A physically based model for the topographic control on shallow landsliding

Abstract

A model for the topographic influence on shallow landslide initiation is developed by coupling digital terrain data with near‐surface through flow and slope stability models. The hydrologic model TOPOG (O'Loughlin, 1986) predicts the degree of soil saturation in response to a steady state rainfall for topographic elements defined by the intersection of contours and flow tube boundaries. The slope stability component uses this relative soil saturation to analyze the stability of each topographic element for the case of cohesionless soils of spatially constant thickness and saturated conductivity. The steady state rainfall predicted to cause instability in each topographic element provides a measure of the relative potential for shallow landsliding. The spatial distribution of critical rainfall values is compared with landslide locations mapped from aerial photographs and in the field for three study basins where high‐resolution digital elevation data are available: Tennessee Valley in Marin County, California; Mettman Ridge in the Oregon Coast Range; and Split Creek on the Olympic Peninsula, Washington. Model predictions in each of these areas are consistent with spatial patterns of observed landslide scars, although hydrologic complexities not accounted for in the model (e.g., spatial variability of soil properties and bedrock flow) control specific sites and timing of debris flow initiation within areas of similar topographic control.

Which data for quantitative landslide susceptibility mapping at operational scale? Case study of the Pays d'Auge plateau hillslopes (Normandy, France)

“…Nevertheless, the indirect susceptibility mapping methods are often considered more objective by scientists. These methods use GIS integrated statistical models based on the spatial relationship between the landslide location and a set of controlling factors, or physically based models analysing the relationships between topographic data and geotechnical parameters, on the basis of infinite slope models (Montgomery and Dietrich, 1994). The indirect methods have been applied and improved by scientists (e.g.…”

Effects of bedrock groundwater on spatial and temporal variations in soil mantle groundwater in a steep granitic headwater catchment

“…[3] Increasing knowledge of water flow processes in headwater catchments, as well as dramatic progress in computer processing capabilities and the establishment of geographic information systems (GISs), have contributed to a number of physically based models for simulating runoff generation [e.g., Beven and Kirkby, 1979;O'Loughlin, 1986;Grayson et al, 1992;Wigmosta and Burges, 1997;VanderKwaak and Loague, 2001;Downer and Ogden, 2004] and shallow landslide occurrence [e.g., Okimura and Ichikawa, 1985;Montgomery and Dietrich, 1994;Wu and Sidle, 1995;Rosso et al, 2006] in headwater catchments. Although these models have succeeded to some extent in simulating saturated areas or streamflow generation and in detecting areas prone to shallow landslides within the catchment, complete agreement between simulated and observed phenomena has, unfortunately, rarely been achieved.…”

Time, space, and episodicity of physical disturbance in streams

“…Shallow landslides are triggered by increased pore-pressure gradients during periods of intense precipitation (Caine, 1980), which can be estimated as a function of rainfall intensity, upslope contributing area, and local slope (O'Laughlin, 1986). These two models point to local surface gradient and specific contributing area as primary topographic controls on shallow landsliding (Montgomery and Dietrich, 1994). Iverson (2000) highlights limitations to the hydrologic assumptions used in this model, but still recognizes the importance of local slope and specific contributing area in setting the antecedent soil moisture conditions that modulate the impact of transient periods of high-intensity rainfall on slope stability.…”

“…Iverson (2000) highlights limitations to the hydrologic assumptions used in this model, but still recognizes the importance of local slope and specific contributing area in setting the antecedent soil moisture conditions that modulate the impact of transient periods of high-intensity rainfall on slope stability. We thus use a function of local slope and specific contributing area (that of Montgomery and Dietrich (1994), with soil parameters held uniform), as a topographic index of slope stability. Using landslide inventories, this index can then be calibrated as a function of relative landslide density.…”