E8A Engineering Consultants Ltd.

Transcription

1 E8A Engineering Consultants Ltd. SILVER CREEK FIRE i DETAILED TERRAIN STABILITY MAPPING SALMON ARM FOREST DISTRICT! Project No #255,1715 Dickson Ave., Kelowna, B.C. CANADA V1Y9G6 - Telephone (250) FAX (250) ! Internet: ke/owna@eba.ca

2 DETAILED TERRAIN MAPPING '''lth I~TERPRETATIONS FOR TERRAIN STABILITY, Sl-RFACE EROSION POTENTIAL, LANDSLIDE-INDUCED STREAM SEDI:\IE~TATION, AND SEDIMENT DELIVERY POTENTIAL SAL;\ION ARM FOREST DISTRICT. Submitted to: TOLKO INDUSTRIES LTD., FEDER.-\TED CO-OPERATIVES LTD., AND THE S~l-\LL BCSINESS FORESTRY ENTERPRISE PROGRAM, BRITISH COLU!vlBIA MINISTRY OF FORESTS Prepared by: EBA ENGINEERING CONSULTANTS LTD. Kelown~ B.C. Project No March, 1999 This project has been funded by FOREST RENEWAL BRITISH COLUMBIA

3 I T ABLE OF CONTENa-S I PAGE I 1.0 INTRODUCTION METHODS Terrain Mapping Mapping Reliability....' Terrain Stability Interpretations...: Surface Erosion Potential Interpretations Landslide-Induced Stream Sedimentation Interpretations Sediment Delivery Potential Interpretations PHySIOGRAPHy Topography and Bedrock Geology I Landscape Evolution and Deposition of Surficial Materials... 7 I 4.0 SURFICIAL MATERIALS AND ASSOCIATED LANDFORMS Till (M) Glaciofluvial Materials (FG)... ~ Colluvium (C) Fluvial Materials (F) Glaciolacustrine Materials (LG) Undifferentiated Materials (U)..., Organic Materials (0)... ~ ACTIVE GEOMORPHOLOGICAL PROCESSESl Rapid Mass Movement (-R, -R") and Slow Mass Movement (-F, -F") Debris Slides (-Rs, -R"s) and Debris! Flows (-Rd, -R" d) Rockfall (-Rb, -R"b) Slump in Bedrock (-Fm, -F"m)... l Slump-earthflow in Surficial Materi~ls (-Fx, -F"x) Gully Erosion (-V) Meltwater Channels (-E) TERRAIN STABILITY, SURFACE EROSION POTENTIAL, LANDSLIDE-INDUCED I STREAM SEDIMENTATON, AND SEDIMENT DELIVERY POTENTIAL: I DISCUSSION AND MANAGEMENT IMPLICA1iIONS Terrain Stability- Discussion... ~...: The Effects of Forest Fires on Terr~ Stability Surface Erosion Potential- Discussion... ~ The Effects of Forest Fires on Surface Erosion Potential Terrain Stability and Surface Erosion Potential- Management Implications Landslide-induced Stream Sedimentation arid Sediment Delivery I I

4 I I I 7.0 RECOMMENDATIONS ACKNOWLEDGMENTS...: REFERENCES CLOSURE APPENDICES Appendix A Appendix B Appendix C Appendix D... Annotated Photographs... Legend... Air photo and TRIM sheets used... Field Forms (separate document) FIGURES Figure 1... Traverse Routes Figure 2... Previous Mapping in Adjacent Watersheds Terrain and Interpretive Maps, although not bound with this document, accompany this report.

5 L' I May, INTRODUCTION, The objective of this project was to prepare detaill terrain stability maps for the area burned during the Silver Creek fire, which had not freviously been terrain mapped. This information is presented on 1 :20,000 scale tery-ain and interpretive maps. EBA Engineering Consultants Ltd. (EBA) completed lfe project for Tolko Industries Ltd., Federated Co-operatives Ltd., and the Small Business Forestry Enterprise Program, Salmon Arm Forest District. Forest Renewal BritiSl:h Columbia provided ~e funding for this project. Terrain mapping and interpretations for terrain st~ ility class, surface erosion potential class, landslide-induced stream sedimentation classj and sediment delivery potential class were carried out according to the provincial standkds (Section 2.0). Terrain mapping was done on approximately 1:15,000 scale, black! and white air photos (post-fire) and 1: 17,000 scale, colour air photos (pre-fire) by air photo interpretation, followed by field checking. This report augments the information that is sh~' on the maps completed for this project. It explains the methodology used, guidelines for assessing the interpretations, and mapping reliability (Section 2.0), and provid~1 an overview of the physiography of the study areas (Section 3.0). Additional info I ation about surficial materials and geomorphological processes (Sections 4.0 and 5.0 and a discussion of terrain stability, surface erosion potential, landslide-induced stream I sedimentation, and sediment delivery potential ratings (Section 6.0) are also included. R~commendations for forestry planning and management that arise out of this terrain analysis are discussed in Section METHODS! T. M I errald appldg I The terrain mapping methods followed the guideli~es and standards set by the Resources Inventory Committee (RIC, 1996) and the Forest Practices Code guidebook (FPC, 1995). Terrain classification followed the provincial systei (Howes and Kenk, 1997). The centre of the project area is located 10 km southwest of Salmon Arm, B.C., and includes the following watersheds: Moutell, A, B, p, Wallensteen, Kernaghan, D, Grier, the north fork of Silver Creek, and most of Wall Cr~ek and Harold's Brook totalling 8165 hectares (see Figure 1). The area burned during the fire includes Silver Creek, Gordon I Creek, and Mt. Ida well, but have been excluded from this project as they were mapped during two projects completed in 1997 (see Table ~). The project area boundary of this project edge-matches to the project area boundary ~f the mapping in adjacent watersheds (including Palmer Creek) to provide seamless terr. n mapping coverage for this area of the Salmon Arm Forest District (see Figure 2).

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44