On the importance of landslide management: Insights from a 32-year database of landslide consequences and rainfall in Hong Kong

Social and economic losses induced by landslides can be reduced by means of effective planning and management. A series of landslide management projects have been implemented for landslide risk reduction since 1977 in Hong Kong. The effectiveness of the landslide management projects needs to be quantified to promote the experience for decision-making. In this study, a database of landslide-induced consequences in Hong Kong from 1984 to 2015 is first compiled. Then the effectiveness of landslide management projects in Hong Kong is evaluated from the implications of the relationship between rainfall and landslide consequences. A new method is proposed to detect the turning years for the management projects by evaluating the coefficient of variation (COV) of dissimilarity. The results are compared to the implementations of landslide management projects in Hong Kong and further verified by the consequences caused by 6 types of slopes. The landslide posed high risks before 2009 and exhibited a decreasing trend. After 2009, the landslide-induced consequences became very small. The years 1992, 2000, and 2008 are identified as the key turning years for landslide management using the proposed method. The landslide management projects work effectively when launched about every eight years. The turning years detected based on proximity of rainfall and landslide-induced consequences agree well with the timings of management projects. The initial Landslip Prevention Measures Programme (LPMP) launched in 1977 might have already reached its limit in 1992. More effort should be put into preventing landslide-caused road failures.