Cost Technical Environment/ Further work Effectiveness in (Design, Effects on Required Technical the longer term Criterion construct, Design Life Amenity Key Risks Intertidal Reef Effectiveness (Design, analysis maintain) Communities in (changing monitoring) PPH MNP climate) Some minor Minor Will require Structure will be Connectivity Large height Extends into Detailed design improvement, improvement, some upgrade of exposed to same as existing. offset between of groyne More sensitive though not but not an existing bigger waves compartments extension zones of the across entire effective long structures to being deeper. from being too MNP, closer to Site Survey beachfront term solution improve Increased full in corners. Retaining reefs. offshore structure Sand blown over Small increases existing integrity. footprint. footpath. in beach width at orientation select spots Rock is more means structure Small change to groynes along coastline. expensive is exposed to sediment Structure transport material. higher wave extends further energies on this through Marine Approximately offshore Average beach $5000/m of alignment National Park. exposing public existing width increase - structure. Less Design will need to larger waves new materials Compartment 1: to consider and deeper required only Construction 0 m conditions in water efforts entering extending Compartment 2: sizing material Extend existing and Marine National Up to +15 m and structure – Park. upgrading Compartment 3: design. structures. Up to +5 m Rock is long Construction lasting and Option effort increased structure will working further last if suitably offshore designed (deeper, larger waves) RANKING BELOW BELOW ABOVE MODERATE HIGH LOW MODERATE HIGH AVERAGE 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 Further work Required (Design, analysis monitoring) Option – Extend existing groynes Some minor improvement, though not across entire beachfront Small increases in beach width at select spots along coastline. Average beach width increase - Compartment 1: 0 m Compartment 2: Up to +15 m Compartment 3: Up to +5 m Minor improvement, but not an effective long term solution Will require some upgrade of existing structures to improve structure integrity. Rock is more expensive material. Approximately $5000/m of structure. Less new materials required only extending existing and upgrading structures. Construction effort increased working further offshore (deeper, larger waves) Structure will be exposed to bigger waves being deeper. Retaining existing orientation means structure is exposed to higher wave energies on this alignment Design will need to consider conditions in sizing material and structure design. Rock is long lasting and structure will last if suitably designed Connectivity same as existing. Increased offshore footprint. Large height offset between compartments from being too full in corners. Sand blown over footpath. Structure extends further offshore exposing public to larger waves and deeper water Extends into More sensitive zones of the MNP, closer to reefs. Small change to sediment transport through Marine National Park. Construction efforts entering Marine National Park. Detailed design of groyne extension Site Survey RANKING BELOW AVERAGE BELOW AVERAGE MODERATE HIGH LOW MODERATE HIGH ABOVE AVERAGE
Point_Lonsdale_Groyne_investigation_-_FINAL_REPORT.docx