[LINK] Floods taking out banking infrastructure

[Birch, Jim]

> Hard surfaces (roads etc) mean that less water is absorbed and more
runs off.

Land surface is more significant in mitigating with flash flooding from
a single deluge.  Once it has been raining hard for a while the ground
is saturated and absorption is minimal.

In the Brisbane situation, there were a number of wet days which soaked
everything followed by (like) 36 hours of continuous heavy storm rain
over all of the Brisbane River catchment, to the northwest and west of
the city.  Rain like this is common enough but having a rainband sit
over the catchment continuously for an extended period is fluky.  The
placement was "perfect".  Watching the meteorology was interesting, if
macabre.

In this weekly rainfall map, the extreme zone (400mm+) more or less
covers the Brisbane River catchment 
http://www.bom.gov.au/jsp/awap/rain/index.jsp?colour=colour&time=latest&
step=0&map=totals&period=week&area=qd

I'll be interested in final assessment of the mitigating effect of the
Wivenhoe Dam.  I guess it will have limited the disaster but was
overwhelmed by the volume of water.

We're running a barbeque lunch here with proceeds to the relief fund.

- Jim


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