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Managing the Floodplain Handbook

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Effective flood risk management can enable a community to become as resilient as is practicable to floods. This is achieved through planning and preparing for, responding to and recovering from flooding.

Effective flood risk management requires a coordinated, multidisciplinary approach across all levels of government and between agencies with different responsibilities. It also requires the support of a range of non-government organisations and industry professionals in a wide range of activities and fields (such as land-use planning), and the active engagement of the community.

The goal of increased resilience to floods requires the management of the flood impacts on both existing developed areas of the community and areas that may be developed in the future. Generally, this involves a combination of flood mitigation, emergency management, flood forecasting and warning measures, land-use planning, and infrastructure design considering the local flood situation and the associated hazards. Decision makers in these areas, insurers and the general public require access to information on flood risk to make informed management and investment decisions.

About this handbook

Purpose: types of flood events covered

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.

Who is this Handbook for?

This handbook aims to provide advice to those with roles in understanding and managing flood risk and its consequences on the community. This may include emergency management practitioners, flood risk managers, land-use planners, engineers, hydrologists, infrastructure providers, and policy and decision makers, within both government and the broader industry. It aims to inform national best practice, and state and territory guidance.

Companion Guides

This handbook is supported by a range of technical guidance and other material.

This handbook should be used in consultation with the relevant jurisdictional agencies. Jurisdictions may have their own specific guidance and documentation which may refer to or be consistent with the best practice guidance provided in this handbook and supporting documents. Jurisdictional advice may include administrative guidance that outlines the relevant jurisdictional: legislative and policy framework; governance arrangements; documentation that supports best practice; terms used that differ from those used in this handbook; and the jurisdictional support available to floodplain management entities (government entities with primary responsibility for managing flooding in an area) to assist them in understanding and managing their flood risk.

At the floodplain specific or study scale, having processes and practices consistent with this handbook and relevant guidelines, can help to ensure that studies completed consider best practice guidance.

Enquiries

Australian Institute for Disaster Resilience
enquiries@aidr.org.au