Transient hillslope response to an incision wave sweeping up a watershed: A case study from the Salmon River
Transient hillslope response to an incision wave sweeping up a watershed: A case study from the Salmon River
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横扫分水岭的切入波的瞬态山坡响应：鲑鱼河的案例研究
DOI：
10.31979/etd.fxy3-f6yp
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
R. Wood
中科院分区：
文献类型：
--
作者：
R. Wood
当河道剖面适应新的下边界条件时，基准面降低往往会导致裂口点向河流网络上游迁移。在陡峭的地形中，裂口的通道会使山谷壁变得过于陡峭，并引发山坡上的侵蚀浪潮。随着土壤从山坡上被剥离，以前扩散的山坡变成了滑坡为主的山坡。扩散景观中的土壤发育良好，直到侵蚀通过缩短土壤停留时间暴露出下面的腐岩。在基准面调整过程中，山坡的侵蚀会使原始景观的残余斑块与新演变的景观并列。最近在爱达荷州中部的切口在鲑鱼河沿岸形成了巨大的河道到山脊的起伏，并导致了大型裂缝点在其许多支流中蔓延。这些小点标记了隆起前的地形（残存的地形）和被侵蚀的地形（更新的地形）之间的边界。在这项研究中，我旨在通过比较遗迹景观和更新景观的形态特征来分析斜坡对裂口通道的响应。建立了一个位于废弃和更新景观上的样带，以测量土壤特性和山脊形态。空间分析使用了国家高程数据集（NED）和高分辨率光探测和测距（LiDAR）高程数据。土壤分析结果表明：(1)更新景观中砾石含量较高，(2)废弃景观中碳含量较高，(3)两种景观类型的平均土壤深度相似（~18 cm）。空间分析结果表明，残废景观的平均坡度为18±7°，更新景观的平均坡度为33±7°。展望岭有三个不同的曲率值：0.0033±0.001（遗迹），0.0219±0.008（刷新）和0.0668±0.009（靠近鲑鱼河）。因此，从这些曲率值可以推断出三组不断增加的相对侵蚀水平。与更新景观相对应的侵蚀速率是场地内大型裂缝的形成原因。大型裂缝点下游的山坡会迅速变陡，景观也会从扩散型完全转变为以滑坡为主。相反，在裂缝点上游观察到的山坡响应不那么剧烈，这是基于河道轻微下降、山谷壁部分过度陡峭和支流子盆地中山坡变陡的证据。对残坡和切前残河道的重建表明，一个小得多的、已灭绝的断裂点先于较大的断裂点，并迅速扩散到源头。
TRANSIENT HILLSLOPE RESPONSE TO AN INCISION WAVE SWEEPING UP A WATERSHED: A CASE STUDY FROM THE SALMON RIVER by Ryan W. Wood Base level lowering often leads to the migration of knickpoints up the fluvial network as the channel profile adjusts to the new lower boundary condition. In steep terrain, the passage of a knickpoint can oversteepen valley walls and trigger a wave of erosion up the hillslopes. As soil is stripped from hillslopes, the previously diffusive hillslopes are transformed to landslidedominated. Soils in diffusive landscapes are well developed until erosion exposes the underlying saprolite by shortening the soil residence times. During base level adjustments, the erosion of hillslopes can leave relict patches of the original landscape juxtaposed with the newly evolving landscape. Recent incision in central Idaho has produced large channel-to-ridge relief along the Salmon River and has resulted in the propagation of large knickpoints into many of its tributaries. These knickpoints mark the boundaries between pre-uplifted terrain (relict landscapes) and freshly eroded terrain (refreshed landscapes). In this study I aimed to analyze the hillslope response to the passage of a knickpoint by comparing morphological characteristics between relict and refreshed landscapes. A transect situated on both relict and refreshed landscapes was established to measure soil properties and ridgecrest morphology. The spatial analysis used the National Elevation Datatset (NED) and high resolution Light Detection and Ranging (LiDAR) elevation data. Soil analysis showed 1) higher percentage of gravel in the refreshed landscape, 2) a higher percentage of carbon in the relict landscape, and 3) similar average soil depths in both landscape types (~18 cm). Spatial analysis showed the mean slope angle in the relict landscape is 18±7 ̊ and 33±7 ̊ in the refreshed landscape. Prospect Ridge has three distinct values of curvature: 0.0033±0.001 (relict), 0.0219±0.008 (refreshed), and 0.0668±0.009 (close to Salmon River). Three sets of increasing relative levels of erosion were therefore inferred from these curvature values. The erosion rate corresponding to the refreshed landscape is responsible for the formation of the large knickpoints within the site. Hillslopes downstream of the large knickpoints are subject to rapid oversteepening and complete landscape transformation from diffusive to landslide-dominated. Conversely, a less dramatic hillslope response was observed upstream of the knickpoint based on evidence of slight channel lowering, partially oversteepened valley walls, and pockets of hillslope steepening in tributary sub-basins. Reconstruction of relict hillslopes and the pre-incisional relict channel suggest that a much smaller, extinct knickpoint preceded the larger knickpoint and rapidly diffused into the headwaters.
影响因子：
3.9
作者：
Hurst, Martin D.;Mudd, Simon M.;Yoo, Kyungsoo
通讯作者：
Yoo, Kyungsoo