Page 89 - Manual for Activities directed at the Underwater Cultural Heritage

on the other hand, a site is forgotten because it reflects a time beyond memory, its scientific significance as evidence of early contact and exchange may be all the greater, whereas a memory regained, may also be a powerful force.
Assessment of vulnerability
Rule 14 requires the assessment of vulnerability to damage of the underwater cultural heritage in question before the start of any project, as well as the vulnerability of the surrounding natural environment. This concerns the potential impact of a proposed intervention. In a dynamic environment, which the underwater world often is, even a small test pit may have huge consequences on long-term stability, if no measures for consolidation are taken simultaneously.
The vulnerability of a site is a two-sided coin. Stability may be jeopardized even by a small intervention. If, on the other hand, sites are discovered as a result of ongoing erosion, non-intervention may be regarded as a bad management choice, as the environment could be too hostile for long-term preservation. In other words: an assessment of the site’s vulnerability may result in arguments for, as well as against, intervention.
In assessing vulnerability it is important not to take any rash action. It might be necessary to decide on full-scale excavation, but temporary measures for stabilization are often faster to be taken and much less expensive. They may gain time for a well- considered decision on the basis of an encompassing research plan and project design. There is also a duty to care for the natural environment in which the site is located. A coral reef or a sensitive ecosystem should not be disturbed without good reason, or without taking care to mitigate negative impacts.
In the assessment, the nature of the deposit and the prevailing environmental conditions will be im- portant. It also needs to be backed up by back- ground studies according to Rule 15. There is usually information available on the prevailing environmental factors and forces on the site and its surroundings. Time series relating to depth enable
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 © Cultural Heritage Agency of the Netherlands/RWS/ Periplus. Multibeam sonar view of an 18th century wreck.The ship is probably from northern Germany, whereas the cargo is partly Iberian, but includes South American palm seeds as well. The methods and techniques applied for scientific studies must be as non-destructive as possible and contribute to the preservation of the remains. Surveys with non-destructive techniques can address large areas.
With multibeam sonars a more detailed and scale-corrected image can be obtained. It can for instance show the extent
of intrusive disturbance. Multibeam can also be
used to monitor gradual change through repeated survey of the same area.
Preliminary work