HR: 1340h
AN: H43D-0521    [Abstracts]
TI: A Probabilistic Model of Rainfall-triggered Shallow Landslides in Hollows: Long-term Analysis and Dependence on Hyetograph Characteristics
AU: Dodorico, P
EM: paolo@virginia.edu
AF: Department of Environmental Sciences, University of Virginia, Charlottesville, VA 22904-4123 United States
AU: * Fagherazzi, S
EM: sergio@csit.fsu.edu
AF: Department of Geological Sciences and School of Computational Science, Florida State University, Tallahassee, FL 32306-4120 United States
AU: Rigon, R
EM: riccardo.rigon@ing.unitn.it
AF: Dipartimento di Ingegneria Civile e Ambientale, Universita' di Trento/CUDAM, Trento, TR 38050 Italy
AB: The long-term temporal evolution of soil thickness in hollows depends on the processes controlling the rates of colluvium accumulation and erosion. Accumulation is due to soil creep and mass-wasting processes from the adjacent slopes, while erosion of colluvial deposits is mainly due to debris flow and landsliding. An analysis of the long-term evolution of colluvial deposits is developed through a stochastic model of soil mass balance at a point accounting for colluvium infilling, expressed as a deterministic function of the deposit thickness, and soil erosion by shallow landslides, modeled as a random (Poisson) process. Landsliding is related to the characteristics of the triggering precipitation through an infinite-slope stability analysis, a kinematic model of hollow response to rainfall, and the intensity-duration-frequency curves characterizing the regime of extreme precipitation. This analysis provides a probabilistic representation of the long-term dynamics at a point of colluvium thickness as a function of the timescale of hollow infilling and of the frequency of triggering rainfalls. The model is solved both numerically and (under simplified conditions) analytically, showing the existence of different regimes in the temporal evolution of soil thickness. The effects of hyetograph shape on the potential for landsliding are also analyzed. An existing pore pressure response model is used to study the effects of unsteady rainfall infiltration in hillslopes and is coupled with simple hyetograph models and to intensity-duration-frequency functions to determine the return period of landslide-triggering rainfall. Results show that hyetographs with a peak at the end of a rainfall event have a stronger destabilizing effect than hyetographs with a constant rainfall or with a peak at the beginning of a storm. Thus the variability of hyetograph shapes adds uncertainty to the assessment of landsliding triggered by rainfall.
UR: http://www.gly.fsu.edu/~fagherazzi
DE: 1625 Geomorphology and weathering (0790, 1824, 1825, 1826, 1886)
DE: 1826 Geomorphology: hillslope (1625)
DE: 1838 Infiltration
DE: 1869 Stochastic hydrology
SC: Hydrology [H]
MN: Fall Meeting 2005