Name Formula for t Remarks Number 1. Kirpich 1077 0.0078- (16.4) 50.385 0.467 "L 2. Kerby 0.828 Applicable to <1300 ft (16.5) 505 r=0.02 smooth pavement 0.1 bare packed soil 0.3 rough bare or poor grass 0.4 average grass 0.8 dense grass, timber 3. Izzard 41.025 (0.007i+K)L0.33 $0.333; 0.667 Applicable to iL < 500 K = 0.007 smooth asphalt 0.012 concrete pavement 0.017 tar and gravel pavement 0.046 closely clipped sod 0.060 dense bluegrass turf (16.6) 4. Bransby-Williams 0.00765L 50.240.1 5. Federal Aviation Agency 0.388 (1.1-C)L0.5 50.333 C=Rational coefficient (16.7) 0.941060.6 6. Kinematic Wave 104503 n-Manning's coefficient for overland flow (16.8) 7. NRCS (SCS) see eqs. (16.9) and (16.10) and open channel travel time where: i = rainfall intensity, in./hr; L = Length of flow path, ft; S = slope of flow path, ft/ft; A = drainage area, acres; and t;= overland flow time, min. A storm drain system is shown in Figure P16.11. For the flow conditions indicated, determine the time of concentration from Point A to Point C using the Kirpich, Kerby, A Bransby-Williams, and Federal Aviation Administration Methods. Paved area, 0.7 km² C=0.9 200 S=3% Bare surface, 0.8 km² C=0.6 S= Drain 500 m V=1.2 mil