The objective of this project is:

1) To get a better understanding of coastal and near-shore processes ruled by erosive waves and sea level rise.

2) To design, test and analyse the performance of a dynamic revetment – new kind of protection falling into the ‘work with nature’ category.

3) To monitor an existing dynamic revetment type and compare its behaviour with laboratory results.

Project outline

Global mean sea level is rising at increasing rate, and this represents one of the main long term coastal hazard. Existing hard engineering coastal defences are neither designed nor efficient against Sea Level Rise (SLR), and therefore are likely to be overtopped and breached during this century.

A recent soft engineering technique named “dynamic revetment” or “cobble berm” has been implemented in some coastal places to protect the hinterland against storm waves and erosion. This type of revetment is not static and moves under waves’ action while dissipating the waves’ energy. By optimising the design of the dynamic revetment as well as the deployment area, this structure is supposed to self-maintain its relative position to sea level under SLR. The cobbles composing such a protection are expected to move landward under SLR, thus keep protecting the hinterland against future extreme wave climate.

The performance of the revetment was tested in the GWK large scale flume, Hannover, Germany, through the ‘DynaRev’ experiment in 2017. The experiment was designed to assess the behaviour and the capacity of the revetment to adapt and protect sandy beach against waves attack and SLR. The experiment was also designed to provide a large range of morphodynamic data required for a better understanding of general coastal processes under SLR. In January 2019, the dynamic revetment of North Cove (figure 1), Washington State, the USA, was monitored for 10 days high energetic condition happening around the spring tide. Surface measurements of the revetment were recorded using a LiDAR in order to assess the behaviour of the structure in real environment.

Science

The laboratory experiment undertaken during this project provided a large and unique dataset on beach profile evolution and dynamic revetment behaviour under sea level rise, erosive and accretive conditions. The field data measured in North Cove are one the rare dataset on active dynamic revetment. This project will help validating or modifying the commonly accepted statements on sandy and composite beach profile evolution. It will also be a strong scientific base regarding to the performance of a dynamic revetment, in order to create a design guideline and eventually lead to more field application of such coastal protection. One of the outputs from this project can be found in the following papers:

Bryan et al. (2019). Breaking Wave Imaging using Lidar and Sonar. IEEE Journal of Oceanic Engineering, PP(99):1-11.

Bayle et al. (2019). Performance Of A Dynamic Cobble Berm Revetment for Coastal Protection. Coastal Engineering. (in submission)

Blenkinsopp et al. (2019). Data in Brief. Coastal Engineering. (in submission)

Impact

This project will have an impact on fundamental coastal science as it will refine the knowledge on coastal dynamic and shore evolution prediction. On the other hand, it will offer a designed and tested structure to protect small asset and habitat from storms and sea level rise. Therefore, through local decision taker, it could help the society to adopt sustainable and resilient coastal defences.

This is the PhD project of Paul Bayle from the Department of Architecture and Civil Engineering. Email address: P.M.Bayle@bath.ac.uk