In a 1% flood, Tuggerah Lakes’ adopted flood study models a 2.24 m AHD peak, against 1994’s 2.23, and 6,581 lots at least partly inundated

If you live near the Tuggerah Lakes foreshore and want to know whether the new flood study changed your flood level, the short answer for the planning flood is: hardly. The study models the 1% AEP flood, one with a 1 per cent chance of being exceeded in any given year, at a peak lake level of 2.24 m AHD, metres above the Australian Height Datum. The 1994 study, whose results the report says form the basis of Council’s currently adopted flood planning levels for Tuggerah Lakes, had 2.23. The report’s own words are that the two are closely aligned.

What did change is the rest of the range, and the count. The study puts more frequent floods lower than the 1994 study did and the rarest higher, and it models 6,581 lots, about one in five of the 34,170 in its study area on our arithmetic, as at least partly inundated in a 1% flood. It covers flooding from the lakes themselves, Tuggerah Lake, Budgewoi Lake and Lake Munmorah, and does not seek to define tributary or overland flooding, which separate studies cover. A block outside its maps can still flood from a creek.

What moved since 1994, and what did not

The lakes normally sit at about 0.3 m AHD, according to the 2014 floodplain plan the report summarises. A 1% flood lifts them to 2.24, about 1.9 m higher on our arithmetic. The largest known flood, on 18 June 1949, reached about 2.1 m AHD; the highest level gauged since gauges went in in 1985 was 1.76 m AHD, at Toukley and the Wallarah Creek bridge on 6 July 2022.

History 2026 study (1994)

Normal lake, typically0.3

6 July 2022, highest gauged since 19851.76

18 June 1949, largest known2.1

1.2220% AEP (1994: 1.36)

1.735% AEP (1994: 1.80)

2.241% AEP (1994: 2.23)

2.74Planning line (1% + 0.5 m); 2070 1% AEP

3.04PMF (1994: 2.70)

The report explains both directions. For frequent floods, about 30 more years of continuous lake records captured a broader range of moderate and minor floods, which earlier data underrepresented, and that pulled the estimates down. For rare floods, it models the entrance at The Entrance scouring open during a flood, uses the 2019 edition of Australian Rainfall and Runoff, and takes more conservative assumptions about ocean levels and entrance blockage, which pushed them up. A statistical check on the lake records alone gives a slightly lower 1% range, 2.13 to 2.21 m AHD.

Source: Table 9.1, Tuggerah Lakes Flood Study Review, hydrologic and hydraulic modelling columns for both studies. The change column is our subtraction.

Lake floods here are slow. The study puts the critical storm durations at 72 to 144 hours, and in the 2007, 2021 and 2022 floods the lakes peaked three to four days after the rain began. That gives time to warn and evacuate, the report says, but the water also goes down slowly, so roads stay shut and properties stay isolated for longer.

Who is in the water

The report names the places most exposed to lake flooding: Chittaway Point, Tacoma and Tacoma South, Tuggerawong, Rocky Point, and The Entrance North behind the Wilfred Barrett Drive levee, which it says commences to overtop between the 2% and the 1% AEP events. It leaves a count of homes and damages to the next stage of the process.

First roads cut, in a 20% AEP flood

• Lucinda Avenue, Killarney Vale
• Aloha Drive, Geoffrey Road, Kalua Drive and Henry Street, Chittaway Point
• Tuggerah Parade, The Entrance
• Some local access roads in Budgewoi Holiday Park

In a 1% flood many more become inundated, including most lake frontage roads in Chittaway Point and Berkeley Vale, Tuggerawong Road and streets in Budgewoi.

Emergency services and schools

• Toukley Marine Rescue: partly inundated in a 20% AEP flood, the building in a 10%
• The Entrance North Marine Rescue: access may be affected in a 5%, the building in a 2%
• Glenvale School: inside the 1% extent, road access cut
• Tacoma Public School: grounds clear of lake flooding, road access cut in a 1%
• SES Wyong: not flood affected; no hospital or ambulance station noted as affected

The planning line and the climate line

Flood controls on development apply inside the flood planning area. The study sets it at the 1% flood plus 0.5 m of freeboard, a safety margin for the uncertainty in the modelling: 2.74 m AHD at the lake, on our arithmetic. The report says the flood planning area will be reviewed at the next stage.

The study also models climate change, on the SSP2-4.5 scenario, which it says is consistent with the council’s draft policy. Higher rainfall intensity and sea level could raise lake flood levels by 0.28 m by 2040, 0.50 m by 2070 and 0.83 m by 2120. By 2070 the 1% flood is modelled to reach 2.74 m AHD, the same height as today’s planning line. By 2120 it is modelled at 3.07, above today’s probable maximum flood. The report is plain that the freeboard was not set for this.

While future climate scenarios and PMF events may exceed the present-day 1% AEP level by more than the adopted freeboard of 0.5 m, this value reflects current planning standards and is not intended to account for future climate change impacts.

Tuggerah Lakes Flood Study Review, Final Report, 15 April 2026, section 11.4

Those impacts, it says, will be dealt with by a Flood Risk Management Policy currently being finalised by Council, with different planning horizons and sea level allowances for different types of development. That is how the report described the policy in April; we have not checked its status since.

What happens next, and who pays

The review is the first of four stages in the floodplain management process. The next is a floodplain risk management study and plan, which is where options to reduce the risk would be proposed: dredging, breakwalls and reopened ocean entrances, a recurring theme in the 35 responses to the exhibition, were ruled outside this study’s scope and pointed there, or to the coastal management program. The council report that recommended adoption, on the 4 August Environment and Planning Committee agenda, was direct about the money: community expectations about the next stage should be managed as no funding has been allocated for this. It named the NSW Government’s Floodplain Management Program as a grant that may reduce the council’s cost, and said the existing 2014 plan is still valid despite the outcomes of this flood study review.

1. September 1994 The Lawson and Treloar flood study for the former Wyong Shire Council; its results still underpin the lakes’ flood planning levels.
2. November 2014 The Tuggerah Lakes Floodplain Risk Management Study and Plan, by WMA Water, built on the 1994 model.
3. 6 July 2022 Lake reaches 1.76 m AHD, the highest gauged since 1985.
4. 9 October to 5 November 2025 Draft review on exhibition; 35 responses.
5. 15 April 2026 Final report issued by Manly Hydraulics Laboratory.
6. 5 May 2026 The Environment and Planning Committee takes up its subcommittee’s recommendation, but sends no recommendation to Council to adopt.
7. 4 August 2026 Officers bring the study back, asking the committee to recommend that Council adopt it.
8. 25 August 2026 Council adopts the review, C-26/1113, 15 to 0.
9. Next, no date Floodplain risk management study and plan; no funding allocated, per the August report.

Sources: Tuggerah Lakes Flood Study Review, sections 1.4, 2.1, 2.2 and 4.4 and the document control page; 4 August 2026 committee agenda, item 4.2; 25 August 2026 minutes.

Our view

The study is good news in one specific sense. The 1% level that today’s planning levels for the lakes rest on has held, after 30 more years of records, a 2022 flood, and a new model the report says matched three recent floods well. Residents who told the exhibition they were worried about building and insurance can read Table 9.1 and see 2.23 become 2.24. That is the lake level, not the map: the new flood planning area is drawn on new terrain data, and we have not compared its extent with the old one.

The reassurance has a short shelf life, and the report says why. The 0.5 m freeboard is there for modelling uncertainty, and the 2070 projection uses up all of it. What planning does about that is left to a policy described in April as being finalised. And the stage that would test what can actually be done for the 6,581 lots inside the 1% flood, and the 2,398 at least partly inundated in a flood with a one in five chance each year, had no funding allocated, by the council’s own report three weeks before adoption. A flood study tells a community where the water goes. It changes nothing on its own. We think the council should fund the risk management plan, or seek the state grant its own report names for it, before the next big wet tests the lakes again.

Where to look up your street

The report says the flood planning area extent is mapped in its Appendix F. The council’s Your Voice Our Coast page for the review, linked below, links the adopted report and its appendices.