Saturday, 13 February 2010

You don't need to be a weatherman ...

.. to know its raining.

I posted last weekend about the rain causing the Molonglo River to flood.  My friend Denis Wilson, blogging from Robertson in the Southern Highlands (about 140km NE of here) also commented on the downpour.

On 12 February I rode further across the Hoskinstown Plain to see whether the floods had resulted in any water getting into Foxlow Lagoon.  The first thing I noticed was this marvellous old tree in Hoskinstown with the branches red and shiny: probably as a result of the storm flogging the foliage across them.

Moving about 2 km further down the road to a gully crossing the road I noticed that the Shire had been active with some serious machinery.  It was evident from the debris in the fences and shrubbery that at some recent stage there had been close to a metre of water running down the road!  Thank goodness they got that cleaned up before the deluge promised for this weekend!

On arriving at the point where I could look down into the Lagoon  I had a lovely sight.  No waterbirds yet, but judging by the bachtrian ruckus there is plenty of food for them in the water!

Moving on to the forecast, the nice Mr Carmody on ABC TV News has been smiling and talking about rain over the weekend.  As he has been subject to some criticism in the past for forecasting large amounts and the result being a flock of incontinent gnats  he kept his powder dry(ish) this time.  The Elders Weather site was a little bolder suggesting
  • 10 - 20mm on Friday; 
  • 40 - 80mm on Saturday; and 
  • 5_10mm on Sunday.

The image to the left shows the radar image as at 14:37 on Saturday 13 February suggesting it was pissing down at the time.  Obeying rule 1 of weather forecasting - look out the window - shows this to be spot on!  Our house is marked with a (barely visible through the blue) red X.  Shortly after this (don't worry about posting times I adjust those to get pages in the order I want) I went off for a walk round the property.  The images and some disorganised text are here.

The Bureau of Meteorology indicated that the more serious rain was going to happen on Saturday evening and perhaps into Sunday morning.  The results are:
  • Friday evening  - 2mm
  • Saturday (morning to lunchtime) - 12.5mm (14.5)
  • Saturday (lunch to tea time) -26.0mm (40.5)
  • Saturday after tea to dark - 6.0mm (46.5)
  • Sunday to 0630 - 19.0mm (65.5)
  • Sunday 0630 -1000 - 16.0mm (81.5)
It is probably noteworthy that by Saturday lunchtime our cumulative rain for the year was above that we recorded up to the end of March 2009.  Then, by 5pm on Saturday we'd got pretty close to the 40mm lower bound on the Elders site, and it was still raining quite steadily with the radar indicating some heavy stuff in our future! 8pm saw 44.5 having visited the gauge so well done Elders!


Denis Wilson said...

Hi Martin
My daughter tells me they got a large dump of rain in Dickson (Nth Canberra) last night, and more forecast this afternoon.
As for the "forecasts" the Bureau is deliberately over-warning these days, in order to "cover their backsides" should there be damage or loss of life from floods, etc.
Your photos show much more run-off from your rain than I got from 300 mm in on day.
The difference is the soil type.
Our soils are highly porous, and rain soaks in much more readily.
Your yellow clay and decomposed granite soils (that's what they look like, anyway) are very hard and do not absorb water readily. Hence more and faster run-off. It can take a week of rain before we get run-off. The soil needs to be totally saturated before run-off occurs with us.

Flabmeister said...


You've picked the soil type rather well. Around the house there is a fair amount of granite (lumps of quartz everywhere). Further up the property, where the photos of Canyon Creek were taken, it is a very clayey soil or outcrops of shale.