WebGIS-based decision support system for soil erosion assessment in Legedadi watershed, Oromia Region, Ethiopia

Figures & data

Figure 1. The location map of the study area.

Figure 2. Flow chart of the methodology.

Table 1. Soil erodibility values for soil types (Helden, 1987).

Soil color	K− factor values
Black	0.15
Brown	0.2
Red	0.25
Yellow	0.3

Figure 3. Overall layout of the Web-GIS monitoring platform.

Figure 4. Iterative model development and its life cycle.

Figure 5. General system architecture-Client computer and Server computer.

Figure 6. Web-GIS Architecture and process line diagram.

Table 2. Details of rainfall station in the Legedadi watershed.

Rain Gauge Station	UTM Coordinates		Elevation (m)	Annual rainfall (mm)
	Easting	Northing
Addis Ababa Observatory	0384451	090108	2386	1220.66
Addis Ababa Bole	0384500	090200	2354	1035.48
Sendafa	0390117	090908	2569	1097.49
Dire Gidib	0385635	090928	2560	1646.91
Chefe Donsa	0390724	085812	2392	948.67

Figure 7. (a) Mean annual rainfall, (b) Distribution of Rainfall erosivity factor (R).

Table 3. Soil classes and respective Soil erodibility (K) factor value.

Soil Class	Area coverage		Soil erodibility (K) factor
	(ha)	(%)	(t ha^−1MJ^−1mm^−1)
Pellic Vertisols	16129.2	76.9	0.22
Orthic Solonchaks	1889.5	9.0	0.175
Calcic Xerosols	2076.3	9.9	0.3
Leptosols	868.8	4.2	0.3
Total	20963.75	100

Figure 8. (a) Distribution of soil types, (b) Distribution of soil erodibility factor (K).

Figure 9. (a) Slope length (X), (b) slope gradient (S), and (c) slope length and steepness (LS) factors.

Table 4. Land-use/land-cover classes with respective Cover−management practice factor (C).

Land-use and land-cover classes	Area coverage		C factor value
	(ha)	(%)
Water body	325.8	1.6	0
Forest	1344.9	6.4	0.05
Settlement	1707.4	8.1	0.99
Cultivated land	9346	44.6	0.15
Open grassland	8239.7	39.3	0.01
Total	20963.75	100

Figure 10. (a) Land-use/land-cover map, (b) Cover−management practice factor (C), and (c) Support practice factor (P).

Table 5. P factor value for land-use and land-cover classes with respect to slope (Wischmeier & Smith, 1978).

Land-use/land-cover class	Slope class	Slope (%)	P factor value
Agricultural land	I	0 − 5	0.11
		5 − 10	0.12
	II	10 − 20	0.14
		20 − 30	0.22
		30 − 50	0.31
	III	>50	0.43
Other land-use class		All	1.00

Table 6. Soil erosion estimation in the study area.

Soil loss	Area coverage
(t ha^−1 yr^1)	(ha)	(%)
0–10	18343.7	87.5
10–20	593	2.8
20–30	322.8	1.5
30–45	316.1	1.5
45–60	201.4	1.0
60–70	105.7	0.5
70–80	131.2	0.6
80–100	140.2	0.7
>100	809.7	3.9
Total	20963.8	100

Table 7. Soil erosion estimation at micro-watershed level in the study area.

Micro-watersheds No	Soil loss	Area coverage
	(t ha^−1 yr^1)	(ha)	(%)
6,11,12,13,14,15,16,17,18,20,21,22,23,24,25,26, 27, 28, 29, 30, 31, 32 and 33.	0.53–18	13128.5	69.8
9	18–37.3	314.6	1.8
5,4,8,10	37.3–59.9	2768.5	14.7
19	59.9–69.9	38.6	0.2
1,2,3,7	69.9–138.4	2562.7	13.6

Figure 11. Soil erosion estimation (a) overall study area, and (b) micro-watershed level.

Figure 12. Developed WebGIS-based soil loss information dissemination user interface.

Helden, U. (1987). An assessment of woody biomass, community forests, land use and soil erosion in Ethiopia. Lund: Lund University Press.

 Google Scholar

Wischmeier, W. H., & Smith, D. D. (1978). Predicting rainfall erosion losses. A guide to conservation planning (USDA Agriculture Handbook n. 537). Washington, DC.

 Google Scholar