164 SITEMONITORING ANDPROTECTION
- the length of time that monitoring is likely to be
required for.
As a result the scale and complexity of monitoring pro-
jects will vary greatly. The following examples indicate
a range of projects and the scale of work that might be
involved:
- Investigation of suspected human interference on a
legally protected site:This may simply involve a sin-
gle visit to the site to check for signs of interference.
Alternatively the site may be checked at regular
intervals. The work involved is unlikely to go
beyond visual survey unless signs of interference are
found. - The completion of a civil engineering project, leading
to fears that nearby submerged archaeological sites
are being affected by erosion:In this case the work
required may involve a single visit to each site to
check for changes, with visual survey recorded
using video or still photography and measure-
ments. A repeat visit may be required to check for
further or longer term change. If long-term effects
are likely, further visits at regular intervals may be
necessary. Coring or test-excavation may be
required if little is already known about the sea-bed
and stratigraphy. Geophysical survey may be
beneficial. - A funded research study of site-formation processes on
an important site:In this case the full range of sci-
entific monitoring techniques may be deployed,
including sampling and experimental work, with
repeated visits on a long-term basis.
The role of biological survey should not be under-
estimated in site-monitoring. The survey and sampling
of marine-boring organisms, bacteria and fungi can be
vital in understanding the way that sites are changing. For
example, some species of marine growth can provide
information on the currents affecting the site and may avoid
the need to employ more expensive techniques such as
data-loggers. At the Duart Point site in Scotland the
distribution and age of organisms such as barnacles has
given important information about the loss of sea-bed to
erosion (Martin, 1995a).
To ensure that data is obtained and used in an
organized and effective way, it is essential to have a
plan for monitoring work. Project planning has already
been discussed in chapter 5. However, there are a few issues
specifically relating to a monitoring project that will be
considered here.
The desk-based assessment (see chapter 5) for a
monitoring project should ensure that there is a clear
understanding of:
- what the shipwreck material is composed of and how
it is distributed; - what the sea-bed is composed of and how it is
likely to be affecting the shipwreck material; - the biology of the site (e.g. marine growth and any
marine (wood) borers present and how they are
affecting the shipwreck material); - the water movement on the site (currents and
waves); - the water itself (e.g. its salinity and pH); and
- outside factors, such as human activity, which may
be affecting the site.
Visual survey: The simplest way to collect monitoring
data is by simple visual survey using divers. This type of
survey is sometimes called a ‘general visual inspection’.
It requires the divers to simply swim around a site and
then record their observations either during the dive or
immediately after it. It relies for its effectiveness on divers
being able to recognize changes in the condition of a site
between visits or over multiple visits. It is therefore car-
ried out most effectively by divers who are already famil-
iar with the site and who have a reasonable technical
knowledge of it. It also tends to be most effective when
the divers follow a fixed route around the site and, if the
survey is to be repeated at intervals, the same divers are
involved.
However, visual survey alone is of limited value in
monitoring archaeological sites under water. Although the
human eye is a very sophisticated observational tool, the
information that can be derived from it depends entirely
on the often-variable knowledge and powers of observa-
tion and recording of the divers involved. Its highly sub-
jective nature means that visual survey is best supported
by other techniques.
Sketch plans are probably the simplest method of
providing supporting information for visual survey. Pro-
vided that the diver is a reasonably competent draughts-
person, a considerable amount of information that
is difficult to describe in a written or verbal format can
be recorded. The results, however, are still likely to be
subjective.Video and still photography: These are very important
methods of supporting diver observations. In the right
conditions, photographic images can provide far more
information than can be gained from the verbal or writ-
ten descriptions of divers. They have the advantage that
they allow a site to be studied remotely, both by divers
and non-divers, without having to revisit it. In addition,
photographs can be used to identify errors in descriptions
given by divers. Photographs taken at different times are
also generally more easily comparable than diver descrip-
tions. As with visual survey, the use of photography to