Bedrock rivers are commonly expected to have steeper and narrower channels than alluvial rivers. However, understanding of bedrock river characteristics has largely been based on small samples of sites in specific climates and upland locations. We provide the first systematic assessment of bedrock and alluvial river channel characteristics for 1274 sites across a broad climatic gradient. We assess whether the width, width-to-depth ratio, and slope of bedrock channels differ from those of alluvial channels and the extent to which these differences are correlated with drainage area, mean annual flow (QMAF), grain size, and lithology. We find that bedrock channels occur at all drainage areas. For the same drainage area, bedrock channels are wider and steeper than alluvial channels. They also have a higher mean annual precipitation and hence QMAF, which likely causes the increased width. After accounting for differences in QMAF, both bedrock and alluvial channels have similar hydraulic scaling. Lithology affects both types of channels in a similar way, with channels on sedimentary lithologies being wider and less steep compared to those on igneous-metamorphic lithologies. Overall, our findings raise new questions about the evolution of bedrock river channels and pave the way for more accurate landscape evolution modeling.

中文翻译：

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基岩河流陡峭但不狭窄：美国各地河流几何形状的水文和岩性控制


通常认为基岩河流的河道比冲积河更陡、更窄。然而，对基岩河流特征的了解很大程度上是基于特定气候和高地地点的小样本。我们首次对跨越广泛气候梯度的 1274 个地点的基岩和冲积河道特征进行了系统评估。我们评估基岩河道的宽度、宽深比和坡度是否与冲积河道不同，以及这些差异与流域面积、年平均流量（QMAF）、粒度和岩性的相关程度。我们发现所有排水区域都存在基岩水道。对于相同的流域面积，基岩河道比冲积河道更宽、更陡。它们的年平均降水量也较高，因此 QMAF 也较高，这可能导致宽度增加。考虑到 QMAF 的差异后，基岩和冲积河道都具有相似的水力结垢。岩性以类似的方式影响两种类型的河道，沉积岩性上的河道比火成岩岩性上的河道更宽且陡度更小。总体而言，我们的研究结果提出了有关基岩河道演化的新问题，并为更准确的景观演化建模铺平了道路。