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<br />WATER AND SEDIMENT ROUTING THROUGH <br />CURVED CHANNELS <br /> <br />By Howard H. Chang,' M. ASCE <br /> <br />A8frrRAcr. A mathematical model for water and sediment routing through <br />curved alluvial channels is developed and applied in a case study. This model, <br />which is for alluvial streams with nonerodible banks, may be employed to sim. <br />ulate stream bed changes during a given flow, thereby providing the necessary <br />infonnation for the design of dikes, levees, or other bank protection. This model <br />incorporates the major effects of transverse circulation, inherent in curved <br />channels, on the flow and sediment processes. In the simulation of the evo- <br />lution in stream bed profile, the effect of transverse flow is tied in with the <br />aggradation and degradation development. River Row through curved chan- <br />nels is characterized by the changing curvature, to which variations of flow <br />pattern and bed topography are dosely related. Simulation of these changing <br />features is based upon the fluid dynamics governing the growth. and decay of <br />transverse ciJ'cu1ation along the channel. <br /> <br />ItmloouCTlON <br /> <br />An important factor that affects the hydraulics of flow, sediment trans- <br />port, and bed topography through curved alluvial channels is the spiral <br />motion or transverse circulation. Greater depths and higher velocities <br />near concave banks produced by the transverse circulation, in addition <br />to aggradation and degradation, are necessary considerations for levee <br />or dike design. The importance of transverse circulation was stressed in <br />a recent evaluation of mobile bed mathematical models by the National <br />Academy of Sciences (3). In this connection, research effort toward im- <br />proved incorporation of the effect of transverse flow in modeling was <br />recommended. <br />A mathematical model for water and sediment routing through curved <br />aUuvial channels is described herein. This model simulates time and spa- <br />tial variations in water level, sediment transport, and bed topography. <br />In the prediction of stream bed profile changes, aggradation and deg- <br />radation are tied in with the effect of transverse flow under the changing <br />channel curvature, Application of this model is limited to alluvial chan- <br />nels with nonerodible banks, large width-depth ratio, and mild curva- <br />lure, all characteristic of natural rivers with bank protection. A case study <br />using this model on the San Lorenzo River in California during a flood <br />event is presented. <br />Analyses of flow and bed topography in curved channels have been <br />accomplished by Yen (26), Engelund (13), Kikkawa et al. (19), Zimmer- <br />mann and Kennedy (28), Falcon Ascanio and Kennedy (14), and Od- <br />gaard (20), among others. Some of these analytical methods are used in <br />the model. However, such methods are generally for curved channels <br />with fully developed transverse flow. Because of the streamwise (lon- <br />'Prof. of Civ. Engrg" San Diego State Vniv., San Diego, Calif, 92182. <br />Note.-Discussion open until September 1, 1985. To extend the dosing date <br />one month, a written request must be filed with the ASCE Manager of Journals. <br />The manuscript for this paper was submitted for review and possible publication <br />on November 30, 1983. This paper is part of the Journal of Hydraulic Engineering, <br />Vol. 111, No.4, April, 1985. @ASCE, ISSN 0733-9429/85/0004-0644/$01.00. Paper <br />No. 19656. <br /> <br />644 <br /> <br />22 <br />