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<br />HYDRAULIC STRUCTURES <br /> <br />DRAINAGE CRITERIA MANUAL (V. 2) <br /> <br /> <br />Photograph HS-S <br /> <br />A vertical hard basin drop structure can be an effective tool for controlling grade, but it is not as <br />desirable as a grouted sloping boulder drop because of safety concerns and aesthetics. <br /> <br />Basic design steps are as follows: <br /> <br />1. The design approach uses the unit discharge in the main and trickle channel to determine <br />separately the water surface profile and jump location in these zones. The overall jump hydraulic <br />problems are the same as previously described. <br /> <br />Chow (1959) presents the hydraulic analysis for the "Straight Drop Spillway." Add subscript (,) for <br />the trickle channel area and subscript (m) for the main channel area in the following equations. <br />The drop number, Do. is defined as: <br /> <br />_ q' <br />D"-~ <br />\gYJ J <br /> <br />(HS-10) <br /> <br />in which: <br /> <br />e <br /> <br />e <br /> <br />q = unit discharge (cfs/ft) <br />Yf= effective fall height from the crest to the basin floor (ft) e <br /> <br />HS-26 06/2001 <br />Urban Drainage & Flood Control District <br />