Flood terms and definitions
The following list of flood terms and definitions are provided to support consistent communication about flooding in Queensland. The flood terms are also published on the Flood Website (Queensland Government) on the flood terms and definitions page. Source references for each term are listed below.
| Flood term | Definition | Source |
|---|---|---|
| Annual Exceedance Probability (AEP) | The likelihood of the occurrence of a flood of a given or larger size occurring in any one year, usually expressed as a percentage. For example, a flood with the frequency of 1% (1 in 100 AEP) has a 1% chance of occurring every year. This equates to a 26% chance of occurring during the typical 30-year mortgage period, or a 55% chance of occurring in an average 80-year lifetime. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 83 (PDF) |
| Catchment | The area of land draining to a particular site. It is related to a specific location and includes the catchment of the main waterway as well as the tributary streams. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 83 (PDF) |
| Catchment flooding | Flooding due to prolonged or intense rainfall (e.g. severe thunderstorms, monsoonal rains in the tropics, tropical cyclones). Types of catchment flooding include riverine, local overland and groundwater flooding. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 83 (PDF) |
| Coastal flooding | Flooding due to tidal or storm-driven coastal events, including storm surges in lower coastal waterways. This can be exacerbated by wind-wave generation from storm events. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 84 (PDF) |
| Cross-section map | Cross-sections are represented on a map by a line drawn and labelled according to its direction e.g. west-east, north-south. Cross-sections can help to understand the profile of the land relative to a water surface level. | Queensland Reconstruction Authority definition for Flood Awareness Maps project |
| Defined Flood Event (DFE) | The flood event selected for the management of flood hazard to new development. This is generally determined in floodplain management studies and incorporated in floodplain management plans. Selection of DFEs should be based on an understanding of flood behaviour, and the associated likelihood and consequences of flooding. It should also take into account the social, economic, environmental and cultural consequences associated with floods of different severities. Different DFEs may be chosen for the basis for reducing flood risk to different types of development. DFEs do not define the extent of the floodplain. The extent of the floodplain is defined by the Probable maximum flood (PMF). | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 84 (PDF) |
| Defined Flood Level (DFL) | Defined flood level (DFL) is the level to which it is reasonably expected flood waters may rise. | MP3.5 - Construction of buildings in flood hazard areas, pg. 4 (Department of Housing and Public Works)(PDF) |
| Effective Warning Time | The effective warning time available to flood-prone community is equal to the time between the delivery of an official warning to prepare for imminent flooding and the loss of evacuation routes due to flooding. The effective warning time is typically used for people to self-evacuate, to move farm equipment, move stock, raise furniture, and transport their possessions. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 84 (PDF) |
| Elevation | Elevation is distance above sea level. Elevations are usually measured in metres. They can be shown on maps by contour lines, which connect points with the same elevation; by bands of colour; or by numbers giving the exact elevations of particular points on the Earth's surface. Maps that show elevations are called topographic maps. | https://education.nationalgeographic.org/resource/elevation/ |
| Existing flood risk | The risk an existing community is exposed to as a result of its location on the floodplain. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 84 |
| Flash flood | Flood that is sudden and unexpected. It is often caused by sudden local or nearby heavy rainfall and characterised by rapid rises in water-levels. It is generally not possible to issue detailed flood warnings for flash flooding. However, generalised warnings may be possible. It is often defined as flooding that peaks within six hours of the causative rain. Under the National Flood Forecasting and Warning Service Level Specification, the Bureau does not provide warning for flash flooding. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 84 (PDF) |
| Flood | Flooding is a natural phenomenon that occurs when water covers land that is normally dry. It may result from coastal of catchment flooding, or a combination of both. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 85 |
| Flood awareness | An appreciation of the likely effects of flooding, and a knowledge of the relevant flood warning, response and evacuation procedures. In communities with a high degree of flood awareness, the response to flood warnings is prompt and effective. In communities with a low degree of flood awareness, flood warnings are liable to be ignored or misunderstood, and residents are often confused about what they should do, when to evacuate, what to take with them and where it should be taken. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 85 (PDF) |
| Flood Behaviour | A term used to describe the pattern, and nature of a flood in terms of characteristics such as depths, velocities and flows. | Guide for Flood Studies and Mapping in Queensland (Department of Resources) pg. 94 (PDF) |
| Flood classification - Major | If the water level reaches the major flood level, large areas are under water. Many buildings may be affected above floor level. Properties and towns are likely to be isolated and major rail and traffic routes closed. Evacuation may be required. Utility services such as power may be affected. | Bureau of Meteorology website - https://www.bom.gov.au/resources/learn-and-explore/flood-knowledge-cent… |
| Flood classification - Minor | If the water level reaches the minor flood level, it causes inconvenience. Low-lying areas next to water courses are inundated. Minor roads may be closed and low-level bridges submerged. In urban areas flooding may affect some backyards and buildings below floor level, and bicycle and pedestrian paths. In rural areas, livestock and equipment may need to be removed. | Bureau of Meteorology website - https://www.bom.gov.au/resources/learn-and-explore/flood-knowledge-cent… |
| Flood classification - Moderate | If the water level reaches the moderate flood level, a bigger area is under water. Main traffic routes may be affected. Some buildings may be affected above floor level. Evacuation may be required. In rural areas, removal of livestock is necessary. | Bureau of Meteorology website - https://www.bom.gov.au/resources/learn-and-explore/flood-knowledge-cent… |
| Flood classifications | Emergency services and flood management authorities classify flooding as minor, moderate or major at key river height gauging stations. Classification levels at each station are decided by local community and state or territory emergency services. The classification is defined by impacts of the water level | Bureau of Meteorology website - https://www.bom.gov.au/resources/learn-and-explore/flood-knowledge-cent… |
| Flood conveyance | Areas where a significant flow of flood water occurs. These areas typically flow continuously from the upper reaches of waterways and flow paths within the catchment to the outlet during a flood. These flows often align with naturally defined channels and are areas that, even if only partially blocked by changes in topography or development, cause a significant redistribution of flood flow or a significant increase in flood levels. They are often, but not necessarily, areas of deeper flow or areas where higher velocities occur. | Flood information to Support Land-use Planning (Australia Disaster Resilience Handbook Collection, Guideline 7-5) pg. 7 (PDF) |
| Flood damage | The tangible (direct and indirect) and intangible costs (financial, opportunity costs, clean-up) of flooding. Tangible costs are quantified in monetary terms (e.g. damage to goods and possessions, loss of income or services in the flood aftermath). Intangible damages are difficult to quantify in monetary terms and include the increased level of physical, emotional and psychological health problems suffered by flood-affected people that are attributed to a flooding episode. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 85 |
| Flood education | Education that raises awareness of the flood problem, to help individuals understand how to manage themselves and their property in response to flood warnings and in a flood event. It invokes a state of flood readiness. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 85 |
| Flood emergency management | Emergency management is a range of measures to manage risks to communities and the environment. In the flood context, it may include measures to prevent, prepare for, respond to and recover from flooding. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 85 |
| Flood emergency management plan | A step-by-step sequence of previously agreed roles, responsibilities, functions, actions and management arrangements for the conduct of a single or series of connected emergency operations. The objective is to ensure a coordinator response by all agencies having responsibilities and functions in emergencies. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 85 |
| Flood emergency response planning | The process to inform the development of flood emergency response plans by providing advice on the variation of hazardous conditions to people, vehicles and buildings within the floodplain. | Flood Hazard (Australia Disaster Resilience Handbook Collection, Guideline 7-3) (Australian Institute for Disaster Resilience) pg. 3 (PDF) |
| Flood forecast locations | A flood forecast location is a gauge used for flood forecast by the Bureau of Meteorology that can measure current water levels and forecasted water levels at the gauge location. Gauge readings and flood forecasts can assist the community in making informed decisions regarding the potential for flooding, and impacts in the local area. A forecast location is a location for which the Bureau provides a forecast of a future water level either as the flood classification that is predicted (minor, moderate or major) or as a level and classification e.g. 4.6 metres – MAJOR flood level. | Flood classifications in Queensland – A best practice guide for local governments pg. 10 |
| Flood forecasts | Flood forecasts are critical to emergency responses to avoid loss of life and limit property damage. Flood forecasters at the Bureau of Meteorology rely heavily on real-time data from radars, rainfall and river water heights. The Bureau uses hydrological computer models to determine: • how much rainfall will run off different parts of the catchment • how water from different tributaries converges in the river network • how long it will take for runoff to reach major waterways • time water will take to travel to known points in the river system. | Flood classifications in Queensland – A best practice guide for local governments pg. 8 |
| Flood fringe | The remainder of the flood extent for the particular event once flood conveyance and storage areas are accounted for. Developing flood-fringe areas is unlikely to significantly alter flood behaviour, beyond the broader impact of changes to run-off because of urbanisation within the catchment. However, other flood-related constraints may exist in flood-fringe areas. | Flood information to Support Land-use Planning (Australia Disaster Resilience Handbook Collection, Guideline 7-5) pg. 7 (PDF) |
| Flood gauge | A flood gauge is a device that measures rainfall, water level, and flow. Flood gauges are types of flood warning infrastructure that measure and capture data and information and contribute to Bureau of Meteorology flood forecasts and warnings. Rain gauges monitor the amount of rain falling on a catchment. River gauges measure water levels along our river systems. Satellites, radars, rainfall and river level gauges are generally the tools that the Bureau uses for their warning predictions. Manual rain and river gauges are read by volunteers who visit the gauge and report to the Bureau on the amount of rain that has fallen or the height of the river on an hourly or daily basis. Learn about the different types of gauges at: https://www.qld.gov.au/emergency/dealing-disasters/disaster-types/flood… | Flood classifications in Queensland – A best practice guide for local governments pg. 9 |
| Flood hazard | Potential loss of life, injury and economic loss cause by future flood events. The degree of hazard varies with the severity of flooding and affected by flood behaviour (extent, depth, velocity, isolation, rate of rise of floodwaters, duration), topography and emergency management. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 85 (PDF |
| Flood hazard area | The area (whether or not mapped) encompassing land lower than the flood hazard level (FHL) which has been determined by the appropriate authority. The area relates to that part of the allotment on which a building stands or is to be erected. | Construction of buildings in flood hazard areas ABCB Standard 2012.3 (Australian Building Codes Board) pg. 6 |
| Flood hazard level (FHL) | The flood level used to determine the height of floors in a building and represents the defined flood level (DFL) plus the freeboard. | Construction of buildings in flood hazard areas ABCB Standard 2012.3 (Australian Building Codes Board) pg. 6 |
| Flood maps | A practical tool for identifying most at risk to flooding. They provide a visual representation of possible flood consequences (i.e. extent, depth, and velocity of flood waters at different gauge heights) and can be used to raise flood awareness in a community by delineating the areas at risk of flooding. | Flood Mapping Implementation Kit (Department of Resources) pg. 19 (PDF) |
| Flood planning area | The area of land below the flood planning level, and is thus subject to flood-related development controls. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 85 (PDF) |
| Flood Planning Level (FPL) | The flood planning level (FPL) combines an adopted defined flood levels (derived from significant historical flood events or floods of specific annual exceedance probabilities (AEPs) with a selected freeboard for floodplain management and development control purposes. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 86 (PDF) |
| Flood proofing of buildings | A combination of measures incorporated in the design, construction and alteration of individual buildings or structures that are subject to flooding, to reduce structural damage and potentially, in some cases, reduce contents damage. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 86 (PDF) |
| Flood readiness | An ability to react within the effective warning time | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 86 (PDF) |
| Flood risk | The potential risk of flooding to people, their social setting, and their built and natural environment. The degree of risk varies with circumstances across the full range of floods. Flood risk is divided into three types – existing, future and residual. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 86 (PDF) |
| Flood risk management | The process applied to enable a community to become as resilient as practicable to floods. This is achieved through planning and preparing for, responding to and recovering from flooding. It requires a coordinated, multi-disciplinary 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, and the active engagement of the community. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. xi |
| Flood severity | A qualitative indication of the ‘size’ of a flood and its hazard potential. Severity varies inversely with likelihood of occurrence (i.e. the greater the likelihood of occurrence, the more frequently an event will occur, but the less severe it will be). | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 86 |
| Flood storage areas | The parts of the floodplain that are important for temporary storage of floodwaters during a flood passage. The extent and behaviour of flood storage areas may change with flood severity, and loss of flood storage can increase the severity of flood impacts by reducing natural flood attenuation. Hence, it is necessary to investigate a range of flood sizes before defining flood storage areas. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 86 |
| Flood study | A comprehensive technical investigation of flood behaviour. It defines the nature of flood hazard across the floodplain by providing information on the extent, level and velocity of floodwaters, and on the distribution of flood flows. The flood study forms the basis for subsequent management studies and needs to take into account a full range of flood events up to and including the probable maximum flood. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 86 (PDF) |
| Flood warning predictions | This is issued by the Bureau of Meteorology and include specific predictions of the severity of expected flooding. | http://www.bom.gov.au/water/floods/floodWarningServices.shtml |
| Flood warnings | Messaging distributed to potential at-risk communities to inform of an emerging flood threat. Effective warning is crucial to support a community's ability to respond to a flood event. Effective flood warnings require effective messages disseminated via an effective system. | Flood Mapping Implementation Kit (Department of Resources) pg. 22 (PDF) |
| Flood Watch | What is a Flood Watch? The Bureau issues a Flood Watch to provide early advice of a developing situation that may lead to flooding. A Flood Watch is not a warning of imminent flooding. A Flood Watch provides information about a developing weather situation including forecast rainfall totals, catchments at risk of flooding, and indicative severity where required. The product also provides links to weather warnings, other Bureau flood-related products, and contact details and information of relevant emergency services. Although there is uncertainty attached to a Flood Watch, its early dissemination can help individuals and communities to be better prepared should flooding eventuate. A Flood Watch may discuss possible snowmelt, local flooding or tidal impacts but a Flood Watch will not be issued solely on the basis of these phenomena. When is a Flood Watch issued? A Flood Watch is generally issued up to four days in advance of the expected onset of flooding. A Flood Watch can be issued before, during and after the rainfall has occurred, depending on the level of maturity of the flood warning systems and services, and flood impact information made available from the local emergency services or state agency. Flood Watches are updated at least daily and finalised once all areas are covered by flood warnings or the risk of flooding has passed. | Bureau of Meteorology website - Flood Warning Services |
| Floodplain | An area of land that is subject to flooding up to and including the probable maximum flood event – that is flood-prone land. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 85 (PDF) |
| Floodplain management plan | A management plan developed in accordance with the principles and guidelines usually includes both written and diagrammatic information describing how particular areas of flood-prone land are to be used and managed to achieve defined objectives. It outlines the recommended ways to manage the flood risk associated with the use of the floodplain for various purposes. It represents the considered opinion of the local community and the floodplain management entity on how best to manage the floodplain, including consideration of flood risk in strategic land-use planning to facilitate development of the community. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 85 |
| Flood-prone land | Land susceptible of flooding by the probably maximum flood event. Flood-prone land is synonymous with the floodplain. Floodplain management plans should encompass all flood-prone land rather than being restricted to areas affected by defined flood events. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 86 |
| Flow | The rate of flow of water measured in volumes per unit time. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 86 |
| Flow conveyance areas | Those areas of the floodplain where a significant flow of water occurs during floods. They are often aligned with naturally defined channels. Flow conveyance paths are areas that, even if only partially blocked would cause a significant redistribution of flood flow or a significant increase in flood levels. They are often, but not necessarily, areas of deeper flow or areas where higher velocities occur, and can also include areas where significant storage of floodwater occurs. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 86 |
| Flow path | During a rain event, rainfall is converted to runoff and is transferred to the catchment outlet through a network of flow paths. These flow paths include overland flow on hill slopes, down tributaries, across floodplains, through natural and artificial storages and along main streams. | Queensland Reconstruction Authority definition for Flood Awareness Maps project |
| Freeboard | Freeboard is the height above the defined flood level (DFL) as determined by the appropriate authority, typically used to compensate for effects such as wave action and localised hydraulic behaviour. | Construction of buildings in flood hazard areas ABCB Standard 2012.3 (Australian Building Codes Board) pg. 6 |
| Frequency | The measure of likelihood expressed as the number of occurrences of a specified event in a given time. Typically measured in terms of Annual Exceedance Probability (AEP). For example, a flood with the frequency of 1% (1 in 100) AEP has a 1% chance of occurring in any given year. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 87 |
| Future flood risk | The risk that new development within a community is exposed to as a result of developing on the floodplain. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 87 |
| Grade (or gradient) | The inclination expressed as the ratio or percentage of unit rise to horizontal distance. | Standards Australia – Construction Dictionary |
| Ground level | Ground level as defined in Schedule 24 of the Planning Regulation 2017 is the level of the natural ground; or if the level of the natural ground has changed, the level as lawfully changed. Ground levels are estimated from light detection and ranging (LiDAR) information or survey sourced from councils. LiDAR information has varying degrees of accuracy. A registered surveyor can be engaged to provide more accurate estimates. | Queensland Legislation – Planning Regulation 2017 – Schedule 24 Dictionary |
| Habitable floor level | The habitable floor level is the floor that has habitable rooms as defined by the National Construction Code. This generally means rooms that have a minimum height requirement of 2.4 metres. A habitable room is defined in the National Construction Code as a room used for normal domestic activities, and includes a bedroom, living room, lounge room, music room, television room, kitchen, dining room, sewing room, study, playroom, family room, home theatre and sunroom; but excludes a bathroom, laundry, water closet, pantry, walk-in wardrobe, corridor, hallway, lobby, photographic darkroom, clothes-drying room, and other spaces of a specialised nature occupied neither frequently nor for extended periods. | National Construction Code - Glossary |
| Hazard | A source of potential harm or situation with a potential to cause loss. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 87 |
| High hydraulic hazard classification | Conditions are unsafe for people and vehicles. Buildings are considered vulnerable to structural damage or failure. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 85 (PDF) |
| High Potential Exposure | High Potential Exposure refers to areas with deep and fast flowing water that can potentially pose a high risk to life and /or cause failure to buildings during a flood event. Typically, these areas are part of or immediately next to a waterway or flow path which experience frequent flooding. In some cases, these areas may not flood as often but still represent a high risk due to the potential danger to people and property. | Queensland Reconstruction Authority definition for Flood Awareness Maps project |
| Historic flood extent | A flood that has occurred in the past and where a map is available to show the extent of the historical flood. No two floods are the same. Each event will vary on depending on a range of factors. Areas which have not flooded before may still flood in future events. | Queensland Reconstruction Authority definition for Flood Awareness Maps project |
| Historical flood | A flood that has actually occurred in the past. | Guide for Flood Studies and Mapping in Queensland (Department of Resources) pg. 93 (PDF) |
| Hydraulic Hazard | The potential for the combination of depth and speed (velocity) of flood waters to cause harm. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) (PDF) |
| Hydraulic model | A computational model that is able to describe or represent the motion of water. The main aim of hydraulic modelling is to understand the movement of floodwaters through a catchment, including flood behaviour such as flood extents, water levels, flood depth, velocity and hydraulic hazard. An appropriately set-up and calibrated hydraulic model can be used to not only describe the details of flood flows and their distribution throughout a river and floodplain system, but also predict the likely impacts that any changes to that system may have on these flows. | Australian Rainfall & Runoff (ARR) – A guide to flood estimation |
| Hydraulics | The study of water flow in waterways; in particular, the evaluation of flow parameters such as water level, extent and velocity. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 87 |
| Hydrograph | A graph that shows how the flow or stage (flood level) at any particular location varies with time during a flood. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 87 |
| Hydrologic analysis | The study of rainfall and runoff process including the evaluation of peak flows, flow volumes and the derivation of hydrographs for a range of floods. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 87 |
| Hydrological model | A computer model that uses rainfall data and estimates of the proportion of the rainfall which turn into runoff and the time which the runoff from each part of the catchment takes to flow into the stream to estimate flow in the stream over time. | Guide for Flood Studies and Mapping in Queensland (Department of Resources) pg. 93 (PDF) |
| Hydrology | The term given to the study of the rainfall and runoff process, in particular the evaluation of peak flows, flow volumes and the derivation of hydrographs for a range of floods. | Guide for Flood Studies and Mapping in Queensland (Department of Resources) pg. 94 |
| Intolerable Risk | A risk that, following understanding of the likelihood and consequences of flooding, is so high that it requires consideration of implementation of treatments or actions to improve understanding, avoid, transfer or reduce the risk. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 87 |
| Inundation | Inundation occurs when water covers land that is normally dry. It may result from coastal, catchment flooding, overland flow or a combination. | Queensland Reconstruction Authority definition for Flood Awareness Maps project |
| Isolation | Flooding can isolate parts of the landscape and cut-off evacuation routes to flood-free land. This can result in dangerous situations, because people may see the need to cross floodwaters to access services, employment or family members. Many flood fatalities result for the interactions of people, often in vehicles with floodwaters. | Flood Hazard (Australia Disaster Resilience Handbook Collection, Guideline 7-3) (Australian Institute for Disaster Resilience) pg. 15 (PDF) |
| Land parcel | A land parcel is a graphical or spatial representation of a property boundary. Land parcels are the building blocks of Council properties. Land parcels (also called lots) are mapped and the title details shown on a Plan of Subdivision. The parcel is a graphical representation of surveyed boundaries together with identifiers such as Lot on plan (or Lot/Plan) description and house numbers. Lot on plan details for Queensland addresses can be searched on the Queensland Geocoder at https://geocode.information.qld.gov.au/ | https://www.data.qld.gov.au/dataset/property-boundaries-parcel |
| Land-use planning | The process by which the use and land is managed for the benefit of the whole community. Land use planning approaches that anticipate likely risk and vulnerability of the population can reduce the potential impact of future disaster events. Responsible land use planning can therefore prevent or reduce the likelihood of hazards impacting on communities and for this reason; land-use-planning is considered an effective preventative measure to mitigate the impact of floods. | Flood Mapping Implementation Kit (Department of Resources) Pg. 9 (PDF) |
| LiDAR | LiDAR stands for Light Detection and Ranging. LiDAR is a remote sensing technology that measures the distance to an object. Aerial LiDAR uses a laser to measure the distance to the ground from the air (usually a fixed wing aircraft) and provides information about the ground elevation and terrain. | Australian Rainfall & Runoff (ARR) – A guide to flood estimation. Pg.82 |
| Likelihood of occurrence | The likelihood that a specified event will occur (see also Frequency). Likelihood of flooding is expressed as the number of occurrences of a specified event in a given time. Typically measured in terms of Annual Exceedance Probability (AEP). For example, a flood with the frequency of 1% (1 in 100) AEP has a 1% chance of occurring in any given year. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 87 |
| Local overland flooding | Flooding caused by localised rainfall-runoff or flow that exceeds the capacity of the drainage network and flows towards a waterway. Overland flow typically occurs immediately following significant rainfall and can be relatively shallower and faster to dissipate than river, creek or coastal inundation. This is also known as stormwater flooding. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 87 |
| Lot and plan description | Every property will have a lot and plan (or Lot/Plan) description, which is the legal identifier of a lot type parcel on a Survey Plan of Registered Title. These are stated in the property section of your contract. Most councils include the lot and plan on rates notices. You can also use the Queensland Geocoder (https://qro.qld.gov.au/definition/lot-and-plan-number-duty/) to find this information. | https://www.resources.qld.gov.au/__data/assets/pdf_file/0011/1592309/lo… |
| Low hydraulic hazard classification | Conditions are generally less hazardous but can be unsafe for small vehicles. All floodwater poses a risk due to unknown ground conditions, pollution, debris or wild animals. It is never safe to drive through or enter floodwaters. Never drive through or enter floodwater. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) (PDF) |
| Low Potential Exposure | Low Potential Exposure refers to areas of the floodplain that are flooded in larger less frequent events, with flow that is either fast moving and shallow or slow moving and deep. | Queensland Reconstruction Authority definition for Flood Awareness Maps project |
| m AHD | The Australian Height Datum is a datum for measuring height or elevation, relative to mean sea level, which is set to 0m AHD. | Intergovernmental Committee on Surveying and Mapping (ICSM) - Australian Height Datum |
| Major Flooding (gauge classification) | In addition to the above, extensive rural areas and/or urban areas are inundated. Many buildings may be affected above the floor level. Properties and towns are likely to be isolated and major rail and traffic routes closed. Evacuation of flood-affected areas may be required. Utility services may be impacted. | Bureau of Meteorology – Definitions and Terminology |
| Minimum habitable floor level | The minimum habitable floor level (HFL) is the minimum specified height for habitable rooms as defined by the National Construction Code. The minimum habitable floor level is often the Flood Planning Level for habitable areas associated with residential development and is based on the Defined Flood Level plus a nominated freeboard. | https://www.abcb.gov.au/sites/default/files/resources/2022/Standard-con… and https://frasercoast.engagementhub.com.au/app/webroot/js/admin_js/kcfind… |
| Minor Flood (gauge classification) | Causes inconvenience and low-lying areas next to watercourses are inundated. Minor roads may be closed and low-level bridges submerged. In urban areas inundation may affect some backyards and buildings below the floor level as well as bicycle and pedestrian paths. In rural areas removal of stock and equipment may be required. | Bureau of Meteorology – Definitions and Terminology |
| Moderate Flooding (gauge classification) | In addition to the above, the area of inundation is more substantial. Main traffic routes may be affected. Some buildings may be affected above the floor level. Evacuation of flood-affected areas may be required. In rural areas removal of stock is required. | Bureau of Meteorology – Definitions and Terminology |
| Moderate hydraulic hazard classification | Conditions are unsafe for vehicles and for children and older people, and become unsafe for all people as the hydraulic hazard increases. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) (PDF) |
| Moderate Potential Exposure | Moderate Potential Exposure refers to areas where the river breaks out and spreads into low lying broader floodplains. These areas are often affected by flood but are typically areas of slow moving deep water. The duration and the depth of flooding can vary depending on what part of the catchment. | Queensland Reconstruction Authority definition for Flood Awareness Maps project |
| Monte Carlo Analysis | A Monte Carlo analysis, or probability simulation, is a technique used to understand the impact of risk and uncertainty in flood models. | Guide for Flood Studies and Mapping in Queensland (Department of Resources) pg. 94 |
| Overland flow | Overland flow is the movement of water across the ground surface following rainfall, when the rainfall is greater than the soil's ability to absorb it. This can be influenced by rainfall, soil saturation, land slope, vegetation cover, and surface characteristics. This usually happens during heavy rainfall in storm season. Overland flow can be hard to predict, with little to no warning time. It usually happens quickly and recedes quickly, but it can still be dangerous and damaging. Overland flow often happens when drains get blocked, causing water to flow down streets or through backyards. Overland flow often occurs at the same time as other types of flooding, but can be independent events. | Regional Guideline for Flood Awareness Mapping and Communication. (pg.6) (PDF) |
| Peak level | The maximum water level. When measuring the size or magnitude of a flood event, it can be expressed in many ways, but the peak level of the water at a particular location in a catchment is a common and easy to measure. | Office of the Chief Scientist (Queensland Government) |
| Peak river height | No changes to previous definition | Australian Water Information Dictionary |
| Planning Scheme | Each local government is required under the Planning Act to have its own local planning scheme. It's a document which informs us - the community, development industry and governments - about how each local government plans to manage growth and change. A local planning scheme outlines what sort of development you can expect in your local area. A local planning scheme regulates what new development should occur in local communities and how. It outlines planning and development aspirations, as well as infrastructure needs. Visit your local government’s website to view their local planning scheme. | https://www.planning.qld.gov.au/planning-framework/plan-making/local-pl… |
| Planning Scheme | Under the Planning Act 2016, each local government planning scheme needs to set out integrated state, regional and local planning and development assessment policies for an entire local government area. | State Planning Policy – July 2017. DSDMIP pg. 3 & 31 (PDF) |
| Potential Exposure | Potential exposure is the potential flooding to the selected land parcel. It looks at the hydraulic behaviour of floods and their likelihood of occurring. It represents the risk resulting from the flood conditions (likelihood of the flood occurring, and the depths and velocities of the floodwaters) independent of the actual use or development of the land within the floodplain, or other factors to flood risk including community vulnerability, isolation or evacuation constraints, impacts to critical infrastructure and the community’s tolerability to flood risk. It’s determined by analysing the likelihood of floods and the hydraulic hazard that occurs during floods of different size and likelihood. | Queensland Reconstruction Authority definition for Flood Awareness Maps project |
| Probability | A statistical measure of the expected chance of flooding. It is the likelihood of a specific outcomes, as measured by the ratio of specific outcomes to the total number of possible outcomes. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 88 |
| Probable maximum flood (PMF) | The hypothetical flood estimate relevant to specific catchment whose magnitude is such there is negligible chance of it being exceeded. It represents the current estimate of a notional upper limit of flood magnitude and no attempt is made to assign a probability of exceedance to such an event. It is also used to define the extent of flood-prone land. The PMF causes the largest scale of flood emergency and is also therefore often used for emergency management planning. | Australian Rainfall & Runoff (ARR) – A guide to flood estimation. (Pg68) (BOOK 8) |
| Probable maximum flood (PMF) | The hypothetical flood estimate relevant to specific catchment whose magnitude is such there is negligible chance of it being exceeded. It represents a notional upper limit of flood magnitude and no attempt is made to assign a probability of exceedance to such an event. It is also used to define the extent of flood-prone land. The PMF causes the largest scale of flood emergency and is also therefore often used for emergency management planning. | Australian Rainfall & Runoff (ARR) –A guide to flood estimation pg.1259 (PDF) |
| Probable maximum precipitation (PMP) | The PMP is the greatest depth of precipitation for a given duration meteorologically possible over a given size storm area at a particular location at a particular time of the year, with no allowance made for long-term climatic trends. It is the primary input to probably maximum flood estimation. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 88 |
| Queensland Flood Assessment Overlay (QFAO) | The Queensland Floodplain Assessment Overlay (QFAO) map identifies potential floodplains that may be at risk from riverine flooding. However, it is not intended to predict riverine flooding for specific land parcels. The map was created through an analysis of drainage patterns using data such as 10-meter contours from the best available elevation models, historical flood records, vegetation and soils mapping, and satellite imagery, rather than a specific flood modelling approach. This data serves as an interim assessment to help Local Government Authorities identify areas that may need further refinement. | Department of Natural Resources and Mines, Manufacturing and Regional and Rural Development |
| Rainfall intensity | The rate at which rain falls, typically measured in millimetres per hour (mm/h). Rainfall intensity varies throughout a storm in accordance with the temporal pattern of the storm. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 88 |
| Rate of rise | The speed at which floodwaters rise over time. A rapid rate of rise can lead to people evacuating being overtaken or cut off by rising floodwaters. It is often associated with high velocities but it can be an issue if access routes are affected by flooding. | Australian Rainfall & Runoff (ARR) –A guide to flood estimation pg.17 & 1082 (PDF) |
| Residual flood risk | The risk a community is exposed to that is not being remedied through establishment risk treatment processes. In simple terms, for a community, it is the total risk to that community, less any measure in place to reduce that risk. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 88 |
| Risk analysis | The systematic use of available information to determine how often specified (flood) events occur and the magnitude of their likely consequences. Flood risk analysis is normally undertaken as part of a floodplain management plan. The floodplain management plan reflects the adopted means of managing flood risk. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 88 |
| Risk management | The systematic application of management policies, procedures and practices to the tasks of identifying analysing, assessing, mitigating and monitoring risk. | Queensland Emergency Risk Management Framework (QERMF) – Risk Assessment Process Handbook pg. 51 (PDF) |
| Riverine flooding | Flooding on normally dry land occurring when water overflows the natural or artificial banks of a stream, river, creek, estuary, lake or dam. Riverine flooding generally excludes watercourses constructed with pipes or artificial channels considered as stormwater channels. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 88 |
| Runoff | During a flood, rainfall is converted to runoff that flows towards the catchment outlet along naturally lower areas of the topography and drains. These flow paths include overland flow on hill slopes, across floodplains, down tributaries and along natural and artificial watercourses. | Australian Rainfall & Runoff (ARR) – A guide to flood estimation. |
| Sheet flow | Sheet flow describes wide (typically shallow) flow. Sheet flow is typically used to describe a type of localised overland flow that is not concentrated to a location by the natural topography or drainage. | Sciencedirect.com |
| Slope | The rise and fall of the terrain surface, also known as its inclination or gradient | Department of Environment, Science and Innovation |
| Storm surge | The increase in coastal water levels above predicted astronomical tide level (i.e. tidal anomaly) resulting from a range of location dependent factors including the invested barometer effect, wind and water set-up and astronomical tidal waves, together with any other factors that increase tidal water level. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 88 |
| Stormwater flooding | Is the inundation by local runoff caused by heavier than usual rainfall. It can be caused by local runoff exceeding the capacity of an urban stormwater drainage systems, flow overland on the way to waterways or by the backwater effects of mainstream flooding causing urban stormwater drainage systems to overflow. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 89 |
| Tailwater | The static or dynamic water level at the downstream boundary of the flood model. | Guide for Flood Studies and Mapping in Queensland (Department of Resources) pg. 94 |
| Temporal pattern | The variation of rainfall intensity with time during a rainfall event. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 89 |
| Topography | Topography is the study and description of the physical features of an area, for example its hills, valleys, or rivers, or the representation of these features on maps. The topography of a particular area is its physical shape, including the elevation of its hills, valleys, and rivers. | Collins Dictionary |
| Treatment options | The measures that might be feasible for the treatment of existing, future and residual flood risk at particular locations within the floodplain. Preparation of a treatment plan requires a detailed evaluation of floodplain management options. | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 89 |
| Tributary | A tributary is a watercourse or waterway that feeds into a larger stream or river. | National Geographic - Education |
| Velocity of floodwater | The speed of floodwaters, measured in metres per second (m/s). | Handbook 7: Managing the Floodplain: A Guide to Best Practice in Flood Risk Management in Australia (Australian Disaster Resilience) pg. 89 |
| Very low potential exposure | Identifies all other areas of the floodplain that have the potential, albeit although very low likelihood, to be affected by extreme flooding events. A flood in these areas would be a rare occurrence and is the most extreme and infrequent event that could occur in the catchment. | Queensland Reconstruction Authority definition for Flood Awareness Maps project. |
| Vulnerability | The characteristics and circumstances of a community, system or asset that make it susceptible to the damaging effects of a hazard. | Queensland Emergency Risk Management Framework (QERMF) – Risk Assessment Process Handbook pg. 51 (PDF) |
| watercourse | A river, creek or other natural watercourse (whether modified or not) in which water is contained or flows (whether permanently or from time to time); and includes: a dam or reservoir that collects water flowing in a watercourse; a lake or wetland through which water flows; a channel into which the water of a watercourse has been diverted; part of a watercourse; and an estuary through which water flows. | Australian Water Information Dictionary |
| waterway | Waterways can flow with fresh or tidal waters, have permanent or temporary flows, be natural or modified (e.g. modified through the construction of drains, floodway's or canals). Waterways do not include isolated bodies of water where no connectivity exists | https://www.business.qld.gov.au/industries/farms-fishing-forestry/fishe… |
QRA Reference: CM QRATF/26/9434, DOC/26/52792 & DOC/26/65574
Last updated: 22 September 2026.