WireWall: a new approach to coastal wave hazard monitoring

Lead Research Organisation: National Oceanography Centre (WEF011019)
Department Name: Science and Technology

Abstract

Many countries with a sea border need manmade defences to protect them from coastal hazards such as flooding. In the UK 3200 kilometres of coastline are defended, particularly in seaside towns and cities. This is to prevent flooding and to protect people, property and infrastructure from the harm caused by large waves that can occur when a severe storm happens at the same time as a high tide. Building strong coastal defences can be costly, often about £10,000 per meter, and needs careful planning.

When planning coastal defences a lot of data are needed to understand the potential hazards that might occur in decades to come. To obtain this data for a particular site usually means monitoring the local tides, wave heights, and beach levels for a period of 5 to 10 years. These data are used in numerical tools (e.g. EurOtop) to test which seawall design is most suitable and how high it needs to be to provide protection for the next 100 years. The tools do this by estimating the "overtopping hazard" for each design, i.e. what volume of water might come over the wall during storm conditions. Accuracy of the tools is assessed by checking outputs against measurements of overtopping volumes during storms. Field experiments have previously used large tanks placed behind the seawall to catch the water that comes over. Such experiments are very costly and can be difficult to do, so only a few have been made - usually at sites with very different structures (e.g. dikes) and for only a few days. They also only provide a limited amount of data and none at all on the speed of the water that overtops: an important factor for public safety. This lack of measurements means there is large uncertainty in the numerical estimates of the hazards, so sea defences are overdesigned to have large safety margins and may therefore cost much more than they need to.

This project aims to take a low-cost instrument that has previously been used to measure waves in the open ocean, and convert it into a system ("WireWall") that will measure coastal overtopping hazard. Recent improvements in technology now make it possible to measure at the very high frequencies required to record the fast moving overtopping water (a few hundred times a second for a jet of water travelling up to 100 mph). The system will employ a 3-dimensional grid of capacitance wires that sense contact with saltwater. This signal will be used to measure the volume and speed of overtopping at vulnerable locations on the 900-meter-long seawall at Crosby in the North West of England. This seawall is reaching the end of its design life and intense monitoring of the local conditions has begun to aid the design of a new wall.

This project includes engineers, environmental hydraulics experts and oceanographers who have complementary field, laboratory and modelling expertise. Our project partners (Sefton Council, Environment Agency, Balfour Beatty, Marlan Maritime Technologies and Channel Coastal Observatory) are involved in commissioning, designing and constructing coastal defences, and include government authorities and private consultancies. They will provide existing monitoring data at Crosby, and will advise on the methods and tools routinely used in the design of a new seawall. We will use this information to optimise the configuration of the WireWall system and its deployment at Crosby. Data obtained by WireWall will improve the tools used when designing the new seawall by calibrating the numerical estimates of overtopping hazards to those observed.

In the future WireWall could be incorporated into new seawall structures to enable long-term monitoring. The ability to observe trends and abrupt changes in hazardous conditions (due to defence degradation, climate change and sea level rise) would support shoreline management plans and provide data to validate operational flood forecasting systems.

Keywords: Shoreline monitoring; Coastal defence; Wave overtopping hazard

Planned Impact

The observations of key overtopping parameters collected by the WireWall system at the Crosby seawall will be used to reduce the uncertainty in overtopping estimates derived from the numerical tools and methods used in industry when designing new coastal defences. In the next 5 years funding for a new 900 m long coastal defence at Crosby will need to be secured through grant aid administered by the Environment Agency and from the Sefton Council's Flood and Coastal Erosion Risk Management resources. The dataset collected at this site will allow validation of the numerical tools and methods used by project partners when designing the new Crosby defence. Use of the tools to simulate a wide range of past storm events that caused overtopping will allow calibration of the site-specific safety thresholds that are needed to inform a) the new seawall design and b) the timing of promenade and car park closures for public safety. By having these valid tools and calibrated safety tolerances our partners will have reduced uncertainties in their wave overtopping estimates and hence a reduced need to overdesign the new defence at Crosby. If construction costs are estimated at £10,000 per linear meter and the WireWall project reduces uncertainty in the overtopping estimates by 10%, this would result in a direct saving of about £500,000 for our partners for this one seawall alone. Scaled up nationally, a similar calculation would give a saving of £125 million on the £2.5 billion that the UK Government has committed to flood defences over the next 6 years. Additional on-going savings will be made through reduced maintenance costs over the 100-year design life of the new scheme. Where the height of a new scheme can be limited the aesthetics of the shoreline may also be enhanced, thus improving the scheme's dual purpose as a public amenity.

The deployment of WireWall at Crosby will be the first step towards the development of an overtopping monitoring system that could ultimately be integrated into new coastal schemes as part of the UK's regional shoreline monitoring programmes. These programmes support shoreline management plans (SMPs). SMPs were adopted in 2001 by Coastal Groups across England and Wales, to deliver management activities that prevent future generations being tied to costly and unsustainable management practises 100 years from now. A long-term national dataset of key wave overtopping parameters (as obtained by WireWall) could provide an evidence base to assess the effectiveness of shoreline management policies and schemes in support of flood hazard management activities. Promotion of the WireWall capabilities through our project's Wider Interest Group (which represents many parties who are involved with the management of, or research into, coastal hazards across the UK) will provide potential opportunities to up-scale the deployments of WireWall to enable cost savings in the implementation of other new defence schemes nationally. Dissemination of the WireWall approach through the Channel Coastal Observatory will ensure consistency in future data collection, processing and management across the National Network of Regional Coastal Monitoring Programmes. This will ensure the value of the dataset grows with each supplementary data collection. Once large enough the observed dataset will enable development of improved empirical methods for use by industry to estimate overtopping hazard specifically for seawall structures. This will be of particular value to our industry partner Balfour Beatty and other consultancies, since current tools are developed primarily from dike and flume experiments.

Continued WireWall deployments at Crosby post-project, and deployments of the system at other sites across the UK, could be achieved through intellectual property (IP) licensing that would allow commercialisation opportunities with our partners Marlan Maritime Technologies and expand their business opportunities.

Related Projects

Project Reference Relationship Related To Start End Award Value
NE/R014019/1 01/01/2018 31/10/2019 £319,740
NE/R014019/2 Transfer NE/R014019/1 01/11/2019 31/12/2019 £53,577
 
Description This collaborative NERC-funded research project, led by the National Oceanography Centre and HR Wallingford, has taken a low-cost instrument, previously used to measure waves in the open ocean, and converted it to deliver an easily relocatable overtopping measurement system - WireWall. WireWall allows coastal overtopping hazards to be assessed more confidently. The WireWall system was tested and refined using flume experiments in HR Wallingford's physical modelling laboratories before being successfully deployed at a coastal site north of Liverpool in October 2018, November 2018 and January 2019. We have developed a system that is capable of measuring horizontal wave overtopping velocity in the field. These data are available through the British Oceanographic Data Centre to be used for the calibration/validation of numerical tools that are used for wave overtopping forecasting and coastal scheme design. The new system collected time-series of observations during typical winter spring tide overtopping conditions that provided site-specific data to:
• calibrate overtopping tools, e.g., the industry-standard empirical rules within EurOtop, for nuisance overtopping hazards;
• validate operational flood forecasting services, including the forecast and alert thresholds applied; and,
• develop site-specific safety tolerances to inform flood risk management plans.
Exploitation Route The specifications for the new wave overtopping measurement system were set by our project partners: Channel Coastal Observatory, Sefton Council, the Environment Agency, Balfour Beatty and Marlan Maritime Technologies. To ensure the approach is relocatable to other sites, a 100+ member strong International Wider Interest Group has been formed representing consultants, engineers, coastal authorities and academics. Through this group the design and data requirements have been specified so that the WireWall system meets the wider needs of coastal practitioners and academic research. To ensure the final data are made readily available all outputs will have linked to Channel Coastal Observatory alongside the Northwest Regional Monitoring Programme. Our observations will be used by the Sefton Council and Environment Agency to refine alert thresholds in the flood forecast systems for Crosby beach and inform the design of a new coastal scheme.
Sectors Digital/Communication/Information Technologies (including Software),Education,Environment

URL https://www.channelcoast.org/ccoresources/wirewall/
 
Description The capability from this project is of interest to the NW coastal group who are interested in transferring it to unban flood management to work towards a networked coastal and inland flood hazard monitoring system. We have formed collaborations to submit EOIs to bid for the January 2021 Government flood innovations call. Our engineering capability also led to commercial work with project partners Balfour Beatty to test filters for a coastal scheme at Anchorsholme in 2020.
First Year Of Impact 2000
Sector Environment
Impact Types Policy & public services

 
Description Coastal REsistance: Alerts and Monitoring Technologies (CreamT)
Amount £734,812 (GBP)
Funding ID NE/V002538/1 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 07/2020 
End 08/2022
 
Title WireWall field deployment Hall Road, Crosby, Liverpool, UK between October 2018 and March 2019 
Description The prototype WireWall measurement system was deployed at Hall Road Crosby (north of Liverpool UK) and measured overtopping eight times between October 2018 and March 2019. Deployments took place during tides with a range greater than the mean spring tide when there was an onshore wind. The system measured the inland distribution of wave-by-wave overtopping discharge and horizontal velocity for a couple of hours either side of high water. Wave and water level data to numerically estimate conditions when monitoring data became available were obtained from the Liverpool Bay WaveNet buoy and Liverpool Gladstone Dock NTSLF tide gauge. A beach profile collected during low water prior to deployment was used in the numerical estimates. During these experiments a time series of data were collected during the overtopping window. Numerical estimates using the SWAN model and the BayonetGPE tool (EurOtop 2018) were compared to the measurements. The observed data archived for the 26th October 2018 and 25th January 2019 represent the horizontal overtopping discharge and horizontal overtopping velocity averaged over different periods selected by the project's wider interest group (5 min and 15 min). The numerical (SWAN-BayonetGPE) data are archived at 15 minute intervals for eight events. 
Type Of Material Database/Collection of data 
Year Produced 2020 
Provided To Others? Yes  
Impact The measurements will be used by local authorities for coastal flood hazard management. Initially they have been used to calibrate the Environment Agency's flood forecast system. 
URL https://www.bodc.ac.uk/data/published_data_library/catalogue/10.5285/acd939f0-38e7-57b0-e053-6c86abc...
 
Title WireWall flume experiments at HR Wallingford 
Description The prototype WireWall measurement system was initially trialled in the controlled environment of HR Wallingford's flume facility during three 5-day periods: 9th July 2018, 20th August 2018, 17th September 2018. An additional 5-day experiment was also run to collect data to compare with BayonetGPE: 3rd September 2018. In all experiments a 1:7.5 scale model of the beach and sea wall structure at Crosby (north of Liverpool, UK) was built within the flume using a laser scan collected 11th December 2013 by the Sefton Council. The flume was 45 m long, 2 m deep and 1.2 m wide. It was equipped with a piston-type wave paddle controlled by HR Wallingford's Merlin software. Wave and water level data to simulate conditions were obtained from the Liverpool Bay WaveNet buoy and Liverpool Gladstone Dock NTSLF tide gauge. During these experiments total cumulative wave-by-wave overtopping data were measured using collection tanks and WireWall. The collection tank data were recorded using small capacitance wire probes within the tanks. For long runs (over 100 waves) numerical estimates using the BayonetGPE tool (EurOtop 2018) was also used to assess its capability at this site. The data archived represented the total volume of water that overtopped the structure during each experiment, which comprised of different wave conditions and still water levels. 
Type Of Material Database/Collection of data 
Year Produced 2020 
Provided To Others? Yes  
Impact The data validated the numerical tools and WireWall system to give confidence in overtopping estimated and measurements at Crosby to be used when designing a new coastal scheme. 
URL https://www.bodc.ac.uk/data/published_data_library/catalogue/10.5285/acd939f0-38e6-57b0-e053-6c86abc...
 
Title WireWall project experiment data generated at NOC 
Description The prototype WireWall measurement system was designed using bucket and balloon tests at the National Oceanography Centre's dockside, Southampton, during April to August 2018. Initially the electronics were configured using a frame of 6 vertical wires through which buckets of water were thrown. Once satisfied the system was recording at an appropriate rate for the wire spacing a single electronics unit was set up with 6 wires positioned horizontally to measure the fall velocity of water under gravity when a balloon full of water was burst at a known height above the top wire. The wires were spaced 10 cm apart. For each balloon test the velocity was calculated between different wire pairs for comparison against Newton's theory. 
Type Of Material Database/Collection of data 
Year Produced 2020 
Provided To Others? Yes  
Impact It helped us design the WireWall field rig. and validate overtopping speed calculations. 
URL https://www.bodc.ac.uk/data/published_data_library/catalogue/10.5285/acd939f0-38e8-57b0-e053-6c86abc...
 
Title WireWall project numerical wave overtopping volume estimates at Crosby Hall Road Carpark (north of Liverpool UK), estimates are for coastal conditions when there is photographic evidence of overtopping occurring 
Description Numerical wave overtopping volume estimates from the BayonetGPE wave overtopping tool associated with the EurOtop (2018) manual and modelled wave and water level conditions at the toe of the structure transformed from nearshore national monitoring networks using the SWAN model. Mean, upper and lower 1st and 2nd standard deviation wave overtopping volumes are estimated by BayonetGPE (generated by HR Wallingford, October 2019) for the Hall Road Car Park, Crosby Beach survey profile (reference: 11A02250). The data are associated with photographs of events when there is a record showing some level of overtopping occurring at Crosby beach. The photographic data were collected for the period January 2013 to December 2017 from Facebook (page: I'm at Crosby Beach and the weather is ...) and project partners. The numerical estimates of overtopping were generated using: beach surveys (available from Channel Coastal Observatory) from 24th February 2017, 4th April 2017, 4th October 2017 and 1st September 1996; a laser scan of the sea wall collected 11th December 2013 (available from Sefton Council); Seazone bathymetry from 05/12/2014, originally collected by the UK Hydrographic Office at 1 arc second; wave conditions (available from WaveNet, Centre for Environment, Fisheries and Aquaculture Science (CEFAS)); water levels tide gauge data (available from the National Tidal Sea Level Facility (NTSLF) who deliver data through the British Oceanographic Data Centre (BODC)). The coastal conditions were transformed to the toe of the existing structure using the 3rd generation spectral wave model SWAN. The bottom friction was set to use bed ripples and a sediment size of 0.23 mm (the Median grain size, d50, for the upper beach at Crosby, KPAL 2010). BayonetGPE was then used to estimate the resulting overtopping discharges. 
Type Of Material Database/Collection of data 
Year Produced 2020 
Provided To Others? Yes  
Impact The data will be used by local authorities to improve coastal flood hazard management. 
URL https://www.bodc.ac.uk/data/published_data_library/catalogue/10.5285/acd939f0-38e5-57b0-e053-6c86abc...
 
Title WireWall project numerical wave overtopping volume for joint wave and water level conditions 
Description Numerical wave overtopping volume estimates from the BayonetGPE wave overtopping tool associated with the EurOtop (2018) manual and modelled wave and water level conditions at the toe of the structure transformed from nearshore national monitoring networks using the SWAN model. Mean, upper and lower 1st and 2nd standard deviation wave overtopping volumes are estimated by BayonetGPE (generated by HR Wallingford, October 2019) for the Hall Road Car Park, Crosby Beach survey profile (reference: 11A02250). The data are associated with joint wave and water level conditions at the Liverpool Bay Wave Buoy Location that form the 1 in 1 year to 1 in 200 year return period curves in a joint probability analysis for the North West Coastal Group delivered by Halcrow in 2011. These return period curves represent the conditions to design new coastal schemes and analyse event severity. The numerical estimates of overtopping were generated using: beach surveys (available from Channel Coastal Observatory) from 24th February 2017, 4th April 2017, 4th October 2017 and 1st September 1996; a laser scan of the sea wall collected 11th December 2013 (available from Sefton Council); Seazone bathymetry from 05/12/2014, originally collected by the UK Hydrographic Office at 1 arc second. The coastal conditions were transformed to the toe of the existing structure using the 3rd generation spectral wave model SWAN. The bottom friction was set to use bed ripples and a sediment size of 0.23 mm (the Median grain size, d50, for the upper beach at Crosby, KPAL 2010). BayonetGPE was then used to estimate the resulting overtopping discharges. 
Type Of Material Database/Collection of data 
Year Produced 2020 
Provided To Others? Yes  
Impact The data will be used by local authorities to improve coastal flood hazard management. 
URL https://www.bodc.ac.uk/data/published_data_library/catalogue/10.5285/ae80bb3c-8aad-4bc7-e053-6c86abc...
 
Description A virtual day at the beach 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact An online event was run through twitter @WireWall_NOC to write community coastal poetry and generate word clouds to increase awareness of coastal hazards.
Year(s) Of Engagement Activity 2020
URL https://www.youtube.com/playlist?list=PLoYJVOchmO7HtiWLMwU8q6WLQcZ91prSf
 
Description Getting our message across with Water Pistols and a little bit of Poetry!! 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact An AGU Blogosphere article was written to communicate with other academics about methods that work well to engage the public.
Year(s) Of Engagement Activity 2020
URL https://blogs.agu.org/sciencecommunication/2020/06/01/getting-our-message-across-with-water-pistols-...
 
Description Isle of Wight Cafe Scientifique presentation 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact A virtual presentation about the WireWall project was given as part of the evening Isle of Wight Cafe Scientifique community group series. There were lots of questions about coastal processes and changing coastal hazards.
Year(s) Of Engagement Activity 2020
 
Description Kirby SciBar presnetation 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact A virtual presentation about the WireWall and CreamT projects was given as part of the evening Kirby SciBar community group series. There were lots of questions about coastal processes and changing coastal hazards.
Year(s) Of Engagement Activity 2020
 
Description New sensors to quantify coastal flood resistance, Nature-based solutions webinar 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact A presentation on new flood hazard monitoring sensors was given as part of a Nature-Based Solutions webinar hosted by the British Consulate in Miami. Lots of questions were asked.
Year(s) Of Engagement Activity 2021
 
Description New sensors to quantify coastal scheme flood resistance and resilience, JSPG-UK-SIN webinar 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Policymakers/politicians
Results and Impact A presentation about new coastal hazard monitoring technology as part of a UK Science and Innovation Network webinar to promote the launch of a special issue in the Journal of Science Policy and Governance. Lots of questions were asked around climate change impacts and Nature-based coastal management.
Year(s) Of Engagement Activity 2020
URL https://www.sciencepolicyjournal.org/news/jspg-and-uk-science-and-innovation-network-special-issue-a...
 
Description Seminar for the Bedford Institute of Oceanography, Fisheries and Oceans Canada 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact A seminar on "New field measurements that support coastal flood hazard management" was given to the Bedford Institute. Lots of questions were asked.
Year(s) Of Engagement Activity 2020
 
Description Sensors to quantify coastal scheme flood resistance and resilience, vICCE presentation 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Conference presentation at vICCE 2020 about the WireWall and CreamT research. There were questions and follow-up meetings with potential collaborators in New Zealand.
Year(s) Of Engagement Activity 2020
 
Description UKRI (NERC) Constructing a digital environment Blog 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact A CreamT Blog was written to engage others in the digital environment community and the public about the development of our telemetry syste that will be used to nowcast flood hazard at Penzance and Dawlish in 2021.
Year(s) Of Engagement Activity 2020
URL https://digitalenvironment.org/a-creamt-that-delivers-health-checked-hazard-warnings/
 
Description WireWall: The Presentation 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact A short clip to quantify the hazardous wave overtopping that occurred at Crosby beach during the WireWall deployments was made at the request of JBA pacific. This was released on YouTube and shared via LinkedIn.
Year(s) Of Engagement Activity 2020
URL https://youtu.be/5h71xuHBySc