Water Stability

Glenelg Drainage Basin Waterway Stability Problems:

Location	Problem
Wando Vale and Ponds Creek	Headward erosion.
Koonong Wootong Creek	Headward erosion.
Wennicott & Den Hills Creeks and Tributaries	Headward erosion.
Dwyers Creek	Headward erosion.
Henty Creek	Breakaway and bank erosion.
Bryans Creek	Sedimentation and subsequent incision.
Wando River and tributaries	Deepening and headward erosion.
Dundas Land Zone streams	Deepening and headward erosion on tributaries.
Wannon River	Existing structures cause deepening. Isolated bank erosion.
Grange Burn, Dwyers Ck, Dundas River	Erosion and sediment inputs to streams.
Stokes and Crawford Rivers	Gullying and erosion.

Also in the Glenelg drainage basin, the RWC (1993) assessed the waterway stability in Bryan Creek downstream of Coleraine identified by the RWC, which are summarised below.

Bryan Creek Erosion Problems:

Category	Description	Length (m)
A	Severe erosion (where the erosion has progressed to a stage where a raw active vertical bank exists).	3 000
B	Moderate erosion (where erosion has not progressed to the vertical bank stage and a sloping bank capable of re-establishing with vegetation still exists).	3 000

An assessment of the Hopkins drainage basin waterway stability problems conducted by the South West Waterways and Drainage Management Study Steering Committee is summarised below.

Hopkins Drainage Basin Waterway Stability Problems:

Location	Problem/Action
Upper reaches of Hopkins, Fiery, Mt Emu and Trawalla Creeks	Severe gullying and erosion. Deteriorating older structures. Downstream sedimentation.
Tributary streams across the catchment	Isolated bank erosion.
Main trunks of Hopkins, Mt Emu, Fiery and Spring Creeks	Sediment inputs from tributaries and subsequent incision.
Chalicum, Fiery Nekeeya Creeks and parts of Hopkins River and Mt Emu Creek	Should remove sediment which is filling channels and causing bank erosion.

Source: Glenelg-Hopkins CMA

The waterway stability in the Portland drainage basin has not been thoroughly assessed (GHCMA, 2001. Some hotspots were identified in the Photographic Reference Set of the Review of Crown Frontage Occupations - Glenelg Region (Lumb et al. 1997).

Although the South West Waterways and Drainage Management Study Steering Committee (1996) identified waterway instability zones, they did not define the precise location where works need to be carried out. Furthermore, no waterway instability zones were identified for the Portland Basin which suggests further investigation is required.

The reports by Drummond & Associates (2000) for the Glenelg Basin, and by Southern Rural Water (1996) for the Hopkins Basin, developed specific programs of activity that defined both locations of works as well as cost estimates.

The order in which waterway stabilisation works need to be undertaken is detailed in the table below. The order was established in accordance with the Rapid Appraisal Method (RAM). The sites referred to in the table below are an example of the sites demonstrating instability within the region.

Waterway Instability RAM Assessment:

Site No.	Waterway	RAM Total
13	Wannon River	4.47
14	Wannon River	3.67
12	Hopkins River	3.54
6	Glenelg River	2.82
11	Hopkins River	2.80
4	Wannon River	2.63
7	Fitzroy River	2.37
15	Mt. Emu Creek	2.37
2	Rocklands Reservoir	2.08
3	Glenelg River	1.92
5	Wannon River	1.83
1	Glenelg River	1.74
16	Hopkins River	1.45
9	Shaw River	1.20
8	Eumeralla River	1.07
10	Darlots Creek	0.95
17	Hopkins River	0.80

Source: GHCMA (2001).

References:

GHCMA. (2001). Glenelg Hopkins Regional Waterway Management Strategy. GHCMA, Hamilton.

Drummond and Associates Pty. Ltd. (1992). Glenelg Catchment Waterway Management Study. Final Report. Victoria.

Rural Water Corporation (1993). Bryan Creek Rehabilitation Program. Environmental Management Section Rural Water Corporation.

South West Waterways and Drainage Management Study Steering Committee (1996). A Proposal for Waterway and Drainage Management in South West Victoria, The Curdies, Hopkins, Portland Coast & Glenelg River Basins, Victoria.

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