Floodway and Flood Fringe Polygons for 1% Annual Exceedance Probability

2026-03-24 updated dataset contains two polygon layers delineating floodway and flood fringe areas for a 1 in 100 (1%) annual exceedance probability flood event across 15 Western Australian river systems and townsites. The Department of Water and Environmental Regulation produced this data to guide floodplain development, with the floodway prohibiting obstructive construction and the flood fringe permitting development under specific building conditions. The dataset is part of a 12-layer floodplain mapping series required for full scope analysis.

Use Cases

• Overlay floodway and flood fringe polygons with land parcel data to assess development restrictions for specific properties.
• Analyze the spatial relationship between flood fringe areas and listed townsites like Bunbury or Carnarvon for urban planning.
• Combine this floodplain layer with other series datasets, such as FPM Flood Level Contours, for comprehensive hydraulic modeling.
• Use the floodway polygon to identify areas where no new buildings are acceptable to enforce regulatory compliance.

Strengths

• Covers 15 distinct river systems and associated townsites across Western Australia.
• Provides two clearly defined polygon types (floodway and flood fringe) with specific regulatory implications.
• Integrates into a structured 12-layer floodplain mapping series for detailed analysis.
• Maintained by the authoritative Department of Water and Environmental Regulation.

Limitations

• Focuses only on major river flooding, excluding stormwater drainage and ecological flood impacts.
• Data completeness requires loading and integrating 11 other dataset layers from the series.
• Specific technical details like polygon count or spatial resolution are not provided.

Provenance

Source

Department of Water and Environmental Regulation, Geospatial and Data Services Manager.

Collection Method

Floodplain mapping produced by the department for development advice.

Time Range

null

Freshness

Last updated 2026-03-24.

Geography

Western Australia, covering 15 river systems including Avon, Blackwood, Swan, and Gascoyne Rivers and their townsites.