The Study Of Suspended Sediment Distribution And Deposition Under Waves-current Interactions Of Xiamen Bay

Estuaries and bays,as important links between mainland and sea,are one of the significant natural environments for human's survival and development.In the past decades,with the rapid development of coastal cities,arises many coastal development and utilization projects,changing the marine hydrodynamic environment.Behaviors of sand in estuary area like suspension,transport and deposition have once again become the hotspots of scholars.A reasonable numerical model of Xiamen Bay was built on related topography,hydrodynamics and sediment data.And it was used to simulate flow field,concentration distribution of suspended sediment,and distribution of erosion and deposition.The main research results were as following:1?Xiamen Bay is a shallow bay with regular semi-diurnal tide.The hydrodynamic features here result from the interaction of tide from Taiwan Strait and runoff from Jiulong river.Under strong influences from terrain,coastline,islands and submerged topography,tidal flow field in Xiamen Bay has large tidal range and strong tidal current.Strong current areas located around Jinmen Island,Eastern waterway and Weitou waterway,where current speed exceeds 1.Om/s.In tidal intel,flow field has a reciprocating flow pattern.At bay mouth area,flow field has a rotating flow pattern.Generally,tidal flow field is dominated by semi-diurnal tide and standing wave and has a similar flood duration and ebb duration.2?The erosion and deposition environment in the studied sea area results from the sediment movement controlled by tidal current mainly,runoff and wave secondly.Tidal flow pattern is key point to the distribution and transport of suspended sediment.Sediment concentration is higher at shallow area and lower at deep area,forming an increasing pattern from outside to inside of bay.There are two relatively high sediment concentration zone.One is at mouth of Jiulong river,where concentration is basically above 0.03kg/m3.The other is at xiang'an-dadeng shoal area,where concentration is above 0.015kg/m3.3?During the typhoon 'Morandi'(#1614),current and wave have strong effect on sediment movement,significantly increasing sediment concentration.Average concentration increases from 0.03 kg/m3 to 0.07kg/m3 in outer of Xiamen Harbour;increases from 0.1 kg/m3.to 0.25 kg/m3 at mouth of Jiulong river.4?At southeast area of Xiamen island,deposition level is stronger under NE wind condition than that under SE or SSW wind condition;erosion level is stronger under SSW wind condition than that under NE or SE wind condition.5?Simulation results of hydrodynamic characteristics and sea bed erosion and deposition evolution characteristics are consistent with observation.The numerical models in this thesis on the whole can simulate flow pattern,wave pattern,suspended sediment distribution and sea bed erosion and deposition evolution characteristics in Xiamen Bay.