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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Timescale dependence in river channel migration measurements
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Timescale dependence in river channel migration measurements

机译：河道迁移测量中的时间尺度依赖

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Accurately measuring river meander migration over time is critical for sediment budgets and understanding how rivers respond to changes in hydrology or sediment supply. However, estimates of meander migration rates or streambank contributions to sediment budgets using repeat aerial imagery, maps, or topographic data will be underestimated without proper accounting for channel reversal. Furthermore, comparing channel planform adjustment measured over dissimilar timescales are biased because short- and long-term measurements are disproportionately affected by temporary rate variability, long-term hiatuses, and channel reversals. We evaluate the role of timescale dependence for the Root River, a single threaded meandering sand- and gravel-bedded river in southeastern Minnesota, USA, with 76 years of aerial photographs spanning an era of landscape changes that have drastically altered flows. Empirical data and results from a statistical river migration model both confirm a temporal measurement-scale dependence, illustrated by systematic underestimations (2-15% at 50 years) and convergence of migration rates measured over sufficiently long timescales (> 40 years). Frequency of channel reversals exerts primary control on measurement bias for longer time intervals by erasing the record of observable migration. We conclude that using long-term measurements of channel migration for sediment remobilization projections, streambank contributions to sediment budgets, sediment flux estimates, and perceptions of fluvial change will necessarily underestimate such calculations. (c) 2019 John Wiley & Sons, Ltd.
机译：准确测量河蜿蜒迁移随着时间的推移对沉积物预算至关重要，并了解河流如何响应水文或泥沙供应的变化。然而，在使用重复空中图像，地图或地形数据的情况下，将低估了对沉积物预算的曲折迁移率或StreamBank贡献的估计，如果频道逆转，则将低估了使用重复空中图像，地图或地形数据的沉积预算。此外，比较通过不同时间尺度测量的信道平面调节被偏置，因为短期和长期测量因临时速率可变性，长期的时期和沟道逆转而不成比例地影响。我们评估了美国明尼苏达东南部的一个螺纹蜿蜒的沙子和砾石和砾石河流的TimeScale依赖的作用，其中76年的空中照片，跨越了横向变化的景观变化时代。统计河流迁移模型的经验数据和结果证实了时间测量尺度依赖性，通过系统低估所示（50年2-15％），并且在足够长的时间尺度（> 40年）上测量的迁移率的收敛性。通过擦除可观察的迁移的记录，通道逆转频率在测量偏压上施加较长的时间间隔。我们得出结论，利用用于沉积物重组预测的频道迁移的长期测量，流班班班湾对沉积物预算，沉积物通量估计和氟尿变革的看法必然低估了这种计算。 （c）2019 John Wiley＆Sons，Ltd。

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