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ESTIMATION OF DAM BREACH PARAMETERS <br /> USING THE MACDONALD&LANGRIDGE-MONOPOLIS OR WASHINGTON STATE METHODS <br /> WITH ALL FAILURE TIMES ESTIMATED BY WASHINGTON STATE METHOD <br /> PROJECT: Foothills Reservoir <br /> BREACH INPUT PARAMETERS: <br /> Select Embankment Type From Drop-Down Menu: EARTHEN(COHESIVE) <br /> Height of water over base elevation of breach(Hw)= 46.6 Feet <br /> Volume of water stored in reservoir at time of failure(V„)= 4138.5 Acre-Feet <br /> Reservoir Surface Area at H„,(As)= 183.0 Acres <br /> Crest width of dam(C)= 15.0 Feet <br /> Height of breach from dam crest to base elevation of breach(Kb)= 50.9 Feet <br /> Slope of upstream dam face(Z„)= 2.7 Z(H):1(V) <br /> Slope of downstream dam face(4)= 2.5 Z(H):1(V) <br /> Breach side-slope ratio(4)= 2.0 Z(H):1(V) <br /> Piping Orifice Coefficient(Cr)= 0.74 Used To Calculate Peak Discharge Through Piping Hole <br /> Dam Size Class: Large Assumes Full Reservoir At Time of Breach <br /> CALCULATED BREACH CHARACTERISTICS: <br /> Breach Formation Factor(BFF)= 192854.1 <br /> Embankment Volume Eroded(V,r)= 38315.7 Cubic Yards <br /> Average Dam Width(W,,,o)= 145.6 Feet(In Direction of Flow) <br /> Average Breach Width(B,9)= 139.6 Feet <br /> Bottom Width of Breach(Bb)= 37.8 Feet <br /> Breach Formation Time(Ti)= 1.61 Hours <br /> Storage Intensity(SI)= 88.8 Acre Feet/Foot <br /> Peak Breach Discharge(QP)= 54988 Cubic Feet per Second <br /> RESULTS CHECK: <br /> Average Breach Width Divided by Height of Breach(BavglHb)= 2.74 If(BavglHb)>0.6,Full Breach Development is Anticipated <br /> Erosion Rate(ER),Calculated as(BavgITf)= 86.8 <br /> Erosion Rate Divided by Height of Water Over Base of Breach(ER/Hw)= 1.9 If 1.6<(ERIHw)<21,Erosion Rate is Assumed Reasonable <br /> ♦ T <br /> 1 III%IMP' xyz , T <br /> T AR <br /> 4e <br /> -''.4 Bb 4 <br /> Figure 1-Breach Variable Definition Sketch <br /> c —>v y • <br /> \,,...,...s.__....____e <br /> a <br /> D <br /> —> D <- < L <br /> Figure 2—Piping Hole Variable Definition Sketch <br /> MLM-WAv2 0 Foothiils.xlsm <br />