Stream Bed and Bank Stabilisation: Mountain Creek. Final Report October 2011.

Abstract

The objective for this study was to assess stream bed and bank erosion processes in a defined reach of Mountain Creek. The assessment process was developed by the Australian Rivers Institute (ARI) in conjunction with the Canadian Rivers Institute and used principles detailed in previous study cases (Newbury et al., 1993). In using this approach, several conclusions can be made about the current condition of the project reach and its trajectory in channel recovery: 1. Slope analysis of Mountain Creek showed the project reach has a similar bed slope to upstream reference reaches and the old channel that was abandoned post 1992. This would suggest down-cutting of the stream bed since the channelisation of the reach has reached an equilibrium. The presence of riffle structures along the project reach and the clay lens that have previously been discussed in other reports may be sufficient to stabilize the current bed slope. Aggradation of the bed is evident in downstream sections of Mountain Creek. 2. The project reach has an inset channel that is similar in width and depth to the upstream reference reaches. The bankfull dimensions of the macro channel in project reach are significantly wider and deeper than the reference reaches or the previous channel. 3. There are still sections of Mountain Creek that are widening due to bank slumping and mass failure. 4. The inset channel has a characteristic discharge similar to the reference reaches 5. The macro channel for the project reach will now contain a 10 yr recurrence period discharge due to the bed degradation and channel widening that has occurred post 1992 6. Consideration of these results would suggest the project reach in Mountain Creek is within stages V and VI of the channel evolution model (Hupp and Simon, 1991).