Elucidating the role of vegetation in the initiation of rainfall‐induced shallow landslides: Insights from an extreme rainfall event in the Colorado Front Range

More than 1100 debris flows were mobilized from shallow landslides during a rainstorm from 9 to 13 September 2013 in the Colorado Front Range, with the vast majority initiating on sparsely vegetated, south facing terrain. To investigate the physical processes responsible for the observed aspect control, we made measurements of soil properties on a densely forested north facing hillslope and a grassland‐dominated south facing hillslope in the Colorado Front Range and performed numerical modeling of transient changes in soil pore water pressure throughout the rainstorm. Using the numerical model, we quantitatively assessed interactions among vegetation, rainfall interception, subsurface hydrology, and slope stability. Results suggest that apparent cohesion supplied by roots was responsible for the observed connection between debris flow initiation and slope aspect. Results suggest that future climate‐driven modifications to forest structure could substantially influence landslide hazards throughout the Front Range and similar water‐limited environments where vegetation communities may be more susceptible to small variations in climate.

[1]  Donald H. Gray,et al.  Forest Vegetation Removal and Slope Stability in the Idaho Batholith , 2017 .

[2]  J. Coe,et al.  The influence of vegetation on debris-flow initiation during extreme rainfall in the northern Colorado Front Range , 2016 .

[3]  A. Ziegler,et al.  The canopy interception-landslide initiation conundrum: insight from a tropical secondary forest in northern Thailand , 2016 .

[4]  Gregory E. Tucker,et al.  Aspect-dependent soil saturation and insight into debris-flow initiation during extreme rainfall in the Colorado Front Range , 2015 .

[5]  Peter Jordan,et al.  Hillslope hydrology and stability , 2015 .

[6]  Jason W. Kean,et al.  New insights into debris-flow hazards from an extraordinary event in the Colorado Front Range , 2014 .

[7]  Paul R. Bierman,et al.  A Cosmogenic view of erosion, relief generation, and the age of faulting in southern Africa , 2014 .

[8]  R. Seager,et al.  Temperature as a potent driver of regional forest drought stress and tree mortality , 2013 .

[9]  S. P. Anderson,et al.  Seismic Constraints on Critical Zone Architecture, Boulder Creek Watershed, Front Range, Colorado , 2011 .

[10]  L. Reid,et al.  Rates, timing, and mechanisms of rainfall interception loss in a coastal redwood forest , 2009 .

[11]  T. Mizuyama,et al.  Hydraulic Properties of Variously Weathered Granitic Bedrock in Headwater Catchments , 2009 .

[12]  J. Roering,et al.  Post-fire geomorphic response in steep, forested landscapes: Oregon Coast Range, USA , 2009 .

[13]  Ning Lu,et al.  Landsliding in partially saturated materials , 2009 .

[14]  Ning Lu,et al.  Infinite slope stability under steady unsaturated seepage conditions , 2008 .

[15]  G. Meyer,et al.  Aspect-related microclimatic influences on slope forms and processes, northeastern Arizona , 2008 .

[16]  A. Skaugset,et al.  Modelling effects of forest canopies on slope stability , 2003 .

[17]  David R. Montgomery,et al.  Shallow landsliding, root reinforcement, and the spatial distribution of trees in the Oregon Coast Range , 2003 .

[18]  Malcolm G. Anderson,et al.  An integrated hydrological model for rain‐induced landslide prediction , 2002 .

[19]  T. Dunne,et al.  Landslides on coastal sage-scrub and grassland hillslopes in a severe El Niño winter: The effects of vegetation conversion on sediment delivery , 2002 .

[20]  Torsten Schaub,et al.  The variability of root cohesion as an influence on shallow landslide susceptibility in the Oregon Coast Range , 2001 .

[21]  D. Hendricks,et al.  The influence of slope aspect on soil weathering processes in the Springerville volcanic field, Arizona , 2001 .

[22]  Renduo Zhang,et al.  Determination of soil sorptivity and hydraulic conductivity from the disk infiltrometer , 1997 .

[23]  Z. Teklehaimanot,et al.  Direct measurement of evaporation of intercepted water from forest canopies , 1991 .

[24]  R. Carsel,et al.  Developing joint probability distributions of soil water retention characteristics , 1988 .

[25]  T. Wu,et al.  Strength of tree roots and landslides on Prince of Wales Island, Alaska , 1979 .

[26]  A. Rutter,et al.  A Predictive Model of Rainfall Interception in Forests. II. Generalization of the Model and Comparison with Observations in Some Coniferous and Hardwood Stands , 1975 .

[27]  A. Priced,et al.  Integrating soils and geomorphology in mountains — an example from the Front Range of Colorado , 2003 .

[28]  G. N. Green.  The digital geologic map of Colorado in ARC/INFO format, Part C. Explanation sheet database , 1992 .

[29]  Gregory N. Green,et al.  The Digital Geologic Map of Colorado in ARC/INFO Format By , 1992 .

[30]  A. Rutter,et al.  A predictive model of rainfall interception in forests, 1. Derivation of the model from observations in a plantation of Corsican pine , 1971 .