Optimum design of level monitoring points for land subsidence

Land subsidence caused by long-term over-exploitation of groundwater is the main geological disaster in the plain area of Beijing, China. To obtain accurate and dynamic monitoring information on land subsidence, primary level measurement is carried out every year. However, there are shortcomings in the existing level monitoring network and development of land subsidence, which require optimization of the level monitoring network for land subsidence. Using a GIS analysis method, a zonal map of influencing factors was created by overlaying three thematic maps including hydrogeological units; the decline rate of the groundwater level in the main mining layer; and the thickness of the compressible layer. The data were classified into 448 zones. Based on the zoning map, we created an optimal design for the location of level monitoring points, locating 220 new points. Kriging interpolation error variance was chosen to evaluate map accuracy. Standard deviation contour maps of the existing level network and the optimized level network were created, and the results showed that the error of the optimized level network was smaller than the existing level network. The method proposed by this paper was reasonable for optimizing a level monitoring network for land subsidence.