completed projects

Timber Groyne renewal programme, winter 2020/21

Part of a 17-year Beach Management Scheme to protect the coastal frontages of Poole and Bournemouth

LEAD AUTHORITY

BCP Council

WORKING WITH

START DATE

October 2020

END DATE

15th March 2021

The 2-year timber groyne renewal project plan

A two-year timber groyne renewal programme

Piling operations at the beach, December 2020

Project Overview

All 53 timber groynes along Bournemouth’s beaches are being renewed, in multiple short phases, as part of the Poole Bay Beach Management Scheme 2015-2032  

These works are part of a two-year, £1.9 million programme to renew eight timber groynes from the boundary of Poole/Bournemouth to the eastern side of Durley Chine.

The fifth short phase took place from October 2020-March 2021 and is the first set of groynes in this two year programme to be renewed.  The works area stretched from the boundary to Middle Chine. Five groynes were deconstructed, and were replaced by four, more evenly spaced ones.

Our contractors, Suttle Projects Ltd, were on site from Monday to Saturday, during normal site working hours. They worked with the lowest tides on a rota system, which meant some work took place outside daylight hours. We anticipated this first phase of the groyne renewal project would be completed by spring 2021, subject to weather conditions and working arrangements based on latest Covid-19 guidance.  We finished three weeks earlier than planned thanks to operating efficiences.

Work on the remaining four groynes is scheduled to start autumn 2021, completing spring 2022.

Deconstructing and reconstructing a timber groyne – how it’s done

Please enlarge images in the gallery for a description of the process

Year 1

Our flyover footage shows four timber groynes due to be deconstructed during Year One, running from Alum Chine west towards the Bournemouth / Poole boundary.

These will be replaced by five new, more evenly spaced groynes (see the plan above).

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

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.

FUNKY FACTS ABOUT POOLE BAY GROYNES

A total of 29 piles are sunk for a timber groyne, each pile is 10m high and spaced 2.5m apart. The King pile (out at sea) is 12.5m high. Piles are driven down to the first solid layer of stable substrate/clay. Each groyne is between 5m-7.5m deep and roughly 75m long. Approximately 225 planks of timber make up a groyne. The top 5 rows are generally constructed using new timber; recycled timber is used for the bottom 12-14 rows.

Visitor access & safety

Access to beach huts is retained. Alumhurst Road car park remains open. Access along the promenade is maintained to allow visitors to safely pass the works, but the beach construction area will be closed for safety reasons.

Heavy machinery will be operating on the beach. Sand becomes very unstable when it is excavated around groynes; for this reason, we ask visitors not to pass the construction zone along the water’s edge, even at low tide. Dogs should be kept on a lead.

Once work is finished, restrictions will remain in place until the sand dries out and becomes more compact and stable underfoot. Small ‘cliffs’ may appear where the sand meets the sea, but wave action will soon sort the sand into a natural beach profile. 

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).

Existing groynes will also be carefully deconstructed to ensure that all suitable materials can be recovered and recycled or re-used in future groyne renewal projects.

Groynes – their role in coast protection

Strategically placed timber groynes slow down the natural process of ‘sediment transport’ of beach material within Poole Bay (primarily from west to east). Piling and planking deep into the beach, to the first solid layer of rock, helps retain the sand within a groyne field. Timber groynes are renewed approximately once every 25 years.

In combination with periodic beach re-nourishment (topping up the beach levels) groynes help protect our promenade and seawalls from undermining, and the cliffs from erosion by wave action. The next beach re-nourishment project is planned for early 2021. 

Previous phases of timber groyne renewal:

  • Winter 2017/18 and 2018/19 – 12 groynes at Southbourne
  • Winter 2016/17 – 8 groynes eastwards from Fisherman’s Walk to Gordon’s Corner
  • Winter 2015/16 – 10 groynes from the east of Boscombe Pier to Fisherman’s Walk