Colluvium supply in humid regions limits the frequency of storm-triggered landslides

Shallow landslides, triggered by extreme rainfall, are a significant hazard in mountainous landscapes. The hazard posed by shallow landslides depends on the availability and strength of colluvial material in landslide source areas and the frequency and intensity of extreme rainfall events. Here we investigate how the time taken to accumulate colluvium affects landslide triggering rate in the Southern Appalachian Mountains, USA and how this may affect future landslide hazards. We calculated the failure potential of 283 hollows by comparing colluvium depths to the minimum (critical) soil depth required for landslide initiation in each hollow. Our data show that most hollow soil depths are close to their critical depth, with 62% of hollows having soils that are too thin to fail. Our results, supported by numerical modeling, reveal that landslide frequency in many humid landscapes may be insensitive to projected changes in the frequency of intense rainfall events.

[1]  L. Band,et al.  Topographic and ecologic controls on root reinforcement , 2009 .

[2]  William E. Dietrich,et al.  Significance of Thick Deposits of Colluvium on Hillslopes: A Case Study Involving the Use of Pollen Analysis in the Coastal Mountains of Northern California , 1984, The Journal of Geology.

[3]  L. Band,et al.  Climatological Perspectives on the Rainfall Characteristics Associated with Landslides in Western North Carolina , 2008 .

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

[5]  D. N. Swanston,et al.  Analysis of a small debris slide in coastal Alaska , 1982 .

[6]  Tomoyuki Iida.  A stochastic hydro-geomorphological model for shallow landsliding due to rainstorm , 1999 .

[7]  J. T. Hack,et al.  Geomorphology and forest ecology of a mountain region in the central Appalachians , 1960 .

[8]  Tomoyuki Iida.  Theoretical research on the relationship between return period of rainfall and shallow landslides , 2004 .

[9]  William E. Dietrich,et al.  EROSION RATES IN THE SOUTHERN OREGON COAST RANGE: EVIDENCE FOR AN EQUILIBRIUM BETWEEN HILLSLOPE EROSION AND SEDIMENT YIELD , 1991 .

[10]  S. Mudd,et al.  Influence of lithology on hillslope morphology and response to tectonic forcing in the northern Sierra Nevada of California , 2013 .

[11]  D. Milodowski,et al.  Objective extraction of channel heads from high‐resolution topographic data , 2014 .

[12]  G. Wieczorek,et al.  Regional debris-flow distribution and preliminary risk assessment from severe storm events in the Appalachian Blue Ridge Province, USA , 2004 .

[13]  J. E. Douglass,et al.  History of Coweeta , 1988 .

[14]  L. Benda,et al.  Stochastic forcing of sediment supply to channel networks from landsliding and debris flow , 1997 .

[15]  F. Nelson,et al.  Periglacial Appalachia: palaeoclimatic significance of blockfield elevation gradients, eastern USA , 2007 .

[16]  W. Dietrich,et al.  Sediment budget for a small catchment in mountainous terrain , 1978 .

[17]  D. Fabel,et al.  Pliocene−Pleistocene incision of the Green River, Kentucky, determined from radioactive decay of cosmogenic 26Al and 10Be in Mammoth Cave sediments , 2001 .

[18]  W. Dietrich,et al.  Geomorphic and paleoclimatic implications of latest Pleistocene radiocarbon dates from colluvium-mantled hollows, California , 1986 .

[19]  A. Pearce,et al.  Influence of cenozoic geology on mass movement and sediment yield response to forest removal, North Westland, New Zealand , 1976 .

[20]  H. Delcourt.  Late Quaternary Vegetation History of the Eastern Highland Rim and Adjacent Cumberland Plateau of Tennessee , 1979 .

[21]  T. Hales,et al.  Southern Appalachian hillslope erosion rates measured by soil and detrital radiocarbon in hollows , 2012 .

[22]  M. Selby,et al.  Hillslope materials and processes , 1982 .

[23]  G. Clark.  Debris slide and debris flow historical events in the Appalachians south of the glacial border , 1987 .

[24]  Corinne Le Quéré,et al.  Climate Change 2013: The Physical Science Basis , 2013 .

[25]  G. Holland,et al.  Tropical cyclones and climate change , 2010, Tropical Cyclone Research and Review.

[26]  Thomas J. Douglas,et al.  Geologic, geomorphic, and meteorological aspects of debris flows triggered by Hurricanes Frances and Ivan during September 2004 in the Southern Appalachian Mountains of Macon County, North Carolina (southeastern USA) , 2008 .

[27]  P. D’Odorico,et al.  A probabilistic model of rainfall‐triggered shallow landslides in hollows: A long‐term analysis , 2003 .

[28]  Lawrence E. Band,et al.  Ecosystem processes at the watershed scale: Mapping and modeling ecohydrological controls of landslides , 2012 .

[29]  Richard M. Iverson,et al.  Landslide triggering by rain infiltration , 2000 .

[30]  N. Trustrum,et al.  Soil depth-age relationship of landslides on deforested hillslopes, taranaki, New Zealand , 1988 .

[31]  K. Wegmann,et al.  Miocene rejuvenation of topographic relief in the southern Appalachians , 2013 .

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

[33]  Michael J. Crozier,et al.  Relative instability of colluvium‐filled bedrock depressions , 1990 .

[34]  William C. Haneberg,et al.  A Rational Probabilistic Method for Spatially Distributed Landslide Hazard Assessment , 2004 .

[35]  B. Collins,et al.  Natural Disturbances and Historic Range of Variation , 2016, Managing Forest Ecosystems.

[36]  D. W. Scott,et al.  Multivariate Density Estimation, Theory, Practice and Visualization , 1992 .

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

[38]  D. V. Griffiths,et al.  Limits on the validity of infinite length assumptions for modelling shallow landslides , 2012 .

[39]  W. Ashe,et al.  The Southern Appalachian Forests , 2013 .

[40]  David R. Montgomery,et al.  Regional test of a model for shallow landsliding , 1998 .

[41]  L. Band,et al.  Simulating vegetation controls on hurricane‐induced shallow landslides with a distributed ecohydrological model , 2015 .

[42]  R. Hatcher.  THE COWEETA GROUP AND COWEETA SYNCLINE: MAJOR FEATURES OF THE NORTH CAROLINA-GEORGIA BLUE RIDGE , 2004 .

[43]  A. Amoozegar.  A Compact Constant-Head Permeameter for Measuring Saturated Hydraulic Conductivity of the Vadose Zone , 1989 .

[44]  W. Culling,et al.  Analytical Theory of Erosion , 1960, The Journal of Geology.

[45]  W. Dietrich,et al.  Analysis of Hillslope Erosion Rates Using Dated Colluvial Deposits , 1989, The Journal of Geology.

[46]  D. Montgomery,et al.  A physically based model for the topographic control on shallow landsliding , 1994 .

[47]  David R. Montgomery,et al.  Forest clearing and regional landsliding , 2000 .

[48]  R. Finkel,et al.  Tracing hillslope sediment production and transport with in situ and meteoric 10Be , 2009 .

[49]  I. Jefferson,et al.  Soil mechanics in engineering practice , 1997 .

[50]  L. Stefanova,et al.  The impact of climate change on rainfall Intensity–Duration–Frequency (IDF) curves in Alabama , 2013, Regional Environmental Change.

[51]  D. Or,et al.  Spatial characterization of root reinforcement at stand scale: Theory and case study , 2012 .

[52]  Paul V. Bolstad,et al.  Predicting Southern Appalachian overstory vegetation with digital terrain data , 2004, Landscape Ecology.

[53]  H. Maring,et al.  Journal of Geophysical Research , 1949, Nature.

[54]  M. Stoffel,et al.  Effects of climate change on mass movements in mountain environments , 2012 .

[55]  F. Swanson,et al.  Sediment Budgets and Routing in Forested Drainage Basins , 2006 .

[56]  M. Brandon,et al.  A Fluvial Record of Long-term Steady-state Uplift and Erosion Across the Cascadia Forearc High, Western Washington State , 2001 .

[57]  W. Dietrich,et al.  Late Quaternary history of colluvial deposition and erosion in hollows, central California Coast Ranges , 1990 .