RECONNAISSAN[ E

TERRAIN STABILITY APPING OF

V ASEUX CREEK AND SHUTTLEWORTI CREEK WATERSHEDS

PREP ARED FOR:

WEYERHAEUSER CANADA LTD .. I

OKANAGAN FALLS UN!

PREPARED BY:

Denny Maynard, M.Sc., P.<feo DENNY MAYNARD & A : SOCIATES LTD. North Vancouver, BC

~~EsS7;;.0.

II' 'I • ~ PROVINCE ( "

OF i D. E. MAYNAI1D :

~ BRITISH : \. Q COLUMB1A '\ ,r

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March,1999

TABLE OF CONTE TS

1.0 rnTRODUCTION ........................................................................................................... 1 2.0 SURVEY AREA: LOCATION AND PHYSIOG HY ................................................ 2 3.0 SURVEY l\1ETHODS AND RELIABILITY ................................................................... 4 4.0 GEOLOGY AND TERRAIN CLASSIFICATION ........................................................... 9

4.1 Bedrock Geology .......................................................................................................... 9 4.2 Geomorphic History .................................................................................................... 10 4.3 Terrain Materials, Landforms, and Processes .............................................................. 12

5.0 TERRAIN STABILITY ASSESSMENT ....................................................................... 17 6.0 REFERENCES .............................................................................................................. 22 7.0 ACKNOWLEDGMENTS .............................................................................................. 24

APPENDIX 1 Photographs

MAPS

Terrain classification and stability assessments are portra ed on the following B.C.G.S. TRIM map sheets: 82E 014, 023, 024, 025, 033, 034, and 035.

1.0 INTRODUCTION

Reconnaissance terrain stability mapping (R TSM) of the atersheds of Vaseux and Shuttleworth

creeks, in the Penticton Forest District, was requested b Weyerhaeuser Canada Ltd. for their

Okanagan Falls Unit. The project was funded by Forest R newal BC .

. The objective of the project was to identify all unstable r potentially unstable land areas at a

mapping scale of 1 :20,000 for the total watershed area of approximately 37,767 ha. This report

discusses the methods and results of the terrain stability m pping which involved a terrain survey

intensity level (TSIL) D analysis of the terrain landsca e and an assessment of the potential

effects of conventional forest harvesting on terrain stabilit .

Data and interpretations are presented at a level which e suitable for helping to plan forestry

development, but are not usually detailed enough t allow for site-specific, operational

recommendations and decisions.

Fieldwork for the project was carried out during early Oc ber 1998. Final interpretations of the

aerial photographs and digital map production occurred between December, 1998 and March

1999. All GIS work and final map and report preparatio were completed in late March, 1999;

the mapping has been submitted as both digital and hard- py (paper) products.

Denny Maynard & Associates Ltd. . Vaseux Creek and Shuttleworth Creek Watersheds Page 1

i I

2.0 SURVEY AREA: LOC liON AND PHYSIOGRAPHY

The adjacent watersheds of Vaseux and Shuttleworth cre ks drain westerly from the Okanagan

Highlands (figure 1), a subdivision of the Interior Plateau hysiographic region (Mathews 1986).

The Highlands consist of rounded mountains and ridges d rather uniform, low relief plateau

topography with a median elevation of about 1600 m (ph to 1); Mount Baldy, at 2300 m a.s.l. in

the southeastern comer of the map area is the highest oint, with most ridge-crest elevations

about 1800-1900 m.

Vaseux Creek drains the larger area, about 29,180 ha, and ·s fed by its main tributaries of Dutton,

Solco, Underdown, and McIntyre creeks. Shuttleworth watershed to the north of Vaseux, is

considerably smaller (about 8590 ha) and narrower, wi only two main tributaries (Maurice

Creek and Kilmer Creek from Allendale Lake) joining from the north side. The main-stem

channels are 20-30 km in length from their eastern head aters to Okanagan Valley; their mid to

lower reaches are entrenched in tightly-confined valleys hich drop relatively steeply from the

plateau surface to their fan apexes at about 350-400 m ele ation.

Forest stands are dominated by lodgepole pine in the ,ghland portion of the watersheds and

interior Douglas fir in the lower or western parts; pondef sa pine and western larch also occur as

secondary species. Much of the upland forest has been m I dified, historically by natural wildfrres

and more recently by clearcut logging (photo 1).

Precipitation on the Okanagan Highlands may be two to hree times that occurring along the dry

Okanagan Valley, much of it (greater than 50%) falling snow. Thus, snowmelt processes are

important factors in controlling streamflow runoffwhich pically peaks between April-June.

An extensive road network exists throughout most ofthes watersheds with only the lower valley

of Vaseux Creek being inaccessible to vehicle access. The R-201 main-line logging road

originates at the Weyerhaeuser Canada Ltd. mill site in (j)kanagan Falls, BC and follows up the

south side of Shuttleworth Creek. Ok Falls is located ~ the south end of Skaha Lake, 15 km

south of Pen tic ton, BC.

Denny Maynard & Associates Ltd. Vaseux Creek and Shuttleworth Creek Watersheds Page 2