Dr: Diameter of Rootwad

Dp: Basal Diameter Dr: Diameter at the tip

+

_ es

Lp: Length of the rootwad

$+ .

Lp: Length of the bole

Project: | Steelhead Haven Landslide, North Fork Stillaguamish river approximately RM 20.0

Typical: Definition of log characteristic metrics

Design By Tracy Drury Notes Date
Drawn By Tracy Drury 1/25/00



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Future vegetated area

Steelhead Haven landslide

Log revetment A .
Storage for landslide materials

New river channel Low flow water surface elevation

ls 200 ft rl 500 ft >< 500 ft 50 ft

Cross-section

1250 ft

Project: | Steelhead Haven Landslide, North Fork Stillaguamish river approximately RM 20.0

Typical: | Expected post project conditions for cross-section A - A’

Design By Tracy Drury Notes Date

Drawn By Tracy Drury 1/19/00



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Goldbasin Landslide:

Slope failures that occurred in 1998 and 1999 filled the channel that was toe cutting the
landslide. This has forced the river away from the landslide and has relocated the river in
a desirable location. The objective of revetment A is to prevent the river from eroding its
way back through these fines to the toe of the slope re-establishing undesirable
conditions. Revetment B is positioned to increases the residence time of flows draining
the slide by creating a settling pond for fines. The exact location of revetment B may
change based upon optimal site conditions to achieve this goal.

The expected post project conditions would be the same as post construction conditions
with the exception of scour pool development local to revetment A. Revetment
construction, specifications, and log metrics for Goldbasin slide are the same as those
presented for Steelhead Haven. The specifications for revetment A at both sites are
identical. Similarly, the specifications for revetment B at Goldbasin are the same as the
specifications for revetments B, C, and D at Steelhead Haven.




Preliminary design proposal for treatment of the
Hazel and Goldbasin Landslides

prepared by

Tracy Drury

for

United States Army Corps of Engineers

and

The Stillaguamish Tribe of Indians

The proposed treatment of these landslides is a series of Large Wood Debris (LWD)
revetments that will eliminate toe cutting of the landslides and prevent failure materials
from being immediately transported downstream. These revetments will be similar in
structural composition to the Phase I and II Engineered Log Jam (ELJ) projects that have
been constructed on the North Fork Stillaguamish (NFS) river. The enclosed document
includes preliminary plans for applications at each landslide, project specifications, and
initial budgets.


Steelhead Haven Landslide

Landslide material storage

Pseudo beaver dam complex

Mobile debris accumulation

< in stagnation point

Project: | Steelhead Haven Landslide, North Fork Stillaguamish river approximately RM 20.0

Typical: | Plan view of expected post project conditions

Design By Tracy Drury Notes Date
Drawn By Tracy Drury 1/19/00



Log revetment D

Log revetment C

Ne

Log revetment B

Right Bank

Existing rip rap

Low flow water surface

_

\

___$§ ase

100 ft 500 ft rl 250 ft | 600 ft 50 ft
B B'
Cross-section
<t- >
1500 ft
Project: | Steelhead Haven Landslide, North Fork Stillaguamish river approximately RM 20.0
Typical: | Placement of log revetments B, C,and D and expected conditions for cross-section B - B’
Design By Tracy Drury Notes Date
Drawn By Tracy Drury 1/23/00



B

Log revetment B

Log revetment A

Log revetment C

Log revetment D

Existing Channel

Project: | Steelhead Haven Landslide, North Fork Stillaguamish river approximately RM 20.0

Typical: Plan view of existing conditions and proposed project placement

Design By Tracy Drury Notes Date

Drawn By Tracy Drury 1/19/00



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Revetment A

Revetment B
Goldbasin Landslide

Project: | Goldbasin Landslide, South Fork Stillaguamish river at Verlot

Typical: Plan view of existing conditions and proposed project placement

Design By Tracy Drury Notes Date

Drawn By Tracy Drury 1/27/00



Goldbasin Landslide

Log revetment B US Forest Service campground

Former channel filled by landslide failure
Low flow water surface elevation
y Me
77 Nah
PRERA| y
+
100 ft 150 ft 150 ft 50 ft
; +l. + i
B B'
Cross-section
it >
450 ft

Project: | Goldbasin Landslide, South Fork Stillaguamish river at Verlot

Typical: | Proposed placement of log revetment B and existing conditions for cross-section B - B'

Design By Tracy Drury Notes Date

Drawn By Tracy Drury - 1/27/00



Hazel / Steelhead Haven Landslide:

The Hazel landslide is commonly known as the Steelhead Haven slide to the local
community. Because of this and that other projects in the Hazel area have been
constructed and/or are under consideration, I will refer to this landslide as Steelhead
Haven from this point on. The series of revetments proposed at the Steelhead Haven
landslide would eliminate toe cutting of the slide and create setting ponds for fine
materials delivered to the mainstem from the multiple streams that drain the slide area. In
addition, these structures will create adult Chinook holding habitat similar to that of the
North Fork Stillaguamish (NFS) Engineered Log Jams (ELJs) and mainstem off-channel
habitat currently lacking in the NFS. Revetment A would isolate the landslide from the
mainstem NFS and eliminate the toe cutting which is considered a critical factor in the
stability of the landslide as a whole. The structure will also create deep pools critical for
adult Chinook holding. Revetments B, C, and D will create a series of settling ponds to
help decrease the magnitude of fine sediments delivered to the mainstem NFS. These
revetments will also create a pseudo beaver-pond network providing mainstem off-
channel habitat. Initially the area created between the landslide and revetment A will be
quite expansive and largely a habitat component. As the creeks drain the slide and
deliver fine sediment, an increasing volume of this area will be converted to fine
sediment storage. Over time it is possible that the entire area between revetment A and
the landslide will be converted to fine sediment storage. It is also possible that
stabilization of the landslide will occur prior to filling the entire storage area and that
some off channel habitat will remain over time. Uncertainty remains with respect to the
eventual equilibrium condition as well as the time frame of development. An additional
habitat component that will develop is a log raft in the stagnation point that will be
created by the interaction of the river and revetment A. This will result in an excellent
feeding zone with cover for juveniles and adult stream fishes.


Table of Contents:

Hazel / Steelhead Haven

Plan view of existing conditions and proposed project placement

Proposed placement of log revetment A and existing conditions for cross-section A-A’
Expected post project conditions for cross-section A-A’

Placement of log revetments B, C, and D and expected conditions for cross-section B-B’
Plan view of expected post project conditions

Cross-section of revetment A

Definition of log characteristic metrics

Specifications for revetments

Estimated Cost

Goldbasin

Plan view of existing conditions and proposed project placement

Proposed placement of log revetment A and existing conditions for cross-section A-A’
Placement of log revetments B and expected conditions for cross-section B-B’

Estimated Cost


Log revetment

Stacked members A

Low flow water
surface elevation

25 ft

mar 60 - 80 ft >|

Project: | Steelhead Haven Landslide, North Fork Stillaguamish river approximately RM 20.0

Typical: | Cross-section of revetment A

Design By Tracy Drury Notes Date

Drawn By | Tracy Drury 4/19/00



Goldbasin Landslide

4 Log revetment A US Forest Service campground

Former channel filled by landslide failure
Low flow water surface elevation
i

100 ft 150 ft 150 ft
es rh
A A'
Cross-section
<¢ >
450 ft

Project: | Goldbasin Landslide, South Fork Stillaguamish river at Verlot

Typical: | Proposed placement of log revetment A and existing conditions for cross-section A - A’

Design By Tracy Drury Notes .Date

4/27/00

Drawn By Tracy Drury