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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />Surface depression storage losses and water intercepted by trees, bushes, and other <br />vegetation play an important role in the hydrologic cycle and the determination of rainfall available <br />for runoff. The COOP method requires estimation of these losses for both impervious and <br />pervious areas to facilitate the calculation of the effective rainfall for each storm event. Values <br />for surface depression storage and interception losses were selected in accordance with the values <br />presented in the USDCM (Volume 1, 1978). Infiltration, depression storage, and decay <br />coefficient values incorporated into the hydrologic model are presented in Table 4,1. <br /> <br />4.4 Hydraulic Modeling Parameters <br /> <br />Several hydraulic modeling parameters are required by the UDSWM2-PC model to <br />simulate the routing of storm flows through the storm sewers and open channels, The parameters <br />required by the model to simulate the routing of stormwater through storm sewers are listed <br />below: <br /> <br />1. Pipe diameter <br />2, Pipe length <br />3. Invert slope <br />4. Manning's n <br />5. Maximum headwater depth <br /> <br />For the modeling of open channels, the hydraulic parameters required by the UDSWM2- <br />PC model are as follows: <br /> <br />1. Bottom width of channel or channel cross section <br />2. Length of channel <br />3, Invert slope <br />4. Channel sideslopes (XH: IV) <br />5. Manning's n <br />6. Maximum flow depth <br /> <br />Where appropriate, data for each of the parameters were recorded during the field reconnaissance <br />and surveying efforts, <br /> <br />T:\OPENlCoweitiOllcoweJdOJ InJ rpJ. wpd <br /> <br />4,7 <br /> <br />September 8, J 999 <br />