Sea State Report Suffolk Year 3 and Summary for October 2006 – September 2009
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Sea State Report Suffolk Year 3 and summary for October 2006 – September 2009 RP040/S/2014 July 2014 Title here in 8pt Arial (change text colour to black) i We are the Environment Agency. We protect and improve the environment and make it a better place for people and wildlife. We operate at the place where environmental change has its greatest impact on people’s lives. We reduce the risks to people and properties from flooding; make sure there is enough water for people and wildlife; protect and improve air, land and water quality and apply the environmental standards within which industry can operate. Acting to reduce climate change and helping people and wildlife adapt to its consequences are at the heart of all that we do. We cannot do this alone. We work closely with a wide range of partners including government, business, local authorities, other agencies, civil society groups and the communities we serve. Published by: Shoreline Monitoring Group Environment Agency Kingfisher House, Goldhay Way Orton Goldhay, Peterborough PE2 5ZR Email: enquiries@environment- agency.gov.uk www.environment-agency.gov.uk Further copies of this report are available from our publications catalogue: © Environment Agency 2014 http://publications.environment- agency.gov.uk or our National Customer All rights reserved. This document may be Contact Centre: T: 03708 506506 reproduced with prior permission of the Environment Agency. E: [email protected]. ii Sea State Report RP040/S/2014 Suffolk Contents 1 Anglian Coastal Monitoring 1 1.1 Wave & tide monitoring 1 1.2 Sea State reports 3 1.3 Acoustic Wave and Current meter 3 1.4 Directional Waverider Mark III wave buoy 4 1.5 Instrument data return 5 1.6 Instrument locations 5 2 Wave statistics 8 2.1 Monthly and annual means 8 2.2 Significant wave height 11 2.3 Wave direction 14 2.4 Peak period 15 2.5 Wave height and direction occurrences 17 2.6 Peak period, mean period and significant wave height 18 2.7 Wave energy 19 3 Temperature 23 4 Sea level and tides 24 5 Storminess and extremes 26 5.1 Storm wave events 26 5.2 Monthly wave maxima 26 5.3 Monthly temperature maxima 28 5.4 Highest Suffolk storm event 2008-9 28 5.5 Surge events 29 5.6 Highest Suffolk surge events 2008-9 29 5.7 Storm calendars 30 5.8 Maximum sea level 31 6 Summary 33 List of Tables Table 1.1: Deployment locations between 2006 – 2009 of Suffolk instruments 6 Table 2.1: Monthly mean significant wave height Hs (m) (Year 3) 8 Table 2.2: Annual mean significant wave height Hs (m) for all years (2006-9) 8 Table 2.3: Monthly mean maximum wave height Hmax (m) in Year 3 9 Table 2.4: Annual mean maximum significant wave height Hmax (m) for all years (2006-9) 9 Table 2.5: Monthly mean peak wave period Tp (s) (Year 3) 9 Table 2.6: Annual mean peak wave period Tp (s) for all years (2006-9) 10 Table 2.7: Monthly mean wave period Tz (s) (Year 3) 10 Table 2.8: Annual mean wave period Tz (s) for all years (2006-9) 10 Table 2.9: Monthly modal wave direction Mdir (°) (Year 3) 11 Table 2.10: Monthly modal wave direction Mdir (°) (2006-9) 11 Table 2.11: Instruments and associated thresholds 12 Table 2.12: Wave height and direction frequency at AWAC S13S Southwold North between October 2006 to September 2009 17 Table 2.13: Wave height and direction frequency at AWAC S14S Dunwich Bay between October 2006 Sea State Report RP040/S/2014 Suffolk iii to September 2009 17 Table 2.14: Wave height and direction frequency at AWAC S15S Sudbourne between October 2006 to September 2009 18 Table 2.15: Wave height and direction frequency at AWAC S16S Bawdsey between October 2006 to September 2009 18 Table 3.1: Monthly mean temperatures at Suffolk instruments (Year 3) 23 Table 4.1: Monthly mean sea levels relative to Ordnance Datum Newlyn for Year 3 24 Table 4.2: Tidal harmonics derived from Gardline Environmental’s 60-constituent harmonic analysis of the Year 3 AWAC data 24 Table 5.1: Monthly maximum significant wave heights Hs (m) in Year 3 27 Table 5.2: Monthly maximum wave heights Hmax (m) in Year 3 27 Table 5.3: Monthly maximum peak wave period Tp (s) in Year 3 27 Table 5.4: Monthly maximum mean wave period Tz (s) in Year 3 28 Table 5.5: Monthly maximum temperature (°C) 28 th Table 5.6: Storm event statistics on 10 March, 2008 from AWAC S13S 29 Table 5.7: Surge events (residuals greater than 1 m ODN) in Year 3 29 List of Figures Figure 1.1 Map of instrument locations 2 Figure 1.2: Map of Suffolk instrument deployments 7 Figure 2.1: Significant wave height Hs (m) between October 2006 to September 2009 for the AWAC S13S at Southwold North and the Southwold Approach wave buoy (SWB1) 12 Figure 2.2: Significant wave height Hs (m) between October 2006 to September 2009 for the AWAC S14S at Dunwich Bay and the Southwold Approach wave buoy (SWB1) 12 Figure 2.3: Significant wave height Hs (m) between October 2006 to September 2009 for the AWAC S15S at Sudbourne Beach and the Southwold Approach wave buoy (SWB1) 13 Figure 2.4: Significant wave height Hs (m) between October 2006 to September 2009 for the AWAC S16S at Bawdsey Cliffs and the Southwold Approach wave buoy (SWB1) 13 Figure 2.5: Wave direction (°) plots for each AWAC and Southwold DWR between October 2006 to September 2009 14 Figure 2.6: Frequency distribution of wave period Tp (s) recorded by SWB1, Southwold from October 2006 to September 2009 15 Figure 2.7: Frequency distribution of wave period Tp (s) for each AWAC from October 2006 to September 2009 16 Figure 2.8: Joint distribution of significant wave height Hs (m), peak wave period Tp (s) (coloured points) and mean wave period Tz (s) (black points) between October 2006 to September 2009 19 Figure 2.9: Wave spectra plot for S13S at Southwold North during the month of March 2008 20 Figure 2.10: Wave energy and wave period distribution over frequency for all years (2006 – 2009) 21 Figure 2.11: Comparison of the annual average wave energy Tz (m2/Hz) in all spectral bands at each AWAC and for all years 21 Figure 3.1: Monthly mean temperatures all years (2006-9) 23 Figure 4.1: Sea level at each AWAC (S13S, S14S, S15S and S16S) in Year 3 25 Figure 5.1: Storm events (all years) that crossed site thresholds 31 Figure 5.2: Surge events (all years) 31 Figure 5.3: Maximum sea levels recorded at each AWAC in each year 32 List of Photos Photo 1: Deployed directional Waverider buoy 4 Photo 2: Deployed Waverider buoy 5 iv Sea State Report RP040/S/2014 Suffolk 1 Anglian Coastal Monitoring 1.1 Wave & tide monitoring The Shoreline Monitoring Group (SMG) based within the Flood & Coastal Risk Management department of the Environment Agency (EA) provides strategic monitoring of the Anglian coast through the Anglian Coastal Monitoring (ACM) project. Phase VII of this programme ran between 2006/07 and 2010/11. For wave and tide monitoring, a network of five Directional Waverider (DWR) buoys and 20 Acoustic Wave and Current meters (AWACs) measured offshore and nearshore sea conditions respectively, along the regional frontage over a three year period (2006 – 2009). The AWACs were recovered in 2009; the West Silver Pit wavebuoy was also recovered due to its proximity to the wavebuoy deployed at Inner Dowsing. The Southwold Approach and South Knock DWR buoys are now managed by the UK Coastal Monitoring and Forecast service (UKCMF). In Phase VIII of the programme, additional wavebuoys were deployed off Chapel Point in Lincolnshire, Happisburgh in Norfolk and Felixstowe in Suffolk. All seven deployed wavebuoys provide real-time wave spectra and GPS positions via satellite link. The real-time wave data is uploaded to the WaveNet website (WaveNet, 2014) which is maintained by the Centre for Environment, Fisheries and Aquacultural Science (Cefas) on behalf of the Department for Environment Food & Rural Affairs (Defra); here, members of the public are able to access the programme’s real-time monitoring data. The data collected over the three-year period has proved to be of significant value. It has provided valuable observations of the Anglian coastal sea state which were previously only modelled. In addition, following recovery of the AWACs, the coincidental logging of offshore and nearshore data has allowed development of statistical models that provide inshore wave conditions calculated from offshore buoy observations. These models have been used to create lookup tables for use in flood forecasting. The Anglian network is now part of a national programme supplying real time data to the UK Meteorological Office to be integrated into the Environment Agency’s National Flood Forecasting System and wave overtopping models. It is envisaged that, in time, the buoy data will continue to provide input into wave models and help to build a dataset for statistical forecasting of extreme conditions to assist in flood forecasting and flood risk management. It is also hoped that the wave and currents data may be combined with sediment models to identify the transportation and movement of sandbanks, annual beach sediment movement and erosion following storm events, and the impact of sea level rise throughout the region. Furthermore, the data will provide baseline design statistics to inform future coastal and marine planning, construction projects, and further climate research and monitoring of sea level rise.