Abstract A rivers’ longitudinal gradient (i.e. slope) is a key parameter in fluvial hydrology, hydraulics, and geomorphology. It affects a multitude of fluvial variables such as flow velocity and sediment transport. Limitations in river slope data, both its availability and accuracy, constrain the fidelity of fluvial modeling, particularly at larger or global scales. Traditional slope calculation algorithms cannot accurately predict river slopes as these are based on cell-by-cell calculation, which is only suitable for hillslopes and small mountainous streams. This paper presents a methodology for calculating global river slope and a procedure to upscale it for relatively coarse resolution, suitable for global scale modeling. The methodology is based on a simple principle of calculating slope from elevation depression over the length of a river segment, which is automated to allow global scale calculations. Version 1.0 of the Global River-Slope (GloRS) geospatial dataset is introduced and shown to be a step improvement over a previous product (NHDplus for the contiguous United States) and compares favorably to observed slope data collected from the literature. Statistical analysis of Earth’s continents and large basins highlights interesting spatial trends. A semi-empirical regression analysis between basin-average river slope and other basin-scale parameters show that terrain slope accounts for 67% of the variability in basin-average river slope, with average discharge, sediment load and basin temperature contributing additional improvements to global predictions of 3%, 4%, and 3%, respectively.

中文翻译：

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全球河流坡度：新的地理空间数据集和全球尺度分析

摘要 河流的纵向坡度（即坡度）是河流水文学、水力学和地貌学中的一个关键参数。它影响多种河流变量，如流速和泥沙输移。河流坡度数据的局限性，包括其可用性和准确性，限制了河流建模的保真度，尤其是在更大或全球范围内。传统的坡度计算算法无法准确预测河流坡度，因为它们基于逐个单元计算，仅适用于山坡和小山溪。本文提出了一种计算全球河流坡度的方法，以及一种将其放大以获得相对粗略分辨率的程序，适用于全球尺度建模。该方法基于一个简单的原理，即从河段长度上的高程洼地计算坡度，该原理是自动化的，可以进行全球尺度计算。引入了 Global River-Slope (GloRS) 地理空间数据集的 1.0 版，并证明它比以前的产品（美国本土的 NHDplus）有了进一步的改进，并且与从文献中收集的观测坡度数据相比具有优势。对地球大陆和大型盆地的统计分析突出了有趣的空间趋势。流域平均河流坡度与其他流域尺度参数的半经验回归分析表明，地形坡度占流域平均河流坡度变异的67%，平均流量，