IFA Maritime Affairs Group - Response to BMAPA & RCHME consultation paper 'Marine Aggregate Dredging and the Historic Environment'

General Comments:

1. A very welcome and timely update to the JNAPC's Code of Practice for Seabed Developers and one which will promote and broaden the interests of our maritime heritage resource. The clearly written guidance should be suitable for all levels of reader and will hopefully aid and encourage seabed developers to develop their responsibility for the marine historic environment.

2. The Guidance Note is in line with current archaeology and conservation policies and mention of the IFA and PPG 16 in particular, is crucial in integrating marine archaeological policy within the mainstream terrestrial policies. However, these policies would appear to be limited to England and reference should be made to heritage policy in other home countries, as appropriate.

3. In general, it would be preferable if all statements of recommendation could be phrased 'must' rather than 'should' but it is recognised that this is largely a response to differentiating recommendations that have statutory backing (i.e. law) and those that do not (but are desirable in professional practice). The sections on Mitigation and Monitoring are examples where the use of firmer language may have a more desirable influence on developers.

4. The Guidance Note outlines the current importance of marine aggregates in the UK economy but does not predict future usage or make comment on the possibility of sustainable use of resources in the marine environment. Positive indications on both issues are desirable and relevant in light of the Government's policy on Sustainable Development.

Technical Comments:

1. In the Methods of Archaeological Investigation, the section on Bathymetric Surveys should include its use in detecting wrecks buried under low mounds etc., and in Sidescan Surveys it should mention that 100% coverage (at appropriate ranges and graze angles) is required before it can be described as adequate for archaeological purposes.

2. In the same section, mention is made of monitoring wrecks that have been dredged around. We are unaware of any study that has been undertaken on the effects of dredging around wrecks that have been left in an exclusion zone; this may be an appropriate study for the industry to fund, benefiting both long term commercial and archaeological interests.

3. In the section The Possible Effects of Aggregate Extraction on the Marine Historic Environment, hydrodynamics are not addressed and are likely to play an extremely important role in post-dredging processes. Although the section does state that suspended sediments from the dredge plume may act to deposit material on wrecks, thus aiding preservation, no mention is made of the hydrodynamic environment. Dredging of large volumes of marine aggregate will generally result in extreme changes in the morphology of the seabed at the dredge site. Changes in morphology will always result in changes in the hydrodynamic regime of the area on a scale larger than the actual dredge area. These changes inevitably result in changes in depositional and erosive patterns adjacent to and extending away from the dredge site, and will therefore effect potential wrecks not only in the vicinity of the dredge area, but also in areas far removed from the site. Locally increased depositional rates will be a bonus for wreck preservation, but erosion will have a detrimental effect. Mention should also be made of submerged landscapes as well as wreck sites as these could be significantly affected by changes in sediment transportation.

MAG 12/12/01