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<br />Colorado River, so non-native fish could easily enter the Colorado River. In addition to the <br />likelihood of floodwaters entering the three lakes, there are clear signs that bank erosion is a <br />major concern at Duke Lake and Connected Lakes. The site has historically been a part of the <br />Colorado River floodplain and it has experience substantial channel migration in the past. Bank <br />protection measures undertaken by Mesa ~ounty since 1984 have themselves experienced erosion <br />damage, The dikes that were constructed since 1984 as part of the park improvements do not <br />appear to have been designed to withstand erosion from a 50-year or a 100-year flood. While, <br />some sections of the levee are above the 100-year flood elevation and provide an aesthetically <br />pleasing place to walk or fish, they do not provide 50-year or 100-year flood protection. In <br />addition, they were not designed with higher velocities or higher flood stages resulting from <br />floodplain constriction in mind. The levee would not experience overtopping during a 10-year <br />flood, but there would be streambank erosion if no additional bank protection were installed, <br /> <br />Subsection 5.4 <br /> <br />Mitieation Analvsis <br /> <br />Even with the substantial work that has been done at the state park, at the residential areas within <br />the Connected Lakes subdivision and at the Pepsi-Cola Plant since 1984, there is additional work <br />that would have to be done to provide 50-year and 100-year flood protection. The levee system <br />would need to be raised to keep Duke Lake (and, therefore, Connected Lakes) out of the 50-year <br />floodplain. That levee and the existing dike around the remainder of the site would clearly <br />require erosion and slope protection. The erosion protection would need to be engineered to <br />mimimize the risk of undermining by a flood. There would need to be additional freeboard in <br />some locations. Before such mitigation measures were undertaken, an engineering analysis would <br />be needed. A 50-year flood protection project may be feasible for the stream reach from the <br />Redlands Parkway upstream to Highway 340. <br /> <br />13.3 <br />