June 2022 G-01483.84-017-R-Rev0 Because the 40 Table 16: SCS General input parameters. Parameter Input value Notes: Design life Temporary Less than 10 years Rainfall depth (1:10 AEP) 266 mm HIRDS V4: 24 hour rainfall depth Climate change increase (1:10 AEP) RCP 6.0 20312050 HIRDS V4 Aerial reduction factor 1.0 WRC, 2018 Soil group type Soil group D Defined by WRC, 2018 as: greater than 40% clay and less than 50% sand CN Number (Clean water catchments) 84 Pasture or grass land in fair condition (WRC, 2018) Initial abstraction (Clean water catchments) 1.3 mm WRC, 2018 CN number (WRS catchments) 30 WSP-Golder previous experience with WRS modelling Initial abstraction (WRS catchments) 30mm WRC, 2018 Time of concentration Varies = 0.0195 ( 3 ) 0.385 Tc = Time of concentration (minutes) L = Longest flow path (m) H = Height difference along longest flow path (m) (WRC, 2018)
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