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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />stream end of the lining waS undermined resulting in the loss of 0 few panels of <br />concrete Ii ni ng. <br /> <br />The land adjacent to the creek in this reach, except for a 1,200 foot <br /> <br />portion to the south which is within Rotella Park, is partially developed in multi- <br /> <br />family housing and is projected to be fully developed in the near future. A new <br /> <br />development of multi-family housing is presently under construction to the south <br /> <br />of the creek between Rotella Park and York Street. Seven acres of this develop- <br /> <br />ment is within the present 100-year flood plain. The land to the south of the <br /> <br />creek near ExploradorCalle is planned for single-family housing development in <br /> <br />the future. This planned development contains about 1.5 acres within the present <br /> <br />flood plain. <br /> <br />The fact that considerable development is proceeding within the present <br />flood plain zone led to the conclusion that this reach of channel should be investi- <br />gated to determine if the channel could be economically designed to contain the <br />100-year flood flows. <br /> <br />The upstream, concrete lined channel was investigated first and it was <br /> <br />found that extending the concrete lining up about four feet and providing low <br /> <br />dikes along the channel provided on economical solution to containing the 100- <br /> <br />year flood flow within this portion of the reach. <br /> <br />It was determined that the velocities at the downstream end of the con- <br />crete lined portion of the reach wi II be quite high necessitating the use of an <br />energy dissipator. The existing slope of the unlined channe I is such that drop <br />structures would be required in this reach. Various combinations of drop structures <br />and energy dissipators were investigated. It was determined that the optimum cost <br />was approached as the excavation was increased and the number of drop structures <br />decreased. The Final layout for the downstream portion of this reach consists af <br />one concrete lined drop/energy dissipating structure located at the downstream <br />end af the concrete lined channel and two grouted riprap drop structures. A grass <br /> <br />111-5 <br />