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SECTION 2 <br />FAIRMONT PARK EAST <br />DRAINAGE ANALYSIS <br />2.1 Overland and Street Flow <br />Good engineering design practice allows proposed sheet flow to follow natural contours <br />of existing topography toward the receiving drainage channels. This is done by designing <br />roadway profiles below natural ground and sloped to carry extreme even overland flow <br />toward the receiving channel. Sags along a roadway profile are intended to collect storm <br />runoff in inlets of a storm sewer system that is designed to carry a specific rainfall <br />frequency. It is cost prohibitive to design a storm sewer system to carry flow from an <br />extreme event; therefore, overland sheet flow paths are used to convey excess runoff <br />toward the receiving drainage channel. <br />Fleetwood Drive is a 26-foot wide, concrete curb -and -gutter roadway section that is <br />elevated above intersecting streets along its alignment. The intersecting residential <br />streets drain away from Fleetwood Drive toward inlets located in a sag in the street <br />profile. These low points collect water from contributing lots and roadway surfaces and <br />during frequent storm events cause ponding to occur. Areas of reported street ponding <br />and repetitive flood loss data are shown in Exhibits 3, 4 and 5. Ponding levels are shown <br />to increase to levels approaching 18-inches above the top of curb before overflowing into <br />adjacent areas. <br />2.2 Hydrology <br />The contributing drainage area for Fairmont Park East Sections Two through Four was <br />determined using LiDAR generated from Tropical Storm Recovery Program (TSRP) by <br />Harris County and is 106.6 acres. The Rational Method was used to calculate storm <br />1-3 <br />Klotz Associates Project No. 0127.009.000 Fairmont Park East & Brookglen Drainage Study <br />May 2009 City of La Porte <br />