Understanding shoreface nourishment better
Expert(s) |
Jebbe van der Werf
Shoreface nourishment – depositing sand below the waterline to counter coastal erosion – is one of the measures used to protect vulnerable coastal areas. This approach is used widely, particularly where large amounts of sand are available. Despite years of field measurements, laboratory experiments and model studies, the effect of shoreface nourishment is still difficult to predict and more knowledge is needed. This is the conclusion of researchers from Deltares, Twente University, Utrecht University, Delft University of Technology, Rijkswaterstaat, the U.S. Army Engineer Research and Development Center, and Technical University of Denmark in their new study.
More knowledge required in four areas
Shoreface nourishment involves depositing sand in the sea at a depth of 4 to 10 meters in a dynamic part of the coast where the bed level varies considerably and where morphological patterns are complex. This variability makes it difficult to establish a clear understanding of how the sand spreads and the long-term effects on the coastline. The researchers identified four major knowledge gaps:
- Sand distribution: It is not yet clear enough how the applied sand spreads around the coastal zone.
- Design variables: Little is known about the effect of design variables such as volume, location, and grain size on the effect duration, and effectiveness of nourishment operations.
- Cumulative effect: The long-term effect of repeat nourishment on the scale of tens of kilometres and over decades is largely unknown.
- Limitations of computing models: The present numerical models cannot yet reliably predict morphological development as a whole.
Call for collaboration and knowledge development
To establish a better understanding of, and to predict the effects of shoreface nourishment, the researchers have drawn up a research agenda. It will focus on collecting and analysing new field data, improving models, and developing guidelines for design and monitoring.
This is urgently needed, particularly in the light of climate change and sea level rise. How do you design nourishment approaches that will be effective not only today but also fifty years from now? Although the Netherlands leads the way in the use of shoreface nourishment, using some five million m³ of sand annually, this approach is also being used increasingly in countries including Germany, Denmark, the USA, South Korea and Australia.
Jebbe van der Werf, the lead author and a researcher at Deltares and Twente University: “Despite decades of research, the behaviour of shoreface nourishment remains difficult to predict. With this study, we show that there are still many uncertainties about sand distribution and the cumulative effects of repeated nourishment operations. By recognising the gaps in our knowledge, we can measure more precisely, improve our models, and ultimately design climate-robust nourishment approaches.”
Contribution to resilient coasts
With this study, the researchers are contributing to a scientific basis for future coastal management. By making targeted investments in knowledge and monitoring, policymakers and engineers can design nourishment approaches that are ecologically sound, cost-effective and climate-robust.
The study is one of the results of the SOURCE research project. SOURCE stands for Sand nOURishment strategies for sustainable Coastal Ecosystems. The six-year study began in 2024 and it is being conducted by a research consortium of Deltares, Twente University, Utrecht University, Delft University of Technology, WUR, Wageningen Marine Research, the HZ University of Applied Sciences and the Vrije Universiteit, Amsterdam.
The paper has been published in Elsevier’s Earth Science Reviews under the title ‘Shoreface nourishments: Research advances and future perspectives’.
