Littoral

Littoral ocean science activities include the development of capabilities for the prediction of waves, currents and morphological change in the littoral zone as part of Rapid Environmental Assessment activities for Bluelink partners.

Image of littoral model output
CSIRO

A satellite image of a beach, and current forecasts based on high-resolution (5m) lidar bathymetry (middle) and a low-resolution 250m national data set

 

Littoral tools provide information on wave propagation and breaking, currents, rip-currents, and sediment transport right up to the beach face at spatial resolutions down to a few meters.  In combination with ROAM-Atmosphere, they enable operational decision making and risk control for nearshore activities, such as amphibious landings in support of humanitarian relief or defence activities.

Key papers on this work include: Contardo & Symonds (2015)Contardo & Symonds (2016).

 


ROAM-Surf

The ROAM-Surf tool uses the XBeach-SurfBeat model to provide information on conditions to be expected in the littoral zone. The model is phase-averaging with fully resolved infragravity motions. It forecasts wave breaking, currents, and rip-currents right up to the beach face at spatial resolutions down to a few meters.  In combination with ROAM-Waves and ROAM-Atmosphere, ROAM-Surf enables operational decision making and risk control for nearshore activities, such as amphibious landings in support of humanitarian relief or defence activities.

Access to ROAM-Surf is provided via a web interface similar to the ROAM-Waves, ROAM-Ocean and ROAM-Atmosphere tools. CSIRO has extended these tools by developing customised reporting formats for the forecasts that translate model outputs into metrics that are of value for decision-makers in the field. An example is the ROAM-Surf Report Viewer (below) which shows significant wave height and breaker type (top left) and current speed and direction (bottom left). The panels on the right, from top to bottom, show information on significant wave height, breaker characteristics, currents and water/bed level (including danger levels based on under-keel clearances) from the rectangular transect outlined in the left panels.

As for ROAM-Ocean, the effectiveness of these tools is limited by bathymetric knowledge at the coastal sites.

ROAM Surf model output
CSIRO

ROAM-Surf Report which shows significant wave height and breaker type (top left) and current speed and direction (bottom left). The panels on the right, from top to bottom, show information on significant wave height, breaker characteristics, currents and water/bed level (including danger levels based on under-keel clearances) from the rectangular transect outlined in the left panels.

 

 


ROAM-Littoral Connectivity

A project is under development to improve boundary forcing in ROAM-Surf by reducing the gap between the spatial scale of inputs and the ROAM-Surf grid. Currently, global forecast models are used to force the regional ROAM atmosphere, wave and ocean component models, whose outputs are then used to force the higher-resolution ROAM-Surf. Improvements will be made by introducing coupling mechanisms between the spectral wave models and coastal circulation models and/or the use of phase-resolved wave physics. In addition, the performance of an unstructured mesh will be assessed against traditional regular or curvilinear grids.

 


Reports

The Bluelink littoral team has prepared a report titled “Hydrodynamic Modelling for Nearshore Predictions” (Contardo et al. 2020).

The Bluelink Littoral Working Party, including both CSIRO and Defence participants, prepared the following 2019 report: “Morphological Data Requirements and Related Recommendations for Accurate Littoral Forecasting V 1.0” (Hoeke et al. 2019).

A guidance document on mooring design and deployment has recently been published by the Bluelink littoral team in collaboration with the University of Western Australia: “Mooring Design and Operational Guidelines for Lightweight Wave Buoys” (Martini et al. 2021).


See also

For more details on the science, see the Sea Level, Waves and Coastal Extremes Team.