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<br />, <br /> <br />Chapter I <br />INTRODUCTION <br /> <br />. <br /> <br />. <br /> <br />The installation of engineering works in a natural stream channel <br /> <br />inevitably affects the level of water flowing in the channel. The <br />influence of an obstruction in a channel upon the longitudinal <br /> <br />elevations of the water surface, either upstream or downstream of the <br /> <br />obstruction, is referred to as the backwater effect. Knowledge of the <br /> <br />magnitude of the backwater effect is essential where rights of third <br /> <br />parties are likely to be affected - and this is almost always the case. <br /> <br />Evaluation of the magnitude of the backwater effect is necessary <br /> <br />prior to commencement of design work in order to define both the scope <br /> <br />of work and precautionary measures. Such evaluation has been accom- <br /> <br />plished for many years by the application of various formulas and <br /> <br />procedures for calculation of water surface elevations. These <br /> <br />calculations are generally a trial and error process based upon <br /> <br />computation of hydraulic energy at various cross-sections of flow. <br /> <br />Fortunately, the advent of electronic computers has allowed much of <br /> <br />the repetitive calculation to be done by machine. By use of computers, <br /> <br />many routine calculations can be accomplished, thus allowing the <br /> <br />engineer time for planning and review of the larger aspects of a <br /> <br />project. <br /> <br />. <br /> <br />< <br /> <br />. <br /> <br />. <br /> <br />Problem <br /> <br />There may be several locations in a reach of channel affected by <br /> <br />a project for which routine calculations, developed primarily for <br />tranquil flow, are not applicable. This is due to the fact that <br /> <br />routine backwater curve calculations are based upon concepts of <br /> <br />. <br />