The second round of community consultation is now open on the Wallarah Creek Catchment Floodplain Risk Management Study and Plan.
Feedback from the first round revealed concerns about upstream development and increase in impervious surfaces, lack of routine maintenance and blockage of stormwater pipes/culverts, inadequate stormwater system and lack of kerb and gutter.
This plan effects residents in Blue Haven, Wallarah, Bushells Ridge, Doyalson, San Remo, Charmhaven and Woongarrah, which make up the 33sqkm catchment of largely undeveloped land with two major watercourses, Spring Creek and Wallarah Creek, draining into Budgewoi Lake.
Council’s Director of Environment and Planning, Scott Cox, said this plan focused only on overland flooding within that catchment, and flood management of Tuggerah lakes came under a separate plan.
“The Wallarah Creek plan that we have placed on exhibition has taken into consideration feedback from our initial consultation with these affected communities and now is the time for these communities to make sure that we have covered their areas of concern,” he said.
It provides a set of recommended options on how to best manage the existing, future and continuing flood risk, particularly in flooding trouble spots in Blue Haven, such as Birdwood Dr, Turner Cl, Pinehurst Way, and Allambie Cres, and in San Remo at Costa Ave and Brava Ave.
The report says that most flood level increases are contained close to the main watercourses and to undeveloped land.
Nevertheless, future development has the potential to increase flood exposure and damage with most of the adverse impacts predicted along Birdwood Dr and Turner Cl.
The report says that although most of the upstream catchment area is currently undeveloped, a huge chunk is zoned for industrial uses, and as it is developed, flood flows/discharges are predicted to increase by 30 to 50 percent across most locations.
Flood modification options considered in detail are: Doyalson Link Rd basin; modify Brava Ave floodwall and drainage; creek maintenance and removal of dense vegetation; Spring Creek high flow bypass; modify Allambie Cres channel; enlarge unnamed watercourse between Brava and Costa Aves; dredge Wallarah Creek downstream of Spring Creek confluence; and, Pinehurst Way modified detention basin, stormwater upgrades and flow path reshaping.
The final item was the only flood modification to be recommended.
The work is recommended as a combined project at an estimated cost of $450,000.
An alternative is to undertake flow path reshaping ($100,000) and/or stormwater upgrades ($270,000) as individual projects, however, detention basin modification ($80,000) should be done only in conjunction with the other projects, the report says.
This option involves modifications to the existing spillway of a detention/water quality basin behind 26-28 Pinehurst Way, aiming to reduce the maximum water level in the basin, thereby allowing the existing stormwater system in the street to drain more “freely”.
The spillway will also be widened to allow for a greater outflow capacity once the capacity of the basin is exceeded.
Flow path reshaping would involve an area between 28 and 30 Pinehurst Way, where overland water flows would be better directed to avoid flood risk.
A Doyalson Link Road detention basis is not recommended as it isn’t financially viable at an estimated $2M cost.
However, if it was targeted towards managing the flood risk associated with future development, rather than existing flood risk, a developer contribution plan could help fund construction.
Upgrade of Birdwood Dr was recommended as a long-term strategy, as well as further consideration and consultation with the local community about an extension of Turner Cl to McKellar Bvde.
A $2M upgrade of the Pacific Highway at Charmhaven, which is frequently cut about 100m south of Wallarah Creek bridge during periods of continual heavy rain and flooding, is not considered essential from an emergency response perspective.
To have your say on the flood plan, visit yourvoiceourcoast.com/floodplain before Wednesday, August 5.
Reporter: Sue Murray