03-23-09 Drainage and Flooding Committee meeting minutes

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selected because the transition between upstream and downstream occurs in the low flow section. Increases in discharge from upstream to downstream of the confluence were calculated for a depth of 4-feet to be about 255 cfs upstream and 329 efs downstream or a difference of 74 cfs. For the same depth in tributary B 112-02-00 normal depth flow is calculated to be 1,038 cfs, which is much larger due to its larger cross sectional area. Since no increases in water surface for B112-00-00 are observed, contributing flow from tributary B 112-02-00 will be small compared to flow at normal depth and greater depths at the confluence. This indicates that the depth at the confluence controls flow in 13112- 02-00 due to backwater conditions. 4.4 Conclusions Reductions in water surface at the confluence can be achieved by reducing the backwater influence of B 112-00-00. One way to do this is to increase the cross sectional area of the channel downstream by removing the benches in the channel and eliminating the 20-foot low flow section. In addition to removing the benches or increasing conveyance, detention will have to be considered. Locations for possible detention include an undeveloped area just upstream of Fairmont Parkway on the west bank of B112-00-00, undeveloped area just downstream of Fairmont Parkway on the east bank of B112-00-00 or possible areas north of Spencer Highway to name a few examples. Further studies of these types of improvements are beyond the scope of this study. It is recommended that the City begin coordination efforts with Harris County Pet. 2 and the Harris County Flood Control District to investigate regional or sub -regional options for improvements to reduce water surfaces along B 112-00-00 and perform detailed studies of watershed impacts if these type of improvements are in place. 4-3 Klotz Associates Project No. 0127,009.000 Fairmont Park East & Brookglen Drainage Study May 2009 City of La Porte