Table 2.4 Range of Figures Proposed By Participants of the JNCC 2007 Workshop, Which Could Be Used Together as a Measure of Reefiness
Measure of ‘reefiness’
Elevation (cm)
(average tube height)
Patchiness (% cover)
Consolidation <10%
<5 on Limpenny scale
10‐20%
5 on Limpenny scale. Stones joined by tubes which overlap
Density (maximum per m2 )
Note: The figures presented in the table are a starting point for wider discussion rather than accepted and fully agreed thresholds for Sabellaria reef identification.
64.
Full video analysis and Sabellaria reef assessment results are presented in Appendices K and L.
2.3 Particle Size Distribution (PSD) Analysis 65.
PSD analysis was undertaken at Fugro EMU’s sediment laboratory using in house methods based on BS1377: Parts 1 3: 1990 (dry sieving), and BS 13320:2009 (laser diffraction). The latter method was used when the fine fraction of sediment (<63 μm) was greater than 5% of the total sample by weight.
66.
Representative sub samples of each sediment sample were oven dried to constant weight at 105 ± 5°C before routinely wet sieving to remove silt and clay sized particles of <63μm (unless there was no sample cohesion after drying, where dry sieve analysis only is undertaken). The remaining coarser material was again oven dried to constant weight at 105 ± 5°C followed by dry sieving through a series of mesh apertures corresponding to units as described by the Wentworth scale. The weight of the sediment fraction retained on each mesh was subsequently measured and recorded and merged with the laser diffraction data where appropriate. Sediments were then classified according to the Folk sediment classification system (Folk, 1954).
Benthic Characterisation Report November 2013
East Anglia THREE and FOUR Offshore Cable Corridor
Appendix 10.4 Page 24
<500 500‐1,700 20‐30%
Upright Sabellaria including concretion of substrata
1,700‐3,500 >30%
Intertwinned matrix of upright Sabellaria tubes
>3,500 NOT a REEF <2 LOW 2‐5 MEDIUM 5‐10 HIGH >10
