Doctoral Dissertation Research: Rainfall Characteristics and the Influence of Urban Land Use on Shallow Landslide Initiation in Seattle, Washington

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Shallow landslides often occur on natural hillslopes during rainstorms of high intensity or long duration. While researchers have examined the profound effects that that an urban environment can have on surface hydrology and drainage morphology, relatively little attention has been given to the effects of urbanization on landslide hazards. This doctoral dissertation research project will address the influence of impervious surfaces on shallow landslide occurrence in Seattle, an urban area with a precipitation climatology characterized by winter rainstorms of long duration and low intensity. The project will use a geographic information system (GIS) framework to combine rainfall data from a dense gauge network, high-resolution digital topography, a historical record of landslide occurrence, and a remotely sensed map of impervious surfaces. Analyses of these data will facilitate evaluation of the watershed-scale effects of surface drainage alteration on landslide susceptibility. Research methods will include compilation of historical shallow landslide occurrence and associated precipitation climatology. Empirical relations between rainfall intensity/duration will be defined. Field investigations of large or recent landslides will provide information on the geologic setting, style of landslide failure and deposition, and influence of drainage modifications. To evaluate the effect of impervious surfaces on landslide occurrence, a coupled rainfall-infiltration/slope-stability model will be used to describe the spatial distribution of pore-water pressures at depth during rainstorms in which landslide are known to have occurred.This project will examine the influence of impervious surfaces on landslide hazard in an urban setting where slope failure occurs during rainstorms of low intensity and long duration by applying a coupled, physically based model in a GIS framework. The study will illuminate the processes through which the urban environment has a significant impact on hillslope processes at the watershed scale. In a broader context, the project will add to the understanding of human impact on geomorphic systems. Results from this study should provide predictive and design tools for emergency management and planning. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.