Journal of Resources and Ecology >
Assessing Soil Erosion Susceptibility Using Revised Morgan-Morgan-Finney Model: A Case Study from Kulekhani Watershed, Makawanpur, Nepal
Received date: 2023-08-16
Accepted date: 2023-10-16
Online published: 2023-12-27
The research was conducted within the Kulekhani Watershed with the objective of examining changes in Land Use Land Cover (LULC) dynamics and soil erosion across various LULC categories spanning from 2000 to 2020. The findings regarding the LULC classification in the Kulekhani Watershed revealed a steady rise in forested land, escalating from 60.72% in 2000 to 62.43% in 2010, and ultimately reaching 64.75% of the total area by 2020. The extent of water bodies exhibited a marginal increase from 1.07% in 2000 to 1.08% in 2020. Correspondingly, barren land expanded from 0.21% to 0.26%, eventually reaching 0.35% over the successive time intervals. Conversely, agricultural land dwindled over these periods, comprising 38% in 2000, 36.24% in 2010, and ultimately declining to 33.82% by 2020. The utilization of the Revised Morgan-Morgan-Finney (RMMF) model for soil loss estimation demonstrated a declining trend in weighted average soil loss during the years 2000 to 2010, followed by a slight increase between 2010 and 2020. The calculated soil loss values were recorded as 8.64 t ha-1 yr-1, 7.12 t ha-1 yr-1, and 7.30 t ha-1 yr-1 for the years 2000, 2010, and 2020 respectively. Similarly, the erosion susceptibility map illustrated a rising pattern in the very low-risk soil erosion zone from 2000 to 2020, primarily prominent within forested regions, while exhibiting a low to moderate susceptibility in agricultural zones. Moreover, barren areas displayed a moderate to high susceptibility to soil erosion. To address these concerns, future endeavors are recommended to encompass afforestation initiatives in barren regions, implement conservation farming practices in agricultural areas, and adopt appropriate measures for road stabilization.
THAPA Rabin , JOSHI Rajeev , BHATTA Binod , GHIMIRE Santosh . Assessing Soil Erosion Susceptibility Using Revised Morgan-Morgan-Finney Model: A Case Study from Kulekhani Watershed, Makawanpur, Nepal[J]. Journal of Resources and Ecology, 2024 , 15(1) : 182 -196 . DOI: 10.5814/j.issn.1674-764x.2024.01.016
Table 1 Input parameter of RMMF model |
Factor | Parameter | Definition and remarks |
---|---|---|
Rainfall | R | Annual or mean annual rainfall (mm) |
Rn | Number of rainy days per year. | |
I | Typical value for intensity of erosive rain (mm h-1); 10 for temperate climates, 25 for tropical climates and 30 for strongly seasonal climates. | |
Soil | MS | Soil moisture content at field capacity or 1/3 bar tension (% w w-1). |
BD | Bulk density of the top soil layer (Mg m-3). | |
EHD | Effective hydrological depth of soil (m); depend on vegetation/ crop cover, presence or absence of surface crust, presence of impermeable layer within 0.15 m of the surface. | |
K | Soil detachability index (g J-1) defined as the weight of soil detached from the soil mass per unit of rainfall energy. | |
COH | Cohesion of the surface soil (kPa) | |
Landform | S | Slope steepness (°). |
Land Cover | A | Proportion between 0 and 1 of the rainfall intercepted by the vegetation or crop cover. |
Et/E0 | Ratio of actual (Et) to potential (E0) evapo-transpiration | |
C | Crop cover management factor; combines the C and P factors of the Universal Soil Loss Equation. | |
CC | Percentage canopy cover, expressed as a proportion between 0 and 1. | |
GC | Percentage ground cover, expressed as a proportion between 0 and 1. | |
PH | Plant height (m), representing the height from which raindrops fall from the crop or vegetation cover to the ground surface. |
Table 2 Input parameter of vegetation |
Land use/cover type | A | C | Et | CC | GC | PH (m) | EHD (m) |
---|---|---|---|---|---|---|---|
Forest | 0.430 | 0.70 | 0.90 | 0.70 | 0.30 | 18.00 | 0.180 |
Agriculture land | 0.250 | 0.50 | 0.670 | 0.50 | 0.50 | 2.00 | 0.120 |
Barren Land | 0.00 | 1.000 | 0.050 | 0.00 | 0.00 | 0.00 | 0.05 |
Note: Data source: Morgan et al., 1984; Shrestha, 1997; Morgan, 2001 and Regmi et al., 2014. |
Table 3 Annual rainfall and number of rainy days per year |
Station | Elevation (m) | Annual rainfall (mm) | Number of rainy days per year |
---|---|---|---|
Chisapani Gadhi | 1729 | 2024.60 | 125.95 |
Markhu Gaun | 1535 | 1373.16 | 107.88 |
Thankot | 1457 | 1733.05 | 119.36 |
Daman | 2265 | 1711.48 | 126.19 |
Note: Source: Department of Hydrology and Meteorology, Kathmandu. |
Table 4 Soil input parameter |
Soil type | MS (%) | BD (g cm-3) | K (g J-1) | COH (kPa) |
---|---|---|---|---|
Loam | 0.20 | 1.3 | 0.8 | 3.0 |
Sandy loam | 0.28 | 1.2 | 0.7 | 2.0 |
Silt loam | 0.25 | 1.3 | 0.9 | 3.0 |
Note: Source: Summarized in Morgan et al., 1982 and Morgan, 2001. |
Table 5 LULC in 2000, 2010 and 2020 |
Class name | 2000 | 2010 | 2020 | |||
---|---|---|---|---|---|---|
Area (ha) | % | Area (ha) | % | Area (ha) | % | |
Forest area | 7560.45 | 60.72 | 7772.69 | 62.43 | 8063.01 | 64.75 |
Agriculture area | 4732.02 | 38.00 | 4513.48 | 36.24 | 4211.55 | 33.82 |
Barren area | 26.19 | 0.21 | 32.15 | 0.26 | 43.29 | 0.35 |
Water body | 133.11 | 1.07 | 133.45 | 1.07 | 133.92 | 1.08 |
Total | 12451.77 | 100 | 12451.77 | 100 | 12451.77 | 100 |
Table 6 Accuracy assessment of the classification |
Class | Forest area | Agriculture area | Barren land | Water body | Row total | User accuracy (%) |
---|---|---|---|---|---|---|
Forest area | 66 | 6 | 3 | 0 | 75 | 88 |
Agriculture area | 2 | 85 | 2 | 1 | 90 | 94 |
Barren land | 1 | 2 | 20 | 2 | 25 | 80 |
Water body | 0 | 0 | 0 | 10 | 10 | 100 |
Column total | 69 | 93 | 25 | 13 | 200 | |
Producer accuracy (%) | 96 | 91 | 80 | 77 | Overall accuracy=90.5% | |
Kappa coefficient = 0.85 |
Table 7 Change pattern for the period of 2000-2010 |
Class (2010) | Area 2010 (ha) | Class (2000) | Area 2000 (ha) | Change in class | Change in area (ha) |
---|---|---|---|---|---|
Forest area | 7772.69 | Forest area | 7560.45 | Forest area - Forest area | 212.24 |
Agriculture area | 4513.48 | Agriculture area | 4732.02 | Agriculture area - Agriculture area | -218.54 |
Barren area | 32.15 | Barren area | 26.19 | Barren area - Barren area | 5.96 |
Water body | 133.45 | Water body | 133.11 | Water body - Water body | 0.34 |
Table 8 Change pattern for the period of 2010-2020 |
Class (2020) | Area 2020 (ha) | Class (2010) | Area 2010 (ha) | Change in class | Change in area (ha) |
---|---|---|---|---|---|
Forest area | 8063.01 | Forest area | 7772.69 | Forest area - Forest area | 290.32 |
Agriculture area | 4211.55 | Agriculture area | 4513.48 | Agriculture area - Agriculture area | -301.93 |
Barren area | 43.29 | Barren area | 32.15 | Barren area - Barren area | 11.14 |
Water body | 133.92 | Water body | 133.45 | Water bodies - Water body | 0.47 |
Table 9 Change pattern for the period of 2000-2020 |
Class (2020) | Area 2020 (ha) | Class (2000) | Area 2000 (ha) | Change in class | Change in area (ha) |
---|---|---|---|---|---|
Forest area | 8063.01 | Forest area | 7560.45 | Forest area - Forest area | 502.56 |
Agriculture area | 4211.55 | Agriculture area | 4732.02 | Agriculture area - Agriculture area | 520.47 |
Barren area | 43.29 | Barren area | 26.19 | Barren area - Barren area | 17.1 |
Water bodies | 133.92 | Water bodies | 133.11 | Water bodies - Water bodies | 0.81 |
Table 10 Area of soil texture class |
Soil texture class | Total area (ha) |
---|---|
Sandy loam | 10554.66 |
Silty loam | 874.44 |
Loam | 812.34 |
Table 11 Average annual rainfall and rainy days of 2000 |
S.N. | Elevation (m) | Rainfall (mm) | Rainy days (days) |
---|---|---|---|
1 | 1729 | 2157.36 | 133.33 |
2 | 1535 | 1439.74 | 117.86 |
3 | 1457 | 1927.41 | 119.57 |
4 | 2265 | 1707.18 | 122 |
Table 12 Average annual rainfall and rainy days of 2010 |
S.N. | Elevation (m) | Rainfall (mm) | Rainy days (day) |
---|---|---|---|
1 | 1729 | 2078.31 | 126.68 |
2 | 1535 | 1414.8 | 113.19 |
3 | 1457 | 1807.78 | 120.19 |
4 | 2265 | 1711.26 | 126.45 |
Table 13 Average annual rainfall and rainy days of 2020 |
S.N. | Elevation (m) | Rainfall (mm) | Rainy days (days) |
---|---|---|---|
1 | 1729 | 2024.60 | 125.95 |
2 | 1535 | 1373.16 | 107.87 |
3 | 1457 | 1733.04 | 119.35 |
4 | 2265 | 1711.48 | 126.18 |
Table 14 LULC class wise average soil loss of the watershed |
Year | LULC class | Minimum (t ha−1 yr−1 ) | Maximum (t ha−1 yr−1 ) | Average soil loss (t ha−1 yr−1 ) | Weighted average soil loss (t ha−1 yr−1 ) |
---|---|---|---|---|---|
2000 | Forest area | 0.0038 | 0.2242 | 0.114 | 8.64 |
Agricultural area | 0.4453 | 42.5339 | 21.4896 | ||
Barren area | 6.4255 | 293.9912 | 150.20835 | ||
2010 | Forest area | 0.0024 | 0.2022 | 0.1023 | 7.12 |
Agriculture area | 0.4422 | 35.9345 | 18.18835 | ||
Barren area | 6.5522 | 293.4507 | 150.00145 | ||
2020 | Forest area | 0.0014 | 0.2242 | 0.1128 | 7.30 |
Agricultural area | 0.4453 | 38.7258 | 19.58555 | ||
Barren area | 6.7434 | 293.1306 | 149.937 |
Table 15 Erosion susceptible classes of the Kulekhani Watershed in different time period |
Erosion susceptible class | Average soil loss range (t ha−1 yr−1) | Area in 2000 (ha) | Area in 2010 (ha) | Area in 2020 (ha) |
---|---|---|---|---|
Very low | <5 | 7416.73 | 7766.41 | 7874.75 |
Low | 5-10 | 577.49 | 572.83 | 556.34 |
Moderate | 10-15 | 1146.58 | 1075.8 | 1137.91 |
Moderately high | 15-25 | 1929.11 | 1729.08 | 1636.32 |
High | 25-50 | 436.74 | 381.41 | 315.27 |
Very high | >50 | 143.4 | 119.99 | 122.9 |
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