Indicator: Riparian vegetation

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What the results tell us for Tumut

See also:
| Pest plant species | Streambank disturbance |

For a map showing the riparian vegetation over the entire Region, Contact us for details of the full report for the Australian Capital Region (available only on CD-ROM).

The Stressed Rivers Assessment Reports (DLWC, 1999) have not provided assessments for the rivers and streams in Tumut Shire, but supporting comments indicate the condition of riparian vegetation (Table 1), which is highly variable throughout the Shire. Catchments which are generally undisturbed, such as the Goodradigbee River and the Tantangara River catchments have good ratings whilst streams and rivers draining highly modified landscapes have riparian vegetation that is in fair to poor condition (Table 1).

Approximately 66% of Tumut Shire falls within unregulated subcatchments. Not all subcatchments listed in Table 1 lie wholly within the Shire. Subcatchments are of differing size, in terms of area and volume of water flowing through them.

About the data

Assessments and comments on riparian vegetation condition and stress for unregulated streams have been provided by the NSW Department of Land and Water Conservation (DLWC). The data are reported in the Stressed Rivers Assessment Report for the Murrumbidgee catchment. The report was published by the DLWC, in Sydney, 1999. Details about the data sources and assessment process are contained in each of these reports. A brief summary about some of the data follows:

Riparian vegetation stress rating

For all catchments except the Murrumbidgee a stress rating has been determined where data were available. Aerial photography was used to assess riparian vegetation, using 1996 colour coverage at 1:25 000 scale (stereo pairs). Native vegetation only was assessed for presence and absence within a 20m buffer strip on both sides of the main stream. Exotic vegetation has not been considered in the assessmentThe criteria for assessment are identified in Table 2.

Within the Murrumbidgee catchment the condition of riparian vegetation was assessed against the following aspects:

Cover of streambank and width of the riparian zone - A measure to identify the amount and extent of riparian vegetation cover

Indigenous cover - A measure to identify the level of weed invasion in the riparian zone as well as the loss of native riparian vegetation due to grazing, planting of exotics and other pressures.

Connectivity - A measure to assess the linkages between remnant patches of riparian vegetation and between the riparian vegetation and other remnants of indigenous vegetation in the landscapes.

Structural integrity - A measure to assess the level of degradation of the riparian vegetation system, in terms of indigenous cover, width of cover, connectivity and diversity of canopy layers.

The Stressed Rivers Assessment Reports provide data on unregulated catchments only. DLWC has defined unregulated streams as "those which do not have major rural dams, primarily for irrigation supply downstream and therefore most water users rely on natural flows for their water supplies" (DLWC, 1999:1). Flows in unregulated streams however, can be and are still affected by town water supply, hydro-electric dams, weirs and other water diversions.

Description: What does 'riparian vegetation' measure?

Which data are collected?

• proportion of streams with intact or regenerated riparian vegetation and the condition thereof (expressed in terms of 1st, 2nd, 3rd stream order)

Why do we report this indicator?

The riparian zone is the strip of land along either side of a stream. Although there is some debate how wide this strip needs to be, it is established that a well-vegetated riparian zone is important because of the potential benefits to the water quality, streambank stability and stream ecology. The condition and extent of riparian zone vegetation is of interest to State of the Environment reporting because of the importance of riparian vegetation to the condition of streams.

Riparian vegetation can reduce the amount of sediment and associated pollutants entering the stream. A well vegetated streambank is resistant to streambank erosion due to the extra stability provided by the roots and other plant material, and because it can reduce flow velocity at the edges of the stream.

Loss of riparian vegetation, through clearing, livestock grazing or recreational uses, means that these benefits are lost and the overall condition of the stream can decline. For this reason, riparian zone revegetation is an important aim of government agencies and many community groups.