T216 Weather-Induced Landslides, Debris Flows, and Rock Fall

Tuesday, 24 October 2017
8:00 AM - 12:00 PM
Skagit 5

VARIABILITY IN SOIL-WATER RETENTION PROPERTIES AND IMPLICATIONS FOR PHYSICS-BASED SIMULATION OF LANDSLIDE EARLY WARNING CRITERIA

Paper number: T216-2
Program: Technical Sessions
Time: 8:15 AM – 8:30 AM

Authors

Abstract

Landsliding is a persistent hazard to human life and will likely remain so as populations continue to expand into failure-prone terrain. Despite the observed connection between the unsaturated zone and the shallow landslide initiation problem, there is considerable uncertainty in how the approaches used to estimate soil-water retention properties affect slope stability assessment. Further examination of this uncertainty is critical to evaluating the utility of hydrologic modeling as a physics-based tool for shallow landslide prediction and early warning. To examine conditions relevant to shallow landsliding, we employ a numerical model of variably saturated groundwater flow parameterized with an ensemble of texture-, laboratory-, and field-based soil-water retention properties for an extensively monitored landslide-prone site. Simulations of soil-water content (θ), pore-water pressure (uw), and the resultant Factor of Safety (FS) show considerable variability across and within these different parameter estimation techniques. In particular, we demonstrate that variability in soil-water retention properties influences predictions of positive uw coincident with widespread shallow landsliding. We also find that the ensemble of soil-water retention properties imposes an order-of-magnitude and two-fold variability in seasonal and event-scale landslide susceptibility, respectively. Despite reduced FS uncertainty during wet conditions, parameters that control the dry end of the soil-water retention function markedly impact the ability of a hydrologic model to capture θ dynamics observed in the field. These results suggest that neglecting variability in soil-water retention properties could be problematic for objective physics-based simulation of landslide early warning criteria.

Geological Society of America Abstracts with Programs. Vol. 49, No. 6

doi: 10.1130/abs/2017AM-297875

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