10-13-08 Drainage and Flooding Committee minutes

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k lot z 4~. ass 0 cia t e 5 improvement since it has the net effect of moving runoff away to a point of discharge just as an inlet into sewer pipe does. Anyone or more of these adequacies can be addressed by sewer or sewer system appurtenance replacement or upgrade. In addition to storm sewer or storm sewer appurtenance replacement, capacity improvement options include addition of parallel sewers, addition of new inlets, realignment of sewers, and introduction of bypass sewers. For planning purposes, sewerage improvements are only categorically identified as sewerage improvements since the choice of a particular improvement technique will depend upon the details of the current sewerage system which are not available for the planning purposes ofthe study. ".- 2.4.4 Channel Capacity Increase Inadequate capacity of an open channel (ditch, bayou or other watercourse) has two important consequences:' potential overflow of the channel during flood conditions; and creation of high tailwaters at storm water sewer outfalls, which in turn reduces storm sewer capacity. Potential methods for channel capacity improvement include the following: . Deepening of a channel: Deepening possibilities will generally be limited, because of flat topography and flowline connection levels at junctions and culvert crossing structures. . Adjustment of the channel bottom slope: Channel slope adjustment will typically be limited for the same reasons as those limiting deepening of a channel. . Channel straightening to reduce energy losses and increase bottom slope: Straightening has limited application in the City because most channels are already quite straight. 2-11 Klotz Associates Project No. 0127.008.000 January 2009 La Porte Citywide Drainage Study City of La Porte