ID not conclusive as you cannot see enough of the head - this looks like the rusty coloured form of the White-lipped Snake that you sometimes see higher up in Namadgi. The darker grey-coloured head marking is not like that found on juvenile brown snakes. see http://museumvictoria.com.au/bioinformatics/snake/images/corolive1.html and also http://www.gondwanareptileproductions.com/dcoronoides.html and http://www.flickriver.com/photos/tags/drysdaliacoronoides/interesting/
WillO stated ID not conclusive as you cannot see enough of the head - this looks like the rusty coloured form of the White-lipped Snake that you sometimes see higher up in Namadgi. The darker grey-coloured head marking is not like that found on juvenile brown snakes. My comments is not a brown snake. Possibly a Pygopus lepidopodus but not likely. Have seen White-lipped snakes with this colouring. GeoffR