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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Channel change, bankfull and effective discharges on a vertically accreting, meandering, gravel-bed river
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Channel change, bankfull and effective discharges on a vertically accreting, meandering, gravel-bed river

机译：垂直积水，蜿蜒的砾石河床的河道变化，满溢和有效排放

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Along the lower reaches of the Waipaoa River, New Zealand, cross-section survey data indicate there was a 23 per cent decrease in bankfull width and a 22 per cent reduction in channel cross-section area between 1948 and 2000, as the channel responded to increased inputs of fine (suspended) sediment following deforestation of the headwaters in late C19 and early C20. We determined the bankfull discharge within a similar to 39 km long reach by routing known discharges through the one-dimensional MIKE 11 flow model. The model runs suggest that the bankfull discharge varies between similar to 800 and similar to 2300 m(3) s(-1) and that the average recurrence interval is 4 2 years on the annual maximum series; by contrast, the effective flow (360 m(3) s(-1) ) is equaled or exceeded three times a year. The variability in bankfull discharge arises because the banks tend to be lower in places where flood flows are constricted than in reaches where overbank flow is dispersed over a wide area, and because scour has counteracted aggradation in some locations. There is no downstream variation in Shields stress, or in relative shear stress, within the study reach. Bankfull shear stress is, on average, five times greater than the shear stress required to initiate motion. At the effective discharge it is more than twice the threshold value. The effective discharge probably has more relevance than the bankfull discharge to the overall picture of sediment movement in the lower reaches of the Waipaoa River but, because width is constrained by the stability and resistance of the bank material to erosion during high flows that also scour the bed, the overall channel geometry is likely determined by discharges at or near bankfull. Copyright (c) 2006 John Wiley & Sons, Ltd.
机译：沿新西兰怀波阿河下游，横断面调查数据表明，随着河道的响应，在1948年至2000年之间，河岸宽减少了23％，河道截面积减少了22％。在C19后期和C20初期上游水源砍伐森林之后，增加了细（悬浮）沉积物的投入。我们通过一维MIKE 11流量模型路由已知的排放量，确定了大约39公里长范围内的堤岸排放量。模型运行表明，满溢流量在大约800和大约2300 m（3）s（-1）之间变化，并且在年最大序列上的平均复发间隔为4 2年;相反，有效流量（360 m（3）s（-1））每年等于或超过三倍。银行满额流量的变化是由于洪水泛滥的地方的河岸往往要比大范围地区的过度银行河道的河岸要低，而且冲刷抵消了某些地方的积水。在研究范围内，Shields应力或相对剪应力没有下游变化。堤岸平均剪切应力平均比启动运动所需的剪切应力大五倍。在有效放电时，它是阈值的两倍以上。有效排放量可能比堤岸满溢流量对怀波阿河下游泥沙运动的整体状况具有更大的相关性，但是，由于宽度受到堤岸材料在高流量期间的侵蚀的稳定性和抵抗力的限制，因此冲刷了河道水流。在河床中，整个河道的几何形状很可能由堤岸或附近的流量决定。版权所有（c）2006 John Wiley＆Sons，Ltd.

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