular, there is a wide range of wave related risks; (3) given the nature of the bay, the communities in the region have varying exposure radii; (4) the region is very rich in terms of available data; (5) the opportunities for testing and comparing both simple and complex methods for evaluating risk are excellent; (6) the scale of the region is considered appropriate

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for a Pilot Study; (7) there are good opportunities for breakwater failure modelling in the region given the various ports, and; (8) there are good opportunities for forecasting improvements given the vulnerability to wave related risks and the varying exposures. A detailed Scope of Works has been provided for the Pilot Study, including a breakdown of all of the tasks required, the outputs that will be delivered and the associated costs. The Pilot Study represents an innovative and ambitious project, including the adoption of ensemble modelling techniques and advanced joint probability analysis; methods which are in keeping with the Environment Agency's new Flood and Coastal Risk Management Risk and Modelling Strategies. Whilst a number of event simulations and outputs are recommended, these recommendations are based on our current understanding of your requirements, gathered through the consultation process, rather than an as yet agreed set of simulations and deliverables. It will therefore be necessary to more formally agree a set of event simulations and deliverables at the start of the Pilot Study. This process may affect the cost estimates provided. 7.2.2 Main Assessment Phase The objective of the Main Assessment Phase will be to produce new coastal flood risk information for the whole of Cornwall and potentially the Isles of Scilly. In practise, the Main Assessment Phase may consist of a series of projects, rather than one large project. The Site Summary Sheets and additional tables presented in this report provide good insight into the scale of work, where priorities should lie, and the methods required for the Main Assessment Phase. The Pilot Study will also provide further insight in this respect. 7.2.3 Data This study included an assessment of the data requirements for the Pilot Study and Main Assessment Phase, set against the methods recommended for the evaluation of flood risk for each community. Whilst these data assessment was reasonably comprehensive, it has not been possible to fully check all data availability and/or quality. It will therefore be necessary to include a data collection and review phase for all subsequent stages of the project, informed by the details provided in the Site Risk Assessment Sheets and Maps. In particular, it is not known whether there is a complete coverage of reliable defence crest levels available, although it is expected that a near complete dataset is. Furthermore, it is expected that a reasonable amount of defence cross-section surveying will be required as part of any subsequent study involving wave overtopping analysis. Some inner harbour bathymetry data is also required. It is expected that these data will be available from the Port Authorities. Recommendations are provided with respect to the deployment of temporary wave buoys and water level gauges. Deployment of these devices would provide useful new data to aid in the calibration and validation of the modelling proposed. However, the deployment of these devices will be expensive. It is therefore recommended that the issue of device deployment is discussed further following the Pilot Study. We note that the Environment Agency owns two wave buoys that are currently not in operation. We would recommend that these buoys are deployed strategically before the winter season in order to obtain new data to aid in future phases of the project. This should be discussed further as part of the Pilot Study.

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A. Site Summary Master Tables

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Appendix A: Site Assessment Summary Sheet (North Coast)

Flood Risk Mechanisms

Estuary/River Indicative number of Still water Wave Breakwater Climate FRS Reference FRS Name Communitiy Grouping River Risk Factor Complexity Factor Prioritisation Factor Wave set-up Wave run-up Wind set-up Defence failure Fluvial flooding Recommended method Data requirements Group properties at risk flooding overtopping failure Change

1 Flexbury 113 3 2 3 No Yes Yes Yes No Yes No Yes Yes 1D/2D TUFLOW None 2 Bude 400 3 3 3 Yes Yes Yes Yes No Yes No Yes Yes 1D/2D TUFLOW None 3 Widemouth Bay 4 1 1 1 No No No No No No No Yes Yes Projection None 4 8 1 2 1 No Yes Yes Yes No Yes No Yes Yes Projection Some limited defence and beach profile data 5 2 1 2 1 No No No No No Yes Yes Yes Yes Projection None 6 Trebarwith Strand 6 1 1 1 No No Yes Yes No No No No Yes Projection Some limited beach profile data 7 7 1 2 1 No No Yes Yes No No No Yes Yes Projection Some limited beach profile data 8 12 2 2 2 No No Yes Yes No No Yes Yes Yes Projection None 9 Portquin 3 1 2 1 No No Yes Yes No No No Yes Yes Projection Some limited beach profile data 10 Polzeath 11 2 2 2 Yes Yes Yes Yes No No No Yes Yes Projection Some limited beach profile data 11 Rock River Camel 7 1 3 2 No Yes Yes Yes Yes Yes No Yes Yes 2D TUFLOW Bathymetric data / beach and defence profile data 12 River Camel 5 1 2 1 No No Yes Yes Yes No No Yes Yes 2D TUFLOW Bathymetric data / beach and defence profile data 13 River Camel 12 2 1 1 No No No No No No No Yes Yes 2D TUFLOW None 14 Wadebridge River Camel 692 3 2 3 Yes No No No Yes Yes No Yes Yes 1D/2D TUFLOW Some limited defence data and channel cross-section data. 15 Sladesbridge River Camel 26 2 2 2 Yes No No No Yes Yes No Yes Yes 2D TUFLOW Some limited defence data 16 Camel Estuary South Shore River Camel 18 2 3 3 Yes Yes Yes No Yes Yes No Yes Yes 2D TUFLOW Bathymetric data / defence profile data 17 Padstow River Camel 201 3 3 3 Yes Yes Yes No Yes Yes Yes Yes Yes 2D TUFLOW Bathymetric data / defence profile data 18 Trevone 0 0 1 1 No No No No No No No Yes No No modelling required. Simply include road in Flood Map None 19 Bay 5 1 2 1 No No Yes Yes No No No Yes Yes Projection None 20 Constantine 0 0 1 1 No No No No No No No Yes No No assessment None 21 Treyarnon 0 0 1 1 No No No No No No No Yes No No assessment None 22 7 1 2 1 No No Yes Yes No No No Yes Yes Projection None 23 20 2 2 2 No Yes Yes Yes No Yes No Yes Yes Projection Some limited defence profile data 24 Watergate Bay 1 1 1 1 No No Yes Yes No No No No Yes No assessment required. Current flood map is sufficient. None 25 Porth 13 2 3 3 Yes Yes Yes Yes No Yes No Yes Yes 2D TUFLOW Some limited defence profile data and river cross-section data 26 5 1 2 1 No Yes Yes Yes No Yes No No Yes Projection Some limited defence profile data 27 , Beach Newquay 8 1 2 1 No Yes Yes Yes No Yes No No Yes Projection Some limited defence profile data 28 Newquay, Towan Beach Newquay 2 1 2 1 No Yes Yes Yes No Yes No No Yes Projection Some limited defence profile data 29 Newquay Harbour Newquay 3 1 2 1 No Yes Yes Yes No No Yes No Yes Projection None 30 Newquay, Newquay 0 0 1 1 No No Yes Yes No No No No No No modelling required. Simply include beach in Flood Map None 31 The Gannel Newquay 50 2 2 2 No No No No Yes Yes No Yes Yes 2D TUFLOW Some limited defence surveying may be required. River cross-section data will also be required. 32 Perranporth 500 3 2 3 No Yes Yes Yes No Yes No Yes Yes 1D/2D TUFLOW Some limited defence profile and crest level data. Cross-section data will also be required. 33 St Agnes 4 1 2 1 No Yes Yes Yes No No No Yes Yes Projection Some limited beach profile data 34 Porthtowan 1 1 2 1 No No Yes Yes No No No Yes Yes Projection None 35 Portreath 320 3 3 3 Yes Yes Yes Yes No Yes Yes Yes Yes 1D/2D TUFLOW Some limited defence profile and crest level data. River cross-section data will also be required. 36 Sands 2 1 2 1 No Yes Yes Yes No Yes No Yes Yes Projection None 37 River Hayle, North Quay and Pool Hayle River Hayle 504 3 2 3 Yes No No No Yes Yes No Yes Yes 1D/2D TUFLOW Bathymetric data / defence data 38 Mellanear Outfall, Hayle Hayle River Hayle 222 3 2 3 Yes No No No Yes Yes No Yes Yes 1D/2D TUFLOW Bathymetric data / defence data. River cross-section data will also be required. 39 Hayle Gate to River Hayle 77 2 2 2 Yes No No No Yes Yes No Yes Yes 2D TUFLOW Bathymetric data / defence data 40 River Hayle 61 2 2 2 Yes No No No Yes Yes No Yes Yes 2D TUFLOW Bathymetric data / defence data 41 Bay 2 1 2 1 No Yes Yes Yes No Yes No Yes Yes Projection Some limited defence profile data 42 Porthminster 1 1 1 1 No No Yes Yes No No No No Yes Projection None 43 St Ives Harbour St Ives 380 3 3 3 Yes Yes Yes Yes No No Yes Yes Yes 2D TUFLOW model and a wave transformation model Deep water bathymetry data, some limited defence surveying. 44 St. Ives North of Harbour St Ives 4 1 2 1 Yes Yes Yes Yes No Yes No No Yes Projection Some limited beach/defence profile data 45 St Ives Beach St Ives 67 2 1 1 No No Yes Yes No No No No Yes Projection None 46 Cove St Ives 1 1 2 1 No Yes Yes Yes No No Yes No Yes Projection None Appendix A: Site Assessment Summary Sheet (South Coast)

Flood Risk Mechanisms

FRS Estuary/River Indicative number of properties at Risk Factor (0=0, 1=1-10, 2=10- Still water Wave Defence Breakwater Fluvial Climate FRS Name Communitiy Grouping River Complexity Factor Prioritisation Factor Wave set-up Wave run-up Wind set-up Recommended method Data requirements Reference Group risk 100, 3=101+) flooding overtopping failure failure flooding Change

1 0 0 1 1 No No No No No No No Yes No No assessment None 2 0 0 1 1 No No No No No No Yes Yes No No assessment None 3 Mousehole 24 2 2 2 No Yes Yes Yes No No Yes Yes Yes Projection Some limited defence and beach/harbour profile data 4 Newlyn Newlyn Mount's Bay 60 2 2 2 Yes Yes Yes Yes No No Yes No Yes 2D TUFLOW model and a wave transformation model Harbour bathymetry data, some limited defence surveying. 5 Newlyn, Coombe River Newlyn Mount's Bay 140 3 2 3 Yes Yes Yes No No Yes No Yes Yes 1D/2D TUFLOW and a wave transformation model Some limited defence profile and crest level data. Channel cross section data will also be required. 6 Newlyn, Wherry Town Lariggan River Newlyn Mount's Bay 205 3 2 3 No Yes Yes No No Yes No Yes Yes 1D/2D TUFLOW and a wave transformation model Some limited defence profile and crest level data. Channel cross section data will also be required. 7 Penzance Chimeny rocks Penzance Mount's Bay 0 0 1 1 No No No No No No No No No No assessment None 8 Penzance Harbour Penzance Mount's Bay 47 2 2 2 No Yes Yes No No No Yes No Yes 2D TUFLOW model and a wave transformation model Harbour bathymetry data, some limited defence surveying. 9 Penzance Harbour Car Park Penzance Mount's Bay 57 2 2 2 No Yes Yes No No Yes Yes No Yes 2D TUFLOW model and a wave transformation model Harbour bathymetry data, some limited defence surveying. 10 Penzance, Harbour Car Park to Ponsandane Brook Penzance Mount's Bay 41 2 2 2 No Yes Yes No No Yes No Yes Yes 1D/2D TUFLOW and a wave transformation model Some limited defence profile data. Channel cross section data will also be required. 11 Penzance Ponsandane to Marazion Marshes Penzance Mount's Bay 500 3 2 3 No Yes Yes No No Yes No Yes Yes 2D TUFLOW model and a wave transformation model Some limited defence profile data may be required. 12 Marazion Marshes Mount's Bay 13 2 2 2 Yes Yes Yes No No Yes No Yes Yes 2D TUFLOW model and a wave transformation model Some limited defence profile data may be required. 13 Marazion Mount's Bay 101 3 2 3 No Yes Yes No No Yes No No Yes 2D TUFLOW model and a wave transformation model Some limited defence profile data may be required. 14 St. Michael's Mount 19 2 2 2 No Yes Yes No No Yes Yes No Yes Projection Some limited defence profile data may be required. 15 Praa Sands 5 1 1 1 No No No No No No No Yes Yes Projection Some limited defence profile data may be required. 16 65 2 2 2 No Yes Yes No No Yes Yes Yes Yes 2D TUFLOW Some limited defence profile data may be required. 17 Loe Bar 0 0 1 1 No No No No No No No No No No assessment None 18 16 2 2 2 No No Yes Yes No No No Yes Yes Projection Some limited breach survey data may be required. 19 Kennack Sands 2 1 2 1 No No Yes Yes No No No Yes Yes Projection Some limited breach survey data may be required. 20 10 1 2 1 No Yes Yes No No Yes Yes Yes Yes Projection Some limited defence profile data may be required. 21 33 2 2 2 No Yes Yes Yes No No No Yes Yes Projection Some limited defence and beach profile data 22 Gillan 5 1 2 1 Yes No Yes Yes No No No Yes Yes Projection Some limited breach survey data may be required. 23 St. Anthony-in- 7 1 2 1 Yes No Yes Yes No No No No Yes Projection Some limited breach survey data may be required. 24 Helford Helford River 23 2 2 2 Yes No Yes Yes Yes No No Yes Yes 2D TUFLOW Bathymetric data / beach and defence profile data 25 Helford River 35 2 2 2 Yes No No No Yes Yes No Yes Yes 2D TUFLOW Bathymetric data and some limited defence and river cross-section data required. 26 Porth Navas Helford River Porthnavas Creek 8 1 2 1 Yes No No No Yes No No Yes Yes 2D TUFLOW Bathymetric data and some limited defence and river cross-section data required. 27 Durgan Helford River 11 2 2 2 No No Yes Yes Yes No No No Yes 2D TUFLOW Bathymetric data and some limited beach profile data required. 28 6 1 1 1 No No Yes Yes No No No No Yes Projection None 29 Falmouth Swan Pool Falmouth 57 2 2 2 Yes No Yes Yes No No No Yes Yes Projection modelling and wave transformation modelling. None 30 Falmouth Inner Harbour Falmouth Fal Estuary 356 3 2 3 Yes Yes Yes No Yes No Yes No Yes 2D TUFLOW model and a wave transformation model Estuary and harbour bathymetry and some defence surveying. 31 Falmouth North Falmouth Fal Estuary 108 3 3 3 Yes Yes Yes No Yes Yes Yes No Yes 2D TUFLOW model and a wave transformation model Estuary and harbour bathymetry and some defence surveying. 32 Penryn Fal Estuary 205 3 2 3 Yes No No No Yes Yes No Yes Yes 1D/2D TUFLOW model Estuary bathymetry and some defence surveying. Channel cross section data will also be required. 33 Flushing Fal Estuary 157 3 2 3 Yes Yes Yes No Yes Yes No No Yes 2D TUFLOW model and a wave transformation model Estuary bathymetry data and some defence surveying. 34 Mylor Churchtown Fal Estuary 16 2 2 2 Yes Yes Yes No Yes No Yes No Yes 2D TUFLOW model and a wave transformation model Estuary bathymetry data and some defence surveying. 35 Mylor Bridge Fal Estuary 39 2 2 2 Yes No No No Yes Yes No Yes Yes 2D TUFLOW model Estuary bathymetry and some defence surveying. Channel cross section data will also be required. 36 Restronguet Fal Estuary 17 2 2 2 Yes No Yes Yes Yes No No No Yes 2D TUFLOW model and a wave transformation model Estuary bathymetry and some beach profile surveying. 37 Perranarworthal Fal Estuary 17 2 2 2 Yes No No No Yes Yes No Yes Yes 2D TUFLOW model Estuary bathymetry and some defence surveying. Channel cross section data will also be required. 38 Devoran Fal Estuary 43 2 1 1 Yes No No No Yes No No No Yes 2D TUFLOW model Estuary bathymetry data. 39 Penpol/Point Fal Estuary 31 2 2 2 Yes No No No Yes No No Yes Yes 2D TUFLOW model Estuary bathymetry data. 40 Feock Fal Estuary 1 1 2 1 Yes No No No Yes No No Yes Yes 2D TUFLOW model Estuary bathymetry data. 41 Cowlands Creek Fal Estuary 10 1 2 1 Yes No No No Yes No No Yes Yes 2D TUFLOW model Estuary bathymetry data. 42 Calenick Creek Fal Estuary 16 2 2 2 Yes No No No Yes No No Yes Yes 2D TUFLOW model Estuary bathymetry data. 43 Truro Fal Estuary 610 3 2 3 Yes No No No Yes Yes No Yes Yes 1D/2D TUFLOW model Estuary bathymetry and some defence surveying. Channel cross section data will also be required. 44 Malpas Fal Estuary 36 2 2 2 Yes No No No Yes No No Yes Yes 2D TUFLOW model Estuary bathymetry data. 45 Tresillian Fal Estuary 32 2 2 2 Yes No No No Yes No No Yes Yes 2D TUFLOW model Estuary bathymetry data. 46 St. Just-in Roseland Fal Estuary 1 1 2 1 Yes Yes Yes No Yes Yes No No Yes 2D TUFLOW model and a wave transformation model Estuary bathymetry data. 47 St. Mawes, Tavern Beach St Mawes Fal Estuary 57 2 2 2 No Yes Yes No Yes Yes No No Yes 2D TUFLOW model and a wave transformation model Estuary bathymetry and some defence surveying. 48 St Mawes the Quay St Mawes Fal Estuary 16 2 2 2 No Yes Yes No Yes Yes Yes No Yes 2D TUFLOW model and a wave transformation model Estuary bathymetry and some defence surveying. 49 St Mawes The Square Kings Road St Mawes Fal Estuary 82 2 3 3 Yes Yes Yes No Yes Yes Yes No Yes 2D TUFLOW model and a wave transformation model Estuary bathymetry and some defence surveying. 50 17 2 2 2 No Yes Yes Yes No Yes Yes No Yes Projection modelling Some limited defence and beach surveying 51 Portloe 2 1 2 1 Yes No Yes Yes No No Yes Yes Yes Projection modelling Some limited beach surveying. 52 8 1 2 1 No Yes Yes No No Yes No Yes Yes Projection modelling Some limited defence and beach surveying 53 2 1 2 1 No Yes Yes Yes No Yes No Yes Yes Projection modelling Some limited defence and beach surveying 54 15 2 2 2 Yes No Yes Yes No No Yes Yes Yes Projection modelling Some limited beach surveying 55 41 2 2 2 No Yes Yes No No Yes No Yes Yes Projection modelling Some limited defence and beach surveying 56 Mevagissey 346 3 3 3 Yes Yes Yes Yes No No Yes Yes Yes 1D/2D TUFLOW model and a wave transformation model Harbour bathymetry data, some limited defence surveying 57 Pentewan Caravan Park 10 1 2 1 Yes No Yes Yes No No No Yes Yes Projection modelling None 58 Pentewan, mouth of St. Austell River 64 2 2 2 No No Yes Yes No No No Yes Yes Projection modelling None 59 Charlestown 0 0 2 1 No Yes Yes No No Yes Yes No Yes 60 Par Harbour Par 3 1 2 1 Yes Yes Yes No No No Yes No Yes 1D/2D TUFLOW model Harbour bathymetry data. 61 Par West Par 284 3 2 3 Yes No No No No Yes No Yes Yes 1D/2D TUFLOW model Some limited defence surveying. Channel cross-section data. 62 Par East Par 300 3 2 3 Yes No No No No Yes No Yes Yes 1D/2D TUFLOW model Some limited defence surveying. Channel cross-section data. 63 Par Beach Par 32 2 2 2 Yes Yes Yes Yes No Yes No No Yes 1D/2D TUFLOW model None 64 6 1 3 2 Yes Yes Yes Yes No Yes Yes No Yes Projection modelling Some limited defence and beach surveying 65 Readymoney 2 1 2 1 No Yes Yes Yes No Yes No No Yes Projection modelling None 66 Fowey River Foy 209 3 2 3 Yes Yes Yes No Yes Yes No No Yes 2D TUFLOW model Estuary bathymetry data. Some limited defence surveying 67 River Foy 6 1 1 1 Yes No No No Yes No No No Yes 2D TUFLOW model Estuary bathymetry data. 68 Rosehill and Victoria () River Foy 132 3 2 3 Yes No No No Yes Yes No Yes Yes 1D/2D TUFLOW model Estuary bathymetry and some defence surveying. Channel cross section data will also be required. 69 Lostwithiel River Foy 53 2 2 2 Yes No No No Yes Yes No Yes Yes 1D/2D TUFLOW model Estuary bathymetry and some defence surveying. Channel cross section data will also be required. 70 River Foy 53 2 2 2 Yes No No No Yes No No Yes Yes 2D TUFLOW model Estuary bathymetry data. Channel cross section data will also be required. 71 River Foy 2 1 2 1 Yes No No No Yes No No Yes Yes 2D TUFLOW model None 72 River Foy 37 2 2 2 Yes Yes Yes Yes No Yes No No Yes 2D TUFLOW model Estuary bathymetry data. Some limited defence and beach surveying 73 Polperro 221 3 3 3 Yes Yes Yes No No Yes Yes Yes Yes 1D/2D TUFLOW model Estuary harbour bathymetry data and some defence surveying. Channel cross section data will also be required. 74 West Looe Looe River 134 3 2 3 Yes Yes Yes No No No No No Yes 2D TUFLOW model Estuary bathymetry data. Some limited defence surveying 75 St. Martin's Copse & Sandplace Looe River 6 1 2 1 Yes No No No Yes No No Yes Yes 2D TUFLOW model None 76 East Looe Looe River 411 3 2 3 Yes Yes Yes No No No No No Yes 2D TUFLOW model Estuary bathymetry data. Some limited defence surveying 77 Looe Beach Looe River 101 3 2 3 No Yes Yes Yes No Yes No No Yes 2D TUFLOW model Some limited defence surveying 78 21 2 2 2 No Yes Yes No No Yes No Yes Yes Projection modelling Some limited defence surveying 79 Seaton 50 2 2 2 No Yes Yes No No Yes No Yes Yes Projection modelling Some limited defence surveying 80 0 0 1 1 No No No No No No No Yes No No assessment None 81 15 2 2 2 Yes No Yes Yes No No No Yes Yes Projection modelling Some limited defence surveying 82 72 2 2 2 No Yes Yes Yes No Yes No Yes Yes Projection modelling Some limited defence surveying 83 Picklecombe Point 1 1 2 1 No Yes Yes Yes No No No No Yes No assessment None 84 Cremyll River Tamar The Sound 16 2 2 2 Yes Yes Yes Yes No No No No Yes 2D TUFLOW model and a wave transformation model Estuary bathymetry and some defence and beach surveying. 85 Empacombe River Tamar Millbrook Lake 2 1 2 1 No Yes Yes No Yes No No No Yes 2D TUFLOW model and a wave transformation model Estuary bathymetry and some defence and beach surveying. 86 Millbrook River Tamar Millbrook Lake 212 3 3 3 Yes Yes Yes No Yes Yes No Yes Yes 1D/2D TUFLOW model and a wave transformation model Estuary bathymetry, some defence and beach surveying and channel cross-section data. 87 St. John River Tamar St John's Lake 4 1 2 1 Yes No No No Yes No No Yes Yes 2D TUFLOW model None 88 Torpoint River Tamar River Tamar 177 3 2 3 No Yes Yes Yes Yes No No Yes Yes 2D TUFLOW model and a wave transformation model Estuary bathymetry and some defence and beach surveying. 89 Wilcove River Tamar River Tamar 10 1 2 1 Yes No Yes Yes Yes No No Yes Yes 2D TUFLOW model Estuary bathymetry and some beach surveying. 90 Polbathic River Tamar Polbathic Lake 14 2 2 2 Yes No No No Yes No No Yes Yes 2D TUFLOW model None 91 St. Germans River Tamar 10 1 2 1 Yes No No No Yes No No Yes Yes 2D TUFLOW model None 92 Tideford River Tamar River Tiddy 7 1 2 1 Yes No No No Yes No No Yes Yes 2D TUFLOW model None 93 Notter Bridge River Tamar 9 1 2 1 Yes No No No Yes Yes No Yes Yes 2D TUFLOW model None 94 Forder River Tamar River Lynher 22 2 2 2 Yes No No No Yes No No Yes Yes 2D TUFLOW model None 95 Saltash River Tamar River Tamar 64 2 3 3 Yes Yes Yes Yes Yes Yes No Yes Yes 2D TUFLOW model Estuary bathymetry and some defence and beach surveying. 96 South Pill River Tamar River Tamar 2 1 2 1 Yes No No No Yes No No Yes Yes 2D TUFLOW model None 97 Landulph River Tamar Kingsmill Lake 3 1 2 1 Yes No No No Yes Yes No Yes Yes 2D TUFLOW model None 98 Cargreen River Tamar River Tamar 26 2 3 3 Yes Yes Yes Yes Yes Yes No Yes Yes 2D TUFLOW model Estuary bathymetry and some defence and beach surveying. 99 Salter Mill River Tamar River Tamar 2 1 2 1 Yes No Yes Yes Yes No No Yes Yes 2D TUFLOW model Estuary bathymetry data. 100 Halton Quay River Tamar River Tamar 4 1 2 1 Yes No No No Yes Yes No Yes Yes 2D TUFLOW model Estuary bathymetry data. 101 Cotehele River Tamar River Tamar 2 1 2 1 Yes No No No Yes No No Yes Yes 2D TUFLOW model Estuary bathymetry data. 102 Calstock River Tamar River Tamar 28 2 2 2 Yes No No No Yes Yes No Yes Yes 2D TUFLOW model Estuary bathymetry data and some defence surveying. 103 Gunnislake River Tamar River Tamar 14 2 2 2 Yes No No No Yes Yes No Yes Yes 104 Morwellham River Tamar River Tamar 2 1 2 1 Yes No No No Yes No No Yes Yes 105 Heron's-Reach River Tamar River Tamar 12 2 2 2 Yes No Yes Yes Yes No No No Yes 2D TUFLOW model Estuary bathymetry data and some beach surveying. 106 Bere Ferrers River Tamar River Tavy 17 2 2 2 Yes No Yes Yes Yes No No Yes Yes 2D TUFLOW model Estuary bathymetry data and some beach surveying. 107 Tamerton Foliot Plymouth River Tamar Tamerton Lake 25 2 2 2 Yes No No No Yes Yes No Yes Yes 2D TUFLOW model Some defence surveying. 108 Ernesettle Royal Navy Armament Depot Plymouth River Tamar River Tamar 43 2 2 2 Yes Yes Yes Yes Yes No No No Yes 2D TUFLOW model Estuary bathymetry and some defence and beach surveying. 109 to Devonport Plymouth River Tamar River Tamar 366 3 3 3 Yes Yes Yes Yes Yes Yes No Yes Yes 2D TUFLOW model Estuary bathymetry and defence surveying. 110 Mountwise to Milbay Dock Plymouth River Tamar River Tamar 1865 3 3 3 Yes Yes Yes Yes Yes Yes Yes Yes Yes 2D TUFLOW model Estuary bathymetry and defence surveying. 111 Coxside Plymouth River Tamar River Plym 1066 3 3 3 Yes Yes Yes Yes Yes Yes Yes Yes Yes 2D TUFLOW model Estuary bathymetry and defence surveying. 112 Cattedown (Plymouth) Plymouth River Tamar River Plym 15 2 2 2 No Yes Yes Yes Yes Yes No No Yes 2D TUFLOW model Estuary bathymetry and defence surveying. 113 Prince Rock (Plymouth) Plymouth River Tamar River Plym 272 3 2 3 Yes Yes Yes No Yes Yes No No Yes 2D TUFLOW model Some defence and beach surveying. 114 Crabtree and Superstore Plymouth Plymouth River Tamar River Plym 159 3 3 3 Yes Yes Yes No Yes Yes No Yes Yes 2D TUFLOW model Some defence and beach surveying. 115 Efford Marsh **Longbridge (Plymouth) Plymouth River Tamar River Plym 77 2 2 2 Yes No No No Yes Yes No Yes Yes 1D/2D TUFLOW model Some defence surveying and channel cross-section data. 116 Marsh Mills (Plymouth) Plymouth River Tamar River Plym 38 2 2 2 Yes No No No Yes Yes No Yes Yes 1D/2D TUFLOW model Some defence surveying and channel cross-section data. 117 Chelson Meadow (Plymouth) Plymouth River Tamar River Plym 52 2 3 3 Yes Yes Yes No Yes Yes No Yes Yes 2D TUFLOW model Some defence and beach surveying. 118 Hooe Lake and Radford Park **Oreston and Turnchapel (Plym) Plymouth River Tamar River Plym 217 3 2 3 Yes No No No Yes Yes No Yes Yes 2D TUFLOW model Estuary bathymetry and some defence surveying. 119 Mount Batten (Plymouth) Plymouth River Tamar The Sound 32 2 2 2 No Yes Yes Yes No Yes No No Yes 2D TUFLOW model Estuary bathymetry and some defence and beach surveying. 120 Fort Bovisand River Tamar The Sound 0 0 1 1 No No No No No No No No No No assessment None 121 Wembury River Tamar The Sound 2 1 2 1 No No Yes Yes No No No Yes Yes Projection None 122 Steer Point River Yealm River Yealm 0 0 1 1 No No No No No No No No No No assessment None 123 Newton Ferrers and Noss Mayo River Yealm Newton Creak 86 2 2 2 Yes No Yes Yes Yes No No Yes Yes Projection None

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