The Sewerage Pump Station at south Narrawallee Beach was identified as being at risk of erosion and/or inundation by the Shoalhaven Coastal Zone Management plan in 2018. A number of potential risk mitigation approaches were considered, including a rock armoured seawall, geobag seawall and relocation of the sewage unit, however beach scraping and dune restoration were identified as the most cost beneficial option. Sand from the intertidal zone was scraped into the dune area in 2021 and 2022 to rebuild the foredune to a height of 6m AHD and 1V:6H foredune seaward slope face. This was immediately followed up with revegetation with tube & 300mm pot size stock, cuttings of native dune species, and installation of sand fencing and jute matting to assist stabilisation and plant establishment. Larger plants were installed 3-4 months later. A storm swell event in April 2022 unfortunately eroded part of the newly built dune before the plantings had established a stabilisation function. The beach was scraped again shortly afterward to rebuild the dune. This was again followed up with further revegetation, sand fencing installation and weed control. The dune stabilisation works have been monitored and maintained by the Council on an ongoing basis since implementation.

Beach renourishment

Method: Scraped

Sand source: Same sediment compartment

Sand volume (m2): 2000 (2021), 1368 (2022)

Sand placement: Dune area

Frequency of renourishment: Twice

Date of first renourishment: 2021

Date of last renourishment: 2022

Dune replanting or construction

Method: Revegetation, Rehabilitation, Sand fencing

Rehabilitation - method: Restrict pedestrian access, Weed control

Revegetation - species: Tube stock and cuttings of dune species immediately post nourishment. Carpobrotus glaucescens, leptospermum laevigatum (tube stock), Banksia integrifolia (300mm pots), Correa alba (140mm pots) planted 2-3 months post nourishment.

Sand fence material: Plastic sediment fencing initially installed replaced with biodegradable alternative on second stage. Biodegradable alternative consisting hessian Cloth, galvinised wire, and timber posts. Approximately 250m2 of jute mesh installed directly on sand.

Sand fence configuration: Alongshore, Perpendicular to shore (encasing newly planted area)

Sand fence height (m): 600mm