【摘要】：河口海岸地區(qū)是人類開發(fā)海洋資源的前沿地帶，與人類生產(chǎn)、生活息息相關(guān)。由于河口地區(qū)受到徑流、潮流等因素的影響，其水沙動力特性非常復(fù)雜；對徑流、潮流和懸沙等因素的行為特性進行深入分析和探索具有重要的理論研究意義和實踐價值。 本文以大沽河口作為研究區(qū)域，通過觀測數(shù)據(jù)搜集、整理與分析、數(shù)值計算等手段，探討了大沽河口的徑流、潮流耦合作用下的水動力以及泥沙輸移擴散行為特性。分析結(jié)果發(fā)現(xiàn)： （1）當枯期5年一遇、洪水期5年一遇、洪水期50年一遇的洪峰分別作用時，徑流量越大，徑流影響的區(qū)域越大。非恒定徑流對河口區(qū)域的最大影響范圍一般發(fā)生在落急時刻附近，上述典型洪水徑流影響范圍分別為29.65km2、103.22km2、161.66km2，徑流最小影響范圍一般發(fā)生在漲急時刻附近，，影響區(qū)域分別為8.2km2、52.4km2、98.8km2。 （2）分析了徑流對潮位和潮流速的影響。結(jié)果發(fā)現(xiàn):河流近海段和口外海濱段潮位均有明顯變化；距離河口越近，潮差變化越��；對低潮位的影響大于高潮位。徑流量較大時，河口下游水體運動方向與徑流方向基本一致；徑流量的大小對河口下游潮流速和流向均會產(chǎn)生一定影響。 （3）恒定徑流的懸沙濃度一定時，近海段水體中的懸沙濃度與徑流量大致呈正比關(guān)系；洪水期50年一遇恒定徑流條件下，48小時后懸沙濃度最高可達4.8kg/m3，分布在距離河口4~5倍河寬處；河口下游的沖刷范圍與恒定徑流作用時間有關(guān)，時間越長，海床沖刷范圍越大。其中72小時后最大沖刷范圍約103.6km2；徑流量增加使得河流近口段范圍增加，河口段范圍下移，形成的淤積范圍減小，淤積強度有所增加，且淤積位置逐漸遠離河口。 非恒定來水來沙條件下，落急時刻懸沙濃度相對較大，最大可達3.0kg/m3；漲急時刻懸沙濃度相對較小，懸沙濃度變化主要集中在近口段，最大值約為1.5kg/m3。非恒定來水來沙條件下，河口附近均會形成東北-西南走向的沖淤帶。跟其它潮流典型時刻相比，落急時刻的潮流速和水力挾沙力相對較大，沖淤范圍也相對較大；具體來說：河流近口段的沖刷強度可達0.01m；距離河口4~7倍河寬處平均沖刷強度約為0.01m；距離河口2~4倍河寬處，均會形成淤積帶，其平均淤積強度在0.02m以上，最大淤積強度可達0.06m。 研究結(jié)果可以為大沽河河口的防洪和岸灘保護等工作提供一定的參考依據(jù)。
[Abstract]:Estuarine and coastal areas are the frontier of human exploitation of marine resources, which are closely related to human production and life. Because estuarine area is influenced by runoff and tidal current, its hydro-sediment dynamic characteristics are very complicated, and it has important theoretical research significance and practical value to deeply analyze and explore the behavior characteristics of runoff, tidal current and suspended sediment. Taking the Dagu Estuary as the study area, the hydrodynamic and sediment transport and diffusion behaviors of the Dagu Estuary under the coupling of runoff and tidal current are discussed by means of observation data collection, collation and analysis, numerical calculation and so on. The results are as follows: (1) the larger the runoff is, the greater the runoff is when the Hong Feng of the dry period is once in 5 years, the flood period is once in 5 years and the flooding period is once in 50 years. The maximum influence range of unsteady runoff on estuarine region generally occurs near the precipitous moment. The above typical flood runoff impact range is 29.65km 2103.22km 2161.66km2, and the minimum runoff impact range usually occurs near the rising precipitous time. The effects of runoff on tidal level and tidal current velocity were analyzed. The influence areas were 8.2 km2 ~ (2) ~ (2) ~ 52.4 km ~ (2) ~ (2) ~ (2) ~ (-) ~ (98.8) km ~ (2) ~ (2) respectively. The results show that there are obvious changes in the tidal level in both the offshore section and the offshore section of the river, the closer the river is to the estuary, the smaller the variation of tidal range is, and the effect on the low tide level is greater than that on the high tide level. When the runoff is larger, the direction of water movement is basically the same as the direction of runoff, and the magnitude of runoff has a certain influence on the velocity and direction of tidal current. (3) when the concentration of suspended sediment in constant runoff is fixed, The suspended sediment concentration in the offshore water is approximately proportional to the runoff, and the maximum suspended sediment concentration can reach 4.8 kg / m ~ (3) after 48 hours under the condition of constant runoff in the flood period of 50 years, and is distributed at a distance of 4 times the river width from the estuary. The scour range of the lower reaches of the estuary is related to the action time of the constant runoff, the longer the time is, the larger the scouring range of the seabed is. After 72 hours, the maximum scour range is about 103.6 km ~ 2, and the runoff increases the range of the near mouth of the river, the range of the estuary moves down, the range of the formed silt decreases, the sediment intensity increases, and the deposition position is gradually far away from the estuary. Under the condition of unsteady water and sediment supply, the suspended sediment concentration is relatively large at the precipitous moment, the maximum is 3.0 kg / m ~ (3), and the suspended sediment concentration is relatively small in the rising moment, and the change of suspended sediment concentration is mainly concentrated in the near mouth, the maximum value is about 1.5 kg / m ~ (3). Under the condition of unsteady water and sediment, the erosion and siltation zone of northeast-southwest strike will be formed near the estuary. Compared with other typical tidal currents, the tidal current velocity, hydraulic sediment carrying capacity and scour and siltation range are relatively larger in the falling and precipitous period, specifically, the scour intensity of the near mouth of the river can reach 0.01 m. The average scour intensity is about 0.01m at the river width of 4 ~ 7 times from the estuary and 0.06m at the river width of 2 ~ 4 times of the estuary. The average siltation intensity is more than 0.02m and the maximum siltation intensity can reach 0.06m. The results can provide some references for flood control and beach protection in Dagu River estuary.
【學(xué)位授予單位】：中國海洋大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TV148

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