Drainage and Flooding Report January 2009

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klutz associates • Improvement of sheet flow paths by reduction of blockages • Introduction of a new or emergency sheet flow path • Lowering of street elevations to promote drainage by reducing obstruction to flow • Adding capacity to existing ditches or introducing drainage swales • Improving or realigning a key existing storm sewer to provide increased capacity Addition of street inlets 24 Probable Causes and Potential Remedy of Drainage and Flooding Problems Subdivision areas (and areas in close proximity) with significant drainage problems have been identified above (see Table 2-2). Evaluation of these problems based upon information provided by the City, review of information in previous drainage reports, site inspection; proximity to potential flooding sources (i.e., bayous and channels), and hydrologic and hydraulic modeling to identify the probable cause of flooding. Identified potential causes for reported or otherwise identified drainage or flooding problems are the following: lack of overland flow path, prohibitive flow path elevations, insufficient storm sewerage, and lack of channel capacity. Remedy of problems are intended to address the root cause of the problem but could consist of a combination of various techniques for remedy. 2.4.1 Sheet Flow Ponding and Paths Ponding in localized areas (such as at street intersections or at the end of a cul-de-sac) due to inability of accumulating runoff waters to drain away from the accumulating area because of the lack of a overland flow path: If a sheet flow pathway (or a drainage relief structure, such as a relief storm sewer or relief swale, which achieves the same effect) can 2-9 Klotz Associates Project No. 0127.008.000 La Porte Citywide Drainage Study January 2009 City of La Ports°`