Quantitative analysis of soil erosion causative factors for susceptibility assessment in a complex watershed

Figures & data

Figure 1. Cameron highlands watershed, Malaysia

Figure 2. Soil loss map and erosion maps CFs (a) Soil loss map (b) Drainage density map (c) Lineament density map (d) NDVI map (e) LST map (f) SMI map (g) Rainfall erosivity factor (h) LS-factor (i) Erodibility factor (j) Land-use composition

Figure 2. (Continued)

Table 1. Descriptive statistic of Cameron Highlands watershed

Category	Variables	Units	Average	Standard deviation	Coefficients of variation	Minimum	Maximum
Response	Erosion	ton/ha/yr	0.762	0.672	0.882	0.04	2.93
Dynamic CFs	SMI	None	0.086	0.026	0.297	0.02	0.13
	NDVI	None	0.510	0.063	0.123	0.26	0.61
	LST	None	23.680	0.779	0.033	22.30	26.26
	Erosivity	MJ mm/ha/yr	2288.441	99.250	0.043	2104.32	2529.56
Static CFs
	Length-Slope	None	3.015	0.537	0.178	1.82	4.56
	Drainage density	km/km^2	8383.859	5263.121	0.628	673.97	21,236.37
	Lineament Density	None	0.243	0.076	0.312	0.11	0.39
	Erodibility (K)	ton ha/MJ/mm	0.017	0.140	0.001	0.014	0.020
% Land-use	Agriculture	%	22.304	20.315	0.911	0.07	91.30
	Forest	%	69.514	26.268	0.378	0.00	99.03
	Urban	%	8.131	8.994	1.106	0.00	34.62
	Water	%	0.051	0.344	6.704	0.00	2.74

Table 2. Summary of the model

Block	R	R^2	Adjusted R^2	Std. Error of the Estimate	R^2 Change	Sig. F Change	Durbin-Watson
1	0.423^a	0.179	0.123	1.02054	0.179	0.019
2	0.684^b	0.468	0.422	0.82843	0.289	0.000
3	0.727^c	0.528	0.479	0.78681	0.060	0.009
4	0.832^d	0.692	0.654	0.64123	0.164	0.000	2.282

a CFs: LinDen, DranDen, LSfactor, K-factor, NDVI; b CFs: LinDen, DranDen, LSfactor, K-factor, NDVI, LST; c CFs: LinDen, DranDen, LSfactor, K-factor, NDVI, LST, Erosivity; d CFs: LinDen, DranDen, LSfactor, K-factor, NDVI, LST, Erosivity, SMI.

Figure 3. Residual plots of standardized residuals against predicted values

Table 3. Analysis of variance (ANOVA)

Block	Item	Sum of squares	df	Mean square	F	Sig.
1	Regression	13.362	4	3.341	3.207	.019^a
	Residual	61.448	59	1.041
	Total	74.811	63
2	Regression	35.006	5	7.001	10.201	.000^b
	Residual	39.805	58	0.686
	Total	74.811	63
3	Regression	39.523	6	6.587	10.641	.000^c
	Residual	35.287	57	0.619
	Total	74.811	63
4	Regression	51.785	7	7.398	17.992	.000^d
	Residual	23.026	56	0.411
	Total	74.811	63

a, b, c and d define the significance of CFs in each model Block, df = degree of freedom.

Table 4. Model parameters for each block

Block		Unstandardized coefficients		Standardized coefficients	t	Sig.	Collinearity Statistics
	CFs	Beta (β)	Std. Error	Beta (B)			Tolerance	VIF
1	(Constant)	−1.615	1.654		−0.977	0.333
	NDVI	−3.116	2.275	−0.179	−1.370	0.176	0.811	1.233
	K-factor	0.051	0.028	0.025	0.212	0.024	0.654	1.110
	LSfactor	0.453	0.260	0.223	1.741	0.087	0.847	1.181
	DranDen	−1.05e-06	0.000	−0.051	−0.416	0.679	0.93	1.076
	LinDen	4.839	1.955	0.337	2.475	0.016	0.753	1.328
2	(Constant)	−20.77	3.666		−5.666	0.000
	NDVI	−1.252	1.876	−0.072	−0.668	0.507	0.786	1.273
	K-factor	0.045	0.015	0.012	0.122	0.222	0.542	1.041
	LSfactor	0.425	0.211	0.209	2.010	0.049	0.846	1.182
	DranDen	−5.65e-07	0.000	−0.027	−0.275	0.785	0.928	1.078
	LinDen	5.122	1.588	0.356	3.226	0.002	0.752	1.329
	LST	0.768	0.137	0.549	5.616	0.000	0.961	1.041
3	(Constant)	−34.665	6.211		−5.581	0.000
	NDVI	−2.716	2.309	0.156	1.176	0.244	0.468	2.138
	K-factor	0.051	0.101	0.025	0.231	0.102	0.264	1.140
	LSfactor	0.437	0.201	0.215	2.175	0.034	0.846	1.182
	DranDen	−4.13e-07	0.000	−0.020	−0.211	0.833	0.927	1.079
	LinDen	5.549	1.516	0.386	3.660	0.001	0.744	1.344
	LST	0.909	0.140	0.650	6.494	0.000	0.827	1.209
	Erosivity	0.004	0.001	0.333	2.701	0.009	0.544	1.839
4	(Constant)	−98.222	12.692		−7.739	0.000
	NDVI	−6.387	1.998	0.368	3.196	0.002	0.415	2.410
	K-factor	0.364	0.084	0.042	0.412	0.047	0.254	1.200
	LSfactor	0.566	0.165	0.279	3.425	0.001	0.828	1.207
	DranDen	2.14e-06	0.000	0.103	1.288	0.203	0.854	1.171
	LinDen	2.468	1.358	0.172	1.817	0.075	0.616	1.624
	LST	3.455	0.480	2.470	7.198	0.000	0.047	1.417
	Erosivity	0.001	0.001	0.113	1.042	0.302	0.468	2.135
	SMI	82.184	15.05	1.929	5.461	0.000	0.044	2.694

Note: DranDen = Drainage density, LinDen = Lineament density, K-factor = Soil erodibility.

Table 5. Pearson correlation matrix for the selected erosion CFs

CFs	*Soil loss	NDVI	K-factor	LS-factor	DranDen	LinDen	LST	Erosivity	SMI
*Soil loss	1.000
NDVI	−0.283	1.000
K-factor	0.012	0.001	1.000
LSfactor	0.061	0.167	0.001	1.000
DranDen	−0.082	0.230	0.017	0.155	1.000
LinDen	0.327	−0.385	0.001	−0.370	−0.073	1.000
LST	0.576	−0.188	0.010	−0.001	−0.081	0.033	1.000
Erosivity	0.173	−0.603	0.014	−0.102	−0.151	0.173	−0.176	1.000
SMI	−0.368	−0.065	0.001	−0.113	−0.043	0.159	−0.934	0.378	1.000

Note: *Transformed soil loss values, DranDen = Drainage density, LinDen = Lineament density.