In this case literally, as can be see in the CCTV video linked here.
It’s a classic example of a problem called subsidence. When cities expand, the water delivery systems often lag, which means that people use well water. Many wells result in the lowering of the water table, which in turn results in the ground sinking as the space between the grains of soil (referred to technically as the “voids” or “pores”) contracts.
This problem is not unique to Beijing; Houston experienced it during the 1950’s and 1960’s, along with many communities along the Gulf Coast. The result was that areas near bodies of water were susceptible to damage not only from storm surges but in some cases from high tide.
The Chinese solution to the problem is to run water from the Yangtze in the south, which is helping to mitigate the subsidence.