GEMS was commissioned by URS Australia to carry out environmental modelling studies to assist in the assessment of water quality impacts deriving from the Geraldton Port Enhancement Project, and associated Town Beach Foreshore Redevelopment. 

The project will deepen and widen the existing shipping channel by using a cutter-suction dredge to break up the limestone bedrock followed by a trailer-suction hopper dredge to recover and relocate this material. The dredging program continued for 10 months between October 2002 and July 2003. Apart from the two dredging sources of suspended fines, periodic releases from the hopper dredge to establish an artificial reef in deep waters south-west of Point Moore will provide a third source of suspended sediments.

There are water quality concerns about the distribution and effects of suspended fines over reef, seaweed and seagrass areas in the Champion Bay-Point Moore-Port Grey area and also at the seawater intakes are operated by processing companies for holding live rock lobsters.

Model prediction

              Model prediction of the turbid plume on December 18, 2002.

The primary requirements of the modelling study were therefore to quantify and describe the water quality changes associated with:

• The dispersal and fate of suspended fines generated from the three dredging sources during the construction phase, and
• The post-project exchange of waters between the ocean and the Town Beach and harbour areas.
• Moving dredges/methods etc.

During this project detailed verification of the ocean model (GCOM3D) and the sediment transport model (SEDTRAK) was carried out against in situ measurements of total suspended solids, aerial photographs and satellite photographs. The modelling predictions were in good agreement with all three data sources.

Satellite photo of the turbid plume on December 17, 2002.