Map Notes Flood behaviour This map does not show ﬂooding from local The ﬂood extents shown are a prediction of land A ﬂood occurs when a pipe, channel or creek stormwater drains that can occur as a result affected for the speciﬁc level of risk. They do not cannot carry the volume of water in the system. of localised heavy rainfall. Nor does it show necessarily indicate the threat to buildings located When this occurs, ﬂoodwaters travel across the ﬂooding that may occur as a result of interaction on that land. Flood assessment for particular sites land and can damage property and threaten safety. with adjoining catchments. In particular, ﬂood extents requires more detailed interpretation, survey and Flooding is a natural event. in the area between Mile End and the northern side hydraulic analysis. of the Airport are possibly greater than shown The extent of ﬂooding shown on this map is based due to the effect of runoff from those areas. The limit of ﬂooding shown is not a boundary on predictions of ﬂood behaviour of the Similarly this map does not show ﬂooding from either between ﬂood prone and ﬂood free land. watercourses (channels and creeks). the Sturt River or the River Torrens, both of which Larger ﬂoods could inundate areas outside the have a very low probability. areas shown. Localised ﬂooding from street drainage is not shown on this map and it can occur in severe The data on this map is based on survey, hydraulic Watercourses storms in most areas of the catchment. and hydrological modelling in 2002 of accuracy Properties directly adjacent natural watercourses sufﬁcient for broad-scale ﬂood risk management and are ﬂood-prone irrespective of their status on This map is intended to help promote public planning. The modelling reﬂects current practice but this map. Actual ﬂood extents will vary from one awareness of the ﬂood hazard from the Brown Hill there are uncertainties associated with the data on ﬂood to another because they are affected by and Keswick Creek systems and assist people who which the models are based and, therefore, on the earthworks, debris blockages, further development undertake development in the area. ﬂood extents shown on this map. within the catchments and other factors. Limitations and other important The predicted ﬂood extents are not based on Disclaimer notes about this map historical ﬂoods. Actual ﬂood extents will vary from one ﬂood to another because of earthworks, debris This map is provided on the basis that those This map delineates areas south and west of blockages, further development within the responsible for its preparation and publication Adelaide assessed as subject to ﬂoods from Brown catchments and other factors. do not accept any responsibility for any loss or Hill Creek, Keswick Creek, Park Lands Creek and damage alleged to be suffered by anyone as a Glen Osmond Creek. result of the publication of the map and the notations on it, or a result of the use or misuse of the information provided herein. Flood depth zones Light blue (Depth less than 0.1metre) Dark blue (Depth 0.1metre to 0.25metre) During a 1 in 100 year ﬂood it is expected During a 1 in 100 year ﬂood it is Coloured bars relate that water will be less than 100 millimetres expected that water will be between to map above (4 inches) above the ground level. In most 100 and 250 millimetres (4 to 10 inches) cases houses will not be affected. above the ground level and some houses may be affected. Brown Hill and Keswick Creeks ﬂoodplain inundation map 1 in 100 year ﬂood Purple (Depth 0.25metre to 0.5metre) Light pink (Depth 0.5metre to 1.0metre) Dark pink (Depth greater than 1metre) During a 1 in 100 year ﬂood it is expected During a 1 in 100 year ﬂood it is expected Flooding will reach a depth of greater than that water will be between 250 and that water will be between 500 millimetres one metre (about 3 feet). Property damage 500 millimetres (10 to 20 inches) above and one metre (20 inches to about 3 feet) is likely and these areas have a hazard rating ground level. Property damage is possible and above ground level. Property damage is likely of high to extreme. these areas have a medium hazard rating. and these areas have a high hazard rating. 1 in 100 year ﬂoodplain The beneﬁts of ﬂoodplain mapping Areas where water depth is greater or areas near watercourses where the velocity of water is high A ﬂoodplain is an area of land subject to The ﬂoodplain study and map will help Councils are more hazardous and evacuation to higher inundation by water from a watercourse. make planning decisions for safe and orderly ground may be required. Residents in these areas Over a very long period of time a ﬂoodplain will development. should have a plan in the event of rising be inundated to various degrees on different ﬂoodwaters. occasions. The map identiﬁes those areas The map will also help the Board and Councils vulnerable to ﬂooding in a 1 in 100-year ﬂood with the development of appropriate planning Important things to consider in the event of from the watercourses. A ﬂood of such a policies and ﬂood management, prevention a ﬂood are: magnitude would be expected to occur on and mitigation initiatives. These may take average about once every 100 years and some time to develop, assess and then fund. • Avoid fast ﬂowing water. Remember that at consequently there is a 1 percent chance Considerable State and Local Government stormwater inlets in the street there may be (1 in 100) of a ﬂood of this magnitude in any negotiations will be involved. eddies that could be dangerous. one year. Of course ﬂoods do not occur on a regular basis and a 1 in 100 year ﬂood need not Impact on development in the • Avoid wading, even in shallow water, and if occur in every 100 year period. Conversely there ﬂoodplain you must enter shallow ﬂoodwater, wear solid could be several ﬂoods that exceed the 1 in 100 shoes and check depth with a stick. Councils will take the ﬂood mapping into year ﬂood within any period of 100 years. account when they make decisions on • If you have time, elevate valuable possessions development applications. This might, for in your home (personal papers, photo albums, It is important to note that greater ﬂoods example, require ground ﬂoor levels for new family mementos, electronic equipment etc as than that shown on the map are possible. structures to be raised to ensure that they are high as possible. The 1 in 100 year ﬂood is chosen as it is above the likely ﬂood level. internationally recognised for urban planning and • Turn off electricity, gas and water. development purposes. In due course each Council’s Development Plan • Listen to the radio for information will be changed to ensure that development is and updates. Why the map was made planned in a way that recognises the location The ﬁrst step in ﬂood management is to have up- of ﬂood prone areas Insurance to-date information about the extent of ﬂooding. Questions about insurance should be directed to The area was last mapped in 1984 and with In the meantime developers should discuss their your insurance company. development occurring over the last 20 years and speciﬁc situation with their local Council before the very considerable advances in ﬂood modelling committing to a project. Property values and mapping techniques, it was considered prudent to improve the level of knowledge and Flood warnings It is important to note that the ﬂoodplain understanding of ﬂood potential. mapping study has not changed the likelihood A ﬂood monitoring system known as ALERT has of a severe storm occurring. The existence been installed by Councils and the Bureau of This up-to-date ﬂoodplain mapping study will of the ﬂoodplain map does not increase the risk Meteorology. It consists of a network of rainfall inform residents, Councils and the State of being ﬂooded. and water level stations connected to computers Government and help better prepare mitigation at the Bureau’s ofﬁces at Kent Town and the SES strategies for ﬂoods. It will assist Councils with A recent report prepared by the Natural Hazards at Mitcham. When heavy rain falls, the rainfall planning decisions to ensure development takes Research Centre based at Macquarie University alarms are triggered, and emergency response place in a safe and orderly manner. indicates that experience in Australia and overseas staff are alerted to the potential for ﬂoods. is that there should be no long-term impact on How the map was made However ﬂoods are generated so quickly property values as a result of the release of the along Glen Osmond Creek and Park Lands ﬂoodplain maps. The mapping was produced by specialist water Creek in the Unley area that it is not realistic resource consultants Hydro Tasmania using to expect any prior warning of ﬂoods. Further information state of the art survey and computer modelling The situation with Brown Hill Creek and areas technologies that provide the best possible If you require further information contact your further downstream along Keswick Creek estimation of ﬂood behaviour. The study was one local Council or the Patawalonga Catchment is a little better as a major ﬂood will take longer of the most advanced and complex ﬂoodplain Water Management Board. to rise and it is possible some ﬂood warnings studies undertaken in Australia. can be issued via the media. City of Adelaide 8203 7203 What to do in a ﬂood City of Burnside 8366 4200 Personal safety is the most important City of Mitcham 8372 8888 consideration during a ﬂood. Although ﬂoods greater than the 1 in 100 year ﬂood are possible, City of Unley 8372 5111 it is important to remember that the vast majority City of West Torrens 8416 6333 of the ﬂoodplain shown on the map is very shallow and consequently of low to medium risk. Patawalonga Catchment In areas of shallow ﬂooding, driving or walking Water Management Board 8271 9190 from your home could be more hazardous than staying at home. Patawalonga Catchment Water Management Board Brown Hill and Keswick Creeks Floodplain Mapping Study History Floodplain mapping is being progressively undertaken across metropolitan Adelaide. Assessments and ﬂood management strategies have already been put in place for the River Torrens and the Sturt River. In conjunction with local Councils, the Patawalonga and Torrens Catchment Water Management Boards are now assessing other watercourses including Brown Hill and Keswick Creeks in the Patawalonga Catchment and First, Second, Third and Fourth Creeks and other areas in the Torrens Catchment. The mapping for Brown Hill and Keswick Creeks is now completed. The map on this fact sheet results from a detailed two-year study for the Brown Hill and Keswick Creeks Flood Management Group. The Group is made up of the Patawalonga Catchment Water Management Board, the City Councils of Adelaide, Burnside, Mitcham, Unley and West Torrens and State Government representatives. The study was undertaken for the Group by water resources consultants Hydro Tasmania. Since European settlement, thousands of residential, commercial Fact Sheet and industrial properties have been developed on the Brown Hill and Keswick Creeks ﬂoodplains across an area of some 60 square kilometres. The Patawalonga Catchment Water Management Board convened the Brown Hill and Keswick Creeks Flood Management Group to provide a forum to focus on matters of ﬂooding and watercourse management in and along the Brown Hill and Keswick Creeks system. Just over 5,000 residential and commercial properties are within the 1in100 year ﬂoodplain (see back page for deﬁnition). About 3,700 properties (74%) are in very low hazard areas with less than 100 millimetres (4 inches) of ﬂood depth. The ﬂood damage bill from the 1 in 100 year ﬂood is estimated to be between $100 and $200 million.