QUANTITATIVE ASSESSMENT OF GEOLOGICAL-ENVIRONMENTAL QUALITY OF THE LAND ALONG GUANGDONG COAST

The land along the Guangdong coast is not only a relatively developed economical region,but also a friable geoenvironmental region. In the past few decades earthquake, soil erosion,ground lollapses, landslides, karstic sink, ground fissure, land subsidence, soft soil foundation deformation, etc. have caused considerable property damage and casualties, which is greatly related to the evolution of geoenvironment in the region. In the case it is very necessary to assess geoenvironment quality of the region. The occurrence of geological hazards reflects the variation of structure and state of geoenvironment in the region, which is further controlled by the geoenvironmental factors. Based on the investigation and statistic analysis of formation conditions of geologic hazards and influencing factors, the geoenvironment quality of the region can be divided into tectonic stability, slope stability, and foundation stability, then an index system for three layer surfaces was set up for geoenvironmental quality assessment. It includes active faults, earthquake activities, relief height, slope gradient, gulch incision density, soil erosion intensity, densities of collapses and landslides, soil mass bearing capacity, and ground fissure density. The geoenvironment quality is classified into five classes: best, good, moderate, worse, and worst, with linear subjection function of the indices and the weightings of 9 factors given by experts. A fuzzy mathematic model for multifactor comprehensive assessment was developed. Based on the model190 elements for the region were calculated with Fortran program. The result isshown in a zonation map of the geoenvironment quality, from that the result can be compared with the essential situation of the geoenvironment in the region, and it further indicates that the Fuzzy mathematic model developed is feasible and rational, and 17 geoenvironment quality subzones were distinguished. The result of assessment and zonation provide a necessary and sufficient information to users for urban construction planning, land rational use, and construction of major engineering works in the region.