Field experimental study on the effect of thawed depth of frozen alpine
meadow soil on rill erosion by snowmelt waterflow
Abstract
Soil erosion by snow or ice melt waterflow is an important type of soil
erosion in many high-altitude and high-latitude regions. The snowmelt
waterflow erosion process, affected by soil freeze and thaw, is highly
dynamically variable. In this study, field experiments were conducted to
investigate the effects of thawed depth of frozen soil profile on
snowmelt waterflow erosion of alpine meadow soil in the spring. The
experiments involved five thawed depths from 0 to 100 mm under two
snowmelt waterflow rates of 3 L/min and 5 L/min. The unthawed soil or
shallow-thawed depth of 10 mm significantly altered the runoff and
sediment production mechanism, including a significant delay of the
runoff generation time and change of hydrograph and sedigraph. When the
soil was frozen, the topsoil was structured with large open voids, to
retain water and impede flow. This resulted in runoff generation time
that was greatly lagged and soil erosion in the initial stage that was
inhibited. The relationship curve of runoff and sediment concentration
showed two-stage patterns that characterized a limited sediment supply
in the early stage and hydrodynamic-controlled processes in the later
stage. The deep-thawed cases (≥ 30 mm) showed similar hydrograph and
sedigraph patterns with unfrozen soil condition. The findings of this
study provide guidance for the future improvement of erosion model of
partially thawed soil. Keywords: snowmelt waterflow erosion; thawed soil
depth; soil freeze and thaw; runoff generation; sediment rating curve