Groynes

Protect
Written By Frank Hangler

Groynes are rigid structures, typically constructed using heavy materials extending from the upper shore to the water.[^1] They are used in combination with beach nourishment by trapping beach material that is transported during high wave conditions.[^2] Groynes can be constructed using various materials including timber, steel, concrete to rubble-mounds. Each material has different strengths and weaknesses and life expectancies. Long-term maintenance is required, and the replacement of groynes are common in flood management plans. As a response to downdrift erosion construction of groynes should be accompanied by a regular recycling or nourishment program.[^3]

Types of groyne

  • Wooden groynes usually consist of one or two-row palisade structures that are usually permeable. Wood groynes are cheap but have low durability.
  • Rock groynes are simple to construct and have long durability. They can also be dismantled and reinstalled
  • Concrete groynes are usually constructed from prefabricated boxes or reinforced concrete hence they are very durable and long-lasting. However, they require a foundation with a high load-bearing capacity
  • Rubble-mound groynes can be built using loose mounds of stones or other materials, e.g., tetrapods [^13]

✓ Benefits

  • Creates an opportunity for beach widening which is valuable to recreational tourism.
  • Traps sediments and widens beach thereby reducing erosion and increasing wave energy dissipation.
  • Acts as a sturdy structure which can be used for long term stabilization of coastline
  • Can be used in tandem with other approaches, e.g., beach nourishment and hard engineering measures
  • Enjoys widespread global acceptance based on experience with design and construction.

✗ Challenges

  • Provides limited protection against extreme storm events
  • Reduces transport of sediments down the coastline
  • Causes downdrift erosion
  • Complementary to artificial nourishment, e.g., could reduce positive impacts on coastlines down-drift
  • Rip currents may occur adjacent to groynes presenting hazards to bathers and other users
  • May lead to sediment loss during storm events
  • May negatively impact coastline appearance, given its unnatural, shore perpendicular structure [^14]

Example projects

Citations

<! data-preserve-html-node="true"-- Regular citations --> [^1]: The Arlington Group Planning Architecture Inc., et al. Sea Level Rise Adaptation Primer. pp. 68. https://www2.gov.bc.ca/assets/gov/environment/climate-change/adaptation/resources/slr-primer.pdf [^2]: “Groynes.” Groynes | Coastal Management Webguide - RISC KIT, https://www.coastal-management.eu/measure/groynes-0. [^3]: Ibid. [^4]: Aberdeen Beach Case Study. University of Aberdeen, pp.8. https://www.abdn.ac.uk/geosciences/documents/Aberdeen_Beach_-_Case_Study.pdf. [^5]: Ibid, 8. [^6]: Ibid, 8. [^7]: Ibid, 8. [^8]: Crescent Beach Erosion Protection. pp. 2. https://www.surrey.ca/bylawsandcouncillibrary/CR_1999-C413-5243.pdf. [^9]: Ibid, 2. [^10]: Cresecent Beach Climate Change Adaptation Strategy. City of Surrey, June 2009, pp. 8. https://www.surrey.ca/files/CrescentBeachClimateChangeAdaptationStudyReport2009.pdf.
[^11]: Ibid, 8. [^12]: Ibid, 8. [^13]: CHAPTER - 4 GROYNES TYPE BUNDS: FUNCTION AND EFFECTS ON SHORELINE https://shodhganga.inflibnet.ac.in/bitstream/10603/174903/16/13_chapter%204.pdf [^14]: Climate Technology Center and Network. (nd). Climate Change Adaptation Technologies for Water A practitioner’s guide to adaptation technologies for increased water sector resilience WATER ADAPTATION TECHNOLOGY BRIEF. Groynes. https://www.ctc-n.org/sites/www.ctc-n.org/files/resources/groynes.pdf

<! data-preserve-html-node="true"-- Images --> [^i1]: Aberdeen Beach Groynes. https://www.pressandjournal.co.uk/wp-content/uploads/sites/2/2015/03/Aberdeen-beach-weather.jpg. [^i2]: C., Arnold. A Groyne at Crescent Beach. https://upload.wikimedia.org/wikipedia/commons/thumb/e/e1/Cresbeach-groyne.jpg/1280px-Cresbeach-groyne.jpg. [^i3]: Figure 1. The constructor. (2020). Gyrones and their classification. https://theconstructor.org/water-resources/hydraulic-structures/groynes-classification/30554/
[^i4]: Figure 2. https://www.dreamstime.com/photos-images/aberdeen-scotland-beach.html

Frank Hangler
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