Abstract
Erosion of freeze-thaw soil by meltwater from snow/glacier is one of the main erosion types in high altitude or latitude regions. This study aims to experimentally measure soil erosion processes over partially-unfrozen soil slopes in laboratory. The experiments including three slope gradients of 10°, 15°, and 20°, three water flow rates of 1, 2, and 4 L/min (0.06, 0.12, and 0.24 m3/h), and three thawed-soil depths of 1, 2, and 5 cm were conducted to measure sediment concentration and calculate its delivery rate under seven slope lengths of 0.5, 1.0, 2.0, 3.0, 4.0, 5.0, and 6.0 m. The sediment delivery rates from nonfrozen soil slopes under the corresponding slope gradients, flow rates, and slope lengths also were measured as control treatments. Results showed that the sediment delivery rate from both partially-unfrozen and nonfrozen soil slopes increased logarithmically with slope length. The sediment delivery rate from partially-unfrozen soil slope increased with the increased slope gradient and meltwater flow rate significantly, and the effect of water flow rate on it was greater than that of slope gradient. The thawed-soil depth did not significantly affect sediment delivery rate. The sediment delivery rate from a partially-unfrozen loamy soil slope averagely was 11.4% smaller than that from nonfrozen soil slope. This study is helpful to understand the erosion process of thawing-soil by meltwater from snow/glacier.
Highlights
Freeze-thaw (FT) soil erosion is one of the soil erosion types in high altitude and/or high latitude regions[1,2,3,4], and the area suffering FT erosion is about 1.28 million km[2] in China and accounts for 13.31% of its total arable land acreage[5]
The soil erosion amount from a partially-unfrozen soil slope could increased by 1.4–4.0 times than that from a nonfrozen soil slope, and this multiple would increase with the increase of initial soil water content[21]
The variation of sediment delivery rate with slope length is shown in Fig. 1 under different thawed-soil depths, slope gradients, and meltwater flow rates
Summary
Freeze-thaw (FT) soil erosion is one of the soil erosion types in high altitude and/or high latitude regions[1,2,3,4], and the area suffering FT erosion is about 1.28 million km[2] in China and accounts for 13.31% of its total arable land acreage[5]. Under the partially-unfrozen soil, there exists an impermeable layer below the thawed soil that prevents water infiltrates into deeper soil layer[24], and results in an increased lateral subsurface flow and a serious soil erosion loss in spring[25,26]. The thawing of soil increases its water content These are responsible to the high runoff, great sediment content, and serious soil erosion loss in spring[30,31]. An enormous studies have been conducted on the effect of FT cycle on soil erosion, the studies on the process and mechanism of soil erosion caused by meltwater in high altitude cold regions are rare due to the limitation of field observation and monitoring technology. This study aims to (1) study sediment delivery during the soil thawing process; (2) determine the variation of sediment delivery rate on partially-unfrozen soil with slope length, slope gradient, thawed depth, and meltwater rate; and (3) analyse their impacts on sediment delivery rate of partially-unfrozen soil slope
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