| Estuarine and coastal area is a frontier area of human exploitation of marine resources, and itclosely related to human production and daily life. Due to the coupled effect of runoff and tide atestuary area, the dynamic characteristics of water and suspended sediment are very complicated.The study on the behavioral characteristics of runoff, current and suspended sediment is ofsignificance on theoretical research and practical value.In this paper, Dagu estuary was selected as the research area to investigate the hydrodynamiccharacteristics and sediment transport with data analysis and numerical simulation methodsetc.The results show：(1) When floods in5years and in50years occur respectively, the influence area increaseswith increasing flow rate of runoff. Generally speaking, the maximum influence area ofunsteady runoff occurs near the fall peak time, and the corresponding influence areas ofaforementioned floods are29.65km2,103.22km2and161.66km2respectively. The minimuminfluence area of unsteady runoff occurs near the rising peak time, and the correspondinginfluence areas of aforementioned floods are8.2km2,52.35km2and98.80km2respectively.(2)The runoff influence on the tide level and current is analyzed. The change of tidal leveldecreases with decreasing distance from river entrance, and the influence at low tide level isgreater than that at high tide level. When the runoff is large, the runoff direction decides the maindirection of runoff and tide current. The flow rate of runoff influences the current velocity anddirection more or less.(3)When the suspended sediment concentration (SSC) is a constant of runoff, SSC in estuarywater is basically proportional to that of runoff. When the steady flood in50years occurs, themaximum SSC can up to4.8kg/m3,which locates in the region of4~5times width of riverestuary after48hours. The estuarine bed deformation range increased with the increasing runoffduration time approximately. After72hours, the maximum scour area increases up to103.6km2. With the increase of runoff flow rate, river estuary range increases. Furthermore, the bed siltingarea decrease, but the siltation intensity increases.With the condition of unsteady runoff and SSC, SSC is relatively large at fall peak time,which can reach about3.0kg/m3, and SSC is relatively small at rising peak time. SSC changemainly in the river mouth section，and its maximum value can reach up to1.5kg/m3. Meanwhile, abed deformation section will occur from northeast direction to southwest direction. Comparedwith other time, current velocity and sediment carrying capacity are relatively larger at fall peaktime, leading to a larger scour and silting area. In details, the bed scour value near the river mouthsection reaches about0.01m. The average bed scour value is about0.01m, where locates in4~7times river mouth width. A deposition area occurs, locating in2~4times river mouth width, itsaverage silting value is greater than0.02m, and its maximum value is about0.06m.The results can provide a certain reference for engineering of Dagu river estuary flood controland coastal protection. |
