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为了说明天然冲积河流存在极限流速,整理了长江、松花江等20条冲积河流上25个水文站的日均流量、日均水位、实测大断面、日均含沙量等水文资料,利用水流连续性方程,由日均流量和过水断面面积求出断面平均流速。结果表明,天然冲积河流断面平均流速随着流量的增加而增大,达到一定流量后,断面平均流速趋近于一个极限流速。天然冲积河流流量较大时通过增加过流断面面积使得流速始终低于极限流速。人类活动会影响冲积河流的极限流速。
In order to illustrate the limit flow velocity of natural alluvial rivers, hydrological data such as average daily flow rate, average daily water level, actual measured large section and average daily sediment concentration of 25 hydrological stations in 20 alluvial rivers such as the Yangtze River and Songhua River were sorted out, Sex equation, the daily average flow and cross-sectional area of the cross-sectional average flow velocity. The results show that the average velocity of natural alluvial river cross-section increases with the increase of flow rate. After reaching a certain flow rate, the average velocity of cross-section approaches a limit velocity. When the natural alluvial river flow is larger, the flow rate is always lower than the limit flow rate by increasing the cross-sectional area of over-flow. Human activities affect the alluvial river flow rate limit.