Review of Cabling Techniques and Environmental Effects Applicable
Review of Cabling Techniques and Environmental Effects Applicable
Review of Cabling Techniques and Environmental Effects Applicable
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Potential impacts <strong>and</strong> mitigration measures<br />
Figure 5.2: Cable burial noise (North Hoyle Offshore Wind Farm)<br />
Source: After Nedwell et al., (2003)<br />
The example in Nedwell et al. (2003) only covers one installation method in<br />
one type <strong>of</strong> substrate. It is possible that certain burial tools in certain seabed<br />
sediments may produce noise at a higher level than recorded at North Hoyle.<br />
Further information is required on the noise levels associated with other forms <strong>of</strong><br />
cable installation before any clear guidance on the expected levels <strong>of</strong> associated<br />
disturbance to fish <strong>and</strong>/or mammals can be made. However, the early indications<br />
are that there is no significant impact from cable burial noise on fish species. In<br />
addition, no harmful events have been reported from the well established subsea<br />
telecommunications industry. For a more detailed assessment <strong>of</strong> the effects <strong>of</strong><br />
man made noise on fish see Nedwell et al. (2003). For further information on<br />
noise effects on marine mammals see Section 5.6.1.<br />
Turbidity<br />
A reduction in light levels within the water column can create a number <strong>of</strong><br />
adverse effects on fish <strong>and</strong> shellfish resources. Long term increases in turbidity<br />
will reduce the extent <strong>of</strong> the photic zone (the depth to which light can penetrate<br />
the water column) resulting in changes to flora <strong>and</strong> fauna. Cable laying operations<br />
result in temporary increases in suspended sediment which, while generally not<br />
sufficient to alter biotopes, will impact upon sensitive species or those reliant on<br />
certain levels <strong>of</strong> visibility.<br />
Decreased visibility through increased concentrations <strong>of</strong> suspended sediments<br />
can affect predatory fish such as mackerel (Scomber scombrus) <strong>and</strong> turbot (Psetta<br />
maxima), which rely on vision to detect <strong>and</strong> locate prey, leading to decreased<br />
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