Criterion Technical Technical Cost Design Life Amenity Key Risks Environment / Further work Effectiveness Effectiveness in Required (Design, Effects on the longer term construct, Intertidal Reef (Design, analysis (changing maintain) Communities in monitoring) climate) PPH MNP Improved width Improved width Combination of Timber is less Less impact on Increased Large rocks on Detailed design: across entire across entire timber and rock durable and not beach number of beach rock flats. Rock groynes study area. Even study area. Even proves nearly as a strong as rock. connectivity structures. Moderate spread of sand spread of sand effective, but at Improved with less large Timber Groynes Timber change to region across across cheaper cost alignment will rock structures groynes structures create sediment compartments compartments reduce repeat but large rock Breakwater Timber vertical drop-off transport. wave impact structure within Average beach As waves and Approximately between Construction structure. But vicinity of key width increase - storm get bigger $3500/m of compartments Timber shorter location on the efforts within Site Survey limits wave structure & Compartment 1: Climbing, trip Marine National structures to site. energy reaching Requires further Up to +25-30 m Rock limit exposure to hazards. Park. the location environmental Compartment 2: Approximately wave energy where beach Structure Works onshore Rock assessment and Breakwater Up to +10 m $5000/m of most desired, Rock is long extends further and offshore monitoring at structure Compartment 3: offshore enabling sand lasting and and around More Up to +10 m build up near Works will be structure will exposing public headland environmental Small shops. onshore and last with site to larger waves impacts with Limits wave offshore. specific design. and deeper energy reaching structure located water with the location Advise angling nearer to where beach headland – rock structure more Combination: most desired, in to average pools – enabling sand wave direction build up near shops. Option RANKING VERY HIGH HIGH VERY HIGH HIGH VERY HIGH ABOVE AVERAGE VERY HIGH VERY HIGH
Criterion Technical Effectiveness Technical Effectiveness in the longer term (changing climate) Cost (Design, construct, maintain) Design Life Amenity Key Risks Environment / Effects on Intertidal Reef Communities in PPH MNP Further work Required (Design, analysis monitoring) Option – Combination: Rock & Timber Groynes with Small Breakwater Improved width across entire study area. Even spread of sand across compartments Average beach width increase - Compartment 1: Up to +25-30 m Compartment 2: Up to +10 m Compartment 3: Up to +10 m Limits wave energy reaching the location where beach most desired, enabling sand build up near shops. Improved width across entire study area. Even spread of sand across compartments As waves and storm get bigger limits wave energy reaching the location where beach most desired, enabling sand build up near shops. Combination of timber and rock proves nearly as effective, but at cheaper cost Timber Approximately $3500/m of structure Rock Approximately $5000/m of structure Works will be onshore and offshore. Timber is less durable and not a strong as rock. Improved alignment will reduce repeat wave impact structure. But shorter structures to limit exposure to wave energy Rock is long lasting and structure will last with site specific design. Advise angling structure more in to average wave direction Less impact on beach connectivity with less large rock structures but large rock structure within vicinity of key location on the site. Increased number of beach structures. Timber structures create vertical drop-off between compartments Climbing, trip hazards. Structure extends further offshore exposing public to larger waves and deeper water Large rocks on rock flats. Moderate change to region sediment transport. Construction efforts within Marine National Park. Works onshore and offshore More environmental impacts with structure located nearer to headland – rock pools Detailed design: Rock groynes Timber groynes Breakwater Site Survey Requires further environmental assessment and monitoring at and around headland RANKING VERY HIGH HIGH VERY HIGH HIGH VERY HIGH ABOVE AVERAGE VERY HIGH VERY HIGH
Point_Lonsdale_Groyne_investigation_-_FINAL_REPORT.docx