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<br />k lot z ~~~ ass 0 cia t e s <br /> <br />Flood control projects are intended to provide a high level of flood protection, with their design <br />based upon an extreme flood event as defined by a 1 OO-year rainstorm event (i.e., only a 1 in 100 <br />chance of occurring in anyone year). <br /> <br />All flood control projects are either 1) channel widening; 2) channel lining with concrete when <br />right-of way is insufficient for widening; 3) diversion of flood waters to a detention pond <br />(referred to simply as a "diversion pond"); or some combination of these three. All channel <br />widening or lining projects also include, as part of the project, a detention pond to mitigate <br />(hence the name "mitigation pond") the adverse downstream impacts arising from the enhanced <br />discharge capabilities of the improved channel. Project costs include land acquisition costs. <br /> <br />Because of the high level of protection they provide, chmmel improvement and detention pond <br />projects are more expensive than relief swale projects. Based upon their relatively low <br />cost/benefit values, eight channel improvement and diversion pond projects are recommended to <br />address eight areas of significant flooding problems; these projects are listed on the following <br />page. The recommended improvement and pond projects are separate projects and can be <br />individually constructed as funds become available. The various cost/benefit ratios, all of which <br />are $87,500 or less, can be used to help define priorities for construction. <br /> <br />Projects with higher cost/benefit ratios could be selected to address other flooding problem areas; <br />these less economically efficient projects are given in Table ES-1 (the Engineering Summary <br />following this Executive Summary discusses these other projects in more detail). One of these <br />projects, for example, is a linear detention pond previously proposed by others along channel <br />F216-00-00 (Project 46 in Table ES-1 and Figure ES-4 at the end of this summary). The <br />approximate location of all evaluated projects is shown in Figures ES-I to ES-6. Pond location, <br />size and configuration are all approximate. <br /> <br />Total expenditures for projects will depend upon the projects selected for construction. Total <br />cost and cost-benefit as well as availability of construction funding and the opportunities for <br />construction phasing will have to be considered in project selection. The cost-benefit ratio of <br />ES-3 <br /> <br />Klotz Associates Project No. 0127.008.000 <br />January 2009 <br /> <br />La Porte Citywide Drainage Study <br />City of La Porte <br />