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Flood data added to ACTMAPi

By 17 December 2013 7

Simon Corbell is sharing the joy that we can now map flood data:

Minister for Police and Emergency Services, Simon Corbell, today launched new flood data on the ACTMAPi website aimed at advising Canberrans which areas are at risk from riverine floods.

“The ACTMAPi website shows the one-in-100-year flood level areas in the ACT,” Mr Corbell said.

“The flood data on the ACTMAPi website shows areas where there may be riverine flooding as a result of a major flood event that leads to the breaking of banks of a river or other similar large tributaries.”

Whilst most Canberra homes may not be subject to riverine flooding, people should not assume that they are not subject to any flood risk at all. They could still potentially be subject to flash flooding. This localised flooding occurs when heavy rain cannot drain away quicker than it falls.

“The Molonglo River is the most obvious risk of riverine flooding, should there be a one-in-100-year flood event with the river.

“As a well planned city, almost all homes in the ACT are built above the one-in-100-year flood level. The level of risk to Canberra residents from a riverine flooding event such as the Molonglo or another stream or tributary breaking its banks is very low.

“This new data will inform Canberrans on appropriate actions they can take such as obtaining home and contents insurance policies for their property.

“Ongoing work is being undertaken in relation to studies of other creeks outside the Molonglo River such as Sullivan’s Creek, Yarralumla Creek, Long Gully Creek, Weston Creek, Woolshed Creek, Tuggeranong Creek, Isabella Weir and Ginninderra Creek systems. As this information becomes available, it will be added to the ACTMAPi website towards the end of 2014.

I’d love to show you what it looks like but the whole thing doesn’t work on a mac (even the supposedly HTML5 links need silverlight)

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7 Responses to Flood data added to ACTMAPi
#1
davo10112:09 pm, 17 Dec 13

Doesn’t work in Winblows Explorer with Siverlight installed either.

#2
c_c™2:34 pm, 17 Dec 13

That’s very strange, I was using ACTMAPi to check out the Territory Plan and just two weeks ago on a Mac running Mountain Lion and it worked fine in Safari. Judging by the error message it looks like they’ve stuffed up the coding on the site.

#3
HiddenDragon4:57 pm, 17 Dec 13

For those who do not have ready access, some interesting and important notes, including re the 1971 “supercell”:

“Flood Map

IMPORTANT NOTICE

The ACT Government is providing this flood data for information purposes only. This data is derived from the best available modelling of the catchments and watercourses. The ACT Government cannot and does not guarantee the accuracy and completeness of any data and information contained on this site as, among other reasons, there may have been changes to land use, flow paths or rainfall estimates since the modelling was done. The ACT Government disclaims liability to any person who acts in reliance on the information provided on this site or contained within the reports or plans on it whether that liability is in negligence or on any other legal basis. Persons who would otherwise seek to rely on the data and information contained on this site should make their own inquiries and seek their own expert advice.

Users of this site should also note that currently data is available only for the Molonglo River, including Lake Burley Griffin. Data for creek systems in Canberra is not displayed because the available data is based on older contour data, past land use and superseded flood models and rainfall estimates. Much of this information is currently being revised and will be displayed on ACTMAPi when it becomes available.

Questions and answers related to the ACT flood map on the ACT Government’s ACTMAPi website

Q1 WHAT IS A FLOOD?
A flood is defined as the covering of normally dry land by water that has escaped or been released from the normal confines of a lake, river, creek or other natural watercourse, a reservoir, canal or dam.

Q2 WHAT IS A FLASH FLOOD?
Flash flooding is localised flooding that occurs when heavy rain cannot drain away quicker than it falls. A flash flood is defined by the speed of flooding, not the source or location of flooding. Flash flooding is typically caused by short duration storms over a localised area or catchment. The Bureau of Meteorology describes flash flooding as “Flooding occurring within about six hours of rain, usually the result of intense local rain and characterised by rapid rises in water-levels.” A local example of a flash flood is the “supercell” thunderstorm that hit Woden in January 1971 where the Canberra Times reported rainfalls up to 100mm in 1 hour were recorded by private rain gauges in the suburbs of Farrer and Torrens.

Q3 WHAT IS FLOOD RISK?
Flood risk includes both the probability of a flood occurring and the consequences if a flood occurs. The consequences of a flood are in turn affected by the number of people and properties exposed to floodwater and the vulnerability of these people and properties. For example, a river might burst its banks regularly, but if this flooding occurs in an isolated area where there are no people or infrastructure, then the flood risk is considered to be low. Similarly, a river might flood very rarely, but if many people and properties are located near this river and they live in dwellings that are vulnerable to floodwater damage, then the flood risk will be higher.

Q4 HOW PRONE IS CANBERRA TO FLOODS?
Canberra planning has always taken into account the need to avoid development in flood prone areas. Since the 1970s planning for new urban development in the ACT has kept development above the 1% Annual Exceedance Probability (AEP) flood level. The local stormwater system is designed to cope with the 1% AEP storm flows through a combination of piped flows and overland flows. However, no areas are completely immune to flooding. Floods greater than the 1% AEP are possible, and extremely intense local rainfall can cause localised flash flooding.

Q5 WHAT IS A 1% AEP FLOOD?
The 1% AEP flood is a theoretical flood that is estimated to have has a 1% chance of being equalled or exceeded in any year. For example, if you experienced a 1% AEP flood last year, the chance of experiencing a similar magnitude flood this year is still 1%, regardless of when the previous 1% AEP flood was experienced. The 1% probability is calculated using computer modelling, historic rainfall and runoff records and a range of other assumptions. The value of the 1% AEP is an estimate that will change as the climate changes and as more historic rainfall and flooding information is gathered over time that might change assumptions used in the modelling and estimations.

Q6 WHAT DO ACT FLOOD MAPS SHOW?
The ACTMAPi flood map shows an estimate of the areas likely to be flooded during a 1% AEP flood – also previously known as the 100 year flood line. The ACT flood map shows flooding extents for riverine flooding only i.e. flooding from named watercourses such as rivers and creeks.

Q7 WHEN ARE ACT FLOOD MAPS BEING RELEASED?
The ACT flood maps show the 1% AEP flood for the Molonglo River from Yass Road downstream to the Lake Burley Griffin surrounds and further downstream to below Coppins Crossing. There is a program to update flood studies over the next three years for creeks and some major stormwater channels within and adjacent to urban areas. Once these studies are completed, the 1% AEP flood extents will be made available on the ACT Government’s ACTMAPi website.”

#4
c_c™9:28 pm, 17 Dec 13

Not much to see here, it’s only the 1 in 100 year data. The flood that overtopped the cotter dam during construction in March 2012 was more than a 1 in 100 AEP event.

Much more interested to see the 200 and 500 yr data, they do have it, at the very least for the NCA land around the Molonglo basin.

#5
PoQ3:37 pm, 03 Jan 14

You may want to play with this. IIRC, if all the ice melts, the Murray-Darling will flood to Wagga.

Some clever-dick has extended Google-maps to show the effect of sea-level rise:

http://www.isciencetimes.com/articles/6293/20131110/sea-level-rise-mapped-drown-town-visualization.htm

http://www.southernfriedscience.com/?p=15682

#6
HiddenDragon4:10 pm, 03 Jan 14

PoQ said :

You may want to play with this. IIRC, if all the ice melts, the Murray-Darling will flood to Wagga.

Some clever-dick has extended Google-maps to show the effect of sea-level rise:

http://www.isciencetimes.com/articles/6293/20131110/sea-level-rise-mapped-drown-town-visualization.htm

http://www.southernfriedscience.com/?p=15682

That will surely be factored into household insurance premiums…..

#7
Aeek8:07 pm, 03 Jan 14

The Murray’s salt level will go up, or down? Either way, there will be more fires for Abbot to fight.
Some guys light fires so they can be a hero. That’s illegal, but destroying the planet is ok.

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