Table 5-3 Evaluation of Options Detailed analysis – Criterion Technical Technical Cost Design Life Amenity Key Risks Environment Further work Effectiveness Effectiveness in /Effects on Required (Design, the longer term Intertidal Reef construct, (Design, analysis Communities in (changing maintain) monitoring) PPH MNP climate) Some sand is Similar to Design & Existing Beach Public Safety - No further Run a controlled being held on existing, though Construction - structures connectivity influence. trial of the Large height beach, but not likely to erosion N/A currently same as existing. redistribution offset between continuous. effects. Likely to damaged. sand within the compartments No change to be exacerbated Already failing. compartment at from being too with SLR and Continual Footprint same current effects calmer times of full in corners. Strong maintenance is as existing. experienced by increases in year. Creates a drop dependence on strength and likely required to Alignment and Noting that the intertidal off between seasonal frequency of structures due to size appear to structures are reef compartments. influence. storm events existing design be ill-designed, undersized. communities (poor alignment, but are still Nothing undersized, no functional. Sand blown over Do Conditions are core and filter Likely to worsen footpath. – likely to remain layers). with time unless similar, if not Associated costs significant worsen Option will be minor repairs are overtime. ongoing repairs undertaken. to relay and replace displace rocks RANKING LOW LOW LOW LOW LOW LOW N/A MODERATE
Table 5-3 Evaluation of Options – Detailed analysis 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 – Do Nothing Some sand is being held on beach, but not continuous. Strong dependence on seasonal influence. Conditions are likely to remain similar, if not worsen overtime. Similar to existing, though likely to erosion effects. Likely to be exacerbated with SLR and increases in strength and frequency of storm events Design & Construction - N/A Continual maintenance is likely required to structures due to existing design (poor alignment, undersized, no core and filter layers). Associated costs will be minor ongoing repairs to relay and replace displace rocks Existing structures currently damaged. Already failing. Alignment and size appear to be ill-designed, but are still functional. Likely to worsen with time unless significant repairs are undertaken. Beach connectivity same as existing. Footprint same as existing. Noting that structures are undersized. Public Safety - Large height offset between compartments from being too full in corners. Creates a drop off between compartments. Sand blown over footpath. No further influence. No change to current effects experienced by the intertidal reef communities Run a controlled trial of the redistribution sand within the compartment at calmer times of year. RANKING LOW LOW LOW LOW LOW LOW N/A MODERATE
Point_Lonsdale_Groyne_investigation_-_FINAL_REPORT.docx