Strengths

  • Useful on steep, fast-flowing streambanks.
  • Can restore riparian vegetation and habitat.
  • Enhance conditions for colonization of native plants.
  • Serves as habitat for birds, animals, insects and other organisms that in turn are fed upon by fish and other higher organisms.
  • Provides shade to the stream - lowering water temperatures, offering protection from predators, and generally improving fish habitat.
  • Very cost-effectiveness, using locally available materials and low-cost labour in comparison to more elaborate civil engineering works.

Limitation

  • As brush mattresses use dormant cuttings, they must be installed during the non-growing season.
  • Should be initiated in conjunction with a revegetation strategy as it is more difficult to establish supplementary vegetation once the mats become established.
  • Not recommended for streambanks steeper than 2.5:1 nor should they be used on streambanks where mass wasting (movement) occurs.
  • Must have a secure toe.
  • Only effective on upper slopes, and large amount of live material required to cover bank.

Brush mattress

Application: Bridges, canals, culverts and drains, dykes, embankments, floodgates, stormwater outflow

Description: A brush mattress is a protective mat of interlaced live branches placed on a slope or streambank and staked sufficiently to hold it in place using wire or twine, live stakes, and dead stout stakes. It is a simple and cost effective means of protecting the soil surface on slopes from erosive forces through the creation of a dense stand of woody vegetation which will eventually root along the entire length of the structure and provide long-term vegetation stabilization. The brush mattress has the potential to immediately slow velocities along the bank and accumulate sediment flowing down the streambank which can improve non-point pollution control. This technique is often used in conjunction with other methods that protect the toe of the slope from undercutting, such as wattles, tree or rock revetments.

Contribution to climate resilience: A brush mattress protects the soil surface of slopes from erosion via root stabilization, and by slowing down surface water velocity and increasing infiltration. By accumulating sediment, it can also reduce road maintenance and improve the quality of water in runoff entering streams. Because it is constructed using local labour and locally available materials, it can be repaired quicker than traditional civil engineering structures.

Supplementary sources of information:

http://projects.geosyntec.com/npsmanual/Fact%20Sheets/Brush%20Mattresses.pdf

http://www.ontariostreams.on.ca/PDF/OSRM/Tech12.pdf

http://www.spa.usace.army.mil/Portals/16/docs/civilworks/regulatory/Stream%20Information%20and%20Management/ERDC%20Brush%20Mattresses.pdf

http://www.ernstseed.com/products/bioengineering/brush-mattresses-and-wattles-fascines/

Background image credit: ICEM

This resilience-building measure is sourced from the Water Resource Adaptation Guide (2019) published by the National Council for Sustainable Development at the Ministry of Environment in Cambodia. The full Guide is available to download at URL https://ncsd.moe.gov.kh/sites/default/files/2019-10/Water%20Resources%20Adaptation%20Guide_March%202019_En.pdf