Bournemouth Beach Timber Groyne renewal 2020-2022

Timber used for the new groynes

Each new groyne will be constructed using a mix of new tropical hardwood timber and recycled tropical hardwood planking, from previously deconstructed timber groynes, when available.

Hardwoods used will be Greenheart - a pale yellow to dark olive green wood from Guyana, South America, and Ekki - a dark red / deep chocolate-brown wood from West Africa and the Congo. These timbers have been selected for their strength, durability and resistance to marine life which can destroy wood by boring into and eating it.

What's eating our timber groynes?

Gribble! These tiny worms (Limnoria terebrans) were first discovered in 1799 and they attack marine timbers. Gribble burrow into groyne timbers, creating long tunnels just beneath the surface; the holes they leave behind eventually weaken the wood, causing it to crumble and rot. This is one of the reasons we renew our groynes every 25 years approx.

Gribble resemble tiny yellowy-pink lice about the size of a grain of rice, but they are actually very small crustaceans. Crustaceans are animals that usually have a hard covering, or exoskeleton, jointed legs and two pairs of antennas, or feelers. Other examples of crustaceans are crabs, lobsters, shrimps, and barnacles.

FUNKY FACTS ABOUT POOLE BAY GROYNES

A total of 29 piles are sunk for a timber groyne, each pile is 10m long and spaced 2.5m apart. The King pile (out at sea) is 12.5m long. Piles are driven down to the first solid layer of stable substrate/clay. Each groyne is between 5m-7.5m deep and roughly 75m in length. Approximately 225 planks of timber make up a groyne. Generally only the top 5 rows are constructed using new timber; recycled timber is used for the bottom 12-14 rows. Timbers unsuitable for re-use on new groynes are recycled for other projects; for example in 2022, for cladding and decking at Durley Hub at Durley Chine, and as part of a footbridge created at a flooded wetland scheme in the Tamar Valley AONB, Cornwall.

You'll find more information on projects that reuse BCP groyne timber at our Recycling & Reusing page.

Environmental considerations

All the groyne renewal works will be carried out in accordance with the Marine Management Organisation licence and planning consent. Additionally, new tropical hardwood timber used for this project is certified sustainable by the Forestry Stewardship Council (FSC).

The old groynes will be carefully deconstructed to ensure that all suitable materials can be recovered and recycled or re-used in future coastal projects.

Groynes - their role in coast protection

Beach material generally moves from west to east in Poole Bay. The strategically placed groynes are renewed approximately once every 25 years and slow down the natural processes. Piling and planking deep into the beach to the first solid layer of substrate/clay helps retain the sand within the groyne field.

In combination with periodic beach renourishment (topping-up the beach levels) the groynes also help protect the seawalls and cliffs from erosion. We last renourished some of the beaches from Poole to Southbourne in early 2021 [project details here].