Research On Characteristics Of Land Subsidence And Storm Surge And The Environmental Effects In The Huanghe River Delta, China

This paper addresses the land subsidence and sediment transport under large wind and waves in the Huanghe River delta, including the causes and mechanisms of land subsidence and the effects on the deltaic evolution and environment, the effects of storm surge on the coastal zone and sediment transport, in light of repeated leveling data, groundwater withdrawal information, hydrological records, sediment mechanics parameters, field measurements, water depth data, remote sensing interpretation and so on, integrated with RS and GIS technologies and the 3D model ECOMSED with the wave parameters from the wave model SWAN. The main reasons of land subsidence in the northern Xiaoqing River areas are tectonic subsidence and shallow strata sediment consolidation with the subsidence rate of 4~5mm/a. Groundwater withdrawal is the main factor for the land subsidence in southern Xiaoqing River irrigation areas with the subsidence rate of 10~25mm/a. In recent years, there have been two rapid subsidence areas named Dawang town and Yingli town with the areas of 203km~2. Land subsidence impacts not only on the regional environment but also the changing patterns of estuary channel. It not only pricks up the coastline erosion of Diaokou River mouth, but also affects the whole process of flow channel evolution. From the mode that how the land subsidence treat on the current channel it can be seen that the Qingshuigou channel is in a relatively stable at this stage. The storm surge can make great damage on the coastal areas with the clay bank serious erosion and tidal creeks change greatly. The water depth, tidal current, suspended sediment and historical meteorological data were used to estimate the changes of the suspended sediment concentrations (SCC) and the bed scour and siltation (BSS) caused by the large wind and waves. Comparing the simulations with the in situ data found that the simulation results were reliable. The results showed that the sediment transport changed greatly in the near-shore areas under large wind and waves, with the SCC 10 times and the BSS one hundred times larger than those under the normal weather. The results also showed that the changes of the BSS have taken a great impact on the river estuary sandbar evolution under large wind and waves. Overall, the land subsidence and storm surge disasters have made great impacts on the environment and evolution of Yellow River Delta. The sea-level rise will reach 16~18cm in the next 40 years, global warming makes the land subsidence and storm surge hazards more severe in this areas.