Data for: Quantifying Bankfull Flow Width Using Preserved Bar Clinoforms from Fluvial Strata

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.

从河流沉积地层中恢复古活动河道几何形态，对于限定古陆表环境的水沙通量至关重要。目前已有基于大量野外观测、数值模拟与物理实验的可靠方法，可从保存的沉积体中估算满岸水深与河床坡度；但目前仍缺乏类似工具以量化满岸河道宽度。本研究整合了覆盖11条河流（尺寸跨度达两个数量级）的134个河曲弯段的高分辨率激光雷达（LiDAR）数据，以此建立满岸河道宽度与河道沙坝斜层宽度（即岸附河道沙坝的残留地层界面）之间的可靠经验关系。本研究采用双参数Sigmoid（sigmoid）函数对沙坝横截面形态进行参数化，将沙坝宽度定义为拟合所得Sigmoid曲线95%渐近线之间的横流距离。将这一沙坝宽度的客观定义与贝叶斯线性回归分析相结合后，本研究证实实测满岸河道宽度为河道沙坝宽度的2.34±0.13倍。本研究通过覆盖所有气候带的河曲河道沙坝与满岸宽度野外观测数据（决定系数R²=0.79），以及河流沉积地层中河道沙坝斜层宽度与泥塞宽度的同步观测数据（R²=0.80）对模型进行了验证。本研究还证实，沙坝的横向床面坡度与河曲曲率呈负相关关系，这与理论预期一致。本研究结果提供了一种简单易用的量化指标，可从保存的沙坝斜层中反演古河道宽度。