13 April, 2012

Branching out - Moorabool Falls

And then one became two...
I am definitely not a geologist, but there is something rather cool about the fact that a waterfall can be in one place in one era and can then wind up a couple of kilometres upstream the next. Or, in the case of the Lal Lal and Moorabool Falls, can end up in two different places on two separate waterways.
Confluence of the Moorabool River West Branch and Lal lal Creek at the
top of Bungal Dam
Having finished our lunch and looked to see what von Guerard found so interesting about Lal Lal Falls that he was moved to paint them in 1853, we jumped back in the car and zipped round to Harris Road to the start of a walking track which leads to another nearby waterfall. This second feature of the landscape is the Moorabool Falls, located on the west branch of the Moorabool River, a short distance above its confluence with Lal Lal Creek.
My last post described how the Lal Lal Falls have been busily migrating up the creek, cutting through the relatively recent basalt lava flows of the last few tens of thousands of years. Meanwhile, over on the West Moorabool, the Moorabool Falls were busy making progress of their own, working their way through a different part of the same basalt flow.
Granite Falls, a series of cascades which flow over granite remains about
400m up the Moorabool West Branch from its confluence with Lal Lal Creek
In fact, a little research tells me that the two falls were originally one and the same. A few million years ago, water flowed over the edge of the basalt at a single "knickpoint" in the west branch of the Barwon. Some more research and I now know that a knickpoint is the point at which a sudden change occurs in the slope of a river, being much lower downstream of the knickpoint where water has carved a deeper path. It is often associated with "headward erosion" which is caused by the flow of water at the mouth of a stream eroding the riverbed.
Moorabool Falls, April 2012

In the case of the Lal Lal and Moorabool Falls, headward erosion began at a single knickpoint below the junction of Lal Lal Creek and the Moorabool West Branch. Over time and as the erosion reached the confluence of the two streams, the single waterfall, divided into two and the erosion continued up both branches. That which occurred in Lal Lal Creek has so far moved over 1,600m to the present site of the falls, whilst the erosion of the West Moorabool has traveled some 1,400m upstream to where the Moorabool Falls are now.
Moorabool West Branch just below Moorabool Falls
These falls are not so large as the Lal Lal Falls, dropping only 27m in total, nor do they have the striking basalt columns of the other falls. This is because the lava at this point cooled more quickly and unevenly than elsewhere.
West Moorabool between Moorabool Falls and Bungal Dam
Our walk to these falls also provided me with another piece of information. One which is slightly at odds with a previous post. The information board at the falls informed me that Moorabool was a Wathaurong word possibly meaning "mussel" or perhaps "stone curlew". A source I referred to in a previous post, indicated that the name was derived from the Wathaurong word "moora" meaning ghost. Another alternative it gave was that Moorabool may also refer to a nocturnal bird called a "cooloo" which could not be seen but whose call could be heard. Bush Stone-curlews are predominantly nocturnal birds whose breeding call is a long drawn out wail described as sounding like "werlooooo", so perhaps these two sources were not so much at odds as they might first have appeared.
I have never seen a Bush Stone-curlew, nor do I know if they were ever found on the banks of the Moorabool River.

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