Groundwater fluctuations during a debris flow event in western Norway – triggered by rain and snowmelt
<p>Pore pressure is crucial in triggering debris slides and flows. Here we present measurements of groundwater pore pressure and temperature recorded by a piezometer 1.6 m below the surface on a slope susceptible to debris flows in western Norway. One of the largest oscillations in data collec...
Main Authors: | , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2021-07-01
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Series: | Hydrology and Earth System Sciences |
Online Access: | https://hess.copernicus.org/articles/25/4147/2021/hess-25-4147-2021.pdf |
Summary: | <p>Pore pressure is crucial in triggering debris slides and
flows. Here we present measurements of groundwater pore pressure and
temperature recorded by a piezometer 1.6 m below the surface on a slope
susceptible to debris flows in western Norway. One of the largest
oscillations in data collected over 4 years coincided with a debris flow
event on the slope that occurred during storm Hilde on 15–16 November 2013.
More than 100 landslides were registered during the storm. Precipitation
totaled about 80–100 mm in 24 h, locally up to 129 mm, and an
additional trigger factor for the landslides was a rapid rise in air
temperature that caused snowmelt. In the studied slope a fraction of the
precipitation first fell as snow. On 15 November, the groundwater level in
the hillslope rose by 10 cm/h and reached 44 cm below the surface. At
the same time, air temperature rose from 0 <span class="inline-formula"><sup>∘</sup></span>C to over 8 <span class="inline-formula"><sup>∘</sup></span>C, and the groundwater temperature dropped by 1.5 <span class="inline-formula"><sup>∘</sup></span>C.
The debris flow probably occurred late in the evening of 15 November, when
the groundwater level reached its peak. Measurements of the groundwater in
the hillslope in the period 2010–2013 show that the event in 2013 was not
exceptional. Storm Dagmar on 25–26 December 2011 caused a similar rise in
groundwater level but did not trigger any failures. The data suggest that
during heavy rainstorms the slope is in a critical state for a landslide to
be triggered for a short time – about 4–5 h.</p> |
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ISSN: | 1027-5606 1607-7938 |