Effects of rainfall intensity on the sediment concentration in the Loess Plateau, China

doi:10.1007/s11442-020-1737-4

Abstract

Abstract:

To study the effects of changes in the rainfall intensity on sediment concentrations in the Loess Plateau, the observed rainfall intensities and sediment concentrations from three typical small watersheds were used to analyze the relationship between these parameters. The results showed that the sediment concentration generally increased with the increasing rainfall intensity on slope scale. However, at watershed scale, a significant threshold phenomenon was observed for the effects of the rainfall intensity on the sediment concentration. When the rainfall intensity exceeds the threshold, the flood sediment concentration will no longer increase with the increase in the rainfall intensity. The rainfall intensity threshold increased with increasing vegetation coverage. The rainfall intensity threshold was 10-15 mm/h during 1956-1969, reached 20 mm/h from 1990 to 1997 and is approximately 40 mm/h at present. Due to a rainfall intensity of 10-15 mm/h almost happened every year, the vegetation did not change much from the 1950s to 1980s. Sediment yield mainly depends on soil erosion caused by surface flow, but the surface flow speed does not increase indefinitely with the increase in the flow discharge. Thus, the annual maximum sediment concentration of the tributaries in the loess area has been basically stable before the 1990s.

Key words: Loess Plateau, loess hilly region, rainfall intensity, sediment concentration, influence

LIU Xiaoyan, DANG Suzhen, LIU Changming, DONG Guotao. Effects of rainfall intensity on the sediment concentration in the Loess Plateau, China[J].Journal of Geographical Sciences, 2020, 30(3): 455-467.

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	Subwatershed					Small watershed
	Tuanshangou	Shuiwanggou	Tuan- yuangou	Qiaogou		Peijiamao			Liujiagou	Shejiagou
Area (km²)	0.18	0.107	0.491	0.44		39.5			21.0	4.72
Period (years)	1961-1969	1959-1967	1958-1961	1990-1997	2007-2018	1990-1997		2007-2018	1960-1969	1963-1969
Vegetation coverage (%)	10-30			36-47	55-75		36-47	55-75	10-30

	Runoff plots located at an upper hillslope						Runoff plots composed of hillslope and valley side slope (entire slope)
	No. 2	No. 3	No. 4	No. 5	Duanchuan 1	Duanchuan 2	No. 7	No. 9
Slope length (m)	40	60	20	20	7.57	20.1
Area (m²)	647	970	324	350	31.5	208	17200	4580