Portuguese Bend Landslide, Palos Verdes Hills, California

Unsaturated Flow Processes and the Onset of Seasonal Deformation in Slow‐Moving Landslides

“…Our motivation for this work is that large, deep‐seated, slow‐moving landslides, which are often referred to as earthflows (Hungr et al., 2014; Keefer & Johnson, 1983; Lacroix et al., 2020), play a fundamental role in the development of topographic relief (Mackey & Roering, 2011), the delivery of sediment to river channels (Finnegan et al., 2019; Mackey & Roering, 2011; Roering et al., 2015; Simoni et al., 2013), and the evolution of drainage networks (Bennett, Miller, et al., 2016; Shobe et al., 2020). In addition, earthflows represent a chronic source of damage to infrastructure such as railroads, utility pipelines, and highways (e.g., Alberti et al., 2020; Merriam, 1960). Thus it is important to develop and apply models that can be used to better understand landslide behavior.…”

An examination of seasonal deformation at the Portuguese Bend landslide, southern California, using radar interferometry

“…As the modest success of the dewatering campaigns and rainfall driven acceleration suggest, the landslide depends greatly on groundwater and pore pressure [ Ehlig , 1992]. Multiple studies [ Merriam , 1960; Vonder Linden , 1989; Ehlig , 1992] agree that the displacement continues due to the constant coastal erosion at the toe of the slide.…”

Landslide Sensitivity and Response to Precipitation Changes in Wet and Dry Climates

“…We then confirmed that the InSAR signals corresponded to true landslides by overlaying the InSAR velocity maps onto DEMs, Google Earth imagery, and previously published landslide inventories. We began searching for active landslides by examining the InSAR velocity in well‐known landslide areas in northern California (Bennett, Miller, et al., 2016; Handwerger, Fielding, et al., 2019; Kelsey, 1978), central California (Booth et al., 2020; Cohen‐Waeber et al., 2018; Finnegan et al., 2019; Scheingross et al., 2013; Wills et al., 2001), and southern California (Calabro et al., 2010; Jibson, 2006; Merriam, 1960; Swirad & Young, 2021; Young, 2015). We also examined the InSAR data alongside the California Geologic Survey statewide landslide inventory (Wills et al., 2017).…”

“…Once a hillslope fails as a landslide it can accelerate rapidly and fail catastrophically (Iverson et al., 2015; Jibson, 2006; Shugar et al., 2021), move downslope slowly for years to hundreds of years (Mackey et al., 2009; Nereson & Finnegan, 2019; Rutter & Green, 2011), or move slowly for a period of time before stabilizing or failing catastrophically (Agliardi et al., 2020; Handwerger, Huang, et al., 2019; Iverson, 2005; Kilburn & Petley, 2003). These different behavioral modes have important consequences for hazard assessment because fast‐moving landslides can move at rates up to tens of meters per second and can easily claim lives (Iverson et al., 2015; Shugar et al., 2021), while slow‐moving landslides move at rates of meters per year or less and can damage infrastructure (Lacroix, Handwerger, et al., 2020; Merriam, 1960).…”