DETAILED TERRAIN MAPPING WITH INTERPRETATIONS FOR SLOPE STABILITY, EROSION POTENTIAL AND SEDIMENT TRANSFER. DILLARD CREEK FRBC Project # TO-96187

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1 ,, DETALED TERRAN MAPPNG WTH NTERPRETATONS FOR SLOPE STABLTY, EROSON POTENTAL AND SEDMENT TRANSFER DLLARD CREEK FRBC Project # TO Prepared by Blythe Killam, B.Sc., G..T. For Weyerhaeuser Canada Ltd. Armstrong, B.C. February 1996 J.M. Ryder and Associates, Terrain Analysis nc. P.O. Box 45005, Dunbar Postal Outlet Vancouver, British Colu~bia, V6S 2M8

2 (1) ntroduction CONTENTS (2) Methods. (2.1) Terrain Mapping (2.2) Slope Stability and Erosion Potential nterpretations (2.3) Sediment Transfer nterpretations (2.4) Mapping Reliability (3) Physiography (4) Surficial Materials and Associated Landforms. (4.1) Till (M). (4.2) Colluvium (C). (4.3) Fluvial Materials (F, FA) (4.4) Glaciofluvial Materials (FG) (4.5) Organic Materials (0). (4.6) Undifferentiated Materials (U). (4.7) Bedrock (R) (5) Active Geomorphological Processes (5.1) Slow Mass Movement (-F) (5.2) Rapid Mass Movement (-R) (5.3) Gully Erosion (-V) (5.4) Surface Seepage (-L). (6) Stability, Erosion Potential & Sediment Transfer: Discussion. (6.1) Slope Stability and Erosion Potential. (6.2) Sediment Transfer (7) Recommendations Acknowledgments References Appendix 1: Annotated Photographs Appendix 2: Terrain Map Legend Pocket: Blackline Print of 1 : Scale Terrain and Slope Stability Map

3 J.M. Ryder and Associates, Terrain Analysis nc. Stc.# Dunbar Street. Vancouver, B.C. Mailing Addl"C8s: Box 45005, Dunbar P.O., Vancouver, B.C. V6S 2M8 Phone: (604) Fax: (604) w. E. Collen, R.P.F. FRBC Project Leader Weyerhaeuser Canada Grandview Nursery R.R. 3, St Anne Road Armstrong, B.C. VOE BO February 10, 1997 Re: Detailed Terrain Stability Mapping, Dillard Creek Community Watershed, Merritt Forest District Dear Mr. Collen: ncluded in this package: Air photos with detailed terrain mapping, soil drainage, and slope classes and slope stability, erosion potential, and sediment transfer interpretations. Two mylar and three paper copies of two maps, one shows the basic data: terrain, soil drainage, and slope classes, the other shows the derived ratings for slope stability, erosion potential, and sediment transfer. Two bound and one unbound copy of the terrain report. hope our product meets your expectations. Thank you for allowing JMRATA the opportunity to do this work for you. f you have any questions please call June or myself. Sincerely, 4~--- "'BlYthe Killam G.. T.

4 LOCATONAL MAP DLLARD CREEK WATERSHED Map scale 1 : Study area boundary Reference: Department of Energy Mines and Resources, Surveys apd Mapping Branch. Part of N.T.S. map sheet No. 92 NE 1978 and part of N.T.S. map sheet NC!. 92 SE

5 (1) NTRODUCTON The objective of this project was to prepare 1 : scale maps of terrain, slope stability, erosion potential, and sediment transfer for the Dillard Creek community watershed, about 4000 ha, for Weyerhaeuser Canada Ltd. Dillard Creek drains westerly into Missezula Lake which is located 32 km north of Princeton, B.C. t occurs near the boundaries of TRM sheets 92H. 078, 079, 088 and 089. Terrain mapping at terrain survey intensity level (TSL) C and interpretations for slope stability and erosion potential were carried out according to provincial standards. Terrain mapping was done by interpretation of 1: scale air photos followed by field checking. Ratings for slope stability, erosion potential and sediment transfer were determined by analysis of terrain information and further air photo interpretation. This report augments the information shown on the maps. t provides descriptions of terrain mapping methodology and mapping reliability (Section 2), a general overview of the physiography of the study area (Section 3), additional information about surficial materials and processes (Sections 4 and 5), and criteria used for slope stability, erosion potential, and sediment transfer interpretations (Section 6). A summary of findings is presented in Section 7. (2.1) Terrain Mapping (2) METHODS Terrain mapping followed the standard British Columbia procedures for terrain classification (Howes and Kenk, 1988), mapping methodology (RC, 1995) and 5-class stability mapping (Forest Practices Code, 1995). Preliminary terrain mapping was done by interpretation of 1: scale air photos (30BCC91 053: ,30 BCC91059: ,142,143, , 30BCC91 060: 44-48). Three field crew days were spent in the area during October 15 to 18, The study area was traversed by vehicle and on foot (Figure 1). Traverses were made through representative polygons of different surficial materials and slopes, with attention focused on those relatively steep slopes likely to be designated as stability class V or V. All field observation sites are shown on the terrain maps. "Ground check sites" were visited, and are distinguished from "visually inspected sites" where reliable visual observations were made from a distance. Field data forms are available upon request. At ground check sites, soil pits were dug where natural exposures such as slide scars, tree-throw hollows, or road-cut exposures were not available for examina1ion. Back in the office, terrain mapping on air photos was corrected in light of field observations. Soil drainage and slope steepness classes were added, 3

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