This handbook provides an outline of best practice and a vision for managing the flood threat to communities inhabiting floodplains in Australia and discusses how to apply information.
This handbook provides advice on management of flooding within the floodplains and catchments of waterways due to the following type of flood events:
- Catchment flooding from prolonged or intense rainfall (e.g. severe thunderstorms, monsoonal rains, tropical cyclones). Sources of catchment flooding include rivers and other watercourses, local overland flow paths and groundwater systems.
Coastal flooding due to tidal- or storm-driven coastal events, including storm surge in lower coastal waterways. This can be exacerbated by wind-induced wave generation. Tsunamis are a specific type of coastal event, which are dealt with in Australian Disaster Resilience Manual 46: Tsunami Emergency Planning Australia and are not considered in this handbook.
- Combinations of both catchment and coastal flooding in the lower portions of coastal waterways where both can be produced by the same storm or a series of storms. How these sources of flooding interact and which is dominant will vary with the location and configuration of the catchment, floodplain and waterway, and the specifics of the storm cells.
This handbook applies to the management of floods in urban and rural areas, including water flowing overland through urban areas to waterways. Its use in different locations should consider the different issues that need to be considered. For instance, in rural floodplains, the scale of flood-dependent ecosystems means that environmental issues and maintenance of flow to these areas is important and needs additional consideration. The duration of flooding is also important to many crops, and needs to be considered in addition to peak flood levels when examining changes to the floodplain. Local overland flood catchments respond quickly to rainfall and specific flood warnings are not generally possible and there may be little or no time to evacuate. Overland flow paths are often ill-defined and may follow roads, go through private property, or be inhibited by buildings and fences. Localised management measures to enable water flow or reduce the vulnerability of property may therefore be necessary to manage flood behaviour and associated risk.