Comparing grain size distribution of sediment and original soil under raindrop detachment and raindrop-induced and flow transport mechanism

Figures & data

Table 1. Characteristics of the soil used in the present study.

Parameter	Unit	Value
Clay (<2 μm)	%	12.9
Silt (2–63 μm)	%	52.8
Sand (>63 μm)	%	34.3
Texture		Silt loam
Bulk density	g cm^−3	1.46
pH	-	7.65
Electrical conductivity	mS m^−1	7.55
Organic matter	%	2.61
Mean weight diameter (dry)	mm	1.38
Mean weight diameter (wet)	mm	0.98

Figure 1. Experimental set-up of rainfall simulation (right), field condition of original site (middle) and schematic of the study watershed (left).

Table 2. Summary of simulated rainfall and runoff characteristics.

Rainfall intensity (mm h^−1)	Rainfall				Runoff
	Median diameter (mm)	Mean velocity (m s^−1)	Kinetic energy of rainfall (J m^−2 mm^−1)	Power (W m^–2)	Power (W m^–2)
30	1.50	6.68	23.41	0.19	0.017
60	1.57	6.91	23.66	0.39	0.033
90	1.58	6.67	21.15	0.54	0.047

Table 3. Result of Tukey test groupings for different variables from rainfall simulation experiments.

Plot slope (%)	Rainfall intensity (mm h^−1)	Time to runoff initiation (s)	Runoff volume (mm^3)	Soil loss (g m^−2 min^−1)
5	30	403.67^d	54 543.33^c	31.16^ab
	60	271.00^c	34 880.00^a	22.19^a
	90	186.33^ab	49 336.67^ab	32.09^ab
15	30	450.00^d	44 390.00^abc	113.81^abc
	60	243.67^bc	38 746.67^ab	103.24^abc
	90	149.00^a	47 946.67^ab	135.28^bc
25	30	556.00^e	41 943.33^ab	135.19^bc
	60	225.00^bc	43 012.00^abc	204.91^c
	90	146.67^a	51 993.33^ab	335.01^d

a, b, c and d are statistically different at P = 0.05 and similar letters are not statistically different at P = 0.05.

Table 4. Result of the t-test for characteristic diameters of sediment and original soil GSDs under different rainfall intensities and slopes.

Type	Slope (%)	Rainfall intensity (mm h^−1)	D10 (μm)	D20 (μm)	D50 (μm)	D84 (μm)	D90 (μm)
Original soil	-	-	1.24^a	3.51^a	25.78^a	183.9^a	262.37^a
Sediment	5	30	0.50^b	1.20^b	4.60^b	12.53^b	19.19^b
		60	0.55^b	1.53^b	6.54^b	31.66^b	63.36^b
		90	0.71^b	1.86^b	7.17^b	28.72^b	47.97^b
	15	30	0.55^b	1.46^b	7.21^b	56.92^b	136.07^b
		60	0.78^b	2.37^b	15.92^b	149.41^b	208.23^b
		90	1.01^b	2.49^b	11.92^b	51.62^b	94.75^b
	25	30	0.55^b	1.69^b	7.66^b	44.63^b	123.36^b
		60	1.04^b	3.03^b	18.38^b	151.30^b	221.17^b
		90	1.05^b	3.19^b	23.38^a	166.80^b	233.69^b

a and b are statistically different at P = 0.05 and similar letters are not statistically different at P = 0.05.

Figure 2. Original soil and effective sediment GSDs under different slopes and rainfall intensities.

Figure 3. Comparison of sediment GSD enrichment or depletion in various size classes under different slopes and rainfall intensities.

Figure 4. Correlation between measured and estimated enrichment ratios of sediment and original soil GSD variables.