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The maximum conveyance was determined for the converged channel by calculating now at <br />bankfull elevation using Manning's Equation with a roughness coefficient of 0.035. This method <br />resulted in an approximate maximum conveyance of 64 CFS. <br />Four study points were chosen to evaluate any overflow that occurs between the airport site and <br />the neighborhood along North Avenue H. Figure 8 presents the location of the study points, located <br />along the northern property boundary of the airport. <br />Figure 8 North Avenue H Study Points <br />The water surface elevation at different storm events was compared to the elevation at the airport <br />property northern boundary, and from that differential the overflow rate was calculated. The <br />existing XPSWMM model was expanded to calculate the overflow rate at each study point. Links <br />were added to simulate runoff leaving the channel and flowing over the northern boundary. The <br />Links were given a width matching the distance to the upstream study point, so that all overflow <br />along the northern airport channels was accounted for in four stream segments. The following <br />tables present the comparison of road elevation, water surface elevation, and overflow rate for <br />existing conditions at each of the four study points. <br />La Porte Municipal Airport — Offsite Drainage Analysis <br />HT&J, LLC, January 2018 Page 14 <br />