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<br />k lot z .~~ ass 0 cia t e s <br /> <br />width of right-of-way for this channel improvement thus consisted of two parts: 1) <br />the approximate existing top width (i.e., bank-to-bank); and 2) an assumed <br />maintenance berm of 20- feet on each side of the channel. <br /> <br />Widening of channels to the point of significant encroachment upon adjacent <br />properties was not considered to be a viable option. Table 4-2 shows the <br />estimated additional channel width that would be required if channel widening <br />with using a 3:1 side slope were used rather than a slope approximately matching <br />the existing side slope. It is noted that significant encroachment upon adjacent <br />properties could be expected if a 3:1 channel slope were consistently used for <br />channel widening. <br /> <br />. Channel lining, which is used as a channel modification when widening, because <br />of adjacent structures or similar limitations, was not feasible. The lining was <br />evaluated as being concrete, which would allow steeper side slopes (1 to1) as well <br />as reduced channel roughness. It is recognized that concrete lining is not a <br />preferred option from an environmental perspective, but it was found to be <br />necessary in some situations. Furthermore, detailed design could consider <br />alternative materials, such as flexible concrete mats of interlocking blocks, partial <br />lining, and geo-cell systems, which typically are more aesthetically pleasing than <br />solid concrete lining (but note, side slope steepness on some of these types of <br />alternatives are quite limited). Right-of-way requirements for the lined channels <br />are similar to widened channels, i.e., existing width at top-of-bank plus a 20-foot <br />maintenance berm of each side of the channel. <br /> <br />. Hydraulic structure modification, in which bridges and culverts are modified to <br />reduce significant channel restrictions and consequent water level impacts: For <br />FEMA-modeled channels, the structures along the channel are virtually all <br />bridges. For bridges along the FEMA-modeled channels, review of computed <br /> <br />4-3 <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 />