Marine Scour Solutions
Protecting critical maritime foundations from high-velocity currents, propeller wash, and severe tidal displacement.
Mitigating erosion where hydraulics meet infrastructure
Erosion beneath wharves, bridge piers, and seawalls is a constant silent threat. CMG’s scour protection team integrates sophisticated modelling software, specialised marine vessels, in-house component fabrication, and ADAS diving crews to install rock, geotextiles, and concrete mattresses designed to stand up to dynamic hydraulic shear forces.
Specialist Scour Engineering
Hydraulic stability under active currents.
BATHYMETRIC SURVEYS & SCOUR AUDITS
Utilising high-resolution Multi-Beam Echo Sounder (MBES) arrays and subsea profiling lasers to map bathymetry, localise sediment loss, and model localised scour behavior under active berths and bridge piers.
ROCK ARMOUR & RIPRAP DESIGN
Hydrodynamic design and execution of heavy rock armour configurations. Engineering rock grading matrices utilising Hudson and Isbash equations to ensure hydraulic stability under high shear stresses.
ARTICULATING CONCRETE BLOCK MATTRESSES
Installation of flexible, high-density Articulating Concrete Block Mattresses (ACBM). Designed as a highly stable, low-profile alternative to riprap in high-velocity draft areas and active shipping paths.
GEOTEXTILE & UNDERLAY FILTRATION
Deployment of needle-punched non-woven geotextile filter layers beneath hard armour structures. Prevents subsea subgrade piping and migration of fine sediments while maintaining clean hydrodynamic venting.
REVETMENT & SHORELINE STABILISATION
Mitigation of shoreline and toe failure along active coastal boundaries. We install composite sheet piling, pile-supported revetment walls, and flexible rock toes conforming to QLD TMR specifications.
PROPELLER WASH MITIGATION
Bespoke protection systems designed to withstand concentrated high-thrust currents from bow thrusters and container ship propulsion systems. Protects pile sockets and prevents structural undermining.
Hydrodynamic Stabilisation
Active subsea scour requires more than generic earthworks; it demands precision engineering targeting localized boundary layer shear stress. CMG integrates advanced numerical modeling with high-grade marine deployment to deliver permanent stabilisation for bridge piers, active berths, and complex underwater batters.
SEDIMENT TRANSPORT & SHEAR MODELING
We calculate dynamic bed shear stress (τ) and sediment critical velocity thresholds under active tidal cycles and extreme Queensland flood events. This eliminates guesswork, ensuring your design prevents localised failure of structural backfills.
ENGINEERED GEOTEXTILE BOUNDARY DESIGN
Our engineers design and specify high-density, needle-punched non-woven geotextile filter layers complying strictly with QLD TMR MRTS06. This interface allows seamless hydrostatic venting while completely preventing sub-grade soil piping and fine sediment washout.
GRADED RIPRAP & ACBM ARMOUR SIZING
We utilise Hudson and Isbash hydrodynamic equations to size stable graded rock armours (MRTS04) and flexible Articulating Concrete Block Mattresses (ACBM). Our systems adapt to shifting bathymetry and neutralise extreme propeller wash and lifting forces.
Frequently Asked Questions
Technical insights regarding our scour remediation methodologies.
How does CMG calculate rock armour sizing and grading to survive Brisbane River tidal forces?
We design scour protection utilising advanced hydrodynamic profiling. By calculating localised depth-averaged velocities and bed shear stresses, we apply Hudson’s and Isbash’s hydrodynamic equations. This determines the median rock mass (W50) and nominal stone diameter (D50) necessary to prevent lifting. Every configuration strictly conforms to QLD Department of Transport and Main Roads (TMR) MRTS04 Earthworks specifications, ensuring our graded rock matrices resist displacement during extreme tidal cycles and major flood events.
What is the role of geotextile underlays under rock armour, and how are they installed subsea?
A geotextile underlay acts as a critical filter barrier. Without it, high hydraulic pressures would pump and wash fine subgrade sediments out through the gaps in the rock armour, leading to localised sinkholes and structure collapse. We specify heavy-duty, needle-punched non-woven geotextiles in accordance with TMR MRTS06. Our ADAS-certified divers and barge-mounted cranes deploy these layers underwater, utilising customised frame spreaders, ballast weights, and specialised subsea steel anchors to prevent shifting in high-current zones.
When are Articulating Concrete Block Mattresses (ACBM) preferred over loose rock riprap?
ACBMs are specified in environments experiencing extreme shear velocities, such as active shipping channels and berth pockets subjected to heavy propeller wash. Unlike loose rock riprap, which requires significant layer thickness and wide batter slopes, ACBMs offer a highly flexible, low-profile, single-layer matrix that links concrete blocks with high-strength polypropylene ropes. This flexible mesh conforms to uneven bathymetry, resists uplifting forces, requires far less draft depth, and accommodates localised soil settlement without losing structural integrity.
How does propeller wash from modern commercial vessels affect berth pocket scour, and how is it remediated?
Modern container ships and tugs generate massive, localised hydrodynamic currents from high-thrust propulsion systems and bow thrusters. These high-velocity water jets directly attack the seabed beneath wharves, digging deep scour pockets that undermine piles and destabilise sheet pile revetments. CMG remediates this by conducting high-resolution side-scan sonar mapping, preparing the berth pocket subgrade, laying down engineered geotextile boundaries, and placing custom-designed ACBM arrays or high-strength subsea grout-filled mattresses to absorb and dissipate the kinetic energy.
How do you conduct bathymetric post-event scour audits following major Queensland flood events?
Following major flood events, high-velocity currents, debris, and suspended sediment loads heavily alter seabed bathymetry and scour existing infrastructure. CMG deploys high-resolution Multi-Beam Echo Sounder (MBES) profiling equipment and side-scan sonar arrays to map changes. We generate detailed 3D digital elevation models (DEM) of the seabed, which our RPEQ-certified engineers compare against historic baseline surveys to identify localised erosion, undermined pile lengths, and structural toe failures, preparing comprehensive, fast-turnaround remedial designs.