The approximate density of sand is 1600 kg/m 3 (100 lb/ft 3 ). For steep slopes ranging from 2 to 20 percent where unit discharge is low, EM 1601 presents a separate design process that is not included in the riprap calculator. The calculation process is as follows: Estimate the volume of sand needed, using geometrical formulas and plans or measurements. As the Froude number approaches 1.0 (critical depth), the user should strongly consider alternative methods. For large flumes (depth 1.2 m+), construction of the approach section can be completed in the field using cement block walls to the appropriate dimensions. For installations immediately downstream of concrete channels, a vertical velocity distribution coefficient of 1.25 (an option in the calculator) should be used due to the difference in velocity profile over the two surfaces.īoth the EM 1601 riprap computation and HEC-RAS model application are suitable for shallow slopes with gradually varied flow. This web page has calculations for four types of flumes - Parshall, rectangular, trapezoidal, and U shape. Parshall flumes are used for open channel flow measurement, especially for flows containing suspended solids, like the flow into a wastewater treatment plant.
LeftSlope (Z1): RightSlope (Z2): Flow discharge. In expanding transitions, flow can concentrate on one side of the expansion and design velocities should be increased. Select unit system: Channel slope: Water depth (y): Flow velocity. In areas where flow changes from tranquil to rapid and then back to tranquil, riprap sizing methods applicable to hydraulic structures (HDC 712-1) should be used. The procedures in this calculator are applicable to gradual transitions where flow remains tranquil. Transitions in size or shape may also require riprap protection. The EM 1601 design guidance applies to riprap design for open channels not immediately downstream of stilling basins or other highly turbulent areas (for stilling basin riprap, use HDC 712-1, EM 1601 Plates 29 and 30).
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