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<br />I <br />il <br />II <br />I <br />I <br />'I <br /> <br />II <br />I <br />I <br />II <br /> <br />I <br />I <br />,I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />SECTION I <br />INTRODUCTION <br /> <br />This document presents an evaluation of and design guidance for drop structures in <br /> <br /> <br />the Denver Metropolitan area for the Urban Drainage and Flood Control District. <br /> <br /> <br />This study will likely prove applicable to similar structures in other regions. After <br /> <br /> <br />a review period, and perhaps further research, the design related material will be <br /> <br /> <br />summarized and published as an amendment to the Urban Storm Drainage Criteria <br /> <br />Manual (ref. 66). <br /> <br />SCOPE OF WORK <br /> <br />The study scope focused on analyzing drDps shDwing design flows up tD 15,000 cfs, <br /> <br /> <br />with primary emphasis Dn grass-lined channels having design flDws up tD 7,500 cfs. <br /> <br /> <br />FIDws less than 500 cfs were addressed fDr small drDps, trickle channels, and IDcal <br /> <br /> <br />drainage "rundDwns" fDr cDnveying minDr tributary flDws intD majDr drainageways. <br /> <br />Numerous drop structure types have been evaluated and categDrized based on similar <br />hydraulic characteristics as follows: <br /> <br />1. <br />2. <br /> <br />Baffled Apron (Chute) Drops. <br />Vertical Drop with Loose Riprap Basin - This includes the District Standard <br />(ref. 63) and several other configurations. <br />Vertical Drop with Hard Basin - This category includes a variety of materials, <br />and configurations including the SCS drop and grouted boulders. <br />Sloping Rock Drops _ This includes drops constructed according to the District <br />Criteria (ref. 63), and other configurations such as stacked boulders. <br />Sloping Grouted Rock Drops - There are a large number of these structures, <br />some were created by design and others were created by maintenance projects <br />which restored Sloping Rock Drops using grout. <br />Sloping Concrete Drops and Other Similar Hard Basins - This category includes <br />U.S. Bureau of Reclamation (USBR) III, IV, and V basins (or equivalents), Saint <br />Anthony Falls (SAF) basin, and basins of similar shape but constructed with <br />materials such as soil cement and roller crete. <br /> <br />3. <br /> <br />4. <br /> <br />5. <br /> <br />6. <br /> <br />1-1 <br />