Modeled stream discharge is often used to drive sediment transport models across channel networks. Because sediment transport varies non-linearly with flow rates, discharge modeled from daily total precipitation distributed evenly over 24-hr may significantly underestimate actual bedload transport capacity. In this study, we assume bedload transport capacity determined from a hydrograph resulting from the use of hourly (1-hr) precipitation is a close approximation of actual transport capacity and quantify the error introduced into a network-scale bedload transport model driven by daily precipitation at channel network locations varying from lowland pool-riffle channels to upland colluvial channels in a watershed where snow accumulation and melt can affect runoff processes. Transport capacity is determined using effective stresses and the Wilcock and Crowe (2003) equations and expressed in terms of transport capacity normalized by the bankfull value. We find that, depending on channel network location, cumulative error can range from 10% to more than two orders of magnitude. Surprisingly, variation in flow rates due to differences in hillslope and channel runoff do not seem to dictate the network locations where the largest errors in predicted bedload transport capacity occur. Rather, spatial variability of the magnitude of the effective-bankfull-excess shear stress and changes in runoff due to snow accumulation and melt exert the greatest influence. These findings have implications for flood-hazard and aquatic habitat models that rely on modeled sediment transport driven by coarse-temporal-resolution climate data.

中文翻译：

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在海洋气候中，降水变率如何控制山区航道网络的床载响应？

模拟河流流量通常用于驱动跨渠道网络的泥沙输送模型。由于泥沙输送随流速呈非线性变化，根据平均分布在 24 小时内的每日总降水量模拟的流量可能会显着低估实际的床载输送能力。在这项研究中，我们假设从使用每小时（1 小时）降水产生的水位线确定的床载输送能力是实际输送能力的近似值，并量化引入由每日降水驱动的网络规模床载输送模型的误差在河道网络位置，从低地池浅滩河道到流域内的高地崩积河道，积雪和融化会影响径流过程。运输能力是使用有效应力和 Wilcock 和 Crowe (2003) 方程确定的，并以通过 bankfull 值归一化的运输能力表示。我们发现，根据通道网络位置，累积误差的范围可以从 10% 到两个数量级以上。令人惊讶的是，由于山坡和河道径流的差异导致的流量变化似乎并不决定预测床载输送能力发生最大误差的网络位置。相反，由于积雪和融化导致的有效岸边超剪应力大小的空间变化和径流变化的影响最大。这些发现对依赖由粗时间分辨率气候数据驱动的模拟沉积物迁移的洪水灾害和水生栖息地模型具有重要意义。