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Guidelines for stabilising streambanks with riparian vegetation / Bruce Abernethy and Ian D. Rutherfurd.

By: Abernethy, Bruce, 1964-.
Contributor(s): Rutherfurd, I. D. (Ian D.) | Cooperative Research Centre for Catchment Hydrology (Australia).
Material type: materialTypeLabelBookSeries: Technical report: no. 99/10Publisher: Clayton, Vic. : Cooperative Research Centre for Catchment Hydrology, ©1999Description: v, 30 pages : illustrations ; 30 cm.ISBN: 187600651X; 9781876006518.Subject(s): RIVER BANKS | STREAMS | WATER QUALITY | RIPARIAN ZONES | LAND USE | AGRICULTURE | PLANTING | VEGETATIONHoldings: GRETA POINT: 556.53:502.171 ABE Also available as PDF document via the Internet.
Contents:
1. Introduction -- 1.1 Purpose of the guidelines -- 1.2 Principles of using vegetation for bank erosion control -- 1.3 Terms -- 2. Guidelines for determining minimum riparian zone widths -- 2.1 Recommendation -- 2.2 Decision tree -- 2.3 Worked example -- 3. Riparian forest structure -- 3.1 Overstorey -- 3.2 Understorey -- 3.3 Groundcover -- 3.4 Macrophytes -- 4. Riparian vegetation and streambank stability -- 4.1 Mass failure -- 4.2 Fluvial scour -- 4.3 Subaerial preparation -- 5. Assessment of existing riparian condition -- 5.1 Reach assessment -- 5.2 Bank assessment -- 5.3 Vegetation assessment -- 6. Riparian plantation design -- 6.1 Background -- 6.2 Site considerations -- 7. Maintenance regimes -- 8. Alternatives to vegetation -- 9. Bibliography -- Appendix A: Assessment tables -- Table 1: Catchment level assessment -- Table 2: Reach level assessment -- Table 3: Site level assessment -- Table 4: Intervention -- Table 5: Reassessment.
Abstract: This report provides guidelines for establishing riparian plantations that will stabilise riverbanks, within acceptable limits. Riparian vegetation interacts with a range of geomorphological, geotechnical, hydrological and hydraulic factors to affect the type and extent of riverbank erosion. The enhanced lateral channel stability offered by well-vegetated riparian zones can also reduce the need for engineered stabilisation and heavy maintenance. The density and type of riparian vegetation cover strongly influence all aspects of riverbank erosion. Riparian forests are typically composed of overstorey, understorey, groundcover and macrophyte species. Vegetation condition is assessed in terms of the Raine and Gardiner (1995) ‘traffic light’ classification: green, yellow red for riparian vegetation in good, intermediate and poor condition. The main consideration when designing riparian revegetation works for bank stability is continuity of cover. Different types of vegetation affect different processes, so it is imperative to assess the dominant erosion process correctly so that appropriate species can be selected for stability. All of the erosion processes that act on banks can be grouped together into three erosion-domains. (1) Subaerial erosion (erosion caused by processes external to the stream such as cattle, or rain splash). (2) Scour (removal of individual sediment particles or aggregates by flow). (3) Mass-failure (slumps). An underlying philosophy of these guidelines is that the dominant bank erosion process changes downstream along a river due to changes in channel scale. The guidelines stipulate minimum riparian zone establishment-widths. Minimum riparian zone widths are calculated individually for each site on the basis of the present site conditions (observed bank geometry) and the past erosion history (measured or estimated bank erosion rate). The basic allowance for the width of any riparian plantation designed for bank stabilisation should not be less than 5 m measured onto the floodplain from the bank crest. As banks become higher they become less stable. Hence, in addition to the basic allowance, we recommend that the width of riparian strips also include a height allowance not less than the height of the bank measured vertically from the bank toe to the bank crest. Time must be allowed for the plants to grow before they can begin to stabilise the bank, so where banks are actively eroding an establishment allowance should also be included in the final riparian zone width. The establishment allowance is determined by multiplying the erosion rate by the time required for the plantation to mature. The material presented in this document is summarised and collated into a series of tables that can be used to guide and focus the practitioner’s approach to planning riverbank stability works with vegetation. The report does not account for ecological, or sediment and nutrient filtering, or other criteria that may dictate specific riparian management regimes beyond those appropriate for bank stabilisation. The width and character of plantations designed for other criteria may be quite different than plantations designed for bank erosion control. Thus, these guidelines should be considered in the light of other requirements for riparian zone management.
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Holdings
Item type Current library Call number Copy number Status Date due Barcode
BOOK BOOK WELLINGTON BOOKS 556.53:502.171 ABE 1 Available B021028

"September 1999"

"Technical report 99/10"--cover title.

Bibliography: pages 24-25.

1. Introduction -- 1.1 Purpose of the guidelines -- 1.2 Principles of using vegetation for bank erosion control -- 1.3 Terms -- 2. Guidelines for determining minimum riparian zone widths -- 2.1 Recommendation -- 2.2 Decision tree -- 2.3 Worked example -- 3. Riparian forest structure -- 3.1 Overstorey -- 3.2 Understorey -- 3.3 Groundcover -- 3.4 Macrophytes -- 4. Riparian vegetation and streambank stability -- 4.1 Mass failure -- 4.2 Fluvial scour -- 4.3 Subaerial preparation -- 5. Assessment of existing riparian condition -- 5.1 Reach assessment -- 5.2 Bank assessment -- 5.3 Vegetation assessment -- 6. Riparian plantation design -- 6.1 Background -- 6.2 Site considerations -- 7. Maintenance regimes -- 8. Alternatives to vegetation -- 9. Bibliography -- Appendix A: Assessment tables -- Table 1: Catchment level assessment -- Table 2: Reach level assessment -- Table 3: Site level assessment -- Table 4: Intervention -- Table 5: Reassessment.

This report provides guidelines for establishing riparian plantations that will stabilise riverbanks, within acceptable limits. Riparian vegetation interacts with a range of geomorphological, geotechnical, hydrological and hydraulic factors to affect the type and extent of riverbank erosion. The enhanced lateral channel stability offered by well-vegetated riparian zones can also reduce the need for engineered stabilisation and heavy maintenance. The density and type of riparian vegetation cover strongly influence all aspects of riverbank erosion. Riparian forests are typically composed of overstorey, understorey, groundcover and macrophyte species. Vegetation condition is assessed in terms of the Raine and Gardiner (1995) ‘traffic light’ classification: green, yellow red for riparian vegetation in good, intermediate and poor condition. The main consideration when designing riparian revegetation works for bank stability is continuity of cover. Different types of vegetation affect different processes, so it is imperative to assess the dominant erosion process correctly so that appropriate species can be selected for stability. All of the erosion processes that act on banks can be grouped together into three erosion-domains. (1) Subaerial erosion (erosion caused by processes external to the stream such as cattle, or rain splash). (2) Scour (removal of individual sediment particles or aggregates by flow). (3) Mass-failure (slumps). An underlying philosophy of these guidelines is that the dominant bank erosion process changes downstream along a river due to changes in channel scale. The guidelines stipulate minimum riparian zone establishment-widths. Minimum riparian zone widths are calculated individually for each site on the basis of the present site conditions (observed bank geometry) and the past erosion history (measured or estimated bank erosion rate). The basic allowance for the width of any riparian plantation designed for bank stabilisation should not be less than 5 m measured onto the floodplain from the bank crest. As banks become higher they become less stable. Hence, in addition to the basic allowance, we recommend that the width of riparian strips also include a height allowance not less than the height of the bank measured vertically from the bank toe to the bank crest. Time must be allowed for the plants to grow before they can begin to stabilise the bank, so where banks are actively eroding an establishment allowance should also be included in the final riparian zone width. The establishment allowance is determined by multiplying the erosion rate by the time required for the plantation to mature. The material presented in this document is summarised and collated into a series of tables that can be used to guide and focus the practitioner’s approach to planning riverbank stability works with vegetation. The report does not account for ecological, or sediment and nutrient filtering, or other criteria that may dictate specific riparian management regimes beyond those appropriate for bank stabilisation. The width and character of plantations designed for other criteria may be quite different than plantations designed for bank erosion control. Thus, these guidelines should be considered in the light of other requirements for riparian zone management.

Also available as PDF document via the Internet.

GRETA POINT: 556.53:502.171 ABE

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