Wave Overtopping System to Improve Coastal Hazard Forecasts

The National Oceanography Center (NOC) developed WireWall, a system designed to measure the speed and volume of overtopping water on a wave-by-wave basis in the field. The aim is to reduce uncertainty in overtopping forecasts and improve hazard warning systems.

Previous field data has been obtained using large collection tanks which can only be deployed for short periods, and are only capable of obtaining data on the total volume of water that has overtopped during a storm, or a high tide event. The tanks used in previous field measurements can only be deployed on a few types of structures, such as, inland of a solid wall at the top of a coastal defence, which means that the amount of data previously obtained in the field is very limited – compared to WireWall which has been designed so that it can be deployed on almost any structure.

Until now, a lack of field data has meant that the prediction tools currently used are based on studies of a limited range of coastal defenses using idealised experiments in flumes. This means that the industry standard tools that are used to predict wave overtopping can have large uncertainties.

A paper published in the Communications Engineering journal highlights the validation of WireWall, and several of the results from the first trial deployments at Crosby, near Liverpool. The validation process took place in the flume facilities of the project partners at HR Wallingford, where a wave machine generated waves similar to those that might be expected at Crosby, and these impacted a 1:7.5 scale model of the Crosby seawall.
In future, WireWall overtopping measurements could be used to improve industry-standard overtopping prediction tools and hence improve flood and hazard forecasts. 

Field measurements of overtopping will also allow experts to study the sort of wind and wave conditions that cause overtopping, which will improve numerical models.