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| Mullum Mullum Creek | |||
| An example of Natural River Capture | |||
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River Capture or River Piracy happens when the head of an
actively eroding stream, which has deeply entrenched itself, has cut back so
far that the bed of a stream lying at a higher elevation is intercepted.The water above the point of capture is diverted into the capturing stream. The head of the capturing stream is now at the head of the captured stream, and the drainage system is radically altered. The additional water accelarates the erosion process, and so the stream rapidly carves a deeper course. The diagram to the left shows 'X' where the Mullum Mullum Creek has captured Heatherdale Creek, a tributary of the Dandenong Creek. |
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The diagram below shows how the Mullum Mullum Creek captured the headwaters of Heatherdale Creek.
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The top part of Heatherdale Creek became a dry valley once its waters had been captured.
Over the years, this dry valley has been used for land-fill, and has progressively been filled in by rubbish and other spoil. Where the capture has occured there is a sharp bend, called the elbow of capture. This sharp bend in the Mullum Mullum occurs upstream of Loughnan / Deep Creek Road where the Creek turns sharply from the East, to the North, below Poynton Avenue escarpment. The steepness of this escarpment is in part due to the tendency of the deeply incised stream to attempt to straighten this bend, following the capture. The original point of capture was probably near the northern end of New Street. About 15 years ago, the creek was realigned and straightened in this area to accommodate the increased run-off from the increasing percentage of hard surfaces upstream, such as pavements and roofs, so the true point of capture is no longer clear. |
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Sources:
"Physiography of Victoria", E. Sherbon Hills, Whitcombe & Tombs Pty. Ltd., 1960. pp112-113. Fig.148 Fig. 150 |
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| Friends of Mullum Mullum Valley | ||
| 53 Aurum Crescent, Ringwood North VIC 3134 AUS | ||