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Adjustment of self‐formed bankfull channel geometry of meandering rivers: modelling study
Earth Surface Processes and Landforms ( IF 2.8 ) Pub Date : 2020-07-29 , DOI: 10.1002/esp.4966 Kensuke Naito 1, 2 , Gary Parker 1, 3
Earth Surface Processes and Landforms ( IF 2.8 ) Pub Date : 2020-07-29 , DOI: 10.1002/esp.4966 Kensuke Naito 1, 2 , Gary Parker 1, 3
Affiliation
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We consider the evolution of the hydraulic geometry of sand‐bed meandering rivers. We study the difference between the timescale of longitudinal river profile adjustment and that of channel width and depth adjustment. We also study the effect of hydrological regime alteration on the evolution of bankfull channel geometry. To achieve this, a previously developed model for the spatiotemporal co‐evolution of bankfull channel characteristics, including bankfull discharge, bankfull width, bankfull depth and down‐channel bed slope, is used. In our modelling framework, flow variability is considered in terms of a specified flow duration curve. Taking advantage of this unique feature, we identify the flow range responsible for long‐term bankfull channel change within the specified flow duration curve. That is, the relative importance of extremely high short‐duration flows compared to moderately high longer duration flows is examined. The Minnesota River, MN, USA, an actively meandering sand‐bed stream, is selected for a case study. The longitudinal profile of the study reach has been in adjustment toward equilibrium since the end of the last glaciation, while its bankfull cross‐section is rapidly widening due to hydrological regime change in the last several decades. We use the model to demonstrate that the timescale for longitudinal channel profile adjustment is much greater than the timescale for cross‐sectional profile adjustment due to a lateral channel shift. We also show that hydrological regime shift is responsible for the recent rapid widening of the Minnesota River. Our analysis suggests that increases in the 5–25% exceedance flows play a more significant role in recent bankfull channel enlargement of the Minnesota River than increase in either the 0.1% exceedance flow or the 90% exceedance flow. © 2020 John Wiley & Sons, Ltd.
中文翻译：
蜿蜒河流的自形成河岸全流道几何形状的调整：模型研究
我们考虑了沙床蜿蜒河流的水力几何形状的演变。我们研究了纵向河流剖面调整的时间尺度与河道宽度和深度调整的时间尺度之间的差异。我们还研究了水文情势变化对河岸河床几何演变的影响。为了达到这个目的，使用了先前开发的用于河岸满河特征时空协同演化模型，包括河岸满水排放，河岸满水宽度，河岸满水深度和河道下坡度。在我们的建模框架中，根据指定的流动持续时间曲线来考虑流动可变性。利用此独特功能，我们可以确定在指定流量持续时间曲线内导致长期河堤变化的流量范围。那是，考察了极高的短期流量与持续时间较长的中等流量的相对重要性。案例研究选择了美国明尼苏达州明尼苏达河（Minnesota River，明尼苏达州河）一条蜿蜒曲折的沙床流。自上次冰河末期以来，研究范围的纵向剖面一直在朝着平衡方向调整，而由于近几十年来水文状况的变化，其整个河床的横截面正在迅速扩大。我们使用该模型来证明，由于横向通道偏移，用于纵向通道轮廓调整的时间尺度比用于截面轮廓调整的时间尺度大得多。我们还表明，水文状况的变化是造成明尼苏达河近期快速扩张的原因。我们的分析表明，与近期流量增加0.1％或流量超出90％的增加相比，近期流量在明尼苏达河河岸满河扩张中增加5-25％的影响更为重要。分级为4 +©2020 John Wiley＆Sons，Ltd.
更新日期：2020-07-29
中文翻译：
蜿蜒河流的自形成河岸全流道几何形状的调整：模型研究
我们考虑了沙床蜿蜒河流的水力几何形状的演变。我们研究了纵向河流剖面调整的时间尺度与河道宽度和深度调整的时间尺度之间的差异。我们还研究了水文情势变化对河岸河床几何演变的影响。为了达到这个目的，使用了先前开发的用于河岸满河特征时空协同演化模型，包括河岸满水排放，河岸满水宽度，河岸满水深度和河道下坡度。在我们的建模框架中，根据指定的流动持续时间曲线来考虑流动可变性。利用此独特功能，我们可以确定在指定流量持续时间曲线内导致长期河堤变化的流量范围。那是，考察了极高的短期流量与持续时间较长的中等流量的相对重要性。案例研究选择了美国明尼苏达州明尼苏达河（Minnesota River，明尼苏达州河）一条蜿蜒曲折的沙床流。自上次冰河末期以来，研究范围的纵向剖面一直在朝着平衡方向调整，而由于近几十年来水文状况的变化，其整个河床的横截面正在迅速扩大。我们使用该模型来证明，由于横向通道偏移，用于纵向通道轮廓调整的时间尺度比用于截面轮廓调整的时间尺度大得多。我们还表明，水文状况的变化是造成明尼苏达河近期快速扩张的原因。我们的分析表明，与近期流量增加0.1％或流量超出90％的增加相比，近期流量在明尼苏达河河岸满河扩张中增加5-25％的影响更为重要。分级为4 +©2020 John Wiley＆Sons，Ltd.
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