Laserfiche WebLink
Table 12 Farrington Drive Overflow Rates Difference (PR EX) <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 />-12.96 <br />-9.10 <br />-6.02 <br />-1.93 <br />-0.17 <br />0.00 <br />2 <br />-24.71 <br />-28.25 <br />-24.21 <br />-17.32 <br />-10.76 <br />0.00 <br />3 <br />-0.07 <br />0.00 <br />0.00 <br />0.00 <br />0.00 <br />0.00 <br />4 <br />8.85 <br />-8.29 <br />-5.20 <br />-2.16 <br />-0.82 <br />0.00 <br />Net: <br />-28.90 <br />-45.63 <br />-35.43 <br />-21.41 <br />-11.75 <br />0.00 <br />With the proposed drainage improvements to the airport property, the overflow rate across <br />Farrington Drive was decreased by approximately 29 cfs for the 100-year storm event and <br />decreased completely (approximately 12 cfs) for the 5-year storm event. Table 12 presents the net <br />change in the overflow rate for all storm events studied. The runoff from 10-year storm event is <br />contained within the roadside ditch. The maximum sheet flow depth is reduced throughout and is <br />limited to 0.21 ft. for 50-year storm event. Though the flow is reduced for 100-year storm event, <br />the maximum flooding depth is unaffected for the 100-year storm event due to the resulting impact <br />of the tailwater conditions. <br />North. Avenue H (North. of Airport) Hydraulic Analysis <br />After the proposed improvements to the La Porte Municipal Airport system were made to the <br />XPSWMM model, the interaction between the airport property and the neighborhoods along North <br />Avenue H were examined again. The location of the study points remained the same, however the <br />northern channels was altered as described in the section "Proposed Improvements" earlier in this <br />report. The same methods were used to obtain values for water surface elevation and overflow rate. <br />The following tables present the water surface elevations, overflow rates, and the comparison of <br />overflow rates between the existing and proposed conditions. <br />Table 13 North Avenue H Water Surface Elevations Proposed 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 />23.07 <br />22.95 <br />22.69 <br />22.69 <br />22.37 <br />22.13 <br />2 <br />23.50 <br />22.81 <br />22.43 <br />22.08 <br />22.08 <br />21.59 <br />21.26 <br />3 <br />23.50 <br />22.80 <br />22.40 <br />22.05 <br />22.05 <br />21.52 <br />21.15 <br />4 <br />22.22 <br />22.73 <br />22.30 <br />1 22.00 <br />1 22.00 <br />21.47 <br />21.10 <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 />23.29 <br />-0.22 <br />-0.34 <br />-0.60 <br />-0.60 <br />-0.93 <br />-1.16 <br />2 <br />23.50 <br />-0.69 <br />-1.07 <br />-1.42 <br />-1.42 <br />-1.91 <br />-2.24 <br />3 <br />23.50 <br />-0.70 <br />-1.10 <br />-1.45 <br />-1.45 <br />-1.98 <br />-2.36 <br />4 <br />22.22 <br />-� <br />0 <br />0.22 <br />0.22 <br />0.75 <br />-1.12 <br />La Porte Municipal Airport - Offsite Drainage Analysis <br />HT&J, LLC, January 2018 Page 20 <br />