Quantifying bankfull flow width using preserved bar clinoforms from fluvial strata
Quantifying bankfull flow width using preserved bar clinoforms from fluvial strata
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DOI：
10.1130/g48729.1
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发表时间：
2021-04
期刊：
影响因子：
5.8
通讯作者：
E. Greenberg;E. al.
中科院分区：
文献类型：
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作者：
E. Greenberg;E. al.
从河流地层中重建活动河道的几何形状是限制古陆地景观中水沙通量的关键。鲁棒的方法，接地广泛的实地观察，数值模拟和物理实验，存在估计的岸流深度和保存存款的渠道河床坡度，但是，我们缺乏类似的工具来量化岸流渠道宽度。我们结合了高分辨率激光雷达数据，从134曲流弯曲横跨11条河流，跨越两个数量级的大小，开发一个强大的，经验关系的bankfull通道宽度和河坝斜坡宽度（残留的地层表面的银行附着河坝）。我们使用双参数S形模型参数化了棒材横截面形状，将棒材宽度定义为拟合S形模型的95%渐近线之间的横流距离。我们将拦门沙宽度的客观定义与贝叶斯线性回归分析相结合，结果表明实测平滩流宽度是河沙宽度的2.34 ± 0.13倍。我们验证了我们的模型，使用现场测量的河坝和bankfull流宽度的蜿蜒河流，跨越所有的气候带（R2 = 0.79）和并行测量的河坝斜坡宽度和泥塞宽度在河流地层（R2 = 0.80）。我们还表明，酒吧的横向床斜率呈负相关的弯曲曲率，与理论一致。结果提供了一个简单、可用的指标，可以从保存的坝坡斜坡中推导出古河道宽度。
Reconstruction of active channel geometry from fluvial strata is critical to constrain the water and sediment fluxes in ancient terrestrial landscapes. Robust methods—grounded in extensive field observations, numerical simulations, and physical experiments—exist for estimating the bankfull flow depth and channel-bed slope from preserved deposits; however, we lack similar tools to quantify bankfull channel widths. We combined high-resolution lidar data from 134 meander bends across 11 rivers that span over two orders of magnitude in size to develop a robust, empirical relation between the bankfull channel width and channel-bar clinoform width (relict stratigraphic surfaces of bank-attached channel bars). We parameterized the bar cross-sectional shape using a two-parameter sigmoid, defining bar width as the cross-stream distance between 95% of the asymptotes of the fit sigmoid. We combined this objective definition of the bar width with Bayesian linear regression analysis to show that the measured bankfull flow width is 2.34 ± 0.13 times the channel-bar width. We validated our model using field measurements of channel-bar and bankfull flow widths of meandering rivers that span all climate zones (R2 = 0.79) and concurrent measurements of channel-bar clinoform width and mud-plug width in fluvial strata (R2 = 0.80). We also show that the transverse bed slopes of bars are inversely correlated with bend curvature, consistent with theory. Results provide a simple, usable metric to derive paleochannel width from preserved bar clinoforms.