Debris Flows and Landslides - River Dynamics and Integrated River Management - page 243

In Hong Kong the government has been increasing the budget for landslide control since the mid 1990s.
Figure 4.66 shows the annual budget and expenditure for landslide control in the period 1977-2000. The
money was used to build anti-landslide structures. Figure 4.67 is a schematic of anchors and concrete piers
used for stabilizing slopes and protecting highways.
Fig. 4.66 Annual budget for landslide control in Hong Kong in the period 1977-2000
Fig. 4.67 Schematic of anchors and concrete piers used for stabilizing slopes and protecting highways
Figure 4.68(a) shows the steep slope in the campus of the University of Hong Kong has been stabilized
with numerous anchors. These anchors bind the surface rocks with the deep rock, which effectively
controls rock falls and avalanches. Figure 4.68(b) shows the concrete piers for landslide control in Danba
in Sichuan Province of China. The county town is located on the banks of the Dadu River and the risk of
landslide is high due to the very steep slope. Drainage systems, piers, and anchors have been constructed
to reduce the risk of landslides throughout china and in mountainous areas world wide.
4.4.2 Prediction and Warning of Debris Flow
4.4.2.1 Prediction of Debris Flow
Prediction of debris flow remains in the development stage. An important routine for prediction of
rainstorm debris flows is to relate rainfall intensity in 10 min and the antecedent rainfall to debris flow.
Chen (1985) analyzed data of nearly one hundred rain storms and tens of debris flows in the watershed of
the Jiangjia Ravine in the Xiaojiang watershed on the Yunnan-Guizhou Plateau of China. The main
results obtained are shown in Fig. 4.69, where I 10 is 10 min rainfall intensity, or the maximum rainfall