Debris Flows and Landslides - River Dynamics and Integrated River Management - page 250

Fig. 4.77 Terraces on slopes mitigate debris flow disasters
planted grass on these slopes. This effectively reduced debris flow disasters. Building soil-retaining structures
at key locations is necessary for preventing landslides and debris flows. It also benefits the formation of a
protective cover of vegetation. In some areas people hammered willow trunks into the gully bed, with
1 m underground and 0.5 m above ground. Sediment carried by debris flows is trapped by the willow
piles. Following sediment deposition in front of the willows piles the willow grew up and became strong.
Willow forests might grow from the debris flow gully and debris flow can be controlled. Figure 4.78 shows
that debris flow control dams and reforestation of the hills as the comprehensive debris flow control strategy
in the Shengou drainage basin have changed the debris flow gully into a forest park in Dongchuan in
Yunnan Province.
Fig. 4.78 Debris flow control dams and reforestation of the hills used as the comprehensive debris flow control
strategy in the Shengou drainage basin have changed the debris flow gully into a forest park of the Dongchuan City;
Yunnan Province
4.4.4 Reclamation of Landslides and Debris Flow Fans
Landslides occur on steep mountains with deeply incised streams. There is a lack of flat land or gentle
slope land in the mountainous areas. Landslides created flat or gentle slope land, which may be reclaimed
for agriculture, residence and urban construction. Figure 4.79(a) shows a landslide deposit on the Xiaojiang
River, which has been reclaimed for agriculture and village. The potential energy of the slope was
released during the landslide and the risk of new sliding is low. Figure 4.79(b) shows the Dongchuan city
town on a huge landslide deposit. The landslide occurred a thousand years ago. The landslide deposit is
stable. A city with a population of a half million has developed on the landslide deposit. Many new
buildings are under construction.