Beach replenishment

Beach replenishment
ENTRY DATE: 19 April 2012| LAST UPDATE: 19 April 2012
Categories: Coastal Regions | Improvement of structures
Technological Maturity: Applicable immediately
Technology Owners:

Consultants, construction firms

Needs Addressed

The need to conserve sandy beaches in regions that may be affected by damage from sea level rise due to climate change as well as from erosion, storm surges, waves and tsunamis.

Adaptation Effects

This method offers protective features (reduces wave run-up and overtopping, and prevents erosion/wear of embankments and seawalls).

Overview and Features

This method supplies sand artificially to the coast line to replenish beaches.

[Static beach replenishment]
Aim is static stabilization of sandy beaches by reducing the amount of sand drift through the use of sand drift control structures. Methods include placement of wave-dissipating blocks (groynes or jetties) extending offshore at right angles to the coastline, or placement of wave-dissipating blocks parallel to the coastline (detached breakwaters), etc.


Groynes/jetties

Detached breakwaters


Source: http://www.ccba.or.jp/koueki/kaikekaigan.htm

[Dynamic beach enhancement]
Aims to stabilize beaches by permitting long-shore sand drift as a source of sand supply to down-current locations. Strategies to prevent beach erosion include beach replenishment by supplying sand in eroded areas down-current by depositing sand in up-current locations (Sand bypass method; see the figure below).

[Beach restoration using ecological mechanisms]
Sand production by transplantation and cultivation of coral and foraminifera

Cost

Costs vary significantly depending on the type and size of beach.

Ease of Maintenance

Ease of maintenance vary significantly depending on the type and size of facility.

Technology Performance

Technology performance vary significantly depending on the type and size of facility.

Considerations (technology transfer criteria, challenges, etc.)

・ These strategies require access to experts with a high level of knowledge about coastal engineering. 
・ It is important to give technical consideration to the special characteristics of each coastline.
・ When considering how to improve the coastline, in implementation of these strategies, it is important to seek consensus with local communities and other stakeholders, as well as cooperation with other operations and administrators.

Co-benefits, Suitability for Developing Countries

・ The strategies can contribute to conservation and protection of the natural environment, and to sustainable development. 
・ Potential environmental functions (seawater purification, resting spots for wildlife, etc.)
・ Human applications (recreation, fishing, etc.)

Examples

Case 1: Tuvalu: Restoring sand projection by transplantation and cultivation of coral and foraminifera
Tuvalu is a flat country with elevation ranging from 1 to 3 meters above sea level, and is threatened with inundation caused by sea level rise as a result of climate change. Meanwhile, coral ecosystems are deteriorating due to an increase in anthropogenic pressure, and land formation by the production of sediment by coral and foraminifera is reportedly declining dramatically. The threat of inundation is increasing, not only from sea level rise but also from a combination of local factors such as population growth and economic development. Coastline protection strategies that fail to consider ecological mechanisms pose a high risk of destroying the mechanisms that sustain the islands in the long term. Thus, in order to develop strategies against sea level rise, it is important to restore the islands in a way that makes them resilient to sea level rise, based on an understanding of the mechanisms of island formation and conservation.
The Japan International Cooperation Agency (JICA) is implementing the “Project for Eco-technological management of Tuvalu against sea level rise " from 2009 to 2014, with the aim of restoring the islands in a way that makes them resilient to sea level rise—through ecological repair and restoration, beach replenishment, and artificial facilitation of transport and sedimentation processes. The project continues to research with the aim of restoring sand production by the transplanting and cultivation of coral and foraminifera, and ensuring the continued survival of the islands in the long run.

Information Resources

・ Public Works Research Center , “Manual for beach replenishment” 
・ JICA Technical Cooperation Project, " Project for Eco-technological management of Tuvalu against sea level rise "
http://www.jica.go.jp/project/tuvalu/0802778/index.html (in Japanese)