Thornleigh flood map & planning overlays
A planning-constraint profile of Thornleigh
(Hornsby, NSW) - 3.87 km², mapped from live council and
state overlay data. This suburb is highly constrained.
Profile updated 26 September 2026.
Suburb-wide figures; the free map shows which overlays touch your lot.
Constraint readout
3.87 km² - this suburb is highly constrained by planning overlays.
Elevation hillshade with street names, clipped to Thornleigh's boundary, with the flood, bushfire and environmental overlays drawn on top. Magenta is where aircraft were observed in the sampled period, brightest below 3,000 ft.
Nearby suburbs, nearest first
Aircraft noise and flight paths over Thornleigh
Two different things, kept apart on purpose. The ANEF contour is the planning instrument - a forecast published per airport that planning schemes use to control noise-sensitive development. Observed overflight is what a sampled aircraft-tracking feed actually recorded over the suburb - where aircraft flew, how low and how often.
Observed overflight - sampled 4 Sep to 26 Sep 2026
typical observed square 7 a day
Night movements: observed, lowest 2,500 ft - night is sampled as often as day, but night traffic is light, so this is a floor and no rate can be put on it.
Traffic is sampled rather than watched continuously, so every figure is a floor: aircraft not captured between samples are not represented. Rates are per 500 m square - the busiest square in the suburb, not a count of flights over the suburb - and a square is only rated where enough traffic was seen to measure it. Altitudes are above mean sea level. Flight paths change with runway use, weather, season and airspace design. This is a record of observed traffic; it is not a noise contour and not a planning control.
Thornleigh at a glance
How Thornleigh is zoned
Buying in Thornleigh? The zoning, flood and bushfire lines on the section 10.7 certificate attached to the contract are mapped controls - see our s10.7 certificate guide.
Across its 3.87 km², Thornleigh is highly constrained by planning overlays. Flood mapping covers the suburb and none of it falls within a mapped flood overlay, and 41% is flagged bushfire-prone. There are 41 heritage-listed sites on record, and the dominant land-use zone is Low Density Residential. The median lot measures about 752 m² across 2,624 parcels.
Who lives in Thornleigh
Census 2021 figures published by the ABS for the Thornleigh suburb boundary itself, not a wider region.
Socio-economic standing
ABS SEIFA 2021 ranks every Australian suburb. Decile 1 is the most disadvantaged tenth of the country, decile 10 the least.
Score 1122, and decile 10 within New South Wales. The national average is 1000.
Age profile
Share of Thornleigh's 8,898 residents in each ABS age band.
Population trend, 2001 to 2025
Estimated resident population of Normanhurst - Thornleigh - Westleigh, the wider ABS statistical area containing Thornleigh. There is no annual population series published at suburb level, so this describes the surrounding area rather than Thornleigh itself.
17,568 in 2001 to 19,875 in 2025, up 13%.
Source: ABS Census 2021 and SEIFA 2021 (Suburbs and Localities), Regional Population (SA2), CC BY 4.0. Small counts are randomly adjusted by the ABS.
Thornleigh data sources and coverage
“Not mapped” means we hold no source layer for this suburb - never an all-clear.
| Dataset | Coverage | Publisher |
|---|---|---|
| Flood mapping | Mapped | NSW Government spatial services, NSW ePlanning and published council flood studies |
| Bushfire-prone mapping | Mapped | NSW Government spatial services, NSW ePlanning and published council flood studies |
| Zoning | Mapped | NSW Government spatial services, NSW ePlanning and published council flood studies |
| Heritage and environment | Mapped where published | NSW Government spatial services, NSW ePlanning and published council flood studies |
| Aircraft noise contours (ANEF) | Not held | NSW Government spatial services, NSW ePlanning and published council flood studies, Defence |
| Observed flight paths | Observed | adsb.lol, under the Open Database License |
| Demographics | Available | Australian Bureau of Statistics (2021 Census and SEIFA) |
Profile last materially updated 26 September 2026. See the methodology and full source list. Source data changes over time and critical decisions should be checked with the responsible authority.
Check a specific Thornleigh address
See exactly which overlays touch a single property - the interactive map is free. Need it on paper? A full planning PDF is just $9.
Aircraft have been seen below 3,000 ft over about 94% of Thornleigh. The report's Aircraft Overflight page narrows that to the address itself: how many aircraft a day, how low, and at what heights.
Published flood models are held over parts of Thornleigh. The free check tells you whether one reaches an address; where it does, a Flood Model Report is +$9 with the planning report.
Building or pricing a slab? The $119 geotechnical desktop report covers geology, soils, bores and an indicative AS 2870 site class for a Thornleigh lot.
See what's in the $9 report →Thornleigh planning - frequently asked
Is Thornleigh flood-prone?
Flood mapping covers Thornleigh and none of the suburb falls within a mapped flood overlay (the council-wide suburb average is 10%). Published flood models are held over parts of Thornleigh; the free check on the Flood Model Report page says whether one reaches a given address.
Is Thornleigh bushfire-prone?
Around 41% of Thornleigh is mapped as bushfire-prone, compared with a Hornsby average of 70%.
Is Thornleigh under a flight path?
Aircraft were observed below 3,000 ft over about 94% of Thornleigh, and over about 100% at any altitude up to 10,000 ft, in the period sampled (4 Sep 2026 to 26 Sep 2026). The lowest measured aircraft was at 1,000 ft, with an average of 2,500 ft. At the busiest point in the suburb about 16 aircraft a day were recorded passing over one 500 m square. Traffic is sampled rather than watched continuously and flight paths change with runway use, weather and season; the ANEF contour is the planning instrument.
What is the zoning in Thornleigh?
The dominant planning zone in Thornleigh is Low Density Residential, though the suburb also includes Public Recreation and General Industrial.
Does Thornleigh have heritage-listed places?
Thornleigh has 41 heritage-listed places on record.
What is the typical lot size in Thornleigh?
Across 2,624 surveyed parcels in Thornleigh, the median lot size is about 752 m². There are also 31 registered easements mapped in the suburb.
Does Thornleigh have a train station?
Yes - Thornleigh has 1 train station: Thornleigh Station. It is also served by 170 bus stops.
What is the population of Thornleigh?
At the 2021 Census Thornleigh had 8,898 usual residents, with a median age of 40 and an average household size of 2.9 people. The wider Normanhurst - Thornleigh - Westleigh statistical area, which contains Thornleigh, went from 17,568 people in 2001 to 19,875 in 2025, up 13%.
Is Thornleigh an advantaged suburb?
On the ABS SEIFA 2021 index of relative socio-economic advantage and disadvantage (IRSAD), Thornleigh scores 1122 and sits in decile 10 of 10 nationally and decile 10 within New South Wales (decile 1 is the most disadvantaged tenth, decile 10 the least).
What is the median household income in Thornleigh?
Median household income in Thornleigh was $2,681 a week at the 2021 Census, against $2,468 for the typical suburb in Hornsby. Median rent was $530 a week and the median mortgage repayment $2,800 a month.
Compare nearby suburbs
| Nearby suburb | Distance | Flood mapped | Bushfire-prone |
|---|---|---|---|
| Normanhurst | 1.4 km | 0% | 31% |
| Westleigh | 1.7 km | 0% | 82% |
| Pennant Hills | 1.9 km | 0% | 65% |
| Waitara | 2.6 km | 0% | 0% |
| Wahroonga Ku-Ring-Gai |
2.8 km | <1% | 30% |
| Hornsby | 3.0 km | 0% | 50% |
| Cherrybrook | 3.5 km | 0% | 40% |
| Warrawee Ku-Ring-Gai |
3.7 km | 3% | 2% |
| Cheltenham | 3.9 km | 0% | 44% |
| Beecroft | 4.0 km | 0% | 28% |