Modelling storm impacts on gravel coasts now possible

Published: 15 February 2016

Gravel beaches occur on many wave-dominated coasts across the world and are widely considered an effective and sustainable form of coastal defense. Despite their societal importance, relatively little research has been directed towards understanding the mechanisms leading to their failure during storms.
Figure2

Storm waves hit Chesil Beach (Dorset, England). Data collected during this storm were used to develop and validate XBeach-G. Photograph courtesy of T. Poate (Plymouth University).

Development of a new, open source, numerical model

Robert McCall addressed the current gap in predictive storm-impact models for gravel coasts in his doctoral research at Plymouth University (UK), in collaboration with Deltares and project partners the Channel Coastal Observatory, the Environment Agency, HR Wallingford and UNESCO-IHE, as a part of the NUPSIG project. His research resulted in the development of a new, process-based, open-source numerical model called XBeach-G.

Simulating the impact of storms on gravel beaches and barriers

The XBeach-G model, which is based on the existing open-source model XBeach, simulates the impact of storms on gravel beaches and barriers by solving the hydrodynamics of individual waves in the nearshore and swash zone, wave run-up and overtopping flows, groundwater processes in the beach and barrier, sediment transport, and morphological change of the beach during the storm.

Substantial improvement over existing models

The model represents a substantial improvement over existing empirical models in its ability to accurately simulate the response of gravel beaches to a wide variety of storms. Application of the model has furthermore increased our understanding of the role of incident-band and infragravity-band waves during storms, and the role of groundwater processes in the stability of gravel beaches and barriers. One of the key scientific papers discussing the development of the XBeach-G model was awarded the Halcrow Prize for the best paper published in the ICE journal ‘Maritime Engineering’.

Easy uptake of the model

To ensure easy uptake of the XBeach-G model by coastal managers and engineering firms, Deltares and Plymouth University have developed a free and easy-to-use graphical user interface (GUI) for the XBeach-G model. Deltares and Plymouth University have furthermore given training and assistance to 40 interested parties in the UK and the Netherlands. The XBeach-G model, model GUI, and validation papers are freely available at the XBeach-G website.

Gravel coasts are common in the United Kingdom, Italy, Croatia, Georgia, Ukraine (Mediterranean and Black Sea), Ireland, Estonia, Latvia, Australia and New Zealand, the United States, Canada, Argentina, Chile and Japan. Dredging companies use gravel to set up a temporary defences. They can also use the model for the design of those defences.