No ropes, Difficult Tubing/Float trip
“Hutt River at Birchville” Flow Gauge readings A good level is for the ‘stage’ to be between 1000m and 1500m
See the Information on http://rivers.org.nz/nz/wellington/hutt/hutt-gorge but note that the flow range here is in relation to the Te Marua gauge, which is upstream of the Birchville gauge.
I haven’t been down it yet, so refer to a full route description in;
“Tararua Adventure Guide” by Jonathon Kennett
Also, see the sketch map on Jonathan Kennets Website.