Central Lowlands Post-Settlement Alluvium Data

Data to accompany: Impacts of geographic variability and geologic history on the distribution of post-settlement alluvium (PSA) across the upper Midwest, USA. Alison M. Anders and Bruce L. Rhoads Catena CATENA_108939 Accepted for Publication 11 Mar 2025 A shapefile of the watersheds included in a meta-analysis of post-settlement alluvium in the Central Lowlands/Midwest USA is included as a zipped archive. A data table with PSA thickness, landscape, climate and soils data from the watersheds is provided as a text file. Accelerated floodplain sedimentation related to agricultural development of uplands has produced post-settlement alluvium (PSA) along rivers throughout the upper Midwest, U.S.A. Landscape characteristics in the region vary geographically in relation to differences in geologic history, yet the extent to which this geographic variability influences PSA accumulation remains unexplored. This study uses existing data to assess how non-dimensional PSA thickness varies with landscape characteristics and climate. Geographic variability is associated with three subregions: 1) areas glaciated during the Late Wisconsin Episode (LWE), 2) areas glaciated during Pre-Illinois and Illinois Episodes (PI&IE), and 3) the Paleozoic Plateau (PP), an area where evidence of Quaternary glaciation is highly localized and does not influence geomorphic characteristics of the landscape. These subregions differ significantly in average geomorphic characteristics, including mean watershed slope (WS), mean local relief (LR), fraction of non-contributing area (NCA), pre-settlement drainage density (DD), and mean normalized river steepness (KSN). Non-dimensional PSA thickness also differs significantly among the subregions, increasing systematically with landscape age; it also is significantly positively correlated with LR, KSN and WS, and significantly negatively correlated with NCA. Non-visibly distinct PSA is present in some LWE watersheds characterized by significantly lower KSN and WS relative to other LWE watersheds in which PSA is visibly distinct. These results indicate that PSA thickness and visibility reflect inherited landscape characteristics, emphasizing the importance of geographic setting, geological history, and geomorphic context for understanding historical river sediment dynamics. Spatial variability in PSA thickness also serves as an indicator of river system sensitivity to human-induced land-use change, which informs river management strategies.配套数据集： 美国中西部地区后沉积冲积层（post-settlement alluvium, PSA）分布受地理变异性与地质历史的影响 Alison M. Anders 与 Bruce L. Rhoads 《Catena》，文章编号CATENA_108939 2025年3月11日接收发表 本数据集包含美国中部低地/中西部地区后沉积冲积层元分析所用流域的Shapefile格式数据，以压缩归档形式提供。另有一份包含各流域PSA厚度、景观、气候与土壤数据的数据表，以文本文件形式发布。 美国中西部上游地区因高地农业开发引发的河漫滩加速沉积作用，在区域内各河流沿岸形成了后沉积冲积层（PSA）。该区域的景观特征随地理区位呈现显著分异，这与各地质历史差异紧密相关，但目前学界尚未明确这种地理变异性对PSA堆积过程的影响程度。本研究依托现有数据，探究无量纲PSA厚度随景观特征与气候条件的变化规律。根据地理变异性特征，研究区域可划分为三个子区域：1）晚威斯康星冰期（Late Wisconsin Episode, LWE）冰川作用影响区；2）前伊利诺伊冰期与伊利诺伊冰期（Pre-Illinois and Illinois Episodes, PI&IE）冰川作用影响区；3）古生代高原（Paleozoic Plateau, PP）——该区域第四纪冰川作用证据极为局限，未对区域地貌特征产生显著影响。 三个子区域的平均地貌特征存在显著差异，包括流域平均坡度（watershed slope, WS）、平均局地地形起伏度（local relief, LR）、非贡献面积占比（non-contributing area, NCA）、沉积前排水密度（drainage density, DD）以及平均归一化河道陡度（normalized river steepness, KSN）。各子区域的无量纲PSA厚度同样存在显著差异，随景观形成年龄呈系统性递增趋势；同时与LR、KSN和WS呈显著正相关，与NCA呈显著负相关。在部分晚威斯康星冰期流域中存在肉眼不可辨识的PSA，这类流域的KSN与WS显著低于其他存在肉眼可辨识PSA的晚威斯康星冰期流域。 上述研究结果表明，PSA厚度与可见性反映了区域继承性的景观特征，凸显了地理背景、地质历史与地貌环境在理解历史河流沉积动态过程中的重要性。此外，PSA厚度的空间变异性亦可作为河流系统对人类土地利用变化敏感性的指示因子，可为河流管理策略制定提供科学参考。