This study presents an integrated approach to evaluate inundation risks, in which an algorithm is proposed to integrate the storm water management model (SWMM) into a geographical information system (GIS). The proposed algorithm simulates the flood inundation of overland flows and in metro stations for each designed scenario. It involves the following stages: (i) determination of the grid location and spreading coefficient and (ii) an iterative calculation of the spreading process. In addition, an equation is proposed to calculate the inundation around a metro station and to predict the potential inundation risks of the metro system. The proposed method is applied to simulate the inundation risk of the metro system in the urban centre of Shanghai under 50-year, 100-year, and 500-year rainfall intensities. Both inundation extent and depth are obtained and the proposed method is validated with records of historical floods. The results demonstrate that in the case of a 500-year rainfall intensity, the inundated area with a water depth excess of 300 mm covers up to 5.16 km². In addition, four metro stations are inundated to a depth of over 300 mm.

This case study presents an investigation on building settlement induced by dewatering for a deep excavation constructed in a deposit in Tianjin, China. The excavation site is located in the Tianjin urban center, around which there are many existing buildings. Geological conditions at the site involve a multiaquifer system with one phreatic aquifer over three confined aquifers. To maintain the stability of the bottom of the excavation, a cutoff wall was used to block groundwater seepage with large diameter wells to lower the groundwater level. Field instrumentation was installed during construction to monitor (1) the quantity of withdrawn groundwater, (2) the groundwater head, and (3) the settlement of surrounding buildings. The field observations yielded the following results and implications: (1) pumping of groundwater could lead to large building settlement and a large area of ground settlement; (2) most of the settlement caused by dewatering did not rebound; (3) the cutoff wall played a significant role in reducing the building settlement during dewatering; and (4) the dewatering-on-demand procedure should be implemented during excavation.