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| Suburban | River | Low-cost | Riverbank erosion | |
| DESCRIPTION | |
| Measures
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Live stakes are an effective and low-cost streambank protection measure where site conditions are not complicated and construction time is limited. They will encourage vegetation from the surrounding area to naturally colonize the river bank and are very often used to anchor and enhance the performance of other bank erosion control materials. The stakes are inserted into the face of the embankment where provided that they are properly prepared and planted, they will take root and grow into bushy plants or trees. Once the roots have developed they spread into a live mat which stabilizes the embankment by reinforcing the soil layer and also through extracting moisture from the soil. Live stakes can be used in combination with dead stakes which are also called posts and are usually cut from untreated hardwoods for better durability. They are usually thicker and longer than live stakes and since they penetrate deeper, provide more immediately effective bank reinforcement where rapid erosion stabilization is required. However, over the longer term, the live stakes will perform better provided that the resulting vegetation continues to grow well. |
| Location
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This is an effective streambank protection measure for the repair of small earth slips and slumps in banks that are frequently wet. Other uses are:
● Enhance conditions for the natural colonization of vegetation from the surrounding plant community. ● Can be used to peg down and enhance the performance of other surface erosion control materials. ● Stabilize intervening areas between other soil bioengineering techniques, such as live fascines. ● Not suitable for rocky slopes, because the stakes cannot be embedded properly, and vegetation will not establish. |
| Design options and performance
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The main aim is to protect the surface from erosion and to reinforce the soil. However, the effectiveness of the measure depends on the depth at which cuttings can be placed and the depth to which the roots can penetrate. The growth rate of roots is related to the number and density of cuttings placed and the native soil characteristics. Time is needed for the roots to grow and become fully effective. Installation is best accomplished in late autumn when plants become dormant, in the winter, or early spring before budding growth begins. Live stakes can be used to anchor and enhance the effectiveness of other erosion protection measures including fascines, coir rolls, berms,d geotextile fabrics. |
| Feasibility criteria
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● Technical design: The size of the cuttings typically varies from 2.5 cm to 5 cm in diameter and from 60 cm up to 1.8 m in length depending on availability and site application. The live stakes are placed in rows perpendicular to the slope face and parallel to the river flow, with a distance between rows of 60-100 cm. A pilot hole is first made with an iron bar or similar tool to facilitate the stake insertion into the ground and then the live cutting is inserted manually into the hole, by tamping the surrounding soil. Materials harvested on site should be installed after a short time, and preferably on the same day they are cut, to prevent the plant from drying out, while materials grown in a nursery can be maintained in moist conditions before being installed.
● Soil media: n/a ● Soil slope: suitable for steep slopes ● Surface cover: n/a ● Materials: Indigenous plant species are preferred but willow species are often used for live stakes since they root rapidly and will start to dry out the bank soon after installation. Other types of woody vegetation suitable for this technique include dogwood, cottonwood and alder. |
| Operation and maintenance | Replacement of some vertical poles which fail to grow may be needed but otherwise, no maintenance is required unless the vegetation impacts other activities in the stream or river bank. |
| Cost and benefits | This is a low-cost measure that becomes more effective at stabilizing the bank as the root systems and foliage grow and can be used in conjunction with other more complex erosion control methods. The main benefits are:
● Once the vegetation becomes established it helps to slow the flow of water in high water flow stages; ● Staking a streambed helps dry out a wet unstable bank and allows it to become more stable; ● Improves the aesthetics of the river bank, adds to the biodiversity of the site and creates new habitats for wildlife. |
| Design solutions | Live cuttings and pole plantings can be used to re-establish vegetation on streambanks, providing erosion control and other benefits. Cuttings are taken from species that root quickly, such as willow and should grow almost immediately to form a protective vegetative layer which helps to prevent soil erosion by reinforcing and binding soil particles together and by extracting excess soil moisture. This is a highly effective measure that can be easily installed and maintained on a wide variety of sites. It applies to all sizes of streams and a wide range of bank characteristics. However, it is most appropriate where erosion is light and washout is unlikely. Live staking is a mainly preventative measure and should be employed before severe erosion problems occur. Because live plant cuttings are more resistant to erosion than traditional seeding techniques, it is beneficial to use them on the lower portions of the bank to moderate flow velocities. They can enhance the performance of surface erosion control materials such as coir mats, create favorable conditions for the natural colonization of vegetation from the surrounding plant community, stabilize intervening areas between other soil bioengineering techniques (such as live fascines), and produce streamside habitat. This practice should be used jointly with other restoration techniques. Success is also dependent on the selection of appropriate plants for the site environment. |
| Environmental performance | ● Repairs small earth slips and slumps that frequently are wet;
● Enhances the performance of geotextile fabric by serving as pegs to hold fabric down; ● Enhances conditions for the natural colonization of vegetation from the surrounding plant community; ● Stabilizes areas among other bioengineering techniques, such as live fascines. |
| Sources | ● ICEM, 2017. Slope Protection Designs and Specifications, TA-8102 VIE: Promoting Climate Resilient Rural Infrastructure in Northern Vietnam, Technical Report No. 18.
● Mississippi Watershed Management Organization, 2017. A Guide to Bank Restoration Options for Large River Systems: Part II Bioengineering Installation Manual. ● United States Department of Agriculture – Natural Resources Conservation Service, 1996. Engineering Field Handbook, Chapter 16: Streambank and Shoreline Protection. ● LaRiMiT – Norwegian Geotechnical Institute (NGI), 2016. NBS for Erosion Control. |
Originally developed under the ADB ‘TA-9417 VIE: Secondary Green Cities Development Project – Output 2: Demonstrated sustainable and resilient development in Hue, Ha Giang and Vinh Yen’. Adapted for the UN-CTCN project ‘Climate risk assessment for subnational adaptation and establishment of a local climate information system for climate change adaptation (LISA) in Cambodia’.
