This technical report summarizes literature pertaining to the impacts of small-stream/ditch channel dredging and maintenance on fish and fish habitat. It describes the findings of a field trial that examined the benefits of MoE recommended mitigative best practices. The report concludes that the impact on fish and fish habitat from channel dredging is significant and that the recommended best practices are effective in reducing these impacts. Dredging of small lowland streams is a common maintenance activity within the agricultural lands of the lower Fraser Valley. Channel maintenance includes the removal of instream vegetation, riparian vegetation and sediment from small channelized streams, on a regular basis, to facilitate greater flow capacity and/or conveyance. Recent declines in the populations of anadramous coastal cutthroat trout and other salmonids in coastal regions of the Pacific Northwest are due, in part, to the degradation of freshwater habitats through human land-uses such as forestry, agriculture and urbanization. With continued growth of urbanization and agro-business in the lower Fraser Basin, these impacts continue to escalate. Programs to restore or protect natural functions to fish habitat must be evaluated and reported methodically if they are to succeed and provide useful information to habitat managers, stakeholders and user groups.
Barrett, Scott. 2006. Mitigating the Impacts of Channel Maintenance in the Lower Fraser Valley - 2003-2004 Field Trial and Literature Review. Ministry of Environment