Sand inundation
Hoylake has an existing and increasingly severe issue of sand blowing onto the promenade, blocking drains and requiring expensive clean-ups. Just 15 plants per square meter will reduce the volume of blow sand in a gale by 90% and stop it completely below force 7. see graph(1). Consequently, a band of vegetation just a few centimeters high has the potential to dramatically reduce the volume of sand reaching the promenade. See for an analysis of the risks posed by the inshore migration of the East Hoyle Bank.
This has already avoided what would have been a disruptive delivery of sand in April 2021, when the vegetation caught and held the vast majority of the sand blowing in from the beach after a 3-day spell of strong NNW winds which coincided with a dry beach (2) As sand from each sand blow incident is trapped by the belt of Puccinellia, the height of the foredunes will rise, providing additional protection. In Swansea, an experimental man-made dune gave complete protection from a single sand storm which required a £20,000 clean-up on the unprotected section.
Storm Surges
Despite the rising beach levels, there remains a potential for catastrophic damage to the promenade and seafront properties should a storm surge coincide with a spring tide, as occurred in December 2013. Sand dunes have the potential to provide protection against such incidents, and studies in the USA have shown that the presence of dunes dramatically reduced damage to properties compared to adjacent areas where dune formation had been deliberately suppressed(5,6) See also (7)
References
1. Aeolian transport over a flat surface by Leo C. van Rijvan Rijn
2. People confused as grass ‘disappears’ from beach after storm, Liverpool Echo 2021
3. The on-going battle to keep Swansea’s sand on the beach and not on the road
4. Case Study: Swansea Sand Dunes – Nature-based solution
5. Charbonneau, B (2015) A Review of Dunes in Today’s Society, Coastal Management 43 pp 465-470
6.Rosenberg, A. 2013. After Destruction of Sandy, Longport Finally Accepting Sand Dunes. The Inquirer. April 12.
7. Sand dune processes and management for flood and coastal defence
