Coastal & Estuarine Processes

Riparian Engineering has extensive scientific knowledge of the coastal and estuarine environment, and we are able to provide our clients with practical, ecological and cost effective engineering solutions. We understand coastal & estuarine landscape geomorphology and how these landscapes were formed throughout the Holocene (last 12, 000 years). We also understand the current day processes  and human use that affect coastal and estuarine landscapes (e.g. waves, floods, tidal flows, storm surges, sediment transport,  vegetation recruitment, aquaculture, dredging, boat waves, wastewater effluent, artifical entrance opening). We can also predict how future sea level rises will impact on coastal and estuarine landscapes and processes in the future.

Specialising in Coastal & Estuarine Processes:

  • Coastal and estuarine geomorphology &
  • Bedload sediment transport
  • Foreshore erosion & shoreline change
  • Channel bathymetry surveys and modelling
  • Wave mechanics and engineering
  • Tidal & flood hydrodynamics
  • Storm surge modelling
  • Tidal flushing, inlet hydraulics & estuarine circulations
  • Mapping coastal & estuarine landscapes (e.g. tidal channels, intertidal wetlands, estuarine floodplain wetlands)
  • Acid sulfate soil assessments
  • Geotechnical engineering
  • Coastal and estuarine process studies
  • Coastal geomorpholog
  • Coastal hazard assessments (Environment NSW)
  • Beach erosion and changes to beach morphology
  • Terrain modelling of Coastal shorelines using LiDAR elevation data
  • Historical foreshore erosion

Channel Bathymetry and Foreshore Erosion Assessment, Coomera River Gold Coast



Foreshore erosion assessment in a River Estuary. The red areas show erosion pre 1960’s and purple areas show erosion post 1960’s. Most of the recent foreshore erosion has occurred in the lower estuary that has been subject to channel dredging.

Riparian engineering utilises the best modelling and analytical techniques to undertake detailed analysis of coastal landscapes and processes. Our modelling specialists are  well versed in a variety of 1D, 2D and 3D models for use in simulating existing conditions and predicting future conditions with and without project scenarios to aid in the plan formulation and design development phases of our clients. We have acquired and/or developed a variety of models or software programs to facilitate our analysis of coastal  and estuarine processes. At the present time, not one model or type of model can be sufficiently general to apply to all situations and engineering applications. Each application depends on a particular project concern and the suitability of available models (software) to address the coastal and estuarine engineering project issues. We  are able to interpret the modelling output from multiple models and create a single model of the estuary or coastal area where various variables can be spatially and temporally related inside a GIS. For example, we can relate flood and tidal modelling data with measured bathymetry changes (erosion and deposition) with foreshore stability assessments. Or we can relate catchment hydrology (floods), tidal exchange, water quality with near shore coastal sediment transport that tends to close the estuary inlets.  Hence we can enables our clients to take a holistic approach to coastal and estuary management, providing them with  cost effective environmental and engineering outcomes.



Estuarine morphological units reconstructed from geotechnical bore logs (sediment stratigrahpy) and morphological analysis of a digital elevation model (DTM) for the Coomera River Estuary. Acid sulfate soils were found across the whole area below the lowest astronomical tide.

Coastal & estuarine  processes are strongly controlled by their underlying morphology. The morphology of estuarine and coastal landscapes has predominantly been determined by rapid increase in sea levels that occurred approximately 11,000 to 8,000 years ago  when sea levels increased by 130 m to todays levels. This geomorphic time period is referred to as holocene marine transgression. During this period, substantial quantities of marine sand were moved in a landward direction from the continental shelf, forming the current coastline (e.g. coastal plains, barrier sand dunes, estuarine lagoons, wetlands and tidal channels).  About  7,000 to 2,500 years ago sea levels were  actually + 1.5 m higher than they are today along the  south eastern coast of Australia, leading to the  formation of estuarine muds  and acid sulfate soils overlaying much of the sand deposits from the initial phase of the marine transgression. Sea levels fell to current day levels approximately 2,500 years ago, which lead to the upstream erosion of fluvial landscapes and the the vertical accretion of fluvial sediments onto the estuarine floodplain. Over the last 2,000 years  sea levels have fluctuated approximately  + /- 1 m leading to a diverse mosaic of estuarine and coastal landscapes uniquely affected by  flood, wind, tidal and coastal sediment transport processes. More recently, estuarine and coastal landscapes have been subject to extensive human development including canals, seaways, and dredged channels that have altered the tidal and hydro-dynamics of the estuary.


Modelled sediment transport in the Coomera River Estuary based on  a two dimensional flood model (1:100 ARI).



Measured bed load sediment transport was calculated by measuring changes to channel bathymetry surveyed before and after a major flood event. Erosion of the estuary channel leads to significant foreshore erosion.


Sampling sediment stratigrphy  in the Coomera River Estuary


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Natural foreshore erosion, showing perched marine muds, and significant estuarine habitat along the eroded foreshore.




A foreshore erosion sequence and specification of restoration targets that can be implemented to arrest erosion.


Bathymetry modelling of the estuary channel combined with foreshore stability assessments. The assessment can be used to distinguish natural foreshore erosion from erosion caused by boat wash.




Foreshore erosion from boat wash. Note Phagmites australis is stabilising the eroded foreshore and this foreshore has a high chance of recovery.



Morphostratigraphic profile of the the lower estuary (floodplain sediments, brown marine muds, and marine sands) with respect to the location of the estuary channel, intertidal wetland and estuary floodplain.



Broadwater channels and islands in Southern Moreton Bay. Mangrove and salt marsh vegetation areas (bright green and brown) have formed on a thin layer of brown estuarine mud approximately 1m deep that overlays on top of tidal sand deposited in the marine transgression. This type of estuarine landscape provides significant refuge for terrestrial and marine biodiversity. The area also has significant community value, who place great importance on it as a natural landscape.