FIELD VARIABILITY OF LANDSLIDE MODEL PARAMETERS

(A.Burton, T.J.Arkell and J.C.Bathurst, Water Resource Systems Research Unit, Dept. of Civil Engineering, University of Newcastle upon Tyne, UK)

In any modelling exercise it is important to quantify the uncertainty associated with areally representative model parameters and the resultant uncertainty in model output. To this end, a rare data set of parameters (slope, soil depth and soil cohesion) relevant to spatially distributed modelling of shallow landslides was obtained from field measurements at 250 points across a 250m square region of a landslide susceptible hillslope in Scotland. Factor-of-safety slope stability was calculated for each data point and for areally averaged values of the parameters for the whole field site. The former case was partially successful at identifying areas exhibiting creep and landslide failure scars whereas the latter did not indicate overall instability. Combined with a limited semi-variogram analysis, these results suggest that a measurement frequency of 10 - 20 m may be appropriate for the spatially distributed modelling of shallow landslides in this case. This frequency is comparable with characteristic landslide scar dimensions for the area.