Blog 10 - Sand Fencing – 20 questions

1) What are they?

a. They are fences usually made of chestnut slats bound together with wire.

2) How do they work?

a. They slow the wind down, so wind-blown sand gets deposited behind them.

b. Plants colonise these sand mounds, building up to become low, hummocky “embryo dunes” (image below). No more than 1m in height, but usually 10s of meters across the upper beach.

3) Why use them?

a. Embryo dunes can act as a buffer to winter storms and supply sand to seaward dunes that may be recovering from previous storms.

b. Sand fencing is a solution to erosion that “works with nature”, rather than against it.

4) Would a concrete wall or rock armour not be better?

a. Both of those try to control nature and have been shown time and again to be poor solutions for sand dunes because:

- They result in the loss of the beach in front of the wall or rock armour

- They bury what they are trying to protect (the beach and sand dunes – the very things we come to the coast to see and enjoy).

- They also increase erosion at their end points, they refocus wave energy at those points (not good for the neighbours!!!).

b. They are “aesthetically non-pleasing”, otherwise known as UGLY.

5) But sand dunes are so fragile, surely concrete is stronger?

Our sand dunes have been flexibly, adapting to storms on our coast for thousands of years. They are well tuned to the massive energy and wildness our coasts experience. They are not fragile, that is our misperception. Using hard engineering locks up sand, lowering the ability of the system to look after itself.

6) Where is sand fencing used?

a. It can be effective on the intersection between the upper beach and the seaward most dune (see image below).

b. It is often used further inland on dune faces that have lost their stabilising vegetation.

c. It has been used during the breeding season to protect ground nesting birds and for other site-specific reasons.

7) What site conditions are needed?

a. The single biggest requirement is that there is a supply of blowing sand. And that is best seen as a wide upper beach, where there is dry sand above the reach of the tides.

8) What sort of configurations are used when installing?

a. Mostly in a “box” formation, similar to an animal enclosure, only for sand fencing they can be considered exclosures – they keep people and animals out. Usually in the order of 5 x 5m squares.

9) Will they restrict access?

a. Within that box yes, but paths can be left between these at certain points to allow access to the beach, or for emergency services etc.

10) Will people ignore them and climb over it? Or vandalised?

a. Maybe, consider getting community groups, local sports teams etc. to help installing them – this will spread the word that the dunes are valued locally and should be looked after.

b. If they are damaged, fix them and keep them in good condition (weekly beach clean groups could do this for something different once in a while).

c. Use locally produced signs to let people know who’s hard work has gone into the sand fencing.

d. Maybe number the boxes and keep a photo record of the progress of the embryo dune building.

11) If sand dunes grow, will they block my view?

a. For the upper beach, probably not. Embyro dunes are low forms. If they join together in later years they may form a low ridge, but if sand fencing is moved seaward each year new low dunes should continue to develop.

12) But will we then lose the beach?

a. No, the beach will maintain its position. If it needs some sand, it will get it from the dunes through wave erosion (strange as that may sound).

13) Is it a permanent answer, that will definitely succeed?

a. Yes and No.

b. Yes, as long as there is a supply of sand, and “we” are accepting that there is no once-off, simplefix. So, we need to adapt our mindset, budgeting and planning accordingly.

c. No, in that trapping sand is only one part of what’s needed and what may happen. Good growing conditions are always present, and a storm can always erode these new dunes. BUT even that is a success, if the storm energy is used up eroding these dunes it means the dunes behind have been spared.

14) When to put them in?

a. In the spring, after the winter storm season (but only if there is available sand above the tide level).

15) When to take them out?

a. It is important to take them out again in the autumn. It is not sensible to leave them to be washed away in the winter storms.

16) How much does it cost?

a. Not sure but a heck of a lot cheaper than the ugly destructive rock armour.

17) Who pays? Who installs them?

a. This varies, I have seen the following cover the costs and do the installation and removal

- local councils

- community groups fundraising

- nationally and internationally funded projects

- NGOs

- landowners.

18) Who looks after the insurance?

a. This seems to fall on the people that install them, for community groups this means they need legal status to be able to hold insurance, or work with a partner that can take the lead.

19) Do you need permits?

a. This varies. Most of our beach-dune sites are in Special Areas of Conservation. They can be owned by individuals, businesses, the government or be part of a commonage. So, talking to all these and other key stakeholder is a very important thing to do before planning for sand fencing.

20) Does anyone have any more questions? I could only think of 19!!!!!!

Email me a question (kevin.lynch@universityofgalway.ie)