The latest update to ARR (2016) has provided new guidance for defining flood hazard categories in a floodplain. The Floodplain Development Manual approach of defining High, Medium and Low hazard has been replaced with six categories, H1 to H6, which define various hazard levels for a person or property exposed to floodwaters. The new hazard categorisation is being used by several Councils in NSW in the latest flood studies.
However, the new categorisation is difficult to implement for shallow overland flows and may overestimate the hazard, in particular if the flow velocity criteria is applied. Careful consideration is warranted for use in shallow overland flows.