Instream wood management

Instream wood management involves the realignment, relocation and/or removal of instream large wood (> 0.1 metre in diameter and 1 metre in length). In general, it is strongly encouraged to leave instream wood where it is. Instream large wood should only be managed if it has collected to the extent where it threatens infrastructure, or it is directing flows into an exposed bank causing unacceptable erosion.

The general aim of managing instream large wood should be to manage the risk that it poses rather than its removal. Therefore, the realignment and relocation of instream wood are preferred management methods. The removal of instream wood should be the last resort. In some high risk circumstances removal may be acceptable, especially if it is an introduced species. These species may not provide the same habitat, hydraulic or geomorphic benefit as native timber.

Potential benefits from this intervention:

• Reduces risk to instream infrastructure (e.g. bridges, piers).
• Reduces localised erosion.
• Retention of large wood instream provides habitat.

Potential negative implications from this intervention:

• Repositioning can reduce the complexity of instream large wood which may result in a loss of important habitat niches.
• Can result in a reduction of hydraulic roughness and increase instream power.
• Can lead to the perception that all instream large wood should be realigned in the direction of flow, relocated or removed.

Intervention considerations:

• Seek appropriate specialist advice and check legal obligations (e.g. permits).
• Existing in-channel large wood should generally be left where it is. This timber is providing an important ecological and hydraulic function in its current position.
• Instream large wood management should only be undertaken if it poses an unacceptable risk.
• Instream large wood that is orientated across a channel will generally have more hydraulic influence (e.g. increase in hydraulic roughness and reduction in stream power) compared to large wood orientated in a downstream direction.
• The emphasis of managing instream large wood should be on the realignment or relocation of the large wood rather than its removal.
• Determine if other infrastructure is threatened and whether it could more efficiently be moved rather than protected.
• Consider if instream large wood is likely to recollect in the same location.
• Safety of volunteers and employees including seasonal exposures (e.g. heat) and high risk areas (e.g. crocodile presence in waterways or areas with soil contaminant risks).

Additional information

Publications:

Brooks, A. 2006. Design guideline for the reintroduction of wood into Australian streams. Land & Water Australia. Canberra.

Price, P. and Lovett, S. 1999. Riparian Land Management Technical Guidelines. LWRRDC. Canberra.

Zhang, N. and Rutherfurd, I.D. 2020. The effect of instream logs on river‐bank erosion: Field measurements of hydraulics and erosion rates. Earth Surface Processes and Landforms, 45(7), pp.1677-1690.

Last updated: 10 June 2022