Seasonal changes in the sediment flux on steep hillslopes in a humid diurnal frost environment

Mountain hillslopes are generally shaped by a combination of various types of sediment transport processes (e.g. surface erosion, soil creep, and dry ravel), which can occur simultaneously in the same area. Since sediment transport is generally affected by multiple microclimatic factors, such as hea...

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Bibliographic Details
Published in:Earth surface processes and landforms 2017-03, Vol.42 (3), p.389-398
Main Authors: Imaizumi, Fumitoshi, Suzuki, Osamu, Togari‐Ohta, Asako
Format: Article
Language:English
Subjects:
diurnal freeze–thaw
dry ravel
sediment flux
soil creep
surface erosion
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Summary:Mountain hillslopes are generally shaped by a combination of various types of sediment transport processes (e.g. surface erosion, soil creep, and dry ravel), which can occur simultaneously in the same area. Since sediment transport is generally affected by multiple microclimatic factors, such as heavy rainfall and changes in ground temperature, the types of predominant sediment transport processes vary by season. We conducted field observations in the southern Japanese Alps in the period from 2009 to 2013, using sediment traps and time lapse cameras, to investigate the seasonal changes in the type and flux of hillslope sediment transport on steep mountains in which both rainfall and diurnal freeze–thaw triggered sediment transport. In winter and early spring, sediment transport via diurnal freeze–thaw (soil creep and dry ravel) was highly active, whereas rainfall‐induced soil creep and selective transport by overland flow were active in summer and autumn when precipitation is abundant (average sediment flux of 0.033 and 0.074 kg m−1 day−1, respectively). Sediment flux was spatially variable and was affected by the form of the slope; sediment flux on the concave slope was higher than on the ridge‐shaped slope during both freeze–thaw and rainfall periods. Sediment flux on an old landslide exceeded that in second‐growth forest regardless of the slope shape. Temporal changes in the sediment flux were not completely synchronized among monitoring plots and were affected by slope shape, grain size, and episodic sediment supply events such as release of sediment from woody debris. Copyright © 2016 John Wiley & Sons, Ltd.
ISSN:0197-9337
1096-9837
DOI:10.1002/esp.3982