JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. ABSTRACT. The effects of an extreme rainfall triggering debris flows (mudflows) in the mountains S of Abisko, N Sweden, in 1979, are evaluated with regard to geomorphological impact. Several older events of debris flows in the same area during postglacial time are evident in the morphology of the slopes. Where such flows have occurred repeatedly, debris accumulations superficially similar to alluvial cones and referred to as debris flow cones are built. An attempt at dating old flows by means of lichenometry indicated at least four earlier events within the last 2700 years in Nissunvagge. A map of the spatial pattern of known rainfall-triggered mass movements in northern Lappland is presented to support the hypothesis of geomorphic impact of extreme rainfall in three area size classes called regions, cells and spots. in Nissunvagge area, N. Sweden. Key: I = Mountain ridge and summit with altitude in meters. 2 = Stream. 3 = Glacier. 4 = Sediment plume in Lake Tornetrask. 5 = Lake. 6 = Railway. 7 = Each arrow shows one large debris flow or a group of smaller ones. 8 = Alluvial fan in valley bottom affected by debris flow flood. Note difference between debris flows deposited as colluvium on U-valley slopes, and those removed by stream flood, at the base of V-valley slopes. The latter arrows reach the streams. ALPINE DEBRIS FLOWS IN NORTHERN SCANDINAVIA Fig. 2. Photograph of section C, Nissunvagge, one month after the debris flows in 1979. Fresh debris flows C20 (left) to C42 (right) appear as white tracks on dark talus slopes and colluvial fans. Valley bottom at 900 m altitude with tundra polygons. Mountain top at 1640 m altitude. Photo N. A. Andersson, 25.7.1979.
ABSTRACT.
Solifluction movement rates from 1952 to 2008 for the Abisko region, northern Sweden, have been compiled and analysed through correlation tests and multiple regression. The temporal analysis is based on two datasets (Lobe11 & gridAB and Line B) from Kärkevagge. The dataset Lobe11 & gridAB show a strong correlation between movement rates and mean annual air temperature (MAAT) and MAAT is also identified as one of the significant contributing parameters in the multiple regression model. No significant correlations were found for the Line B dataset. The spatial analysis indicates generally higher movement rates in the western part of the region and at lower altitudes mainly between 700 and 900 m a.s.l., but the spatial variability is high. To reduce the influence of the temporal variation the data for the correlation tests of the spatial variations were divided into two parts: 1957 to 1980 and 1981 to 2008. The correlation analysis of the dataset 1957 to 1980 shows a significant negative correlation between annual average movement rates and permafrost probability and altitude. The dataset 1981 to 2008 shows a positive correlation between movement rates and wetness index. It is concluded that movement rates may increase with higher MAAT in the western part of the region (Kärkevagge), the spatial variability of movement rates within the region is very high and that altitude (and/or permafrost) together with wetness index are the main controls on the regional spatial variation. The study highlights the limitations in establishing statistical relationships between movement rates and climate using data from different field empirical studies.
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