Potential Structural Options
22 November 2018
The following structural options were assessed and are listed below in order of their draft rankings. Further detailed information can be found by clicking on each option.
FM4 Extraction of Entrance Shoals upstream and downstream of the Ocean St Bridge
Clearing accumulated sand masses upstream and downstream of the entrance bridge, to reduce build-up. This is the current entrance management technique.
Construction of a levee at the rear of properties along Dalpura Street to protect them from flooding
Construction of a levee from Wabash Ave to Washington Ave to protect residential properties from flooding.
FM6 Alkira Circuit Drainage Upgrade
Upgrading the stormwater drainage network under the low-lying Alkira Circuit crossing to prevent overland flow from entering residential properties downstream. The network can cater for frequent events and would be enlarged to cater for infrequent events.
FM14 Ponderosa Parade Drainage Upgrade
Upgrading the stormwater drainage network to contain flows within Narrabeen Creek. The network can cater for frequent events and would be enlarged to cater for infrequent events.
FM11 Tatiara By-pass Overland Flowpath
Lowering of Tatiara Crescent and Nareen Parade to divert flows away from residential properties.
FM2 Reconstruction of Ocean Street Bridge
FM1 Ocean Street Bridge Extension
Removal of the 42 m long embankment on the northern side of the Ocean Street bridge and extension of the existing bridge to provide additional flow area.
Construction of levee on the eastern side of Garden Street in Progress Park to the west of Mullet Creek to protect commercial and residential areas to the west from infrequent flood events.
FM12 Basin at Narrabeen RSL, Pipe Diversion along Tatiara Cres and Nareen Parade to Open Channel
FM5 Ocean Street Bridge Extension combined with Upstream & Downstream Sand Removal
Mechanical excavation of sand. This sand is then mixed with water before being pumped to beach replenishment locations.
FM7 Willandra Road Reserve Culvert Upgrade and Lowering / Detention Basin
Lowering the public reserve and upgrading culverts under Willandra Road to reduce flooding of neighbouring residential properties to the east.
FM8 Willandra Road Culvert Upgrade and Vegetation Removal
Upgrading the culverts under Willandra Road and vegetation clearance downstream of the roadway.
Removal of bed-rock at the Lagoon entrance to increase entrance scour during flood events. The bed-rock would need to be blasted out, or sawn using rock cutters.
FM16/17 Pittwater Road Levee Bank and Lakeside Levee
Construction of two levees in North Narrabeen to protect a large residential area from infrequent flood events.
Construction of a long levee along the eastern bank of Narrabeen Lagoon to protect large areas of commercial and residential properties from infrequent flood events.
FM13 Pittwater Road and Wakehurst Parkway Raising / Levee
Creation of a levee by raising Pittwater Road and Wakehurst Parkway near their intersection by up to 1m for a distance of 450m, with a flood gate at the Nareen Creek crossing.
View Section 11 of the Narrabeen Lagoon Floodplain Risk Management Study for more information
