Meteorological conditions during slush‐flow release and their geomorphological impact in northwestern iceland: a case study from the bíldudalur valley

Abstract

. This paper examines triggering factors and geomorphic significance of slush flows in the Bíldudalur valley, northwestern Iceland. The area is prone to release slush flows from two confined gullies, and at least ten flows have been reported since the beginning of the twentieth century. Despite their short path (600 m) and their moderate magnitude (from 6000 to 8000 m3), slush flows in the Bíldudalur valley represent a serious threat for the local community that is situated within the runout and deposition zones. With the help of meteorological data, the release of known slush flows is examined, highlighting the role of heavy rainfall and rapid snow‐melt during winter cyclonic activity. The geomorphological impact of slush flows is assessed through the characteristics of the landforms produced during the 1997 and 1998 slush‐flow events. It appears that the most obvious characteristics of slush flows in the Bíldudalur valley are the entrainment and deposition of debris, spatially differentiated. Chaotic sedimentation occurs chiefly in the middle part of a clearly concave cone, even if the flows continue beyond the cone.

Meteorology, Topography and Snowpack Conditions causing Two Extreme Mid‐Winter Slush and Wet Slab Avalanche Periods in High Arctic Maritime Svalbard

“…The term ‘slush flow’, as commonly used in Norway (Hestnes and Sandersen, ; Hestnes, ; Hestnes and Bakkehøi, ), was primarily introduced by Washburn and Goldthwait () and applied to small‐scale slope processes confined to drainage basins (e.g. Decaulne and Saemundsson, ), whereas the term ‘slush torrents’ was introduced by Rapp () and used by Barsch et al . () to describe high‐magnitude and low‐frequency events.…”

“…(2004) observed slush avalanches during 16 periods in only 11 winters in Rana, northern Norway. Decaulne and Saemundsson () found a return interval of less than ten years for observed slush avalanches in Iceland. Our investigations suggest even longer recurrence intervals for High Arctic Svalbard.…”

Snow-avalanche and debris-flow hazards in the fjords of north-western Iceland, mitigation and prevention

“…Such dualprocess sites are found in Patreksfjordur, Bildudalur, Bolungarvik (Decaulne 2004) and in Sudavik. In the latter scenario, the role of avalanches in supplying sediment to debris-flow channels has not been measured, but is presumably limited as snow avalanches occurring under present environmental conditions are unable to carry out strong geomorphic work within their track (Decaulne and Saemundsson 2006a).…”

“…Wind, and consequently snowdrift are of primary importance in snow avalanche release (Haraldsdó ttir 2004;Haraldsdó ttir et al 2004). Rapid snowmelt due to rising temperature and/or rainfall is favourable for slush-flow release in suitable areas (Decaulne and Saemundsson 2006a;Saemundsson 1997;Saemundsson and Kiernan 1998). Study of debris-flow triggering factors (Decaulne 2001;Decaulne and Saemundsson 2003;Saemundsson et al 2003;Decaulne et al 2005) strongly underlines the role of rapid snowmelt and long-duration rainfall as prerequisites for debris-flow release in this part of Iceland.…”

An Overview of Postglacial Sediment Records from Colluvial Accumulations in Northwestern and North Iceland

“…Meteorological triggering factors have also been analyzed (Björnsson, 2002;Decaulne et al, 2005;Saemundsson and Decaulne, 2007). A combination of historical, geomorphological and phytogeographical approaches has been used to show that the recurrence frequency of these processes over the last few decades ranges from <0.01-1 y -1 (Decaulne, 2004;2006a).…”