06-23-08 Drainage and Flooding Committee Minutes

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. The 26 repetitive flood loss properties in the study area have made a total of 134 claims for a total of $3,358,943.00 since 1978. . Other properties have been flooded but are not on FEMA's RL list . Of the 26 repetitive flood loss properties, 24 are considered severe repetitive flood loss properties. . Average RL flood claim is $25,000. . Residents report maximum flood depths and duration of four feet for 24 hours. . Flooding is caused by undersized channels and bridge crossings, man-made obstructions to the predominant flow pattern, and a slow moving drainage ditch. . Drainage improvements have been made, however the area continues to flood. Step 3: Mitigation Measures Reviewing the drainage system, the flooding problem, and the types and condition of the buildings in the area leads to the third step in the area analysis procedure - a review of alternative approaches to protect properties from future flood damage. Property owners should look at these alternatives but understand they are not all guaranteed to provide 100% flood protection. Seven approaches were analyzed: 1. Drainage improvements 2. Acquisition of properties in the hazardous area 3. Elevating the houses above the 100- year flood level 4. Constructing small levees or floodwalls around one or more houses 5. Dry floodproofmg 6. Development regulations 7. Purchasing flood insurance coverage on the building Each approach has its pros and cons. Drainage improvements and development regulations need to be implemented by the City or County. The other measures can be implemented by the property owners, but City or County funding can help, especially with acquisition and elevation. I. Drainage Improvements As noted in the problem description (page 8), repetitive flooding in Brookglen is caused by two related drainage problems: 1. The storm sewers are undersized to handle a heavy rain event 2. The two drainage ditches, West Plantation Ditch and Willow Springs Bayou, drain slowly and back up into the neighborhood streets, yards and houses during heavy rains. Larger storm sewers are suggested by the Harris County All Hazard Mitigation Plan and by the Klotz Associates Report #2. The City of La Porte now designs storm sewers to handle flow from a three-year event, however the Harris County Flood Control District Policy Criteria and Procedure Manual calls for storm sewers to be designed for 10 to 100-year storm. Brookglen Area Analysis - DRAFT 16 9/8/2008