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Log Crib Check Dam Performance under Multiple Debris-FlowLoadings – East Gate Landslide, British Columbia, CanadaMatthias Busslinger1*, Matthias Jakob2**†, Richard Singer3, and Ryan Calder4
1

Geoinfra Ingenieure AG, Churerstrasse 44a, 8808 Pfäffikon SZ, Switzerland
BGC Engineering Inc., 500-980 Howe Street, V6Z 0C8 Vancouver, BC, Canada
3
McElhanney Ltd., 200 - 858 Beatty Street, V6B 1C1 Vancouver BC, Canada
4Parks Canada Agency, 301 3rd Street West, V0E 2S0 Revelstoke BC, Canada
2Abstract. Check dams are used in gullies to prevent vertical downcutting of the thalweg. Check dams built
as log crib structures are common in steep creeks prone to floods or debris floods. Recent experience withperformance of log crib check dams subject to debris flow loadings is less common, as those check dams
are often made from reinforced concrete, steel or masonry. This paper summarizes our experience with sixlog crib check dams built in a gully at East Gate Landslide, between Revelstoke and Golden, BC, Canada.
The log crib check dams are subjected to multiple debris flow events every year. The project started as apilot study and the design is adjusted before the next construction season, based on performance experience
with previously built structures.

1 What is a Log Crib Check Dam?
The term Log Crib Check Dam applies to a log crib
structure arranged transverse to the creek with“Konsolidierung”(German:consolidation)functionality. In the context of torrent control,
Konsolidierung means preventing thalweg downcutting
and supporting adjacent, unstable slopes with thesediment retained upstream of the barrier. Log crib
check dams (Fig. 1) are three-dimensional lattice
structures, where transverse and longitudinal logs areconnected by steel nails in current practice (notchingwas traditionally used). The crib is filled withcompacted soil providing stiffness and weight to thestructure. Geotechnically, it functions like a gravity
retaining wall.
Double- or multi-walled log crib systems are called“Krainerwände (crib walls)” in Austria, while in
Switzerland they are typically referred to as“Holzkasten” (wooden box).

feeder gully confluence, the Main Gully developed. This
led to a self-amplifying cycle of downcutting and sideslope landslides (Fig. 2). Since 1999, several debris
flows reached the TCH annually. About three quartersof the sediment is mobilized within the Main Gully
located downstream of the EGL deposit.
The TCH is administered by Parks Canada Agency(PCA). Debris is retained immediately east of the TCH
by two moustache-shaped retention basins (MRB) (seeFig. 2). Annual clean-out volumes are typically about
40’000 m3 but may range up to 80’000 m3 (i.e. thestorage capacity of the MRB).
To reduce the sediment removal efforts and cost, A
three-component gully erosion mitigation strategy wasdeveloped, consisting of; 1) diversions to reduce surface

2 Project Description
2.1 Mitigation Approach
The opportunity to study log crib check dams underdebris flow loading arose at the East Gate Landslide(EGL) within the Glacier National Park, located 3.5hours west of Calgary along the Trans-Canada Highway(TCH). The EGL is a 2,000,000 m3 rock slump that
occurred in 1997, travelled about 1,000 m, but did notreach the TCH at the valley bottom. Downstream of the* Corresponding author: matthias.busslinger@gmail.com†Dr. Matthias Jakob passed away on October 16, 2022.

Fig. 1 Check dam series in the Main Gully at East Gate
Landslide near the end of the 2021 construction season (Photoby McElhanney, R. Singer). For higher quality figures contact
corresponding author or try link to conference presentation.

© The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0(https://creativecommons.org/licenses/by/4.0/).

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3.1 Pilot Study in 2020
A pilot check dam was constructed in 2020 to test
several design parameters and performance under site
conditions. Fig. 3 shows the 2020 Pilot Check Dam after
construction and late in the 2021 freshet.
3.2 Performance Fall 2020 to Freshet 2021
Fig. 2 Reference locations at East Gate Landslide. The pilot
check dam (#1) and check dams #1 to #5 are indicated inyellow.

Overall, the check dam performed well under the debrisflow loading. The 2020 Pilot Check Dam experienced
its first debris flow event (5’700 m3 debris) on
November 5, 2020 without damage; some minor
deposition occurred on the right (in flow direction) wing
wall. However, a ground sill made from logs across thechannel and located several metres downstream to holdriprap in place was destroyed. This was likely due toinsufficient lateral embedment.
During the 2021 freshet, the check dam survived several
debris flow events (individual volumes not surveyed).
By end of May 2021, a total sediment volume of about
29,000 m3 (surveyed) was retained in the MRB. Videocamera recordings documented a range of debris flowhydrographs at the 2020 Check Dam. Some were fairly“smooth” surges, while other surges exhibited highlyvariable discharge (or velocity) even within a singlesurge. This is possibly due to large boulders causing
temporary blockages until momentum pushed themforward again.
The following performance and key issues on thepilot check dam were noted:
1. Global Stability: The check dam performed
satisfactorily and survived the debris flowloadings. No significant global displacements
were noted.
2. Toe Scour: Fig. 3 shows significant toe scour
occurred. In addition, the foundation soil waswashed out under the front mud sill (i.e., lower
most stretcher). This poses a stability concern. Toescour may have been accelerated by loss of theground sill during the November 5, 2020 event.
However, the scour hole may have formed
regardless.
3. Wing wall overtopping: The pilot weir wasintentionally sized relatively small because thenarrow, V-shaped gully cross-section limited theweir dimensions that could practically be built.
Mud deposits, a leaning log, and displaced roll of
flexible pipe are clear evidence of wing wall
overtopping by debris flows, indicating that thepilot weir is undersized. Based on review of video
recordings, wing wall overtopping is interpreted to
be of short duration (a few seconds) and did not
result in abutment scour.
4. Abrasion: Significant abrasion and wear is evident
on the logs (Fig. 3):
a. The corduroy lining of the weir bottom wasinstalled with round tops and flat milled
bottoms. The round tops of the corduroy logs
were abraded and flattened by an estimated 2 toflows in the Main Gully, 2) log crib check dams tocontrol gully grade, limit undermining of gully sideslopes caused by downcutting, and 3) revegetation ofside slopes and eventually part of the slumped landslide
mass to improve slope stability and reduce surface
erosion.
Since the project is located in Glacier National Park,
PCA wanted to use locally (and nearby) sourced timber
for check dam construction rather than concrete or othermaterials. Since experience with log crib check dams inlarge debris flow prone gullies is very limited in Canada,
PCA choose an adaptive implementation approach,which began with a pilot construction in 2020. Per endof the 2021 construction season 6 check dams were built(Fig. 1). As part of the multi-year erosion mitigation
program in the Main Gully we anticipate construction ofroughly 60 log crib check dams and several diversions,as well as re-vegetating a significant portion of thecurrently 60,000 m2 of disturbed gully side slopes.
2.2 Project Settings
The flows in the Main Gully incise into colluvium
deposited by pre-historic landslides. The over steepened
side slopes creep, flow or slide into the Main Gully,
supplying sediment for transport downstream.
The Main Gully starts where several feeder gullies
coalesce (Fig. 2) at the Confluence (elevation 1,200 m).
The bottom of the Main Gully coincides with the MRB
inlet at the fan apex (elevation 890 m), resulting in a
vertical relief of 310 m. The horizontal length of theMain Gully is 725 m (or 780 m inclined). The averagechannel gradient of the Main Gully is 43%.
The catchment area reporting to the MRB inlet is0.68 km2, with a catchment relief of 1,269 m.
Detailed change detection using sequential LiDAR
and photogrammetry data between 2015 and 2019,
showed that the creek alignment in the Main Gully
shifted by as much as 17 m horizontally and eroded 14m vertically.

3 Performance Experience
The experience described below focuses on theperformance of the check dams under debris-flow- andgully side slope loadings. For a more general descriptionof other lessons learned refer to [1].

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B)

Ground sill

Fig. 3 A) 2020 Pilot Check Dam at end of construction (Photo Sept. 5, 2020 by BGC, J. Stratton), note; the downstream log groundsill was destroyed in the Nov. 5, 2020 debris flow event. B) Photo of 2020 Pilot Check Dam taken on June 9, 2021, note; destroyed(sacrificial) corduroy in weir, abrasion and wear on the dam face and scour hole undermining the check dam (Photo by Pierre Friele).

5 cm. The right half of the weir the corduroy
was destroyed.
b. Channel facing sides of the wing walls also
show wear and abrasion but remained intact.
c. Debris has abraded concave shapes into thestretchers and worn the front of exposed
headers on the battered, downstream dam face.
5. Other Wear: A piece of wood was split of thelowermost front stretcher of the left wing wall (Fig.
3), presumably from a point load (boulder or log).
Grade stabilization: The channel base above theweir has infilled with sediment as intended at about
3.5H:1V or 16⁰.
6. Wing wall protection: Backfilling the wing walls
appears to have been a successful strategy to avoid
direct, high dynamic loads on the back of the wingwalls.

• Steel plate armouring made from 12 mm thicksheets of 1.2 m by 2.4 m, was added on top of thecorduroy logs of the weir base and parts of the weirsides (Fig. 6A) to protect against excessive wearfrom the abrasive debris flows. The weir crest wascantilevered far enough in downstream direction toproject the flows beyond the dam face.
3.4 Performance Fall 2021 and Winter 2022
The check dams fared reasonably well through the fall2021 and winter 2022, however in early springlandslides induced large loads on the check dams (Fig.
4). As anticipated, the uppermost check dam (#6 withoutwing walls) was buried by a 13,000 m2 landslide
entering from the left side slope (Fig. 5). By April 26,
2022 the thalweg was pushed to the right of check dam#6, because the right bank had melted earlier (southernexposure) than the centre and dense ice directed thethalweg to the right. To avoid check dam outflanking,the ice was removed and timber deflection logs wereplaced obliquely to the creek flow direction.
Subsequently, the thalweg shifted back on the centre ofcheck dam #6, although by May 11, 2022 #6 was still
not visible under the debris.
Prior to the onset of the debris flow “season” inSpring 2022, another large landslide entered the Main
Gully obliquely from the right bank (Fig. 6A). This
landslide moved at least 10 m (visual estimate) and
induced significant earth pressures on check dams #3,#4, and #5. Fig. 6B illustrates how the right wing walls
were sheared off the lower portion of the check dam androtated forward (in-plan view) by the landslide.
No significant changes were noted for check dams
#1 and #2.

3.3 Design Modifications in Summer 2021
Fig. 1 shows the completed check dam works by end of
the 2021 construction season: repairs were made to thePilot Check Dam (#1), another 4 check dams were built
completely (#2 to #5), while the uppermost (#6) was
only constructed to the weir crest height without wingwalls. Key design modifications made for the 2021
construction season were:
The scour hole underneath the Pilot Check Dam
was filled with rocks and the voids were filled withwet mix grout (200 mm slump number) supplied
by a helicopter drop bucket. Toe scour protection
was repaired by neatly placing large rip rap andconstructing a ground sill made from laterally wellembedded logs. For check dams #2 to #5 a“splashpad” was also made from grouted riprap.

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https://doi.org/10.1051/e3sconf/202341506002#5#1Fig. 5 The wing walls on Check Dam #6 were not built at theend of the 2021 construction season. the landslide enteringfrom the left bank (looker’s right) buried the check dam andnearly caused outflanking. (Photo April 26, 2022 by PCA,
Ryan Calder).

Fig. 4 Looking upstream in the Main Gully. Check dams #1 and#5 labelled for reference. A large landslide enters from the left
(looker’s right) near #5. Another landslide enters from the rightaffecting check dams #3 to #5. (Photo July 13, 2022 byMcElhanney, Richard Singer).

A)

B)

#5

#4

#4

Fig. 6 A) Looking across check dams #4 and #5 at a large landslide moving from the right side slope (looker’s left) directly towards
the camera. Note; the deformations of the right wing walls, while the lower portion of the check dams remained intact. B) Looking
along the face of check dam #4 at the right wing wall which was sheared off and rotated (in-plan view) as the embedded far-end of
the wing wall was moved by the landslide while the weir-end moved less. (Photos May 11, 2022 by PCA, Ryan Calder).

#5Fig. 7 Looking upstream at check dams #2 to #5: Weirs are
partially blocked by debris. No significant toe scour visible. The
upper part of the right wing wall on #4 is missing. (Photo July 13,2022 by McElhanney, Richard Singer).

4Fig. 8 Check dam #5 is loaded and deformed by landslides
from the left (looker’s right) and right. (Photo July 13, 2022
by McElhanney, Richard Singer).

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design improvements with grouted riprap. The
relatively small debris volume mobilized during
the 2022 freshet may also be a factor. A further
contributing factor could be that the debris flows
reached their sediment carrying capacity and could
not entrain more sediment.
• The steel plates provided good abrasion protection.
To ascertain continued gully stabilization, it is now
pertinent to continue check dam construction andinterrupt the cycle of downcutting and side slope
landsliding until stable side slopes have established.

3.5 Performance Freshet 2022
The majority of check dam damage in the spring of 2022
was not attributable to debris flows but rather thelandslide issues described above. The landslide from theright continued shearing off the right wing walls at #3,#4, #5. The large landslide entering further upstream
from the left also sheared check dam #5 in the lower left
side (Fig. 8).
During the 2022 freshet, debris flows deposited
approximately 6’000 m3 of debris (visual estimate) in
the Moustache Retention Basin. This is significantly lessthan the typical annual clean-out volume of about
40’000 m3. Debris flow-related damage included:• Some damage to the weir steel armouring(deformations in general and a torn off sheet at #4).
• Ryan Calder of PCA observed a damaging event
during his May 27th field inspection; knocking thetop of the left wing-wall off at check dam #4(compare Fig. 4 (before) and Fig. 7 (after)).

The authors would like to acknowledge the support of Parks
Canada Agency for this ongoing project.
The BGC Engineering Inc. team – in particular Alex
Strouth – provided constructive feedback and inputs
throughout this project.
Seppi Berwert-Lopes of Belop GmbH in Sarnen,
Switzerland kindly offered his wealth of experience with log
crib check dams.
McElhanney is the overall civil designer and their teamaround Shane Anderson, Patrick Zerr and Nick Guaran greatly
contributed to the success of this project.
Tetra Tech EBA under the guidance of Charles Hunt wasinstrumental in the early gully assessments while Nigel
Skermer encouraged the use of check dams.
The skilled crew at SpiderExcavators from Golden, BC
built the structures in extremely challenging terrain.
This manuscript was prepared on the authors own timewith support from BGC Engineering Inc. and Geoinfra
Ingenieure AG.

4 Conclusions
The key issues during the 2021 freshet were toe scour
and abrasion from the very angular sediment particles
carried by the debris flows. Extensive abrasion and wear
on timber in direct contact with flowing debris –particularly near the weir crest and on the 5V:1H
battered downstream dam face – threatened to shorten
the lifespan of the structures. This illustrates a limitationof log crib check dams in very active‡ gullies. Theseissues were remedied by installation of steel plates over
the weir openings and grouted riprap in the scour pools
below the weirs.
Key issues in 2022 were loads induced by landslides,
entering from the side slopes shearing off wing walls,
and hence causing deformations in the check dams. Thisillustrates the limited capacity to carry earth pressuresfrom side slope movement of log crib structures.
Although log crib check dams may have lower load
carrying capacity compared to concrete check dams,
experience at East Gate Landslide demonstrates aremarkably high tolerance for deformations before thedeformed check dam loses its grade stabilization
functionality.
Despite the significant, landslide induced damage,check dams #1 to #5 maintained their functionality:• The damaged wing walls at check dams #3 to #5
provided sufficient weir functionality to guide
flows. However, partial blockage of the weir crosssectional area (Fig. 7) with debris was noted. This
could be due energy losses at the check dam drops
or simply more viscous rheology of a debris flow
event occurring at the end of the freshet.
• No significant toe scour issues occurred in the2022 freshet, most likely due to the splash padReferences
1.

‡Note: This gully is very active and experiences multiple
debris flow events per year with several 10’000 m3 of
sediment retained annually in the downstream retention
basin.

5M. Busslinger, M. Jakob, and P. Zerr. Treat thesource, not the symptoms – Investing in upslopedebris-flow mitigation at East Gate Landslide(Trans-Canada Highway). XVI PIARC World
Winter Service and Road Resilience Congress,
Feb. 7-11, 2022, Virtual Event Calgary AB,
Canada. (2022)