本文選題：表層懸沙濃度　切入點：多元回歸模型　出處：《華東師范大學》2017年碩士論文

【摘要】：河口懸沙是河口形成和發(fā)育的物質基礎,其動力沉積過程與地貌演變密切相關,對于河槽的自然演變、人工建筑物的安全防護及周邊生態(tài)環(huán)境的治理有著重要影響。受潮汐、徑流、風浪及鹽淡水混合作用影響,河口懸沙濃度變化復雜,隨機特征顯著,至今尚未有較好的表示方法,且由于觀測條件等的影響,長時間連續(xù)的觀測數(shù)據(jù)較難獲得。本文以表層懸沙濃度為著眼點,基于隨機理論,以長江河口上、中、下段固定站位多要素連續(xù)觀測和定點水文資料為依據(jù),分析潮汐、徑流、鹽度、風浪等影響因子對河口懸沙的作用,建立長江河口表層懸沙多元回歸模型計算式,量化各因子在河口不同區(qū)域對懸沙濃度的貢獻,為數(shù)值模擬、航道回淤計算問題等提供重要的參數(shù)。長江口復雜的動力要素和地形特點以及區(qū)域氣候的影響,使得風速、徑流量、潮差、鹽度、懸沙濃度、流速等都呈現(xiàn)了復雜的時空變化特征。受冬夏季風氣候影響,長江口風向以偏北風和東南風向為主;月均徑流量變化顯著,表現(xiàn)為洪季流量高、枯季流量小的特點,潮差變化趨勢則與徑流量相反;懸沙濃度、鹽度和流速的洪枯季、大小潮及漲落潮均值在長江口不同區(qū)域會有所差異,三者的垂向變化上,懸沙濃度和鹽度一般從表層至底層逐漸增大,流速則相反。根據(jù)小波分析和長周期及極端條件作用下的懸沙變化特點,我們發(fā)現(xiàn)懸沙濃度的季節(jié)性變化、大小潮變化等周期性的變化特征與周期性動力因素有關(如徑-潮流的強度的交替),而大風、人為活動等隨機性動力因素作用則會導致懸沙濃度的快速增長。統(tǒng)計表明,徑流量、鹽度、潮差、風速與懸沙濃度變化關系密切,但長江河口上、中、下段不同測站模型的主要影響因子有所差異。徐六涇站懸沙濃度預測模型主要由徑流量、潮差和風速控制;佘山站由鹽度、潮差和風速控制;橫沙站則綜合了以上兩個站點的控制因素,由徑流量、鹽度、潮差和風速共同影響。通過多元回歸方程完成對表層懸沙濃度預測模型的建立,經(jīng)實測資料驗證,模型具有很好的精確度(83.3%)。長江口上、中、下段站點各因子對表層懸沙濃度的貢獻不同:徐六涇站徑流量、潮差、風速所占權重分別為45.6%、40.0%和14.4%,徑流對于懸沙濃度變化影響最大,其次為潮差與風速;橫沙站徑流量、潮差、鹽度、風速所占權重分別為17.9%、47.2%、13.5%和21.4%,潮差是最為主要的影響因子,其次為風速和徑流量,鹽度相對較小;而佘山站潮差、鹽度、風速所占權重分別為43.4%、26.5%、和30.1%,最主要的影響因子也是潮差,其次為風速和鹽度。對比同一影響因子在長江河口上、中、下段對表層懸沙濃度平均值和最大值的貢獻,可以反映其在不同地貌環(huán)境條件下對懸沙濃度的影響強弱。對于平均懸沙濃度貢獻來說:佘山站潮差引起的表層懸沙增量最大;徑流量對徐六涇和橫沙站懸沙濃度貢獻值相近,至口外佘山站,徑流所攜帶的泥沙對表層懸沙濃度貢獻已明顯衰弱;潮差、鹽度和風速引起的懸沙濃度增量從徐六涇至口外佘山站依次遞增。結合各因素引起的最大懸沙濃度變化來看,在一般天氣情況下,風浪作用對表層懸沙的影響弱于潮汐,但在風浪較大的天氣狀態(tài)下,風速引起的表層懸沙濃度變化可達1kg/m3以上,成為懸浮泥沙含量變化的主控因子。模型的計算結果表明:近10多年來在長江來水來沙減少背景下,由徑流攜帶的水體表層懸沙濃度有減小趨勢,致使河口上段地區(qū)表層懸沙濃度減小;但在河口中下段及口外地區(qū),由于徑流作用減弱,表層懸沙濃度在潮汐、風浪、鹽度等因子的共同作用下,未出現(xiàn)顯著變化。
[Abstract]:Suspended sediment is the mouth of the formation and development of the material basis, the sedimentary processes and geomorphic evolution is closely related to natural channel evolution, has an important impact on governance safety protection of artificial structure and the surrounding ecological environment. By tide, runoff, wind and salt water mixing effect of estuary suspended sediment concentration change is complex. The stochastic characteristics significantly, there has not been any good representations, and because of the influence of the observation conditions, long time continuous observation data are hard to obtain. In this paper, the surface suspended sediment concentration as the starting point, based on the random theory, the Yangtze River Estuary, and fixed elements under continuous observation stations and hydrological data point analysis of runoff, tide, salinity, wind and other factors of suspended sediment on the estuary of Yangtze River Estuary, surface sediment calculation formula of multiple regression model to quantify the factors in different regions of the estuary The concentration of suspended sediment contribution for the numerical simulation, the channel siltation calculation provides important parameters. The mouth of the Yangtze River complex dynamic factors and terrain features and regional climate effect, the wind velocity, runoff, tide, salinity, suspended sediment concentration and velocity are presented. By complex spatial and temporal variation characteristics of winter and summer the wind climate, wind direction to the mouth of the Yangtze River and north wind southeast wind; average monthly runoff change significantly, as the flood season flow, flow characteristics of the dry season, tidal and runoff change trend is the opposite; suspended sediment concentration, salinity and velocity of the flood and dry season, and in the mean tidal tide the mouth of the Yangtze River in different regions will be different, the three vertical variation, suspended sediment concentration and salinity generally increases gradually from the surface to the bottom, the velocity of suspended sediment on the contrary. According to the characteristics of wavelet analysis and long cycle and extreme conditions, we found that The seasonal variation of suspended sediment concentration changes, changes in the size of the tide and other cyclical characteristics related to cyclical factors (such as dynamic alternate diameter trend strength), and wind, human activities such as the stochastic dynamic factors will lead to the rapid growth of the suspended sediment concentration. Statistics show that the runoff, salinity, tidal range the wind speed, and the suspended sediment concentrations in the close relationship, but the Yangtze River Estuary, and under different test station main influence factor of a model of difference. Xu six suspended sediment concentration forecasting model Jinghe station mainly consists of runoff, tidal and wind control; Sheshan station by salinity, tidal and wind control; Hengsha station comprehensive the control factors of more than two sites, by runoff, salinity, tidal and wind speed influence. Through multiple regression equation, the prediction model of surface suspended sediment concentration, verified by measured data, the model has good accuracy (83.3%) of Yangtze River. In the mouth, each factor under the site of suspended sediment concentration on surface runoff, the contribution of different: Xu Jing six tide station, wind speed weights were 45.6%, 40% and 14.4%, the biggest impact on the runoff variations of suspended sediment concentration, followed by tidal and wind; runoff, tide difference Hengsha station, salinity the wind speed, the weights were 17.9%, 47.2%, 13.5% and 21.4%, the tidal range is the most dominant factor, followed by wind and runoff, salinity is relatively small; and Sheshan station tidal salinity, wind speed, the weights were 43.4%, 26.5%, and 30.1%, is the main factor affecting the tidal range. The wind velocity and salinity. Compared to the same factors in the Yangtze River Estuary, in the lower section of the surface, the concentration of suspended sediment in the mean and maximum contribution, can reflect the environmental conditions in different topographic effects on suspended sediment concentration. The average intensity for suspended sediment concentration contribution: Sheshan tide station The difference caused by the increment of surface suspended sediment runoff of six; Xu Jing and Hengsha station suspended sediment concentration contribution value similar to the Sheshan station, sediment carried by the surface suspended sediment concentration contribution has been significantly weakened; tide, salinity and wind speed caused by the suspended sediment concentration increment from Xu Liujing to Sheshan station in increasing estuary caused by various factors. Combining with the maximum sediment concentration changes, in general weather conditions, effects of wind waves on the surface of the suspended sediment in the weak tide, but in large waves weather conditions, wind speed caused by surface suspended sediment concentration changes of up to 1kg/ above m3, become the main control factors of changes of suspended sediment concentration model. The calculation results show that nearly 10 years of sediment in the Yangtze River water to reduce the background by runoff water surface suspended sediment concentration decreases, the surface area of upper estuary suspended sediment concentration decreases; but in estuaries There is no significant change in the surface suspended sediment concentration under the interaction of tides, wind waves and salinity due to the weakening of the Runoff Effect in the lower and outside regions.

【學位授予單位】：華東師范大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TV148

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