Flood Risk in Thornleigh, NSW: 2026 Assessment

Thornleigh, located in New South Wales, has a notable flood risk profile based on available data including proximity to waterways, elevation, and historical flood events. The Bureau of Meteorology (BOM) maintains river height and flood warning data for catchments across New South Wales.

Hornsby Shire Council provides flood maps and information for residents.

Thornleigh faces a moderate risk of flooding, primarily from heavy rainfall events and nearby waterways. Properties in low-lying areas are particularly vulnerable.

For a comprehensive property-specific flood assessment including address-level elevation data, flood overlay mapping, and insurance cost estimates, use the ClimateNest full analysis tool. General suburb data cannot replace a site-specific evaluation.

Thornleigh sits within ClimateNest's suburb-level hazard model for flood risk. 9.5% of the suburb's land area is mapped in high-risk flood zones and 82.7% in moderate-risk zones, based on the national hazard overlay. Exposure at this scale varies street by street, which is why an address-level check matters before you buy or insure a specific property in Thornleigh.

Thornleigh (postcode 2120) is tracked in ClimateNest's suburb hazard model, which maps the share of the suburb's land exposed to each hazard at high and moderate levels. The suburb's highest high-risk exposures are bushfire (22.8% of land in high-risk zones), surface flood (10.5% of land in high-risk zones), riverine flood (9.5% of land in high-risk zones). Exposure is not uniform across Thornleigh — individual properties can sit well above or below these averages, so an address-level check is recommended before buying, selling or insuring.