6.11 Naas Management Unit 6.11.1 Site 41 Issue: Bed and bank erosion Location: E 0685848 N 6058358 Waterway: Management Unit: Naas River

Facing downstream from Bobeyan Rd bridge Facing upstream from Bobeyan Rd bridge Condition Assessment:

Erosion along both banks is present at this location of the Naas River. It has been assessed as having a high connectivity for fine sediments due to fine grained sediments eroded from channel banks input directly into channel flow.

Risk Assessment: Likelihood Consequence Trajectory Risk 4 4 4-5 64-80 Risk Rating: Extreme Management Option: Install rock beaching to manage bank erosion. Fencing and vegetation to be undertaken in consultation with the landholder.

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6.11.2 Site 42 Issue: Gully delivering fine sediment to river Location: E 0687487 N 6053278 Waterway: Naas River and gullies Management Unit: Naas River

Large areas of fine sediment deposition Naas River tributary gully, facing upstream

Naas River, facing downstream Rock gabion headwalls on Naas Road

Sand deposition and bank erosion Bank erosion along the Naas River Condition Assessment:

This Naas River is undergoing active incision and reworking of sediments stored in the stream bed, resulting in the mobilisation of a large amount of sand material. Fine sediments are also being reworked from the channel banks. Incoming tributaries are also delivering significant volumes of sediment to the Naas River. The Naas River and incoming tributaries have been assessed as having a high connectivity for fine sediment transfers through to the .

Risk Assessment: Likelihood Consequence Trajectory Risk 132

4 4 4-5 64-80 Risk Rating: Extreme Management Option: Undertake sediment extraction in gully to reduce sediment delivery. Construct pile fields to manage migration of main waterway. Fencing and revegetation of site in consultation with landholder.

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6.11.3 Site 43 Issue: Fine sediment in banks Location: E 0687099 N 6055622 Waterway: Lower Naas River Management Unit: Naas River

Active bank erosion evident Further bank erosion downstream Condition Assessment:

Bank erosion is occurring along the length of the Naas River contributing a relatively high amount of fine sediments downstream. These bank erosion problems are represented at this site, but they extend over kilometres. A high connectivity for fine sediment transfers from eroding banks to the Murrumbidgee River has been assessed. Fine grained sediments eroded from the channel banks are input directly into channel flow, and once in the water column are likely to conveyed efficiently to the Murrumbidgee River contributing to water quality issues.

Risk Assessment: Likelihood Consequence Trajectory Risk 4 4 4-5 64-80 Risk Rating: Extreme Management Option: Construct rock beaching to manage bank erosion. Fencing and revegetation recommended in consultation with the landholder(s).

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6.11.4 Site 44 Issue: Coarse sediment movement Location: E 0687129 N 6051854 Waterway: Naas tributary Management Unit: Naas River

Downstream of the crossing Farm crossing, facing upstream Condition Assessment:

The tributaries of the Naas River are transporting large volumes of sand as bedload. At this location the channel bed has aggraded behind crossing. This site has been assessed as having a high connectivity for fine sediments.

Risk Assessment: Likelihood Consequence Trajectory Risk 4 4 3 48 Risk Rating: Very High Management Option: Undertake managed extraction of local sediment. Fencing and revegetation of site in consultation with landholder.

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6.11.5 Site 45 Issue: Eroding sand bank Location: E 0687305 N 6052700 Waterway: Upper Naas River Management Unit: Naas River

Naas River, facing downstream Widespread bank erosion along Naas River Condition Assessment:

At this site the Naas has experiencing bed incision, bank erosion and channel widening. The right eroded bank is 8 m high and extends over a distance of 800 m. A mixture of sand and fine silt/clay sediments are being eroded from the channel banks. Assessed as having high connectivity for fine sediments, fine grained sediments eroded from bank input directly into channel flow.

Risk Assessment: Likelihood Consequence Trajectory Risk 4 5 4 80 Risk Rating: Extreme Management Option: Install rock beaching to manage bank erosion and channel widening. Fencing and revegetation recommended in consultation with the landholder.

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6.12 River Management Unit 6.12.1 Site 46 Issue: bed erosion Location: E 703062 N 5996476 Waterway: gully Management Unit: Numeralla River

Looking upstream at erosion head Looking downstream over gully Condition Assessment:

This site consists of gully erosion on a tributary which is not clearly connected to the Numeralla River. The secondary erosion head appears to be deepening. IT would appear stock exclusion coupled with revegetation may stabilise the erosion head.

Risk Assessment: Likelihood Consequence Trajectory Risk 2 2 3 12 Risk Rating: Low Management Option: No structural works recommended at this site. Fencing and revegetation recommended in consultation with the landholder.

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6.12.2 Site 47 Issue: Bed and Bank erosion Location: E 707567 N 5985374 Waterway: Carlaminda Road gully Management Unit: Numeralla River

Erosion downstream of road Bank erosion upstream of road Condition Assessment:

This gully is connected directly to the Numeralla River. The gully has minor bed deepening occurring and moderately active bank erosion. It appears likely the current active erosion has worsened during high flow events in 2012. The site can be stabilised with localised rock beaching, battering, fencing and revegetation.

Risk Assessment: Likelihood Consequence Trajectory Risk 3 2 3 18 Risk Rating: Moderate Management Option: Undertake localised bank stabilisation with toe rock beaching and battering. Couple with fencing and revegetation to stabilise the gully.

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6.12.3 Site 48 Issue: Sediment transport Location: E 0710278 N 5995960 Waterway: Numeralla River (township and Management Unit: Numeralla upstream)

Numeralla River, facing upstream Numeralla River, facing downstream Condition Assessment:

Coarse sand and gravel/cobbles (up to 10cm in diameter) are present at this location. Sandbars lack vegetation however the banks appear well stabilised with moderate vegetation present. There have been no reports of channel widening with the recent flood events. Additionally, there are no indications of there being significant inputs of fine sediments. This site is assessed as having a high connectivity for transport of fine sediments.

Risk Assessment: Likelihood Consequence Trajectory Risk 4 2 3 24 Risk Rating: Moderate Management Option: Stabilisation of in stream sediment via construction of pile fields and establishment of in-stream revegetation. Also fencing and revegetation of the riparian zone.

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6.12.4 Site 49 Issue: Sediment transport Location: E 0697040 N 6002681 Waterway: Numeralla River Rose Valley district Management Unit: Numeralla

Numeralla River facing downstream View across Numeralla River

Facing upstream from Rosebrook Rd crossing Facing downstream from Rosebrook Rd crossing Condition Assessment:

Channel bed and banks appear stable and well vegetated. This site has been assessed as having high connectivity for fine sediments due to direct transfer of fine sediments along Numeralla River with high connectivity to Murrumbidgee.

Risk Assessment: Likelihood Consequence Trajectory Risk 4 2 2 16 Risk Rating: Moderate Management Option: No structural works recommended. Fencing and revegetation of site recommended in consultation with the landholder.

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6.12.5 Site 50 Issue: Gully and bank erosion, sediment transport Location: E 0703304 N 6000352 Waterway: Rose Valley Creek Management Unit: Numeralla

Upper reach of Rose Valley Creek, facing upstream Upper reach of Rose Valley Creek, facing downstream

Gully erosion, mid reach Lower reach of Rose Creek

Facing upstream of Numeralla River at Rose Valley Facing downstream of Numeralla River at Rose Rd crossing Valley Rd crossing Condition Assessment:

Active incision and widening of creek reworking fine alluvial sediments is occurring along the Rose Valley. Rose Creek is assessed as having a medium connectivity for fine sediments. Whilst some fine sediment may be transferred through to the Numeralla River, there is a natural potential for these sediments to be deposited across a large alluvial fan prior to flows entering Numeralla.

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Risk Assessment: Likelihood Consequence Trajectory Risk 3 3 2-5 18-45 Risk Rating: Moderate to Very High Management Option: Stabilise alluvial fan using pile fields, construct rock beaching to manage bank erosion. Fencing and revegetation of site in consultation with landholder.

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6.13 Paddys River Management Unit 6.13.1 Site 51 Issue: Bank erosion and sedimentation Location: E 675436 N 6076780 Waterway: Tidbinbilla Creek Management Unit: Paddys River

Sedimentation downstream of the bridge Channel braiding

Major widening and sedimentation Major bank erosion Condition Assessment:

This site is located on Tidbinbilla Creek at Tidbinbilla Station. Downstream of Gilmore Road major channel development has occurred following recent floods with the channel now two to three times wider than the original channel. The channel has chosen a short course abandoning major outside bends with significant erosion and sedimentation. The channel is braided in a number of locations. If left unmanaged, the creek will continue to change course in subsequent major flow events, with significant sediment movement downstream likely. To manage the site, pile fields coupled with fencing and revegetation could be utilised to maintain a preferred channel alignment.

Risk Assessment: Likelihood Consequence Trajectory Risk 4 5 5 100 Risk Rating: Extreme Management Option: Install pile fields to manage migration of creek alignment. Undertake sediment removal to assist in definition of waterway alignment. Fencing and revegetation to be undertaken in consultation with the landholder.

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6.13.2 Site 52 Issue: Bed and bank erosion Location: E 0679874 N 6071561 Waterway: Punchbowl Creek Management Unit: Paddys River

Existing creek crossing Localised sediment build-up

Bank erosion downstream of crossing Bank erosion along right-hand bank Condition Assessment:

This valley comprises a series of valley storages which are partially incised by channels. Sediment delivery to Murrumbidgee is broken up by these series of valley storages. This site is assessed as having medium connectivity for fine sediments. There is a high probability that eroded fine sediments are being deposited and stored along the valley of Punchbowl Creek.

Risk Assessment: Likelihood Consequence Trajectory Risk 2 3 3 24 Risk Rating: Moderate Management Option: Establish in-stream vegetation to trap sediment. Complete fencing and riparian revegetation of site in consultation with landholder.

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6.13.3 Site 53 Issue: Coarse sediment Location: E 0683345 N 6074050 Waterway: Paddys River Management Unit: Paddys River

Downstream of crossing Upstream of crossing Condition Assessment:

Upstream of bridge crossing over Punchbowl Creek, banks are generally stable. Recent floods have resulted in deposition of sand at the channel margins (benches/floodplain). This site is assessed as having medium connectivity for fine sediments; there is a high probability that eroded fine sediments are being deposited and stored along valley of Punchbowl Creek.

Risk Assessment: Likelihood Consequence Trajectory Risk 3 3 3 24 Risk Rating: Moderate Management Option: No structural works recommended. Fencing and revegetation of site recommended in consultation with the landholder

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6.14 Management Unit 6.14.1 Site 54 Issue: Bed and bank erosion Location: E 0698339 N 5975290 Waterway: Upper Rock Flat Creek Management Unit: Rock Flat Creek

Facing downstream of gully Facing upstream of gully Condition Assessment:

Grassed stable channel along Rock Flat Creek. This creek has been assessed as having a low connectivity for fine sediments due to long travel distance to Murrumbidgee water extraction point with opportunities for storage along channel margins and across floodplain storages.

Risk Assessment: Likelihood Consequence Trajectory Risk 2 2 2 8 Risk Rating: Low Management Option: No structural works recommended. Fencing and revegetation of site recommended in consultation with the landholder.

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6.14.2 Site 55 Issue: Sediment transport Location: E 0697788 N 5997896 Waterway: Lower Rock Flat Creek Management Unit: Rock Flat Creek

Facing downstream from Cottage Hill Rd Large gravel material visible on creek bed Condition Assessment:

This site along Rock Flat Creek features several gravel and cobble bars. Active bank erosion is occurring along the left-hand bank is also evident, with the banks exhibiting a silty/sandy material composition. The creek is open to cattle access. The creek has been assessed as having medium connectivity for fine sediments. There is a high potential for deposition and storage of sediments along valley at channel margins and across the floodplain.

Risk Assessment: Likelihood Consequence Trajectory Risk 3 3 4 36 Risk Rating: High Management Option: Localised rock beaching to be installed to manage bank erosion. Fencing and revegetation of site recommended in consultation with the landholder.

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6.15 Strike A Light Creek Management Unit 6.15.1 Site 56 Issue: Sediment transport Location: E 0701980 N 6022208 Waterway: Strike A Light Creek Management Unit: Strike A Light Creek

Strike A Light River, facing downstream from the Strike A Light River, facing upstream from the Jerangle Rd crossing Jerangle Rd crossing Condition Assessment:

This site along Strike A Light River is moderately stable given the high vegetation presence. It has been assessed as having medium connectivity for fine sediments, as it is a considerable distance from Murrumbidgee. There are no indications of significant fine sediment transport in this section of the river.

Risk Assessment: Likelihood Consequence Trajectory Risk 3 2 2 12 Risk Rating: Low Management Option: No structural works recommended. Fencing and revegetation of site recommended in consultation with the landholder.

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6.15.2 Site 57 Issue: Bank erosion Location: E 0707203 N 6021819 Waterway: Wangrah Creek Management Unit: Strike A Light Creek

Upper reach of Wangrah Creek, facing upstream Existing rock chute beside Jerangle Rd

Upper reach of Wangrah Creek, facing downstream Upper reach of Wangrah Creek facing upstream Condition Assessment:

Four metre high banks and fine sediment bars are present at this site. This eroding creek has been assessed as having a high connectivity for transfer of fine sediments. There remains little potential for sediment storage within the channel between here and the Murrumbidgee River.

Risk Assessment: Likelihood Consequence Trajectory Risk 4 3 3 36 Risk Rating: High Management Option: Install Rock beaching to manage bank erosion. Fencing and revegetation of site in consultation with landholder.

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