07-29-09 Drainage and Flooding Committee minutes

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11r. Ron Bottoms, City Manager October 1,2008 Page 3 of 31 k lot z .~. ass 0 cia t e 5 streets. Along with these requirements, the manual indicates that an overland flow path to the storm sewer system's outfall must be provided for the lOa-year event. To provide protection of habitable structures, grading and drainage around a habitable structure must provide a finished floor slab which is at least 1) 12 inches above the top of curb at its highest point along the of the curb fronting the building site; 2) 18 inches above the crown of the road elevation along the road fronting the building site; and 3) 12 inches above the ground elevation along all sides of the building site. Provision is provided for alternative methods of protection with approval of the City Engineer. 2.2 Comparison with Adjacent Communities A review of the design criteria for the City of La Porte and surrounding areas, including Harris County, Pearland, Galveston County, Chambers County, and Brazoria County, found a mixture of municipal storm water or storm sewer design criteria. Both the City of Houston and the City of La Porte have standardized storm sewer design requirements. The nearby cities of Deer Park and Bayiown do not have specific standards that are to be used by the public or engineering consultants for storm water design. Other cities in the region, such as Sugar Land, Pearland, Friendswood, and Missouri City, have storm sewer design requirements. Some cities, such as Mont Belvieu, utilize county standards as surrogates for city-adopted standards. HCFCD has design guidelines available on its website. 2.3 Flood Hazard Requirements Chapter 94 of the City's Code of Ordinances addresses flood hazard and potential construction in special flood hazard areas. Standards applicable to new construction or substantial improvements in special flood hazard zones require a variety of measures for sound construction of structures and installation of utilities to eliminate or reduce damages from floods. These standards also include the following requirements: · Lowest floor elevation of new residential structures must be I-foot above the base flood (lOa-year) elevation · Lowest floor elevation of new non-residential structures must be at or above the base flood elevation (or equivalent structure protection must be provided) Special requirements also apply for manufactured homes to prevent floatation, collapse, or lateral movement. These above requirements for construction in. special flood hazard areas are consistent with many communities in the Houston metropolitan area.