1. PLACER EXAMINATION TECHNIQUES
STREAM MAPPING
PLACER EXAMINATION TECHNIQUES

2. What to Map?

3. Stream Morphology
Represents: flow regimes, deposition and erosion trends, bedrock characteristics, stream gradients
Influences: gravel volumes, gold deposition
Determines: dredge size, sample sites, sample representation

4. Stream Morphology Units
GSA Bulletin, March 1990, v. 102, p
Pools
Riffles
Rapids
Cascades
GSA Bulletin, May 1997, v. 109, no. 5, p
Cascades
Bedrock
Step pool
Plane bed
Pool riffle
Dune riffle
Also use glide and bedrock chute

5. Pool – Flow is tranquil and bed elements are submerged

6. Riffle – roughness is small scale, but small hydraulic jumps form over submerged and partially exposed particles

7. Rapid – roughness is large scale with channel-spanning steps

8. Cascade- Well-developed step-pool sequences and extensive supercritical flow

9. Mapping Features Stream width, length, and trend
Stream bed and bank material
Water depth
Gravel bars
Distinctive features

10. Mapping Features – cont.
Evidence of mining activity
Claim monuments
Structures, roads, trails
Gravel benches and terraces
Tributaries and springs

11. When to Map?

12. When to Map Stream flows and channel change thru season
High flows can be hazardous
Gravel amenable to dredging changes thru season
Best to map in early part of the season
Low flows could result in underestimating gravel resources
Early mapping allows time to develop logistics

13. Mapping Techniques Mark your endlines Two or three people
Water proof paper
Scale ft/inch
Get in and walk the stream or swim
Downstream
Tie in survey
Flag endlines

14. Mapping Technique – cont.
Two person
Three person

15. Equipment Waterproof paper Measurement devices Flagging Camera
Notebook and Clipboard
Measurement devices
Hip chain, tape, range finder
Flagging
Camera
GPS receiver
Dry bags
Water shoes, wet suit

16. Stream Characterization
After mapping is completed
Morphologic units
Lengths and percentages
Dredging sites
Select sample sites
Gravel volumes

17. Claim Boundaries Different ways used to describe Vague descriptions
PLS
Metes and bounds
Gulch
Vague descriptions
May exclude parts of stream
Consider layout when selecting sample sites