[Coral-List] coral sedimentation thresholds for dredge induced sedimentation

[Jeremy J. Sofonia]

Andrew,

Wanted to add:

Also important in estimating potential impacts to benthic primary  
producers is the type of dredge (e.g. cutter suction, trailer hopper,  
etc.), the size of the dredge (m^3), it's power, it's proximity to  
sensitive resources (such as corals), and the duration/ frequency  
they are operating.  Other operational details such as of 'side- 
casting' and 'overflow' rates can also have significant effects  
(positive or negative).  Obviously spoil disposal locations and  
methods should also considered, but keeping in mind that sediments  
released during disposal will behave differently than those suspended  
during cutting (i.e. less fines).

If the program is to run in a working port facility, you'll want to  
look at how local conditions are affected by ongoing operations such  
as berthing and other vessel movements (e.g. tugs can kick up a fair  
bit of sediment/ turbidity in shallow areas).  Contamination such as  
TBT or heavy metals is not uncommon and proper disposal of these  
materials also requires some forethought.

Potential impacts to whales and other cetacens, as well as marine  
turtles should also be investigated.  These can be both direct (e.g.  
physical impact) and indirect (e.g. acoustic, lighting).  Seasonal  
timing of operations is therefore a key avoidance/ minimization measure.

Certainly a lot to think about, but with early (and regular)  
consultation with your environmental authorities, clear communication  
with the proponent, and some good science, the successful management  
of these types of programs is certainly possible.

Hope this was of some help,

Jeremy



JEREMY J. SOFONIA
Senior Marine & Environmental Consultant
SKM Australia Pty. Ltd.

7th Floor, Durack Centre
263 Adelaide Terrace
Perth, WA 6000

http://www.skm.com.au



On 24/01/2007, at 5:43 PM, Andrew_Jamieson at URSCorp.com wrote:

> Dear Coral Listers
>
> I am trying to track down any  research undertaken into tropical coral
> sedimentation thresholds for dredge induced sedimentation - can anyone
> direct me in the right direction ?
>
> Many thanks
>
>
> Andrew Jamieson
> Senior Environmental Scientist
> andrew_jamieson at urscorp.com
>
>
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