Riparian engineering has a strong understanding of the geomorphic, floristic, and physical process affecting coastlines and estuaries and how to engineer and restore them. We can develop cost effective solutions to arrest foreshore erosion that save our clients money and enhance the biodiversity of the foreshore and estuarine environment.
Ecological & Non Structural Protection
- Do nothing and allow erosion processes to take their natural course
- Avoid development and specifying minimum setbacks for development
- Relocating structures that have been developed to close to the eroding foreshore
- Foreshore beach replenishment with dredged bed sediment that are free from acid sulphate soils
- Re-establish mangrove, saltmarsh and terrestrial vegetation along the eroding foreshore
- Increase boundary roughness direct adjacent the eroding foreshore, defecting flows away from the eroding foreshore.
- Reducing boat speed limits and boat traffic near the affected areas.
Structural Protection
Structural solutions that can be utilised to mitigate the threat of erosion include:
- Rock fillets placed in front of the eroding foreshore preventing bat waves from washing up against the bank
- Rock walls and revetment
- Reef balls
- Bank toe protections works
- Rock Groynes that deflect flow away from the eroding bank
Detailed concept plans for Nerang River foreshore restoration works. The design brief was to increase fisheries habitat and prevent further erosion of 800m of eroded foreshore. This site was located in the upper estuary and was subject to fluvial scour, which was the likely cause of erosion along with mass slip due to stormwater drainage issues. We created this foreshore restoration concept design that increased fisheries habitat with reef balls, large woody debris, riparian and mangrove vegetation. We addressed erosion caused by mass slip with improved drainage on site. We also addressed fluvial erosion with the placement of rock groynes and rock revetments. Geotechnical assessments were also undertaken to assess engineering foreshore strength and the potential for acid sulfate soils. Large root wads with trunks attached were used instead of rock fillets as these offered greater habitat value. Boat wash was not a major issue at the site. Also, rock fillets may have been outflanked by flood flows, causing localised scour.
We use geomorphic, floristic, geotechnical and hydraulic assessments to determine appropriate foreshore restoration and engineering techniques that address foreshore erosion, community access and restore the ecological function of the foreshore. A typical foreshore restoration and engineering project includes:
- Assessment of geotechnical, stratigraphic, bathymetry, sediment transport, channel hydraulics, boat waves, vegetation
- A site elevation survey and survey plan
- Acid sulfate soil assessment
- Development of concept plans that best meet the needs of the client, considering the materials available, their budget etc.
- Discussions and meetings are then held with the relevant authorities, (e.g. Council, Environment Protection Authority, Fisheries, Natural Resources)
- Governmental approvals and stakeholder conditions
- Design engineering calculations and drawings are then prepared
- Detailed designs are then prepared using detailed evaluation surveys at a specified scale
- Detailed designs are then submitted to relevant authorities and approval
- Project management & construction
Typical eroded foreshore with intact muddy gravelly toe. The muddy gravelly toe provides excellent substrate for restoration works to be implemented as it is relatively stable and resists fluvial and tidal scour and boat wash. However mangrove seedlings struggle to establish in this substrate and need assistance.
Detailed foreshore restoration designs showing location of structures and vegetation management specifications.
Detailed concept plans for the Coomera River Estuary. This drawing show the morphology and stratigraphic sediment layers, the geotechnical strength of the foreshore, and the location of potential acid sulfate soils (PASS). The foreshore restoration concept design is careful not to disturb PASS, and encourage the restorations of riparian and mangrove vegetation. Rock fillets and large woody debris (LWD) are placed to arrest boat wash and facilitate the recruitment of mangrove vegetation along the intertidal areas of the foreshore.
Restored riverine mangroves and native hibiscus provide long tern foreshore protection, improve fish habitat, and riparian biodiversity.
Rock Fillet J- Hook Type
Detailed concept design for a hardwood timber board walk. The concrete piers in the old boardwalk had collapsed as they had not been installed deep enough into the substrate. Once the substrate eroded the boardwalk collapsed.
The engineered rock fillet