Tin Mine Falls is a waterfall located in the remote Pilot Wilderness Area, part of Kosciuszko National Park in southern New South Wales, Australia. Described from top to bottom, the falls consist of non-segmented tiered cascades over bedrock with a few smaller plunges, followed by a single large plunge into a pool. The falls are recessed into a punchbowl feature making it impossible to view the entire waterfall from a single location on the ground.
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Since no roads or trails go to the falls, access is quite difficult and the falls are rarely visited or photographed (no public photographs are known except those on this page). The closest walking path is the Cascade Fire Trail, which runs South from the Alpine Way just West of Thredbo Village. Satellite imagery of the site is available via Google Maps.
The height of Tin Mine falls is a matter of some controversy,[1] due to two factors:
A number of sources list the height of Tin Mine Falls as 459m (1,381')[2] or 360m (1080'),[3] and quote a story concerning the origin of this figure: "The falls were apparently measured in 1990 by a Dr. John Pease ... using a plumb line"[2]
If true, this height would make Tin Mine Falls the tallest waterfall in Australia and 137th tallest in the world. However, it conflicts with official data from Geosciences Australia, who list the 3 tallest waterfalls in Australia as:
Note the distinction between longest-single-drop height and overall height - many observers will only include vertical plunges when assessing the height of a waterfall.
It has been suggested [5] that the conflict between the reported height and the surveyed topography of the area can be explained by the inclusion of a long series of cascades upstream from the waterfall. Therefore the definition of a waterfall and the chosen measuring process will determine the measured height.
A thorough and widely referenced process for measuring the height of a waterfall can be found here. The crux of the process is that although shallow cascades can be included in a waterfall, they are excluded when the water is not flowing over bedrock. Simpler methods are only really suited to single drop waterfalls.
The lower limit of Tin Mine falls is easy to pinpoint due to the final plunge into a large pool, from which the water flows smoothly. The upper limit is less decisive, because the stream changes from a relatively flat meandering course to the plunge quite gradually. However, a distinct and drastic change occurs at one point where the water transitions from a series of small connected pools with pebbled/mud bottoms to a smooth and fast slide over bedrock.
Above this point, the water is not flowing over bedrock, and is not losing height quickly.
An expedition to capture photographs of the falls was undertaken by Dr. David Rawlinson, Adam Ferguson, Matthew Farrell, Nicholas Wright, Tadhgh Knaggs, and Travis Hogg between 16 and 20 October 2008. If the upper limit of the falls is accepted as described above, the expedition photographs[6] may be used to estimate the height of the falls. Alternatively, the photographs allow readers to judge the height of some subsection of the falls independently.
A pair of fluorescent yellow flags was positioned 10m above the head of the falls by the photographers. The flags were arranged to lie on a plane parallel to the image plane of the photographer. The distance between the centres of the flags was measured with a tape-measure to be 3.1m. These flags are visible in the expedition photographs[6] and provide a scale for the images.
If we additionally assume that the image plane is perpendicular to the ground plane (an imaginary plane Tangential to the surface of the Earth), and that the waterfall flows on a plane that is parallel to the image plane, we can estimate the height by measuring the vertical separation of waterfall head and base in pixels, then scaling using the known distance between the flags.
In photograph [7] the flag centres are located at (2663,131) and (2631,132) using graphics coordinates with origin at top-left. The bottom of the falls is at approximately (796,1932), therefore the height in pixels is 1800. If 32 pixels is 3.1m, then 1800 pixels is 174m. Since the flags were positioned 8m above the top of the falls, the height can be estimated at 166m.
The most significant sources of error in the first method are[8]:
The photographer captured stereo pairs of photographs of the waterfall site with an unknown baseline. By matching interest points between the stereo images, it is possible to produce a disparity map indicating unscaled distance from the camera to any interest point. It is then possible to scale this 3 dimensional model using the positions of the flag scale markers. Finally, a new plane was defined such as to fit interest points generated by the final plunge and at the head of the falls - the base of the falls is closer to the viewer than the head. A parallelogram was fixed to this plane such that its limits matched those of the falls in the photograph. The height of the parallelogram was extracted as 185.5m. Subtracting the extra 8m from the top to the flags gives an overall height estimate of 178m.
A video of the 3-D reconstruction can be found here, showing the plane fitted to the waterfall and matched interest points.
The estimated height of 160-180m corresponds with topography but contradicts Geosciences Australia's list of the tallest waterfalls in Australia (this would make Tin Mine Falls the 3rd highest on the continent). Unless the upper limit of the falls is fixed well upstream, to include a long section of shallow-slope non-bedrock streambed, the rumoured height of 360-459m cannot be substantiated.
