Thursday, 9 April 2015

Mainly watercourses after long rains

We have been through a couple of rather dry months, which led to no flow in the 2 creeks on our block.  That ended on 6 April when we scored 18mm of rain (all of which sank into the ground with little or no run off).  It was followed by 43mm on the 7th and 21mm before dawn on the 8th.  That did run off.

A side effect of this was the postponement of the ANPS Wednesday Walk for the 8th so I went a did a few chores.

As a result of the first chore I strolled down Yass Rd in Queanbeyan to the ACT border.
 The bridge in this image carries the railway line into Canberra.  It also marks pretty much the border of the ACT: I suspect this is a coincidence of interests as the easiest route for the line is to follow the Molonglo which is the border a little to the East.  There was not a pile of stunned birds under the bridge: despite the rulings of some administrators they fly back and forth as though the border didn't exist.

The Molonglo is nearby and had a very good flow as it went under Yass Rd (which has probably changed to Pialligo Avenue when it crossed the border),
This is the old crossing.  A bit narrow for the current level of traffic and rather prone to getting submerged.
On the subject of submerged, here is Briars-Sharrow Rd which I encountered when attempting to go to Bungendore on another chore.  I suspect the sluices have been opened on the Captains Flat Dam.
 The "wading depth" of my Pajero is 70cm and I decided that this was 75cm deep.
There was also a very strong current so I decided that discretion was the better part of stupidity and went via the Kings Highway.  Several kilometres longer, but much quicker than getting the SES to drag me out of the crossing.

While in Bungendore I went to check the Whistling Duck situation which was very positive with 78 birds present.  The dam on Trucking Yard Lane was well supplied with water and they seemed to be finding something to eat in the grass.
Judging by the good flow on the Queanbeyan River as it goes over the weir I suspect the sluices have also been opened at Googong Dam.
There was still a lot of clean air under the Morrisett St bridge.  In the bad floods a few years back the water level would have been well over the railings on the bridge.
The water level in the weir had dropped quite a bit a couple of days later, but still a good flow.

Whiskers Creek didn't go over our drive but did have a good flow in it.  This image was taken at about 11am and at peak - probably about 5am - had covered the grassy patch on the right.
In the afternoon I went up the block to check the situation there.  A good flow in the secondary creek there.
The most interesting aspect of this is the revealed geology.  Below the waterfall (perhaps 50cm high) there is a flat sheet of bedrock.  That is overlain by a layer with many pebbles showing an old water level.  A bit further upstream the pebbles are still the floor of the watercourse.  Then there is a layer of soil suggesting that something - probably roots - has slowed the waterflow allowing the soil to be deposited.

2 comments:

Sharpen said...

Hi Flabmaster, are there caravans in the distance in picture 7 on the other side of the Queanbeyan river. My partner and I free camp sometimes and that looks a nice spot. We also have a diesel Pajero and a 19ft River caravan.
Thanks
Sharon

Flabmeister said...

G'day Sharon
Yep, they are caravans, but in a commercial (not free) campground. When the River really floods - about 6m higher than this - they all get evacuated.

Martin