Environmental Engineering Reference
In-Depth Information
the east loess hilly and gully area; Area III is the west loess hilly and gully area; and Area IV is Loess
Plateau gully area, which is located in the southeasternmost of the Loess Plateau.
Fig. 2.42
Zoning of the Loess Plateau in the Yellow River basin (after Wang and Wang, 2007)
According to the data of vegetation and erosion for the four areas, the parameters
a, c, b,
and
f
are
determined with the diagrams in Fig. 2.41 and using the method of trial and error, as listed in Table 2.3.
With the values of the parameters the vegetation-erosion charts are worked out, as shown in Fig. 2.43.
The four vegetation-erosion charts show that for the sandy and hilly area along the Great Wall, and the
west and east loess hilly and gully areas, Zone C is very small and the points of present status are far from
Zone C. It is almost impossible to develop a sustainable vegetation having capacity of self-restoration.
Only by intensive soil erosion control and reforestation projects on very small watersheds can vegetation
be improved. Even when vegetation is developed a certain amount of human management is still necessary
because Zone C is very small and the vegetation has no capacity of self-restoration.
Table 2.3
Average values of
a, c, b,
and
f
for the four areas in the Loess Plateau and the present vegetation cover
a
nd erosion
Present vegetation
and erosion
Parameters
No Zone
a
×10
3
(1/yr)
c
×10
6
(10
-6
km
2
/t)
b
×10
2
(1/yr)
f
(t/(km
2
.yr
2
)
E
(t·km
-2
·a
-1
)
V
I Sandy and hilly area along the Great Wall
1-1.5
1.3-1.9
2.5-3.3
450-470
0.293
11,500
II East loess-hilly and gully area
1.5-3
1.5-1.8
1.4-2.1
470-520
0.380
11,000
III West loess hilly and gully area
1-2
1.7-2.0
1.4-1.5
450-490
0.309
5,400
IV
Loess Plateau gully area
2-4.5
1.1-1.8
1.1-1.8
300-400
0.440
3,500
For the plateau-gully area in the southeastern most part of the Loess Plateau, the vegetation can be
permanently improved because Zone C is relatively large, which means the vegetation has a capacity of
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