What the draft says floods

The study was prepared for the council by consultants WRM Water & Environment and is dated 25 August 2026. It models how the Macquarie and Bell rivers flood Wellington and Montefiores, the suburb across the Macquarie, for floods from the 20% AEP (a 20 per cent chance in any year) up to the probable maximum flood. Its summary of findings puts the planning-line flood in one sentence: Up to 290 properties would experience above ground level inundation for a 1% AEP event with approximately 157 of those (99 residential) also predicted to experience above floor level inundation.

The damage tables behind that sentence show how the count grows as the flood gets rarer. Residential properties flooded above floor go from 52 in the 2% AEP flood to 99 at 1% AEP, then to 410 at 0.5% AEP and 582 at 0.2% (1 in 500). A flood half as likely as the 1% AEP flood in any year floods more than four times as many residential properties above the floor, on the report's estimates.

  1. 20% AEP: a 20% chance in any year5

  2. 10% AEP20

  3. 5% AEP29

  4. 2% AEP52

  5. 1% AEP: basis of the planning area99

  6. 0.5% (1 in 200) AEP410

  7. 0.2% (1 in 500) AEP582

One square per residential property estimated to be flooded above floor level in each design flood, all drawn to the same scale. From Table 9.2 of the draft Wellington Flood Study (25 August 2026, page 102). AEP is annual exceedance probability, the chance of a flood that size or bigger in any one year. The table's rarest row, an extreme flood listed as 0.002% AEP, has 1,417 and is left off. Non-residential buildings (Table 9.3) are not shown: 58 above floor at 1% AEP, 178 at 0.5%.

The report counts more than 3,100 buildings in its model area and estimates that flooding costs the Wellington community about $3.05 million a year on average in tangible damage, not counting farm losses. It assumes warnings would avert little of that damage (an actual-to-potential damage ratio of 0.9), in part because it has been over 35 years since more widespread damage has been felt in the community so the level of flood awareness is likely low among sections of the community.

Where 1990, 2010 and 2022 sit

Of the three floods the study tested its models against, August 1990 was the highest at both Wellington gauges. The study's gauge table puts it between the 5% and 2% AEP floods on both rivers. It puts November 2022 just above a 5% AEP level in the lower Bell River, but only just above a 20% AEP level on the Macquarie. The 1% AEP flood, the one the planning area is drawn from, is about 1 metre higher than August 1990 in the lower Bell and close to 2 metres higher on the Macquarie.

Nov 2022, 8.07 Dec 2010, 11.03 Aug 1990, 13.06 20% AEP, 7.69 10% AEP, 9.59 5% AEP, 11.35 2% AEP, 13.39 1% AEP, 15.03 0.5% AEP, 16.48 0.2% AEP, 17.02 Recorded floods PMF: 24.26, off the scale
Gauge readings in metres for the Macquarie River at Wellington (gauge 421003), recorded floods on the left and the study's design floods on the right, on one vertical scale with ticks every 2 metres from 6 to 18. From Table 8.1 of the draft Wellington Flood Study (page 85). The probable maximum flood (PMF), modelled without a dam failure, reads 24.26 metres and is off the top.

The rare end of the scale reaches places the common floods do not. The report says the Wellington Police Station and much of Nanima Village are predicted to be inundated in the probable maximum flood (but not in the 0.2% AEP flood), that Wellington Hospital is outside the probable maximum flood extent assuming no dam break, and that for floods rarer than the 2% AEP there are pockets of Wellington and Montefiores that become isolated.

A planning line close to an edge

The provisional flood planning area, the map that would guide future development decisions if the council adopts the study, is the extent of the 1% AEP flood with 500mm of freeboard on top, which the report says is consistent with previous Wellington flood planning guidance. The study's emergency-planning section describes what happens just beyond it:

There is a clear tipping point above the 1% AEP flood event upon which significant areas of Wellington and Montefiores become (or are close to becoming) surrounded by floodwaters.

Draft Wellington Flood Study, section 8.6, emergency response planning, page 92. The report adds that evacuating these low flood islands before they are cut off becomes critical, as there may not be much time between isolation and inundation in very rare floods.

The report is frank that the line itself is soft. On how rough the river channel and floodplain are assumed to be, it says: Peak 1% AEP flood levels were predicted to vary up or down by 0.4 m to 0.7 m with Mannings, which exceeds the freeboard allowance. Allowing for today's climate rather than the historical record raised Macquarie River 1% AEP levels by up to 0.6 metres, which it says is also more than the freeboard, while noting its method for that uplift is likely conservative. Its recommendation: The provisional flood planning level and flood planning area should be reviewed when a floodplain management study update is commissioned.

The line
1% AEP flood extent plus 500mm freeboard (provisional flood planning area, page 94)
Channel roughness
1% AEP levels vary up or down by 0.4m to 0.7m in the sensitivity tests (page 94)
Today's climate
Macquarie River 1% AEP levels up to 0.6m higher than on historical climate (page 94)
Climate in 2100
1% AEP levels about 0.9m higher at both Wellington gauges, and more than double the buildings affected, under the SSP3-7.0 scenario (page 87)
Burrendong Dam
Flood operating rules for the spillway gates not supplied by WaterNSW (page 31)
Not modelled
Overland flow outside the river floodplain (page 94)
What the provisional planning line rests on, and what moves it, as the draft Wellington Flood Study states it (25 August 2026, page numbers as given).

The dam matters because Burrendong, about 20 kilometres upstream, takes in some 98 per cent of the catchment that drains to Wellington, and the report says the operation of its gates has a significant impact on flood flows at Wellington, particularly for frequent floods. The flood operating rules for Burrendong Dam spillway gates were not supplied by WaterNSW for this study. The consultants worked from the recorded flows below the dam instead, and say that Receipt of the dam operational rules from WaterNSW would greatly improve the understanding of flood behaviour downstream of Burrendong dam, including at Wellington. The study also ran a dam failure as a sensitivity test, not a forecast, and concluded that the impact of a Burrendong Dam failure on Wellington would be catastrophic. It gives no likelihood for that scenario.

How to have a say, and what happens next

Submissions go through the council's YourSay page for the study, which also carries the draft report, the depth, velocity, hazard and sensitivity maps, and an Ask us form. The council's release opening the exhibition says an interactive mapping tool is available there for the length of the exhibition. The page says Residents and property owners within the draft flood planning area were notified by mail. Its answers on insurance and sale prices are that the council sets neither, and on why a neighbour can be outside the line when you are inside it: Floodwater does not necessarily follow property boundaries. Submissions containing personal information may be made public in council business papers.

  1. November 2023Council receives $60,000 under the Floodplain Grant Scheme. The same timeline entry records WRM Water & Environment winning the request for quotation.
  2. November 2024Grant contribution increased to $78,000.
  3. January and February 2025Online community survey on past floods.
  4. 25 August 2026Council votes 8-0 in closed session to exhibit the draft for at least 28 days (CCL-2026-8-26).
  5. 4 September 2026, 9amExhibition opens.
  6. 22, 23 and 26 SeptemberInformation sessions at the Wellington Civic Centre and a pop-up at the Wellington Rotary Markets.
  7. Monday 12 October 2026, 9amExhibition closes.
  8. No date givenSubmissions reviewed; a report on the exhibition goes to a council meeting.
Dates as the council's YourSay page for the study gives them (timeline and FAQ, read 9 October 2026), with the vote from the minutes of the 25 August 2026 ordinary council meeting, item 12.1.

The study is the first two stages of the state's flood risk management process, not the last. The council's page says no particular mitigation measure is predetermined by the study; planning controls, emergency management, property-level measures and mitigation works would be weighed in the next stage. We will report what the post-exhibition report to council says about the submissions and the planning line.

Our view

Labelled as opinion. This is a candid document. It does not hide that its planning line sits a short step below the point where Wellington's flood exposure jumps, or that its own uncertainty is bigger than the 500mm buffer on that line. For a resident, the practical reading is that being just outside the provisional flood planning area is not the same as being safe from the river: on the report's own tables, the 0.5% AEP flood puts more than four times as many residential properties above the floor. By our arithmetic, assuming each year is independent, a 1% AEP flood has about a 26 per cent chance of happening at least once in 30 years, and a 0.5% flood about 14 per cent. Two things seem worth putting in a submission before Monday: that the council ask WaterNSW for Burrendong's flood operating rules before the next stage, as the consultants themselves say would help, and that the freeboard question their report raises be settled on the evidence rather than on precedent.

How we sourced this

We read the 115-page draft Wellington Flood Study (WRM Water & Environment for Dubbo Regional Council, report 1942-01-H5 [DRAFT], 25 August 2026) end to end, downloaded from the council's YourSay page, with particular attention to sections 2.2, 3.9, 8 and 9 and the summary of findings. Every figure here is from the report's text and tables; none was read off a map or chart. We read the YourSay page itself (timeline, funding history and FAQ), the council's release opening the exhibition (last edited 7 September 2026), and the minutes of the 25 August 2026 ordinary meeting on the council's meeting portal, item 12.1, whose report was considered in closed session. We kept copies of every document.

Our arithmetic. 187 residential + 103 non-residential = 290 above ground at 1% AEP, and 99 + 58 = 157 above floor, matching the summary; 410 ÷ 99 = 4.1; $2,397,164 + $657,639 = $3,054,803 average annual damage, the report's $3.05 million; 15.03 − 13.06 = 1.97 metres between the 1% AEP flood and August 1990 at the Macquarie gauge, and 9.51 − 8.45 = 1.06 metres at the Bell gauge; 1 − 0.9930 = 0.26 and 1 − 0.99530 = 0.14; 4 September to 12 October is 38 days.

What we have not done. We have not checked any individual address against the maps, asked the council or WaterNSW about the dam operating rules, or read the 2013 Wellington Floodplain Risk Management Study the draft compares itself with. The property counts are the report's modelled estimates, and the report says all model results should be treated as a best estimate only.

Sources

  1. WRM Water & Environment for Dubbo Regional Council, Wellington Flood Study, Macquarie River and Bell River, report 1942-01-H5 [DRAFT], 25 August 2026 (PDF, 115 pages, read 9 October 2026): sections 2.1 and 2.2 (pages 16 to 17), 3.9 (pages 31 to 32), 8.2 to 8.7 including Table 8.1 (pages 79 to 95), 9.2 and 9.3 including Tables 9.2 and 9.3 (pages 101 to 103) and the summary of findings (page 105).
  2. Dubbo Regional Council, Wellington Flood Risk Management, YourSay Dubbo Region (web page, read 9 October 2026): exhibition dates, timeline, funding history, FAQ and submission terms.
  3. Dubbo Regional Council, Wellington flood data shapes study, looks at future (media release, last edited 7 September 2026, read 9 October 2026).
  4. Dubbo Regional Council, Ordinary Council Meeting, 25 August 2026, minutes (meeting portal, read 9 October 2026): item 12.1, Wellington Flood Study for Public Exhibition, resolution CCL-2026-8-26 and its confidential public summary.

Live in Wellington or Montefiores, sit on the floodplain committee, or read the study differently? Tell us and we will check it against the documents and log the outcome here.