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<br />k lot z 4~~ ass 0 cia t e s <br /> <br />EXECUTIVE SUMMARY <br /> <br />A City Wide Drainage Study (CWDS) for the City of La Porte (City) was undertaken to identify, <br />develop and recommend drainage improvements to address drainage problems and lessen <br />flooding and its impacts across the City. Reasons for existing drainage and flooding problems <br />include 1) insufficient flow capacity in ditches and channels, 2) ponding of waters in streets and <br />adjacent properties, 3) undersized storm sewers, 4) temporary blockage of storm water inlets by <br />debris, 5) backup of storm waters in sewers, and 6) lack of overland or sheet flow paths. Also <br />contributing to the drainage problems are natural effects common to coastal areas: Relatively <br />small ground slopes making it difficult to rapidly drain away runoff waters; tides and storm <br />surges causing rising water levels which impede drainage; and frequent but severe storm events <br />with large amounts of rain falling in short periods of time. Future drainage problems can, on the <br />other hand, result if the runoff from future land development is not controlled. Flooding is a fact <br />of life in coastal areas and control of flooding in coastal areas presents significant challenges. <br /> <br />The strategy used to address drainage and flooding issues had two components: 1) remedy of <br />current drainage and flooding problems, and 2) mitigation of future drainage problems. The <br />bases of our recommendations are summarized in the Engineering Summary following this <br />Executive Summary. Details of the engineering analyses leading to the recommendations are <br />provided in the main body of this report. <br /> <br />Current Flooding and Drainage Problems <br /> <br />To address the current drainage and flooding problems, 1) channel improvements, 2) detention <br />ponds for flood flow diversion, 3) storm sewer upgrades, and 4) development of relief swales <br />(i.e., directed sheet flow pathways) options are evaluated. Improvements proposed in prior <br />studies by others were incorporated into the proposed solutions of this study when appropriate. <br /> <br />Relief swales are a very cost effective (i.e., low costlbenefit ratio) drainage improvement. Relief <br /> <br />swales reduce or limit ponding of runoff waters in streets and low lying areas for small to <br />ES-l <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 />