Replication Dataset for "Dune geometry and the associated hydraulic roughness in a fluvial to tidal transition zone at low river flow"

Replication dataset corresponding to the publication "Dune geometry and the associated hydraulic roughness in a fluvial to tidal transition zone at low river flow"This dataset consists of the raw field data, hydraulic model, processed field data and scripts. The contents are described in the word document.<br><br>Abstract: In deltas and estuaries throughout the world, a fluvial-to-tidal transition zone (FTTZ) exists where both the river discharge and the tidal motion drive the flow. It is unclear how dune characteristics are impacted by changes in tidal flow strength, and how this is reflected in the hydraulic roughness. To understand dune geometry and variability in the FTTZ and possible impacts on hydraulic roughness, we assess dune variability from multibeam bathymetric surveys, and we use a calibrated 2D hydrodynamic model (Delft3D-FM) of a sand-bedded lowland river (Fraser River, Canada). We focus on a period of low river discharge during which tidal impact is strong. We find that the fluvial-tidal to tidal regime change is not directly reflected in dune height, but local patterns of increasing and decreasing dune height are present. The fluvial-to-tidal regime change is reflected in dune shape, where dunes have lower leeside angles and are more symmetrical in the tidal regime. The calibrated model is able to estimate local patterns of dune heights using tidally-averaged values of bed shear stress. However, the spatially variable dune morphology hampers local dune height estimations. Changes in dune shape do not significantly impact the reach-scale roughness, and estimated dune roughness using dune height and length is similar to the dune roughness inferred from model calibration. Hydraulic model performance with a calibrated, constant roughness is not improved by implementing dune-derived bed roughness. Instead, large-scale river morphology may explain differences in model roughness and corresponding estimates from dune predictors.

本数据集为对应发表论文《低径流量下河流-潮汐过渡带的沙丘形态与相关水力粗糙度（Dune geometry and the associated hydraulic roughness in a fluvial to tidal transition zone at low river flow）》的复现数据集。本数据集包含原始野外实测数据、水力学模型、处理后的野外数据以及分析脚本，具体内容详见配套Word文档。<br><br>摘要：在全球范围内的三角洲与河口区域中，均存在河流-潮汐过渡带（fluvial-to-tidal transition zone, FTTZ），该区域内河流径流与潮汐运动共同驱动水流。目前学界尚未明确潮汐水流强度的变化如何影响沙丘特征，且尚不清晰该影响如何体现在水力粗糙度之中。为探究河流-潮汐过渡带内的沙丘形态与变化特征，及其对水力粗糙度的潜在影响，本研究基于多波束测深调查数据评估沙丘的空间变异性，并采用经过率定的二维水动力学模型（Delft3D-FM），针对加拿大弗雷泽河（Fraser River）这一砂质低地河流开展分析。研究聚焦于潮汐影响显著的低径流量时段。<br>研究结果表明：河流-潮汐向纯潮汐的流态转变并未直接体现在沙丘高度上，但存在局部沙丘高度升高与降低的分布格局；该流态转变则反映在沙丘形态上，纯潮汐流态下的沙丘背坡角度更低，且形态更为对称。经过率定的模型可利用床面剪切应力的潮汐平均值估算沙丘高度的局部分布，但空间异质性的沙丘形态会阻碍局地沙丘高度的精准预测。沙丘形态变化对河段尺度的粗糙度并无显著影响，基于沙丘高度与长度估算的沙丘粗糙度，与通过模型率定得到的沙丘粗糙度结果相近。采用基于沙丘推导的床面粗糙度，并未提升采用率定恒定粗糙度时的水力学模型模拟性能。相反，大尺度河流地貌或许可以解释模型粗糙度与沙丘预测器对应估算值之间的差异。