[LINK] FLoods taking out banking infrastructure

[Marghanita da Cruz]

Richard Chirgwin wrote:
<snip>
>> 1974, although the flood level peaked at slightly less than the 1974 level.
> I also heard John Birmingham remark on ABC radio that some surprise 
> floods happened because of backup in stormwater drains which could no 
> longer empty into the river (understandably enough).
<snip>

I think he has misunderstood the story. The storm water 
drains may no longer empty directly into the river, but the 
water does have to go somewhere. In Annandale, two wetlands 
have been constructed to filter the water before it enters 
the harbour. However, during major rain events the water is 
still able to run out over the wetlands into the harbour. 
Sometimes the storm water floods the sewers and this 
overflow contamination is a big problem.

In Brisbane, the river level had risen so there would be 
nowhere for the water to go and it possibly backed up the 
storm water channels to find its level.

Hard surfaces (roads etc, mean that less water is absorbed 
and more runs off. Possibly stressing old infrastructure 
even more. Though the problem with these floods seemed to be 
water coming down the rivers from elsewhere.

Marghanita
-- 
Marghanita da Cruz
http://ramin.com.au
Tel: 0414-869202