[Coral-List] Dredging

Robert Bourke rbourke at OCEANIT.COM
Mon Jan 29 13:28:24 EST 2007

Jeremy & C-Listers;

Does anyone have experience with dredging for wetland rehabilitation
adjacent to coral reef ecosystems?

On Oahu, Hawaii there is an interesting system (Kaelepulu Pond /
Enchanted Lake) with a vibrant wetland / estuary ecosystem that has been
completely surrounded by urban development and is impacted by excessive
sedimentation.  While sedimentation in the pond protects the adjacent
reefs off of Kailua Beach, the progressive infilling is actually
decreasing wetland bird habitat as these areas become fast-land
supporting alien grass species. 
Is anyone aware of an actual working mechanism whereby excavated
materials can be segregated, removing the mud fines with replacement of
the large material (algae, oyster shells) back onto the substrate?


Bob Bourke

-----Original Message-----
From: coral-list-bounces at coral.aoml.noaa.gov
[mailto:coral-list-bounces at coral.aoml.noaa.gov] On Behalf Of Jeremy J.
Sent: Saturday, January 27, 2007 4:47 PM
To: Andrew_Jamieson at URSCorp.com
Cc: coral-list at coral.aoml.noaa.gov
Subject: Re: [Coral-List] coral sedimentation thresholds for dredge


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

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,


Senior Marine & Environmental Consultant SKM Australia Pty. Ltd.

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


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
> _______________________________________________
> Coral-List mailing list
> Coral-List at coral.aoml.noaa.gov
> http://coral.aoml.noaa.gov/mailman/listinfo/coral-list

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