Results
Analysis of soil erosion
factors
Rainfall, vegetation, and soil and water conservation engineering
measures are the three major factors affecting soil erosion in the Loess
Plateau. We analyzed the characteristics of erosion conditions in the
watershed through temporal and spatial changes of erosion factors in the
CSLE model. For this purpose, various soil erosion factors in the model
were calculated and presented as a 10 m resolution grid map. The soil
erodibility factor (K), slope length and slope factor (LS), and tillage
measure factor (T) remained unchanged from 2010 to 2020 (Figure 2a-c),
while the rainfall erodibility factor (R), vegetation cover measure
factor (B), and soil and water conservation engineering measure factor
(E) varied with year.
Figure 2d-f is the rainfall erosivity map of Jiuyuangou watershed in
2010, 2015, and 2020 In general, average annual rainfall erosivity from
2010 to 2020 first decreased and then increased. Spatially, the rainfall
erosivity increases from the northeast of the watershed to the southwest
of the watershed.Basin rainfall is concentrated from June to September
but extremely uneven during the year and prone to rainstorm erosion.
Vegetation cover impacts soil erosion development by affecting surface
runoff processes in the watershed. Figure 2g–i shows three-year
vegetation coverage factors from 2010 to 2020. At the same time, areas
with low B values increased from 75% in 2010 to 84% in 2020. The low B
value area gradually expands from the northeastern part of the watershed
to the southern residential area and agricultural land, representing
better vegetation cover and lower erosion risk than the high B value
area. Figure 2j–l shows that
terraces and check dams are the main soil and water conservation
engineering measures in the basin, and unique to the Loess Plateau. The
area of terraced fields continued to decrease from 2010 to 2020, and the
area of check dams increased from 2010 to 2015 and then decreased from
2015 to 2020. Since the project of returning farmland to forest
commenced in 1999, the construction of check dams on the Loess Plateau
started and continued until 2015, when the layout of the dam system was
completed. Due to problems such as sediment deposition and poor
management, the check dam area in 2020 was significantly less than 2015.
Terraces are an important soil and water conservation measure in the
basin, mostly horizontal terraces on ridges. During the study period,
the area of terraced fields in the basin decreased year on year due to
scour damage caused by rainfall and farmland abandonment. In 2020, the
area of terraced fields had declined by 12.3% compared with 2010.