Assessing the value of eelgrass in nature-based coastal defence

Project Information

SHIEELD

Grant agreement ID: 101022685

DOI

10.3030/101022685

Project closed

EC signature date 24 March 2021

Start date 1 February 2022

End date 31 January 2024

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 183 473,28

EU contribution

€ 183 473,28

Coordinated by

POLITECNICO DI TORINO
Italy

Periodic Reporting for period 1 - SHIEELD (Assessing the value of eelgrass in nature-based coastal defence)

Reporting period: 2022-02-01 to 2024-01-31

Summary of the context and overall objectives of the project

The project advances our understanding on how seagrass ecosystems help protecting coastal areas by damping incoming waves and stabilising sediments on the seabed.
The reason why this is important for society is twofold: it informs all stakeholders about the often-neglected effects of seagrass on the physical processes of interest for coastal protection, and it provides new tools to predict the wave damping of seagrass depending on the conditions at a given site.
The overall objectives of the projects are: (1) to quantify the wave damping of seagrass with and without currents, (2) to provide a model of wave damping of seagrass, and (3) to evaluate the effects of seagrass on sediment mobility.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

As first step in the project, we designed and manufactured physical models of seagrass made of plastic material so that they replicated the geometrical and mechanical properties of the natural plants. With such physical models we built seagrass meadows in an open-channel flume facility that allowed generating waves in the absence/presence of a following current. During the experiments we measured the wave height along the seagrass meadow to characterise its wave damping properties.
Thus, we collected the largest dataset of seagrass wave damping to date, which we used to develop a new model for predicting the wave damping of seagrass accurately across a wide range of conditions in the absence of current. These results were disseminated at scientific conferences and with a peer-reviewed publication. As for the wave damping in the presence of a current, our experimental data indicate that the most advanced models underpredict wave damping almost systematically - we disseminated such result at a scientific conference.
In the second part of the project, we conducted field experiments with a portable flume facility to investigate the effects of seagrass on sediment mobility. We ran experiments on both bare beds and on beds within seagrass meadows monitoring the particles being suspended as the flow velocity increased. At each site we collected samples of sediments and seagrass to characterise them.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The project has led to the development of a novel model of seagrass wave damping that works well across a wide range of conditions. By the end of the project, we expect to: (i) develop an additional model that includes the effect of a following current on the wave damping of seagrass, and (ii) to shed a light on how seagrass influence sediment stability.
The models of wave damping can be used by coastal engineers and practitioners to predict the reduction in wave height caused by seagrass meadows and hence allow a more accurate modelling of coastal hydrodynamics. The overall findings of the project will help stakeholders to assess the value of seagrass in coastal protection by providing them with tools to better quantify some of their ecosystem services.

Experimental setup