# Comparing Root Cohesion Estimates from Three Models at a Shallow Landslide in the Oregon Coast Range

^{1}

^{2}

^{*}

## Abstract

**:**

## 1. Introduction

- To reexamine previously published root cohesion estimates for the CB1 landslide by Schmidt et al. [25], which was evaluated before the development of breakage models accounting for progressive root failure. Because root cohesion values for the CB1 slide have been cited and used in subsequent studies [19,21,22,26,27], reexamining these values has implications for these existing studies as well as future investigations.
- To compare the results of these three models at an instrumented landslide site where interpretations have implications for other shallow landslides. Because roots in the landslide scarp were surveyed and measured post-failure, data from the CB1 site is uniquely suited to this purpose.

## 2. Materials and Methods

#### 2.1. Root Breakage Models

_{r}represents the additional shear strength provided by roots [29]. Roots produce an apparent cohesion via fiber reinforcement, hereafter referred to as root cohesion. Most research quantifying root cohesion focuses on the tensile resistance of the root “bundle”. We focus on “breakage” models that calculate maximum tensile resistance of a root bundle where tensile strengths of the individual roots are known [7].

#### 2.2. CB1 Landslide Site

^{2}CB1 catchment was monitored for unsaturated and saturated hydrologic flow response magnitude and pathways in the context of shallow-soil slope stability. CB1 is located below Mettman Ridge in the Oregon Coast Range, approximately 15 km northeast of Coos Bay, Oregon, USA [35]. The ridge crest elevation is approximately 300 m. A detailed physical description of the site and its soils is provided in Montgomery et al. [19] and Anderson et al. [20]. CB1 is one of two adjacent catchments used for experimental work on landslide failure [20,23,24]. The site was clearcut logged in 1987 and replanted with Douglas fir saplings in 1989; instrumentation was installed starting in 1989 and remained in place until November 1996, when it was destroyed by a landslide and the associated debris flow [19]. Figure 1 shows an aerial view of the CB1 catchment immediately after the landslide, and Figure 2 shows photos of the catchment both before and after the landslide taken from the same vantage point.

^{2}and the total length of the upper scar was 58 m. However, roots from only 37 m of the scar perimeter could be collected and measured because of physical disturbance and obstruction by catwalk infrastructure [19].

#### 2.3. Estimation of Root Thread Strength from Experimental Data

#### 2.4. Root Data from the CB1 Landslide Site

^{2}.

#### 2.5. Application of Root Breakage Models

#### 2.5.1. Wu and Waldron Model (WWM)

_{i}is the tensile strength of the i-th root (in units of stress), A

_{i}is area of the i-th root, and R

_{f}is a correction factor for the inclination angle of the root. We use a value of 1.0 for R

_{f}, following the conclusion of Thomas and Pollen-Bankhead [28] that an R

_{f}value of 1.0 was most appropriate for sites with friction angles between 5° and 45° and failure surface angles between 10° and 90°.

#### 2.5.2. Fiber Bundle Model (FBM)

#### Root Bundle Model-Weibull (RBMw)

#### 2.6. Calculation of Root Cohesion

_{b}to the area of the failure surface (A):

^{2}(when binned by segment) and from 0.42 to 3.3 m

^{2}(when binned by 10-cm depth intervals).

## 3. Results

_{b}is the maximum force for the entire bundle, and F

_{(b−k)}is the maximum force for the bundle with all the roots belonging to group k removed. Group k could represent a group of roots at a particular depth, a particular section along the perimeter of the scarp, and/or roots belonging to a specific species.

#### 3.1. Scarp-Averaged Cohesion

^{2}, the root cohesion is 4.6 kPa for the WWM, 1.2 kPa for the FBM, and 0.8 kPa for the RBMw. In their comparative study of the three models, Zydron and Skorski [15] obtained similar results for the relative cohesion estimates for two different tree species. However, the ratios of FBM-estimated cohesion and RBMw-estimated cohesion to the WWM-estimated cohesion, which are 0.18 and 0.26, respectively, are somewhat lower than estimates of comparable ratios from other researchers (see Section 2.1). Results for the scarp-averaged root cohesion are summarized in Table 1.

#### 3.2. Root Cohesion by Depth

#### 3.3. Root Cohesion along the Scarp Perimeter

^{2}and 0.65 m

^{2}. Figure 12 shows that cohesion is highly concentrated within areas that have a high density of elderberry and Douglas fir roots, which have the greatest tensile strengths. For all three models, the cohesion distribution among the different depth/segment sections has a skewness greater than 5, indicating the very high degree of spatial concentration. For the depth/segment sections with the greatest contribution, while most depth/segment sections contribute <1% to the overall root cohesion, the percent contribution for the strongest section is 16% for the WWM, 23% for the FBM, and 12% for the RBMw. Alternatively, the cohesion of the strongest individual section is 123 kPa for the WWM, 99 kPa for the FBM, and 34 kPa for the RBMw, values which are greater than the scarp-averaged cohesion calculated from the respective model by a factor greater than 25. This relation highlights the great spatial variability and localized maxima adjacent to denser, spatially concentrated, plant roots.

#### 3.4. Contribution of Cohesion by Species

## 4. Discussion

## 5. Conclusions

## Author Contributions

## Funding

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## Appendix A

_{max}is the tensile load and a and b are scaling factors.

_{max}is the tensile strength, u is a scaling factor and c is a constant.

## Appendix B

_{0}and E

_{0}are scaling factors for length and elastic modulus, respectively, β and γ are exponents, and r is a scaling factor which accounts for reduction in the elastic modulus due to root tortuosity [13].

_{max}represents the maximum tensile force of the root (Equation (A1)). For a given displacement ∆x, the force mobilized by the bundle is the sum of the forces on each root at that displacement:

_{max}:

_{i}, ∆x) S(∆x* ). The total strength of the root bundle at a given normalized displacement is the sum of forces mobilized by all roots at that displacement:

_{0}is 696 MPa mm, L

_{0}is 335 mm, β is −1, and γ is 0.63. Because the value for E

_{0}accounts for the effects of tortuosity, the tortuosity coefficient r from Equations (A4) and (A5) is effectively equal to 1 [30]. Root force at failure F

_{max}was obtained by Equation (A1) using coefficient values shown in Figure 3.

_{max}, as the displacement where the applied force equals root force at failure F

_{max}. The normalized displacement was estimated as the ratio of the measured displacement to the displacement at failure (Equation (A8)). However, because the displacement is linearly proportional to force, the normalized displacement is equivalent to the ratio of the measured tensile force F

_{meas}to the estimated tensile force at failure F

_{max}:

## References

- Sidle, R.C.; Ochiai, H. Landslides: Processes, Prediction, and Land Use; American Geophysical Union Water Resources Monograph 18; American Geophysical Union: Washington, DC, USA, 2006. [Google Scholar]
- Stokes, A.; Atger, C.; Bengough, A.G.; Fourcaud, T.; Sidle, R.C. Desirable plant root traits for protecting natural and engineered slopes against landslides. Plant Soil
**2009**, 324, 1–30. [Google Scholar] [CrossRef] - Stokes, A.; Douglas, G.B.; Fourcaud, T.; Giadrossich, F.; Gillies, C.; Hubble, T.; Kim, J.H.; Loades, K.W.; Mao, Z.; McIvor, I.R.; et al. Ecological mitigation of hillslope instability: Ten key issues facing researchers and practitioners. Plant Soil
**2014**, 377, 1–23. [Google Scholar] [CrossRef] - Cohen, D.; Schwarz, M. Tree-root control of shallow landslides. Earth Surf. Dyn.
**2017**, 5, 451–477. [Google Scholar] [CrossRef] - Montgomery, D.R.; Schmidt, K.M.; Greenberg, H.M.; Dietrich, W.E. Forest clearing and regional landsliding. Geology
**2000**, 28, 311–314. [Google Scholar] [CrossRef] - Iglesias, V.; Balch, J.K.; Travis, W.R. US fires became larger, more frequent, and more widespread in the 2000s. Sci. Adv.
**2022**, 8, eabc0020. [Google Scholar] [CrossRef] - Dias, A.S.; Pirone, M.; Urciuoli, G. Review on the Methods for Evaluation of Root Reinforcement in Shallow Landslides. In Advancing Culture of Living with Landslides; Mikos, M., Tiwari, B., Yin, Y., Sassa, K., Eds.; Springer: New York, NY, USA, 2017; pp. 641–648. [Google Scholar] [CrossRef]
- Mao, Z. Root reinforcement models: Classification, criticism and perspectives. Plant Soil
**2022**, 472, 17–28. [Google Scholar] [CrossRef] - Wu, T.H. Investigation of Landslides on Prince of Wales Island, Alaska; Alaska Geotechnical Report Issue 5; Department of Civil Engineering, Ohio State University: Columbus, OH, USA, 1976. [Google Scholar]
- Waldron, L.J. The shear resistance of root-permeated homogeneous and stratified soil. Soil Sci. Soc. Am. J.
**1977**, 41, 843–849. [Google Scholar] [CrossRef] - Wu, T.H.; McKinnell, W.P.; Swanston, D.N. Strength of tree roots and landslides on Prince of Wales Island, Alaska. Can. Geotech. J.
**1979**, 16, 19–33. [Google Scholar] [CrossRef] - Pollen, N.; Simon, A. Estimating the mechanical effects of riparian vegetation on stream bank stability using a fiber bundle model. Water Resour. Res.
**2005**, 41, W07025. [Google Scholar] [CrossRef] - Schwarz, M.; Giadrossich, F.; Cohen, D. Modeling root reinforcement using a root-failure Weibull survival function. Hydrol. Earth Syst. Sci.
**2013**, 17, 4367–4377. [Google Scholar] [CrossRef] - Docker, B.B.; Hubble, T.C.T. Quantifying root-reinforcement of river bank soils by four Australian tree species. Geomorphology
**2008**, 100, 401–418. [Google Scholar] [CrossRef] - Zydron, T.; Skorski, L. The effect of root reinforcement exemplified by black alder (Alnus glutinosa Gaertn.) and basket willow (salix viminalis) root systems—Case study in Poland. Appl. Ecol. Environ. Res.
**2018**, 16, 407–423. [Google Scholar] [CrossRef] - Schwarz, M.; Preti, F.; Giadrossich, F.; Lehmann, P.; Or, D. Quantifying the role of vegetation in slope stability: A case study in Tuscany (Italy). Ecol. Eng.
**2010**, 36, 285–291. [Google Scholar] [CrossRef] - Schwarz, M.; Cohen, D.; Or, D. Spatial characterization of root reinforcement at the stand scale: Theory and case study. Geomorphology
**2012**, 171–172, 190–200. [Google Scholar] [CrossRef] - Ghestem, M.; Cao, K.; Ma, W.; Rowe, N.; Leclerc, R.; Gadenne, C.; Stokes, A. A framework for identifying plant species to be used as ‘ecological engineers’ for fixing soil on unstable slopes. PLoS ONE
**2014**, 9, e95876. [Google Scholar] [CrossRef] - Montgomery, D.R.; Schmidt, K.M.; Dietrich, W.E.; McKean, J. Instrumental record of debris flow initiation during natural rainfall: Implications for modeling slope stability. J. Geophys. Res.
**2009**, 114, F01031. [Google Scholar] [CrossRef] - Anderson, S.P.; Dietrich, W.E.; Montgomery, D.R.; Torres, R.; Conrad, M.E.; Loague, K. Subsurface flowpaths in a steep, unchanneled catchment. Water Resour. Res.
**1997**, 33, 2637–2653. [Google Scholar] [CrossRef] - Ebel, B.A.; Loague, K.; Borja, R.I. The impact of hysteresis on variably saturated hydrologic response and slope failure. Environ. Earth Sci.
**2010**, 61, 1215–1225. [Google Scholar] [CrossRef] - Ebel, B.A.; Godt, J.W.; Lu, N.; Coe, J.A.; Smith, J.B.; Baum, R.L. Field and laboratory hydraulic characterization of landslide-prone soils in the Oregon Coast Range and implications for hydrologic simulation. Vadose Zone J.
**2018**, 17, 180078. [Google Scholar] [CrossRef] - Montgomery, D.R.; Dietrich, W.E.; Torres, R.; Anderson, S.P.; Heffner, J.T.; Loague, K. Hydrologic response of a steep, unchanneled valley to natural and applied rainfall. Water Resour. Res.
**1997**, 33, 91–109. [Google Scholar] [CrossRef] - Torres, R.; Dietrich, W.E.; Montgomery, D.R.; Anderson, S.P.; Loague, K. Unsaturated zone processes and the hydrologic response of a steep, unchanneled catchment. Water Resour. Res.
**1998**, 34, 1865–1879. [Google Scholar] [CrossRef] - Schmidt, K.M.; Roering, J.J.; Stock, J.; Dietrich, W.E.; Montgomery, D.R.; Schaub, T. The variability of root cohesion as an influence on shallow landslide susceptibility in the Oregon Coast Range. Can. Geotech. J.
**2001**, 38, 995–1024. [Google Scholar] [CrossRef] - Casadei, M.; Dietrich, W.E.; Miller, N. Controls on shallow landslide size. In Debris-Flow Hazards Mitigation: Mechanics, Prediction, and Assessment; Rickenmann, D., Chen, C., Eds.; IOS Press: Amsterdam, The Netherlands, 2003; pp. 91–101. [Google Scholar]
- Milledge, D.G.; Bellugi, D.; McKean, J.A.; Densmore, A.L.; Dietrich, W.E. A multidimensional stability model for predicting shallow landslide size and shape across landscapes. J. Geophys. Res. Earth
**2014**, 119, 2481–2504. [Google Scholar] [CrossRef] [PubMed] - Thomas, R.E.; Pollen-Bankhead, N. Modeling root-reinforcement with a fiber-bundle model and Monte Carlo simulation. Ecol. Eng.
**2010**, 36, 47–61. [Google Scholar] [CrossRef] - Abernathy, B.; Rutherfurd, I.D. The effect of riparian tree roots on the mass stability of riverbanks. Earth Surf. Process. Landf.
**2000**, 25, 921–937. [Google Scholar] [CrossRef] - Schwarz, M.; Cohen, D.; Or, D. Root-soil mechanical interactions during pullout and failure of root bundles. J. Geophys. Res.
**2010**, 115, F04035. [Google Scholar] [CrossRef] - Preti, F.; Schwarz, M. On root reinforcement modeling. Geophys. Res. Abstr.
**2006**, 8, 4555. [Google Scholar] - Arnone, E.; Caracciolo, D.; Noto, L.V.; Preti, F.; Bras, R.L. Modeling the hydrological and mechanical effect of roots on shallow landslides. Water Resour. Res.
**2016**, 52, 8590–8612. [Google Scholar] [CrossRef] - Emadi-Tafti, M.; Ataie-Ashtiani, B. A modeling platform for landslide stability: A hydrological approach. Water
**2019**, 11, 2146. [Google Scholar] [CrossRef] - Wu, T.H. Root reinforcement of soil: Review of analytical models, test results, and applications to design. Can. Geotech. J.
**2013**, 50, 259–274. [Google Scholar] [CrossRef] - Schmidt, K.M.; Cronkite-Ratcliff, C. Root Thread Strength, Landslide Headscarp Geometry, and Observed Root Characteristics at the Monitored CB1 Landslide, Oregon, USA.; U.S. Geological Survey Data Release; U.S. Geological Survey: Reston, VA, USA, 2022. [Google Scholar] [CrossRef]
- Caplan, J.S.; Yeakley, J.A. Rubus armeniacus (Himalayan blackberry) Occurrence and Growth in Relation to Soil and Light Conditions in Western Oregon. Northwest Sci.
**2006**, 80, 9–17. [Google Scholar] - Burroughs, E.R.; Thomas, B.R. Declining Root Strength in Douglas-Fir after Felling as a Factor in Slope Stability; USDA Forest Service Research Paper INT-190; U.S. Department of Agriculture: Ogden, UT, USA, 1977; 40p. [Google Scholar]
- Mao, Z.; Saint-Andre, L.; Genet, M.; Mine, F.X.; Jourdan, C.; Rey, H.; Courbaud, B.; Stokes, A. Engineering ecological protection against landslides in diverse mountain forests: Choosing cohesion models. Ecol. Eng.
**2012**, 45, 55–69. [Google Scholar] [CrossRef] - Cohen, D.; Schwarz, M.; Or, D. An analytical fiber bundle model for pullout mechanics of root bundles. J. Geophys. Res.
**2011**, 116, F03010. [Google Scholar] [CrossRef] - Giadrossich, F.; Cohen, D.; Schwarz, M.; Ganga, A.; Marrosu, R.; Pirastru, M.; Capra, G.F. Large roots dominate the contribution of trees to slope stability. Earth Surf. Process. Landf.
**2019**, 44, 1602–1609. [Google Scholar] [CrossRef] - Vergani, C.; Schwarz, M.; Cohen, D.; Thormann, J.J.; Bischetti, G.B. Effects of root tensile force and diameter distribution variability on root reinforcement in the Swiss and Italian Alps. Can. J. For. Res.
**2014**, 44, 1426–1440. [Google Scholar] [CrossRef] - Roering, J.J.; Schmidt, K.M.; Stock, J.D.; Dietrich, W.E.; Montgomery, D.R. Shallow landsliding, root reinforcement, and the spatial distribution of trees in the Oregon Coast Range. Can. Geotech. J.
**2003**, 40, 237–253. [Google Scholar] [CrossRef] - Ji, J.; Mao, Z.; Qu, W.; Zhang, Z. Energy-based fibre bundle model algorithms to predict soil reinforcement by roots. Plant Soil
**2020**, 446, 307–329. [Google Scholar] [CrossRef] - Schwarz, M.; Lehmann, P.; Or, D. Quantifying lateral root reinforcement in steep slopes—From a bundle of roots to tree stands. Earth Surf. Process. Landf.
**2010**, 35, 354–367. [Google Scholar] [CrossRef] - Schwarz, M.; Rist, A.; Cohen, D.; Giadrossich, F.; Egorov, P.; Büttner, D.; Stolz, M.; Thormann, J.J. Root reinforcement of soils under compression. J. Geophys. Res. Earth
**2015**, 120, 2103–2120. [Google Scholar] [CrossRef] - Tosi, M. Root tensile strength relationships and their slope stability implications of three shrub species in the Northern Apennines (Italy). Geomorphology
**2007**, 87, 268–283. [Google Scholar] [CrossRef] - Lee, E.T. Statistical Models for Survival Analysis; Wiley: Hoboken, NJ, USA, 1992. [Google Scholar]

**Figure 1.**Post-landslide oblique aerial photo, taken roughly towards the NNW direction, reveals both upslope shallow landslide extent and downslope debris flow scour. Vehicles on the road near the bottom of the image indicate the relative size of the landslide area. Photograph by K.M. Schmidt, U.S. Geological Survey.

**Figure 2.**View of the CB1 catchment (

**a**) before and (

**b**) after the landslide. Both images are taken from the same location at the top of the scarp. The view is to the north, looking directly down the central axis of the hollow. Panel (

**a**) shows some of the instrumentation which was installed at the site before the landslide. The instrumentation included tipping bucket rain gages, tensiometers, piezometers, catwalks to minimize ground surface disturbance, and a downslope weir. Photograph by K.M. Schmidt, U.S. Geological Survey.

**Figure 3.**Field-measured relations of species type with tensile load at failure (solid circles) for a given thread diameter with best fit second-order polynomial model from Equation (A1) (see Appendix A) (except for Douglas fir, where the equation of Burroughs and Thomas [37] was used). Equations are shown for foxglove (

**a**), Douglas fir (

**b**), elderberry (

**c**), blackberry (

**d**), and thimbleberry (

**e**). Panel (

**f**) shows the estimated curves for all species color-coded by the individual species. In all plots, the diameter range of the curves represents the range over which the tensile load was estimated. All data are available in Schmidt and Cronkite-Ratcliff [35].

**Figure 4.**Panel (

**a**) shows the plan view of the landslide scarp perimeter constructed with a tape and compass survey, showing the locations of numbered segments. Only segments where roots were measured are numbered. Segments where no roots were measured (because of obstructions including collapsed soil masses and broken site infrastructure) are shown as dashed lines. Segments of scarp perimeter are constrained to the boundary of the initial landslide and do not include the downslope debris-flow. Data on the location of the scarp segments are available in Schmidt and Cronkite-Ratcliff [35]. Panel (

**b**) shows the location and diameter of live roots in the scarp, showing the depth below ground surface and the position along the landslide scarp perimeter for each root. The vertical dashed lines demarcate the lateral boundaries of each segment along the scarp perimeter, with shaded areas showing the approximate areal extent of each scarp segment. A small amount of “jitter” (Gaussian noise with variances of 0.1 m and 0.01 m in the horizontal and vertical dimensions, respectively) has been applied to the location and depth to visually differentiate roots located at the same perimeter and depth location. Data on the location and diameter of roots are available in Schmidt and Cronkite-Ratcliff [35].

**Figure 5.**Histograms of broken live root diameter for each of the vegetation species identified along the landslide scarp. Histograms of broken live root diameter are shown for foxglove (

**a**), Douglas fir (

**b**), elderberry (

**c**), blackberry (

**d**), and thimbleberry (

**e**). Panel (

**f**) shows the histogram of broken live root diameter for roots of all species together.

**Figure 6.**Histograms of depth below ground surface for the roots of each of the vegetation species identified along the landslide scarp. Histograms of depth below ground surface are shown for foxglove (

**a**), Douglas fir (

**b**), elderberry (

**c**), blackberry (

**d**), and thimbleberry (

**e**). Panel (

**f**) shows the histogram of depth below ground surface for roots of all species together.

**Figure 7.**Estimated normalized displacement data (circles) and curve from the fitted Weibull survival function (see Appendix B). Estimated normalized displacement and fitted Weibull survival curves are shown for foxglove (

**a**), Douglas fir (

**b**), elderberry (

**c**), blackberry (

**d**), and thimbleberry (

**e**). Panel (

**f**) shows the estimated normalized displacement and the fitted Weibull survival curves for roots of all species plotted together.

**Figure 8.**Results from the FBM, showing the number of surviving roots after application of different loads. Vertical dashed line indicates the maximum activated force.

**Figure 9.**Force-displacement curve resulting from the RBMw model. Horizontal dashed line shows the maximum activated force.

**Figure 10.**Root strength variation by depth calculated over the perimeter of the landslide scarp. Panel (

**a**) shows maximum activated force, and (

**b**) shows cohesion, superimposed over the scarp-averaged cohesion values for comparison depicted as vertical dashed lines. Panel (

**c**) shows the cumulative strength contribution with increasing depth for each of the three models. All quantities are calculated over all roots within 10-cm depth increments along the scarp plane; negligible roots intersecting the basal surface are not included.

**Figure 11.**Maximum activated force (

**a**) and root cohesion (

**b**) calculated independently for each scarp segment, showing lateral variation along the perimeter of the landslide scarp. Panel (

**a**) shows maximum activated force, and (

**b**) shows root cohesion, with the scarp-averaged cohesion superimposed as horizontal dashed lines for comparison. Both quantities are calculated within each segment along the length of the scarp perimeter; negligible roots intersecting the basal surface are not included. S1 through S16 denote the scarp segments depicted in Figure 4a.

**Figure 12.**Root cohesion (

**a**–

**c**) and percent strength contribution (

**d**–

**f**) calculated by segment and 10-cm depth bin along the landslide scarp for each of the three models. The distribution of cohesion across different segment and depth bins (

**g**–

**i**) shows that cohesion has a high degree of spatial heterogeneity across the scarp.

**Figure 13.**Contribution of root cohesion by species calculated for each of the three models. Because of the nonlinearity of the FBM and RBMw models, the contributions for FBM and RBMw will not necessarily sum to 100%.

Model | Maximum Force (kN) | Root Cohesion (kPa) | WWM Reduction Factor |
---|---|---|---|

WWM | 101.2 | 4.6 | 1 |

FBM | 26.1 | 1.2 | 0.26 |

RBMw | 18.3 | 0.8 | 0.18 |

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. |

© 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Cronkite-Ratcliff, C.; Schmidt, K.M.; Wirion, C. Comparing Root Cohesion Estimates from Three Models at a Shallow Landslide in the Oregon Coast Range. *GeoHazards* **2022**, *3*, 428-451.
https://doi.org/10.3390/geohazards3030022

**AMA Style**

Cronkite-Ratcliff C, Schmidt KM, Wirion C. Comparing Root Cohesion Estimates from Three Models at a Shallow Landslide in the Oregon Coast Range. *GeoHazards*. 2022; 3(3):428-451.
https://doi.org/10.3390/geohazards3030022

**Chicago/Turabian Style**

Cronkite-Ratcliff, Collin, Kevin M. Schmidt, and Charlotte Wirion. 2022. "Comparing Root Cohesion Estimates from Three Models at a Shallow Landslide in the Oregon Coast Range" *GeoHazards* 3, no. 3: 428-451.
https://doi.org/10.3390/geohazards3030022