Timber groynes are widely used across the SCOPAC region and have been for many years
at some locations. Some operating authorities report that maintenance of these structures
occupies a significant proportion of their revenue coast protection expenditure,
on an annual basis. Others carry out minimal maintenance of structures.
In view of the frequent use of timber groynes, it is quite remarkable that there
are no publications that deal specifically with practical aspects of groyne management.
Although the initial design of groynes is provided in industry standard publications,
maintenance merits minimal discussion and practical issues are never addressed. The
SCOPAC study on Maintenance of Timber Groynes seeks to cover this gap.
Maintenance of coastal structures - Phase 1: Timber groynes
The cost of capital groyne replacement is very high and the effective extension of
life of structures, through efficient maintenance, may make the difference between
financially sustainable systems and those which are not cost effective as a management
Although the current grant aid structure requires applications to be supported by
full life cycle assessment of costs, the funding system does not make full provision
for funding of life cycle maintenance works through grant in aid; this consequently
encourages poor or no maintenance at some locations. Further to this the grant aid
calculations discriminate between EA and local authority schemes, on the basis of
the varied basis for the revenue funding for the two types of organisations. Assessments
do not reflect recent changes to the funding of local authorities, which no longer
identify coast protection as a discrete line within the budget. Examination of structures
within the region suggests that maintenance is conducted very infrequently at many
sites. In fact it appears that some structures may be unmaintained throughout their
life. There is clear evidence that structures can degrade quickly and fail to provide
the function for which they were originally designed. This has a serious implication
for lifecycle costs. In many instances improved maintenance could provide cost effective
extension of life of these structures.
As with many maintenance activities, procedures and processes have been developed
at various locations over many years, often on a trial and error basis. Some of these
processes have resulted in increasingly efficient management. Regrettably these experiences
have hitherto not generally been documented, although internal procedures are often
logged within operating authorities' internal management systems. Changing approaches
to management within coastal operating authorities have meant that there are now
fewer skilled engineers working with these structures on a day to day basis, and
some considerable practical knowledge is gradually being lost. The SCOPAC report
seeks to capture the experiences of local engineers and to share these experiences
with others. The document captures both techniques that have been considered to be
successful, and those which have worked less well. In an attempt to capture the experiences
of less successful approaches, these have been documented but not attributed to specific
sites, thereby providing assessments of techniques that some may be considering.
The objective of the document is not to provide a prescriptive solution to maintenance,
but to offer a range of alternative approaches, and risks together with experiences
of their success. Some of the techniques have generic applicability and others may
be site specific. The document is intended for use by those wishing to share these
The initial design of structures and plan shape layout of groyne systems is dealt
with extremely well elsewhere and the focus of this document is on maintenance of
structures that have already been constructed. Some of the procedures discussed here
should be considered at the design stage however, since they may allow for more efficient
maintenance if integrated into the design process. Since maintenance is not considered
in any detail in these documents, designers of new structures may benefit from the
experiences of structure performance however; this may allow modification of structural
detailing to improve long term performance and life cycle costs. The document provides
details on the following key areas.
A general introduction to groyne structures provides a brief overview of key structure
Life cycle deterioration of structural elements and the range of degradation causes
Larger scale structural failures are discussed in context with initial construction,
structure degradation and beach evolution
Approaches to recording inspections and analysis of life cycle costs are examined,
in conjunction with applications of beach monitoring data.
The relative performance and costs of alternative materials for construction and
repairs are discussed.
Tools and maintenance techniques are discussed and considered for each structural
element of groynes.
Methods of structure modification are addressed to deal with changing site conditions,
which particularly include changes to sediment availability.
The diversity of timber groyne systems within the SCOPAC region is demonstrated with
illustrated examples of the layout and detail of many timber groyne systems across