1. Beach Modelling: Lessons Learnt from Past Scheme Performance Project: SC110004/S Project Summary

2. Contents  About the Project –Background –Project Overview –Project Aim and Objectives –Project Delivery  Phase 1: Scoping Overview  Phase 2: Performance Review and Analysis Overview  Conclusions  Recommendations  Further Information

3. About the Project

4. Background  Beach recharge and management accounts annually for several £million of the UK’s coastal defence capital and maintenance expenditure.  Beach models are used extensively and relied upon to design these schemes ….  ….. but we don’t revisit the results of that modelling to compare with the actual behaviour of the beach

5. Project Overview  Environment Agency commissioned study.  Project examined the behaviour of beaches on eleven sites  Compared actual behaviour with the expected performance from the original modelling and design.  A range of findings have been captured and used to develop guidance for future modelling of schemes

6. Project Aim  The aim of the project was to improve our understanding in this area, identify potential improvements in approach, and consequently lead to more informed decision making in the use of models and tools for beach scheme design and management in the future.

7. Project Objectives  Objectives of the project: –Identify the advantages and limitations of various beach modelling techniques; and –How best to apply these in different situations.  Achieved objectives through desk-based analysis: –Review beach models used in the design of beach scheme design at 11 ‘test-sites’. –Assessment of how the beach has performed using information on post-construction experience and monitoring data. –Compare actual beach performance with pre-construction predictions.

8. Project Delivery  Delivered in two phases: –Phase 1: Scoping –Phase 2: Performance Review and Analysis  Project team: –CH2MHILL Halcrow –Channel Coastal Observatory –plus support  Managed by: –Environment Agency Evidence Directorate (Coastal Flood and Erosion Risk Management R&D team)

9. Phase 1: Scoping - overview  Phase 1 established: –which beach models/techniques are being used for beach design and maintenance purposes; –understanding the assumptions behind those methodologies; –the areas of applicability; and –the management/design decisions for which they go on to support;  Outputs from Phase 1: –Approach for Phase 2 –The identification of candidate sites that could be used for testing and the definition of benchmark tests to be performed in Phase 2. –Included a workshop with range of invited attendees from industry and academia to help refine Phase 1 outputs and identify additional data sources for Phase 2.

10. Phase 2: Performance Review and Analysis - overview  Phase 2 involved: –Developing comparative analysis case studies for each selected site, applying agreed benchmark tests to real observations to provide insight into the predictive capability of models and techniques used for beach design and management. –Included a second workshop with practitioners.  Phase 2 assessments supported by: –Wave analysis for each site –Generic 1-line model tests on variety of parameters.  Outputs from Phase 2: –Guidance in the form of lessons learnt from case studies. –Supporting technical report with details of project development and full case studies.

11. Comparative Analysis

12. Selection of Sites for Comparative Analysis  Key output from Phase 1 was short list of selected sites to investigate further in Phase 2.  In selecting these sites consideration was given to: 1.Ensuring that a sufficiently wide range of modelling/techniques can be covered in the testing; 2.Representativeness of the site characteristics (and therefore applicability of conclusions to other sites); 3.Likelihood of the required information on management activities and past performance being available; and, 4.Complexity of the site and ability to undertake the assessments effectively and efficiently.

13. Selection of Sites Bournemouth Preston Beach Prestatyn Pett Littlestone Folkestone Hurst Spit

14. Covered a range of model types and techniques Modelling approaches

15. Comparative Analysis The predicted and actual beach performance were compared for each site, seeking answers to the following:  Did the beach perform as predicted by the models?  What models were used and how were they applied?  What data was used?  What were the factors that resulted in differences, or similarities between actual and predicted beach behaviour?

16. Comparative Analysis Case Studies – typical structure GENERAL INFORMATION A description of the scheme APPROACH TO MODELLING AND BASIS OF DESIGN Rationale Wave Modelling Approach Beach Modelling Approach Beach data, wave data used Key model runs DESIGN / MODELLING OUTPUTS – PLANS FOR IMPLEMENTATION Expected works and management Expected beach performance BEACH MANAGEMENT AND PERFORMANCE Actual works (construction stage) Actual works (post-construction management) Actual beach performance Actual wave conditions COMPARATIVE ANALYSIS Assessment of actual vs expected Potential reasons for differences Potential reasons for similarities LESSONS Lessons that can be taken from this for others undertaking beach modelling/ design in the future

17. Summary of Key Findings

18. Scheme Performance  Differences between what was modelled and what was implemented.  The translation of model outputs into the design, and beach management activity, is generally poorly recorded.  A difference in wave climate is most commonly the fundamental difference between actual and predicted beach performance.  Beach models are rarely validated or re-visited to examine changes in data, implementation or performance, and inform modification of the beach management regime. Key Findings

19. Conclusions  The physics of beach models are generally sound; it is the appropriate application and interpretation of those models that is key.  Beach models are simplified representations of beach processes; but outputs from these are invaluable for the design and management of beach schemes.  Modelling sensitivities and different scenarios, as well as post-project re-modelling, could deliver more efficient beach management. Key Findings

20.  Define the problem and thus the actual questions and thus answers required from the modelling. Engage expertise early to establish how to address these questions.  Don’t overcomplicate. Recognise limitations and capabilities of models in certain circumstances - model accordingly and deal with uncertainty appropriately  Recognise that models are just part of the toolkit and they do not provide the complete picture …..coastal engineering knowledge and expertise is imperative to effectively understand and utilise the outputs from these different tools Recommendations on Application

21. Deliverable: The Guidance Document

22. About the Guidance – Audience  Aimed at coastal practitioners and those in commissioning organisations who may not have detailed technical knowledge of beach modelling.  Specifically it identifies points to be aware of when beach modelling is being contemplated or carried out.  Should also help the reader gain a better understanding of the approach to modelling, decisions that need to be taken along the way and the outputs expected from it.

23. About the Guidance - Contents  Final guidance provided in Beach modelling; lessons learnt from past scheme performance  Contents: –Section 1: Introduction –Section 2: Summary findings –Section 3: Sites – key lessons to be learned –Section 4: Approach to beach modelling –Sections 5 to 9: Specific model tools and techniques detail –Section 10: Waves for beach modelling –Appendix – Comparative analysis summaries  Additional detail in supporting Technical Report. This includes full case study reports

24. Publication  Published 2 nd May 2014.  Documents are on the Defra/EA R&D website at http://evidence.environment- agency.gov.uk/FCERM/en/Default/ FCRM/Project.aspx?ProjectID=99d a86ad-0a3d-428e-851b- def1b7de47f7&PageID=3679217f- 8f79-4c83-b935-f277aaadbdf1 and GOV.UK at https://www.gov.uk/government/pu blications/beach-management- lessons-learnt-from-past-scheme- performance-of-different- modelling-approaches http://evidence.environment- agency.gov.uk/FCERM/en/Default/ FCRM/Project.aspx?ProjectID=99d a86ad-0a3d-428e-851b- def1b7de47f7&PageID=3679217f- 8f79-4c83-b935-f277aaadbdf1 https://www.gov.uk/government/pu blications/beach-management- lessons-learnt-from-past-scheme- performance-of-different- modelling-approaches

25. Beach Modelling: Lessons Learnt from Past Scheme Performance Project: SC110004/S Project Summary