Criterion Technical Technical Cost Design Life Amenity Key Risks Environment / Required Effectiveness Effectiveness in design/analysis (Design, Effects on the longer term /work construct, Intertidal Reef (changing maintain) Communities in 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 Timber change to region across across cheaper cost alignment will rock structures groynes Groynes structures create sediment compartments compartments reduce repeat Timber vertical drop-off transport. wave impact Approximately between Construction Site Survey structure. But $3500/m of compartments Average beach shorter efforts within structure Timber Climbing, trip Marine National width increase - structures to & Rock limit exposure to hazards. Park. Compartment 1: Approximately wave energy Up to +25-30 m Works onshore $5000/m of Compartment 2: Rock is long and offshore Rock structure Up to +10 m lasting and Works will be structure will Compartment 3: onshore and last with site Up to +10 m offshore. specific design. Advise angling structure more in to average Combination: wave direction – Option RANKING ABOVE ABOVE VERY HIGH HIGH HIGH HIGH HIGH HIGH AVERAGE AVERAGE
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 Required design/analysis /work Option – Combination: Rock & Timber Groynes 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 Improved width across entire study area. Even spread of sand across compartments 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 Increased number of beach structures. Timber structures create vertical drop-off between compartments Climbing, trip hazards. Large rocks on rock flats. Moderate change to region sediment transport. Construction efforts within Marine National Park. Works onshore and offshore Detailed design: Rock groynes Timber groynes Site Survey RANKING VERY HIGH ABOVE AVERAGE HIGH HIGH HIGH ABOVE AVERAGE HIGH HIGH
Point_Lonsdale_Groyne_investigation_-_FINAL_REPORT.docx