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<br />~TEP 10 (continued) <br /> <br />METHOD 1 - THE CONTINUITY EQUATION <br /> <br />Remember the Continuity Equation <br /> <br />Q=AV <br /> <br />Where <br /> <br />Q is flow in cubic feet per second <br />A is cross-sectional area of water in square feet <br />V is water velocity in feet per second <br /> <br />The flow (Q) was already determined through the Hydrologic Analysis <br /> <br />Determine the water velocity (V) <br /> <br />Select the Hydraulk Radius (R) based on the shape of the channel <br />cross-section (see Tabh, of Channel Cross-Section Shapes) <br /> <br />Select the appropriate roughness condition (Manning's n) from the <br />Table of Hydraulic Roughnes:, Conditions <br /> <br />Select the appropriate slope of t:he channd (Flat, Moderate, Steep) <br /> <br />Find the velocity on the Table of Channel Velocities <br /> <br />Calculate th,~ cross-sectional area (A) for water 1 foot deep and see what flow (Q) that <br />yields <br /> <br />Calculate th,~ cross-sectional area (A) for water 2 feet deep and see what flow (Q) that <br />yields <br /> <br />Adjust the depth of flow up or down until the calculaled value of flow (Q) matches the <br />value already determined by the Hydrologic f\nalysis <br /> <br />Note the flow depth which results in the "correct" flow (Q); that is the flood elevation <br /> <br />ONLY USE THE CONTINUITY EQUA:TION WHEN THE CHANNEL VELOCITY IS SLOW <br />ENOUGH (LESS THAN 5 FEET PER SECOND) AND BACKWATER EFFECTS FROM <br />CONSTRICTIONS (I.E. BRIDGES OR CULVERTS) OR FRICTION ARE NOT IMPORTANT <br />