【摘要】：沖溝是由暫時(shí)性表面流沖刷地表而形成的溝道,是聯(lián)系過(guò)去、現(xiàn)在和未來(lái)溝蝕事件的橋梁。沖溝的形態(tài)包括平面、橫斷面和縱剖面,其中沖溝的橫剖面形態(tài)不僅可用來(lái)估算沖溝侵蝕量和沖溝侵蝕速率,也可闡明由下切和側(cè)蝕引起的發(fā)育演化過(guò)程。本研究使用Leica DistoTM D8激光測(cè)距儀于元謀干熱河谷區(qū),測(cè)量456條沖溝橫斷面,之后使用CASS 7.0與Excel 2003軟件繪制并量算沖溝橫斷面形態(tài)參數(shù)。主要結(jié)論如下:(1)選取溝寬不對(duì)稱率(al)、面積不對(duì)稱率(aa)、侵蝕線不對(duì)稱率(aw)、侵蝕面不對(duì)稱率(ar)四個(gè)沖溝橫斷面不對(duì)稱指標(biāo),衡量元謀干熱河谷沖溝橫斷面不對(duì)稱程度。結(jié)果表明:從不同區(qū)域角度分析,以溝寬不對(duì)稱率、面積不對(duì)稱率以及侵蝕線不對(duì)稱率為參照指標(biāo),除茂易村以左傾型橫斷面為主外,其他四個(gè)區(qū)域沖溝橫斷面均以右傾型為主。然而,以侵蝕面不對(duì)稱率為參照指標(biāo),除苴林村以右傾型橫斷面為主,其他四個(gè)區(qū)域均以左傾型橫斷面為主。從不同部位角度分析,溝身、溝口均以右傾型橫斷面為主,溝口在溝寬不對(duì)稱率和面積不對(duì)稱率為參照指標(biāo)衡量時(shí),以右傾型為主,在侵蝕線不對(duì)稱率和侵蝕面不對(duì)稱率為參照指標(biāo)衡量時(shí),以左傾型為主。元謀干熱河谷區(qū)沖溝橫斷面以右傾型為主,其次為左傾型,準(zhǔn)對(duì)稱型最少。(2)左傾型、準(zhǔn)對(duì)稱型和右傾型橫斷面數(shù)量隨橫斷面深度的增加,均呈現(xiàn)減少趨勢(shì),且三類沖溝橫斷面的深度都主要集中在0-8m之間。其中,深度在0-4m之間的左傾型、準(zhǔn)對(duì)稱型和右傾型的沖溝橫斷面,分別占各自總數(shù)的44.22%、43.36%和48.98%;在4-8m之間的三類沖溝橫斷面,分別占各自總數(shù)的41.50%、44.25%和37.24%。從不同類型橫斷面的寬度來(lái)看,三類沖溝橫斷面的數(shù)量均隨其寬度的增加呈現(xiàn)先增加后減小的趨勢(shì):左傾型、準(zhǔn)對(duì)稱型和右傾型的橫斷面數(shù)量均在8-16m區(qū)間內(nèi)增加到最大,分別占各自總數(shù)的54.42%、59.26%和47.45%,之后隨著橫斷面寬度的增加,橫斷面數(shù)量逐漸減小。左傾型、準(zhǔn)對(duì)稱型和右傾型橫斷面數(shù)量隨著面積的增加,均呈現(xiàn)減少趨勢(shì),且三類沖溝的橫斷面面積都主要集中在0-50m2之間,分別占各自總數(shù)的53.74%、50.44%和54.08%。從不同類型橫斷面的寬深比來(lái)看,左傾型、準(zhǔn)對(duì)稱型和右傾型橫斷面數(shù)量隨著橫斷面寬深比的增加呈現(xiàn)顯著增加后急劇減小的趨勢(shì):三類沖溝橫斷面數(shù)量均在2-4區(qū)間內(nèi)增加到最大,分別占各自總數(shù)的70.07%、74.34%和58.16%,最后隨著橫斷面寬深比的增加,橫斷面數(shù)量迅速減少�？傊�,以深度、寬度、面積和寬深比為參照指標(biāo)時(shí),左傾型、準(zhǔn)對(duì)稱型和右傾型橫斷面之間并沒有比較明顯的差異。(3)元謀干熱河谷區(qū)獨(dú)特的氣候條件和土壤性質(zhì)使該區(qū)沖溝侵蝕極其嚴(yán)重。研究發(fā)現(xiàn)沖溝橫斷面不對(duì)稱形態(tài)受土壤性質(zhì)、溝底匯流方向、植被條件以及潛蝕地貌等因素影響。該區(qū)土壤性質(zhì)上下層差異明顯,表層為土壤膠結(jié)性較好,干燥時(shí)異常堅(jiān)硬的古紅土層,下層為粉砂質(zhì)沉積巖,土質(zhì)多為壤質(zhì),較松軟。沖溝兩側(cè)土體的抗侵蝕能力的不同是造成橫斷面呈不對(duì)稱形態(tài)的關(guān)鍵因素。水流在經(jīng)過(guò)彎道時(shí),會(huì)在離心力的作用下對(duì)兩側(cè)產(chǎn)生差異侵蝕——“凸岸堆積,凹岸侵蝕”,也會(huì)影響橫斷面形態(tài)的實(shí)際表現(xiàn)。加之,植被條件——植物根系對(duì)溝區(qū)土體的撐托作用,會(huì)在局部范圍內(nèi)影響橫斷面形態(tài)特征。溝區(qū)的潛蝕地貌(陷穴、豎井、土橋、淘洞等)會(huì)加速溝壁、溝底的崩塌和塌陷,從而在很大程度上影響沖溝橫斷面形態(tài)的特征。
[Abstract]:A gully is a channel formed by a temporary surface flow that washes away the surface of the earth. It is a bridge connecting past, present and future gully erosion events. The gully morphology includes plane, cross-sectional and vertical profiles, in which the cross-sectional shape of the gully can be used not only to estimate gully erosion amount and rate, but also to illustrate the development caused by undercutting and lateral erosion. In this study, 456 gully cross-sections were measured by Leica DistoTM D8 laser rangefinder in Yuanmou dry-hot valley area, and then the shape parameters of gully cross-sections were plotted and calculated by CASS 7.0 and Excel 2003 software. The main conclusions are as follows: (1) The asymmetric rate of gully width (al), the asymmetric rate of area (aa), the asymmetric rate of erosion line (aw), and the invasion rate were selected. The results show that the asymmetry ratio of gully width, area and erosion line are taken as the reference indexes from different regional perspectives. Except Maoyi Village's left-leaning cross section, the other four areas are taken as the main index. However, with the asymmetry of erosion surface as the reference index, except for the right-inclined cross section in Chuilin village, the left-inclined cross section is the main one in the other four areas. The cross section of gullies in Yuanmou dry-hot valley is mainly right-dipping type, followed by left-dipping type, and the number of quasi-symmetrical type is the least. (2) Left-dipping type, quasi-symmetrical type and right-dipping type cross section increase with the depth of cross section. The depth of the three types of gullies is mainly between 0-8m. The left-dipping, quasi-symmetrical and right-dipping gullies account for 44.22%, 43.36% and 48.98% of the total respectively, and the three types of gullies between 4-8M account for 41.50%, 44.25% and 37.2% of the total respectively. 4%. The number of three types of gullies increases first and then decreases with the increase of their width. The number of left-leaning, quasi-symmetrical and right-leaning gullies increases to the maximum in the range of 8-16m, accounting for 54.42%, 59.26% and 47.45% of their total, respectively, and then increases with the increase of their width. In addition, the number of cross-sections decreased gradually. The number of left-dipping, quasi-symmetrical and right-dipping cross-sections decreased with the increase of the area. The cross-sectional areas of the three types of gullies were mainly concentrated in the range of 0-50m2, accounting for 53.74%, 50.44% and 54.08% of the total respectively. The number of the three types of gullies increased to the maximum in the 2-4 range, accounting for 70.07%, 74.34% and 58.16% of the total respectively. Finally, the number of the three types of gullies decreased rapidly with the increase of the ratio of width to depth. When the ratio of width, area and width to depth is the reference index, there is no obvious difference between left-dipping, quasi-symmetrical and right-dipping cross-sections. (3) The unique climatic conditions and soil properties in Yuanmou dry-hot valley make the gully erosion extremely serious. Influenced by the conditions and the buried erosion landforms, the soil properties in this area are obviously different between the upper and lower layers. The surface layer is the paleo-laterite layer with good soil cementation, which is abnormally hard when dry. The lower layer is silty sedimentary rock, and the soil is mostly loam and soft. Factors. When water flows through a bend, it will erode the two sides differently under the action of centrifugal force - "convex bank accumulation, concave bank erosion". It will also affect the actual performance of cross-sectional morphology. In addition, vegetation conditions - - the supporting effect of plant roots on the soil in the gully area will affect the cross-sectional morphological characteristics in a local scope. Geomorphology (caves, shafts, earth bridges, caves, etc.) can accelerate the collapse and subsidence of gully walls and the bottom of the gully, thus greatly affecting the characteristics of gully cross-sectional morphology.
【學(xué)位授予單位】：西華師范大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：S157.1

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