SPATIAL MODELING OF RAIN-TRIGGERED LANDLSIDES A CASE STUDY IN SOUTHERN LEYTE PROVINCE, PHILIPPINES

摘要

Almost all preparatory and triggering causal factors are well set in place in the case of Philippines torn ake its sloping te rrains vu lnerable to landsli des; the history of landslide occurrences stands as foolproof evidence. A review of the past even ts however indicates that rainfall has, inter alia, been offering the triggering effect to cause most of the devastating landslides. A number of such landslides have occurred in the Southern Leyte province of Philippines causing considerable loss of life and damage to properties. Facilitating towards managing the associated landslid erisk in South ern Leyte it was aim ed at delineating the areas that are pro ne to rain -triggered Ian dslides. The SINMAP modd which combines a mechanistic slope stability model with a steady-state hydrology model was employed in way accomplishing this, much needed, task. Elevation data in the form of a raster GIS layer was the main input for the model. Mapping of past lands lide initiation points was al so completed with the aid of satellite based remotely sensed data and a GPS survey. The SINMAP m odel, with a careful attribution of the requi site geotechnical and hydraulic parameters, delineated 47% of th e study area w hich is about 850 km~2 to be unstable and quasi-stable under extrem e rainfall events recorded in the past. T his zonation of landslide hazard was considered to be very satisfactor y as 82% of the total recorded la ndslides were found to fall in the unstable regions.