河口水动力与河床形态关系的研究

Study of hydrodynamics and morphology relationships for macro-tide estuaries

按造床流量的定义,分别对潮汐河口各种频率的涨、落潮输沙大小进行了对比计算,得出包括年平均迳流的年平均落潮流量的造床作用为最大,故以落潮流量作为河口的造床流量较合理。潮汐河口可分为一般河口和有涌潮的河口两种类型,一般河口的断面特征取决于平均落潮流量和平均含沙量。而有涌潮的河口,其河宽决定于平均涨潮流量,相应的水深、纵向河宽放宽率、河床比降则与涨、落潮流量和含沙量都有关。为此本文建立了一系列河口动力与河床形态间的经验河相关系式,对浙江省的五条主要河口的断面特征(半潮面积、河宽、水深)、宽深比、纵向河宽放宽率、面积放大率、纵向河床底坡、弯道特征均进行了验证,其平均误差在10%以内,90%点据误差小于20%,其中断面与落潮流量关系式经一定的转换后,表明许多稳定河口的断面面积即为临界起动流速所要求的断面。

By the definition of bed forming discharge, sediment transports during flood tide and ebb tide of various tidal frequencies were calculated for a tidal estuary. The results show that the bed forming effects are the strongest at annual average runoff combined with mean ebb tide, so the bed forming discharge of this estuary should be the ebb-tide discharge. Tidal estuaries can be categorized as two types, namely general estuary and tidal bore estuary. The former＇s characteristics of cross section depends on average ebb-tide discharge and average sediment concentration, while for the latter, its width of cross section depends on average flood-tide discharge, and its corresponding depth, longitudinal widening rate and bed slope of river channel are determined by both flood-tide and ebb-tide discharges and sediment concentration. This paper formulates a series of empirical relationships between hydrodynamics and morphology for macro-tide estuaries. Using the measured cross-sectional bed profiles of five estuaries in Zhejiang province, we have verified these formulas of river regime, including cross-sectional area, width and depth, width-depth ratio, widening rate, expanding rate of cross-section area, river bed slope, etc. Their average calculation errors are less than 10%, and the calculations with errors exceeding 90% are less than 20%. The formulas, through certain conversion, show that the cross sections below half-tide levels correspond to the ones for sediment recipient motions.