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GITY OF EVERETT STORMWATER MANAGEMENT MANUAL _ <br /> `'� Ta61e 5.2 Rainfall Coefficients <br /> coeffcient Mean Recurrence Interval MRI <br /> 2 r 5 r 10 r 25 50 r 100 r <br /> m 3.69 5.20 6.31 7.83 8.96 10.07 <br /> n 0.556 0.570 0.575 0.582 0.585 O.SBE <br /> The runoff cocfficient represents the portion of rainfall that becomcs runoft Table 53 givcs �unoff <br /> coeFficient values ro be used (or stortn cooveyance calculations in ihc City of Everett. <br /> Table 5.3 Runoff Coefficients for Use with the Rational Method <br /> GENERAL LAND COVER <br /> LAND COVER C LAND COVER C <br /> Dcnse Forest 0.10 Playgrounds 030 <br /> Light Forest 0.15 Gravel Arca; 0.80 <br /> Pavement and 0.90 <br /> Pasture 0.20 Roofs <br /> �: <br /> Lawns 0.25 Open Water I.00 <br /> SWGLE FPu'�IILY RESIDEiJT1AL AREAS <br /> (Density is in dwclling uniu per gross acre) <br /> DGNSI'CY C DENSfCY C <br /> 0.20 0.17 3.00 0.42 <br /> 0.40 0.20 3.50 0.45 <br /> 0.80 0.27 4.00 0.48 <br /> 1.00 030 4.50 0.51 <br /> t.50 0.33 5.00 0.54 <br /> 2.00 036 5.50 0.57 <br /> 2.50 039 6.00 0.60 <br /> 5.4 Single Event Hydrograph Method <br /> Two examples of single-cvcnt hydrograph methodology are the Soil Conscrvation Scrvice Unit Hydrograph <br /> (SCS[JH)and the Santa Barbaro Unit Hydrograph(SBUH). <br /> In the following sections,the key elements of hydrograph analysis are presented,including the design storm <br /> hyctograph, runoff parameters,and hydrograph synthesis, routing, summation and phasing. <br /> Volume I-Minimum Technical Requirements <br /> S3 <br />