The Estimation Of Shallow Sediment Compaction And Natural Land Subsidence Rate In The Yellow River Delta

Using a stratified summation method based on soil mechanics with152boreholes obtained from the Comprehensive Engineering Geological andHydrogeological survey (1987) we estimate the land subsidence in the Yellow RiverDelta due to shallow sediment loading. Results show that almost the whole YellowRiver Delta is influenced by land subsidence which caused by shallow sedimentloading. The settlement changes from157mm to1398mm and the average is669mm.The settlement shows an increasing trend from the southwest to the northeast. Ourestimates also suggest that soft soil layer is the major contribution to the landsubsidence which accounts for65%of the total area compaction settlement. Based onthe location of Paleo-shoreline in the Yellow River Delta, the original time and degreeof consolidation are determined. The subsidence rate of the borehole which containthe thickest soft soil layer in the east of1955shoreline is6.6mm/a; the subsidencerate of the borehole which contain the thickest soft soil layer between the1855and1955shoreline is3.4mm/a; the subsidence rate of the borehole which contain thethickest soft soil layer between the1855shoreline and the boundary of ModernYellow River Delta is1.3mm/a; the subsidence rate of the borehole which contain thethickest soft soil layer in the west of Modern Yellow River Delta is0.6mm/a. Theresults is reasonable after comparing with the benchmarks which near10boreholes.Furthermore, the contribution of shallow sediment compaction to land subsidence iscomputed. The results range from2.1%to15.0%, and the average is4.0%. Shallowsediment compaction is expected to still have a long term influence in the YellowRiver Delta.The background value of natural land subsidence is estimated by Using twochenier ridges in the Yellow River Delta. The results show that since the chenierⅠ (Xinhu-Kenli-Xiazhen,2000a B.P.) formed, the rate of natural land subsidence is1.59mm/a, and since the chenierⅡ(Niuzhuang-Dingzhuang,7764a B.P.)formed, therate of natural land subsidence is0.21mm/a.The sediment consolidation in the Yellow River Delta is not finish yet, and thewhole region is still showing a trend of subsidence. Considering the Intensifiedhuman activities we can conclude that the Yellow River Delta is still under the presserof land subsidence in the near future. The suggestion of land subsidence preventionand control advises is provided from Four aspects, including damage control measures,subsidence speed control measures, subsidence monitoring measures andLegal measures.