Assessing the performance of timber groynes at Bournemouth Beach
A 29 year field-test of 5 different species
Bournemouth Borough Council: £10,000 contribution (2015-2017)
Deconstructed timber groynes stored in the Solent car park depot, Hengistbury Head
As part of the groyne renewal programme at Bournemouth beach that commenced in Spring 2015, five of the old groynes that were built as an experiment between 1985 to 1987 to assess the performance of different timber types in the field were deconstructed. These included groynes constructed of Greenheart, Ekki, Balau, Jarrah and Opepe, proving to be a golden opportunity to assess the relative merits of the 5 timber types after a 29-year field test.
Bournemouth Borough Council carefully dismantled each groyne, numbering each plank to record its original location, in terms of distance from seaward end and its level. Any planks that were “unworn” were set aside for re-use in new groynes and were not assessed further. Any “worn” planks were assessed to determine the extent of gribble infestation and the degree of abrasion.
The SCOPAC funds were used as a contribution towards the scientific analysis undertaken by John Williams of TRADA. In summary, the field data clearly show that the best performing species was Ekki (the most costly timber) followed by Greenheart, in terms of abrasion resistance and to a lesser extent gribble resistance. Although groyne planks comprising, Opepe, Jarrah and Balau did not fail prematurely en masse, they did not provide the same consistent length of service life as Greenheart or Ekki, or opportunity for re-use. Some of these field test results were in contrast to laboratory experiments.
For more information, the following reports and presentations are available:
Bournemouth groyne field
Comparison of the performance of lesser used species (LUS) at Bournemouth against previous laboratory-based research
Summary Report, November 2018
PDF (5Mb) / RSK Environment Ltd
Evaluating the performance of the different timber species will inform future groyne engineering decisions regarding choice of material for Risk Management Authorities across the SCOPAC region. Furthermore, any guidance developed on the re-use of timber will contribute to significant savings in capital expenditure on future schemes.
Preliminary evaluation of timbers from deconstructed groyne 31 and assessment of the feasibility for their re-use in the Bournemouth/Boscombe groyne field
PDF (1Mb) / Exova BM TRADA, 31st January 2017
Inspection of planks from groyne No. 32
PDF (4Mb) / RSK Environment Ltd, November 2018
Preliminary evaluation of planks from deconstructed groyne No. 33 and piles from groyne Nos. 33 and 35 and assessment of the feasibility for their re-use in the Bournemouth/Boscombe groyne field
PDF (3Mb) / Exova BM TRADA, 27th July 2017
Preliminary evaluation of timbers from deconstructed groyne No. 35 and assessment of the feasibility for their re-use in the Bournemouth/Boscombe groyne field
PDF (2Mb) / Exova BM TRADA, 24th April 2017
Assessing the feasibility of resawing greenheart piles into groyne planks
PDF (7Mb) / RSK Environment Ltd
East Brothers Timber Ltd., sawmill visit report April 2018