本文選題：地貌動(dòng)力過(guò)程　切入點(diǎn)：后退速率　出處：《南京大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：鹽沼作為濱海濕地的重要生態(tài)類型,對(duì)于保護(hù)海岸帶環(huán)境及濱海城市、加速沿海土地增長(zhǎng)、擴(kuò)大海岸帶的人類可利用空間、增加碳埋藏、減緩全球氣候變暖以及為海岸帶生物提供棲息場(chǎng)所等具有重要研究?jī)r(jià)值。同時(shí)鹽沼對(duì)沉積結(jié)構(gòu)和構(gòu)造的良好連續(xù)性和保存潛力,使其成為判別古環(huán)境和研究古海平面變化的重要材料�；セ撞蓰}沼前緣作為鹽沼-潮灘耦合系統(tǒng)中兩者相交界的重要地帶,發(fā)育有獨(dú)特的地貌形態(tài),研究其動(dòng)態(tài)變化過(guò)程有助于深化對(duì)鹽沼-潮灘耦合系統(tǒng)的認(rèn)識(shí)以及預(yù)測(cè)鹽沼未來(lái)的演變趨勢(shì)。2012年12月、2013年9月和2014年7月在江蘇中部海岸鹽城濕地珍禽國(guó)家級(jí)自然保護(hù)區(qū)的核心區(qū)測(cè)量了互花米草鹽沼邊緣陡坡的形態(tài)參數(shù),應(yīng)用邊緣波理論對(duì)陡坡韻律性形態(tài)的形成機(jī)理進(jìn)行初步解釋;觀測(cè)了互花米草鹽沼前緣光灘上的潮流、波浪以及懸沙濃度,并采集了光灘底質(zhì)表層樣和短柱樣進(jìn)行粒度分析,初步分析了鹽沼前緣的沉積動(dòng)力過(guò)程;結(jié)合2008～2014年的灘面高程數(shù)據(jù)和2005～2014年的遙感影像資料,探討了該研究區(qū)鹽沼前緣的地貌演化過(guò)程以及未來(lái)演化趨勢(shì)。根據(jù)鹽沼邊緣陡坡形態(tài)參數(shù)及其相關(guān)性,可將韻律性陡坡形態(tài)劃分為兩種類型,凹槽長(zhǎng)度、寬度和陡坡高度較大但空間分異較小的陡坡(第一種類型)和凹槽長(zhǎng)度、寬度和陡坡高度較小但空間分異較大的陡坡(第二種類型),分別對(duì)應(yīng)鹽沼邊緣陡坡演化的不同階段。邊緣波理論僅能夠解釋第一種陡坡韻律性形態(tài)的成因,這可能與第二種類型陡坡形態(tài)未達(dá)到均衡態(tài)有關(guān)。通過(guò)計(jì)算潮流和波浪引起的流速及底部切應(yīng)力以及分析互花米草鹽沼前緣光灘的底質(zhì)粒徑特征,發(fā)現(xiàn)該研究區(qū)光灘底質(zhì)以砂質(zhì)粉砂和粉砂質(zhì)砂為主,觀測(cè)期間波浪作用占主導(dǎo),沉積物以懸移輸運(yùn)為主;懸沙濃度為1.0～4.0 g/L;沉積物的懸移輸運(yùn)率為0.01～0.3 kg/m/s。灘面高程變化率在-10~(-5) m/s量級(jí),相當(dāng)于0.2 m/yr的下蝕速率。對(duì)比遙感影像識(shí)別方法、地形測(cè)量對(duì)比方法和沉積動(dòng)力計(jì)算方法,分析結(jié)果表明研究區(qū)光灘出現(xiàn)侵蝕后退的時(shí)間不晚于2010年,侵蝕后退速率在200 m/yr左右,下蝕速率達(dá)0.2～0.5 m/yr;互花米草鹽沼邊緣出現(xiàn)侵蝕后退的時(shí)間不晚于2012年,侵蝕后退速率在20 m/yr左右。用于計(jì)算鹽沼邊緣后退速率的Schwimmer經(jīng)驗(yàn)公式方法在該研究區(qū)不適用�；セ撞蓰}沼前緣水動(dòng)力條件、沉積動(dòng)力過(guò)程的分析結(jié)果表明,波浪是光灘和鹽沼邊緣侵蝕后退的主要水動(dòng)力。結(jié)合互花米草生態(tài)位和研究區(qū)沉積物供應(yīng)狀況,分析認(rèn)為互花米草鹽沼邊緣后退時(shí)尚未達(dá)到生態(tài)位下限,目前出現(xiàn)的侵蝕后退主要是由沉積物供應(yīng)減少和波浪作用加強(qiáng)引起的。沉積物供應(yīng)減少,光灘不斷侵蝕后退,至鹽沼邊緣時(shí)導(dǎo)致鹽沼前緣灘面坡度增大,波浪作用增強(qiáng)而作用于鹽沼邊緣,導(dǎo)致鹽沼邊緣陡坡的形成。鹽沼邊緣陡坡形態(tài)的演化發(fā)育過(guò)程正是鹽沼邊緣侵蝕后退的過(guò)程,在光灘侵蝕后退至鹽沼邊緣時(shí),波浪下切導(dǎo)致局部根墊倒塌形成凹口切入平直的鹽沼邊緣,然后凹口溯源侵蝕形成凹槽和鹽沼殘留脊,最后殘留脊被切斷,以開始下一回次的侵蝕過(guò)程。
[Abstract]:As an important coastal wetland marsh ecological types, for the protection of coastal environment and coastal city, to accelerate the growth of coastal land, the coastal zone can be used to expand the human space, increase carbon burial, slowing global warming and provide habitat for coastal biological etc. it has important research value. At the same time on the deposition and structure of salt marsh for good and the preservation potential, make it become an important material for distinguishing the environment and study the sealevel changes. The marsh front as an important area for salt marsh tidal coupling system in two intersecting circles, the development has unique landform and its dynamic change process is helpful to deepen the understanding of salt marsh tidal coupling system.2012 and the future trend forecast in December and July 2014 September 2013, in Jiangsu, the central coast of Yancheng Wetland National Reserve. The core area of the measurement of morphological parameters of the marsh edge slope, application of edge wave theory in steep rhythm form the forming mechanism of the preliminary explanation; the marsh on the beach front light wave and tide observation, suspended sediment concentration, and collect the light flat substrate surface layer and short column sample size analysis, preliminary analysis of the sedimentary dynamic process of salt marsh in front of; the combination of remote sensing image data of 2008~2014 years of the beach surface elevation data and 2005~2014 years of the study area, the salt marsh pioneer landform evolution and future evolution trend. According to the morphological parameters of the steep slope marsh edge and its correlation can be rhythmic form steep slope is divided into two types. The length, width and height of a large but steep spatial differentiation of small slope (the first type) and groove length, width and height of slope is small but the spatial differentiation of large The steep slope (second types), corresponding to the different stages of evolution. The marsh edge slope edge wave theory can only explain the genesis of the first steep rhythmic patterns, which may be related to second types of slope morphology did not reach equilibrium. And the bottom velocity caused by calculating the tidal current and wave shear stress and analysis of Spartina alterniflora front mudflat sediment grain size characteristics found in the study area, mudflat sediment with sandy silt and silty sand, during the observation wave dominated by suspended sediment transport; suspended sediment concentration is 1 ~ 4 g/ L; suspended sediment transport rate is 0.01 ~ 0.3 kg/m/s. height of beach the rate of change in the sediment of -10~ (-5) m/s magnitude, erosion rate equivalent to 0.2 m/yr. Compared the recognition method of remote sensing image, calculation method of topographic contrast method and sedimentary dynamic analysis results show that the study area, mudflat eroded Back no later than 2010, the erosion rate is about 200 m/yr, erosion rate of 0.2 ~ 0.5 m/yr; the marsh edge erosion occur no later than 2012, the erosion rate was about 20 m/yr. For Schwimmer empirical formula method to calculate the rate of back marsh edge is not applicable in the study area. The marsh in front of the hydrodynamic conditions, the analysis results of sediment dynamic processes show that the wave is the main hydrodynamic mudflat and salt marsh edge erosion. Combined with the ecological niche and the study area of Spartina alterniflora sediment supply situation, analysis the marsh edge back has yet to reach niche limit, there is mainly backward erosion reduced by sediment supply and wave action strengthening caused. Sediment supply reduced, mudflat eroded back to the marsh edge lead salt marsh front Beach The increase of the slope wave enhanced and the effect on the marsh edge, resulting in the formation of steep slope. The evolution of salt marsh edge edge steep shape development process is the marsh edge erosion, beach erosion in the light back to the marsh edge, waves lead marsh edge local root mat collapse cut straight notch is formed, then notch headward erosion groove is formed and salt marsh residual ridge, the residual ridge was cut off, to start the next time the erosion process.

【學(xué)位授予單位】：南京大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P748;P737
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本文編號(hào)：1620911