06-23-08 Drainage and Flooding Committee Minutes

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It would be very expensive to replace the existing storm sewer system with larger pipes. However, Klotz recommends constructing an overland sheet flow path, which provides a clear route located over the ground for stormwater to quickly flow into drainage canals, at the north end of Gladwyne Lane. Figure 3-1 is a photograph of a sheet flow path. When Gladwyne and the other streets fill up with stormwater, the sheet flow path would drain the water directly to West Plantation Ditch. The effectiveness of this approach is dependent on the ditches being able to accept the stormwater and carry it downstream. This won't happen if they are already full or backing up, which is reported to happen at the same time the streets flood. Residents report that the channels need better maintenance and there are conflicting reports as to whether the bridge at Fairmont Parkway constricts flows. Both of these concerns need further investigation by the City or the Flood Control District. II. Acquisition Figure 3-1: Sample sheet flow path (from Klotz Report) This measure involves buying one or more properties and clearing the site. If there is no building subject to flooding, there is no flood damage. Acquisitions are usually recommended where the flood hazard is so great or so frequent that it is not safe to leave the structure on site. An alternative to buying and clearing the whole subdivision is buying out individual, "worst case," structures with FEMA funds. This approach would involve purchasing and clearing the lowest or the most severe repetitive flood loss homes. If FEMA funds are to be used, three requirements will apply: 1. The applicant for FEMA must demonstrate that the benefits exceed the costs, using FEMA's benefit/cost software. 2. The owner must be a willing seller. 3. The parcel must be deeded to a public agency that agrees to maintain the lot and keep it forever as open space. Problems: 1. High cost and difficulty to obtain a favorable benefit-cost ratio, which demonstrates the cost-effectiveness of a proposed project, in shallow flooding areas 2. Not everyone wants to sell their home, so a checkerboard pattern of vacant and occupied lots often remains after a buyout project, leaving "holes" in the neighborhood 3. There is no reduction in expenses to maintain the neighborhood's infrastructure, although the tax base is reduced 4. The vacant lots must be maintained by the new owner agency, and additional expense is added to the community. Brookglen Area Analysis - DRAFT 9/8/2008 17