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Table 8 North Avenue H Water Surface Elevations Existing Conditions <br />Study <br />Point <br />Road <br />Elevation <br />WSE <br />100-yr <br />50-yr <br />25-yr <br />10-yr <br />5-yr <br />2-yr <br />1 <br />23.29 <br />23.65 <br />23.63 <br />23.61 <br />23.58 <br />23.55 <br />23.50 <br />2 <br />23.50 <br />23.00 <br />22.92 <br />22.84 <br />22.71 <br />22.58 <br />22.41 <br />3 <br />23.50 <br />22.98 <br />22.90 <br />22.82 <br />22.69 <br />22.56 <br />22.39 <br />4 <br />22.22 <br />22.87 <br />22.77 <br />22.69 <br />22.56 <br />22.43 <br />22.23 <br />Study <br />Point <br />Road <br />Elevation <br />Difference (WSE <br />- Road El.) [ft] <br />100-yr <br />50-yr <br />25-yr <br />10-yr <br />5-yr <br />2-yr <br />1 <br />2 <br />23.29 <br />23.50 <br />-0.50 <br />i <br />-0.58 <br />-0.66 <br />, <br />-0.79 <br />-0.92 <br />-1.09 <br />3 <br />23.50 <br />-0.52 <br />-0.60 <br />-0.68 <br />-0.81 <br />-0.94 <br />-1.11 <br />4 <br />22.22 <br />„,,,,,,,,,,,,,,, <br />r <br />Table 9 - North Avenue H Overflow Rates Existing Conditions <br />Study <br />Overflow Rate (cfs) <br />Point <br />100-yr <br />50-yr <br />25-yr <br />10-yr <br />5-yr <br />2-yr <br />1 <br />11.63 <br />9.84 <br />7.87 <br />5.81 <br />4.36 <br />1.08 <br />2 <br />0.00 <br />0.00 <br />0.00 <br />0.00 <br />0.00 <br />0.00 <br />3 <br />0.00 <br />0.00 <br />0.00 <br />0.00 <br />0.00 <br />0.00 <br />4 <br />73.90 <br />46.59 <br />28.25 <br />10.01 <br />2.23 <br />3.01 <br />Total: <br />85.53 <br />56.44 <br />36.12 <br />15.83 <br />6.59 <br />4.09 <br />The water levels overtop into the neighborhood along North Avenue H at Study Points 1 and 4. <br />The City of La Porte design standards require the neighborhood storm sewer system to maintain <br />an HGL below the street gutter elevation during the 5-year storm event. However, this is beyond <br />the scope of this report and HT&J did not evaluate the neighborhood storm sewer system. <br />A total of approximately 86 cfs of sheet flow is introduced to the neighborhood during the 100-year <br />storm event, and approximately 7 cfs is introduced during the 5-year storm. This likely results in <br />roadway conveyance during this storm event. Total sheet flow introduced will result in an increase <br />flooding in the neighborhood, but the extent is not uniform throughout. The resulting additional <br />flooding depth varies from 0.01 ft. to 0.65 ft. in the existing conditions. <br />La Porte Municipal Airport - Offsite Drainage Analysis <br />HT&J, LLC, January 2018 Page 15 <br />