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Stream morphology, changes and recovery, following the 1992 washout-flow Donna Creek Mackenzie Forest District
Bird, Steve A.
Donna Creek, situated in north central B.C. west of Mackenzie B.C., was severely impacted by a large magnitude landslide during spring runoff, June 1992. Catastrophic seepage face erosion and subsequent debris flow surges transported 422,500 m3 of material into Donna Creek. Large quantities of sediment entering Donna Creek, combined with high spring runoff, triggered a debris flood that transported debris 6 km down Donna Creek to Manson River. The event was determined to have been caused by the capture and routing of water along roads constructed for forest development. An intensive survey was undertaken along the valley flat (stream and flood plain) to document and assess changes in stream channel morphology. The data provided a detailed documentation of channel impacts/morphometric changes from this huge landslide event. The longer term channel response to this large magnitude event is not known. A wealth of information in channel measurements, 35mm photography and air photography exist for Donna Creek between the landslide event and the Manson River This detailed collection of morphometric data shortly after the landslide event now provides a unique opportunity to re-measure and document channel changes and stream recovery. The knowledge gained through a documentation of the stream channel processes will have provincial wide implications in similar stream systems for riparian assessment, up slope management practice and stream channel rehabilitation techniques. Research objectives: 1. Re-measurement of the morphological features and changes experienced in Donna Creek channel 15 years after the 1992 event. 2. Comparison of the measured 1992 data to the 2007 data to determine the changes and recover rates for Donna Creek; 3. Describe sediment transport and channel processes; 4. Assessment of the suitability of channel works undertaken in 1992 in light of present channel changes and sediment transport; 5. Preparation of an extension report for forest practitioners and scientific publication for the earth science community/professionals undertaking channel assessments. Field survey for this research will follow the methods as presented in the report prepared by Hogan and Wilford (1992) for the previously defined stream reaches. Channel survey will include measurements and observation on the longitudinal profile (thalweg distance, water surface, water depth, bar type, bar extent, bank height, and bank full width), large organic debris (quality, orientation, function), surface sediment morphology and morphology description according to Hogan (1989) and Hogan and Bird (1998). GIS data capture and mapping of the channel will also be undertaken for the years with quality air photographs (1989, 1992, 1994, 1996, and 2002) following methods summarized by Ashmore and Church (1998). The research will provide necessary scientific information on stream channel process and recovery from landslides. The information will help in decisions as to the most suitable rehabilitation techniques for similarly impacted streams and will help provide information toward the development of practices dealing with riparian zone rehabilitation province wide.
Report Number
Interim research report
Appendix I Donna Cr maps 1989-2007
Appendix II Donna Cr mosaic 1989-2007

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