Groundwater fluctuations during a debris flow event in western Norway – triggered by rain and snowmelt

Abstract. Pore pressure is crucial in triggering debris slides and flows. Here we present measurements of groundwater pore temperature recorded by a piezometer 1.6 m below the surface on slope susceptible to flows western Norway. One largest oscillations data collected over 4 years coincided with flow event that occurred during storm Hilde 15–16 November 2013. More than 100 landslides were registered storm. Precipitation totaled about 80–100 mm 24 h, locally up 129 mm, an additional trigger factor for was rapid rise air caused snowmelt. In studied fraction precipitation first fell as snow. On 15 November, level hillslope rose 10 cm/h reached 44 cm surface. At same time, from 0 ∘C 8 ∘C, dropped 1.5 ∘C. The probably late evening when its peak. Measurements period 2010–2013 show 2013 not exceptional. Storm Dagmar 25–26 December 2011 similar but did any failures. suggest heavy rainstorms critical state landslide be triggered short time – 4–5 h.