10-13-08 Drainage and Flooding Committee minutes

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k lot z ~~. ass 0 cia t e 5 2.2 Watersheds and Primary Surface Drainage The City lies in three major watersheds (see Exhibit 2-2): the Armand Bayou Watershed, the Clear Creek Watershed, and the Lower San Jacinto/Galveston Bay Watershed. 2.2.1 Armand Bayou Watershed The Armand Bayou Watershed lies on the southern and western side of the City. The watershed drains in a generally southern direction to Clear Creek. Much of the western portions of the City watershed lie in this watershed; many of the residential areas of the City are located in this watershed as well. The primary drainage channels and their major tributaries in this watershed are listed in Table 2-1 and shuwn in Exhibit 2-6. Drainage area sizes and levels of current development for these channels and tributaries are also summarized. It should be noted that these watercourses drain highly developed areas, but there are some large undeveloped tracts especially along Big Island Slough (B 1 06-00-00). It should also be noted that the majority of Willow Spring Bayou (B 112-00-00), Tributary 1.78 to Willow Spring Bayou (BI12-02-00), and Spring Gully (BI09-00-00) are outside of La Porte's city limits, thus affecting the available remedies for these watercourses. There are several homes in this watershed with severe flood damage and repetitive losses. However, review of previously estimated flood plains, as published by Federal Emergency Management Agency (FEMA) flood insurance rate maps (FIRMs) for the primary channels in this area indicate major channel flood levels are within the banks of the channels throughout most of the watershed except in the Spencer Highway Estates Subdivision and the Brookglen Subdivision (see Exhibit 2-5). 2-3 Klotz Associates Project No. 0127.008.000 January 2009 La Porte Citywide Drainage Study City of La Porte