Vegetation-Erosion Dynamics - River Dynamics and Integrated River Management - page 85

It must be noted that the vegetation cover V in the differential equations is calculated in different
ways for different erosions because different erosions can be controlled by different types of vegetation.
Figure 2.32(a) shows that herbaceous vegetation on the Qinghai-Tibet Plateau completely controls splash
erosion and sheet erosion but does not control gully erosion. Figure 2.32(b) shows that herbaceous
vegetation in the Xiaojiang River basin on the Yunnan-Guizhou Plateau controls rill erosion. Figure 2.32(c)
shows that shrubs and trees in Lixian County on the Loess Plateau control gully erosion. Nevertheless,
not all erosion can be controlled by vegetation. Figure 2.32(d) shows that well developed complex vegetation
consisting of trees, shrubs, and grasses on the Chenyoulan River in Taiwan, China could not control bank
failure, which was caused by channel erosion during the flood on August 8, 2009. Several buildings fell
into the river and one building was suspended on the cliff.
(a) (b)
(c) (d)
Fig. 2.32 (a) Herbaceous vegetation on the Qinghai-Tibet Plateau controls splash and sheet erosions but not gully
erosion; (b) Herbaceous vegetation in the Xiaojiang River basin controls rill erosion; (c) Shrubs and trees on the Loess
Plateau control gully erosion; (d) Channel erosion caused bank failure on the Chenyoulan River in Taiwan, China
(See color figure at the end of this topic)
In the differential equations, the vegetation cover, V , is the coverage ratio of vegetation consisting of
grasses for studying the vegetation-erosion dynamics in the Qinghai-Tibet Plateau because there is no
intensive gully erosion and rill and sheet erosions are the main type of erosion in the area. Whereas for
studying the vegetation-erosion dynamics in the Xiaojiang River basin, where gully erosion is intensive
and is the dominant erosion type, the value of V in the differential equations is the vegetation cover of trees
and shrubs. Herbaceous vegetation is not counted in this case because grasses cannot control gully erosion.
2.3.2 Application of Vegetation-Erosion Dynamics
The vegetation-erosion dynamics model is first applied to the Loess Plateau and Yunnan-Guizhou Plateau