1. Short Course on Gullies and Streams Tom Millard, Vancouver Forest Region

2. Objectives Report on recent studies Provide an update on GAP changes

3. Debris definitions Woody debris - “slash” Landslide debris - includes woody debris, rocks, soil, mud Debris flows and debris torrents - types of landslides

4. Water transport of woody debris Woody debris floats downstream during floods Small WD easier to float than large slash Flood may also transport small or moderate amounts of sediment Channel bed and banks remain relatively unchanged Occurs in any gradient channel

5. Debris flow (or debris torrent) Debris flows almost always starts as a landslide into a gully channel Needs a steep channel to start in (>30%) Almost all wood and sediment is eroded - channel often scoured to bedrock Often no channel bed or banks remain Woody debris does not start a debris torrent

6. History of GAP Started with a district request to identify gullies that would respond badly to logging Became a guidebook in 1995, first formal procedure for identifying different gully hazards and risks to downstream resources Recognized in 1995 that the procedures were preliminary and needed to be tested Studies undertaken from 1996 - 2000 have resulted in changes to the GAP

7. Section 2: Water Transport Potential

8. Water transport potential assessment Objective: to identify channels that will be disturbed if logged, or if woody debris is left in the channel. Disturbance: Erosion of channel banks and bed, woody debris jams, avulsions (breakouts), transport of woody debris into fish reaches

9. No slash movement

11. Little slash movement

12. Little - moderate slash movement

13. Moderate slash movement

15. Extensive slash movement

16. Severe slash movement

19. Old assessment method

20. Van. Island & Boston Bar Slash in Streams Studies Objective - to identify channels that become disturbed if slash is left in the channel after yarding is completed Channel disturbance = high water transport potential

21. Vancouver Island study location Near Nitinat Lake, Southwest Vancouver Island Winter floods from rain storms Mostly rocky terrain, coarse grained soils “Nitinat”

22. Boston Bar study location All streams located with Anderson River basin, east of Boston Bar Almost Interior conditions Snowmelt dominated floods Deep, fine-grained till soils “Anderson”

23. Slash in Streams Study Methods Select streams logged 5 - 15 years ago, with the slash left in the stream Inventory amount and types of disturbance Collect data on width, depth, gradient, and other variables that may be used to predict disturbance Streams <5 m wide

24. Disturbance Large sizes of woody debris transported Large amounts of woody debris transported Frequent and large woody debris jams Channel and bank erosion

25. Severe disturbance

26. Predictor variables Channel width and depth Gradient Channel location Channel and bank types Size of sediment moving

27. Results Nitinat (Vancouver Island) study - 99 stream reaches Anderson River (Boston Bar) study - 42 stream reaches

37. Significant predictors of channel disturbance Channel width, depth, and area - width is best Size of sediment transported in the stream

38. Channel width and size of woody debris moved

39. Jam volume and width: Nitinat

40. Jam volume and width: Anderson

41. Sediment size and woody debris size moving

42. Jam volume and sediment size: Nitinat

43. Jam volume and sediment size: Anderson

44. What about gradient? Gradient has no real effect Steeper streams have more channel roughness Lower gradient streams are more able to float woody debris

45. Useful predictors of water transport potential Channel width (could also use channel area, but no better) Size of sediment moving in channel In these two studies, size of woody debris moving in channel was used as an response variable, but - can also be used as a predictor prior to harvesting

46. Water transport assessment and cleaning strategies