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I I I I I I I I I I I I I I I I I I I The meandering in this reach serves to retard the flow velocities. The Ward Canal crosses the channel at station 87+00 in a concrete flume. The channel reach immediately below and above Alameda Parkway have average slopes of 4.7% and 5.2%, respectively. The slope near the upper study limit reaches 7%. The 100 year flows are contained within the K. Drainagewa~ Drainageway L is a left bank tributary to Bear Creek, draining the southeast flank of Green Mountain. 1, Station 205+00 to 0+00, Upstream Study Limits to Confluence with Bear Creek~eets 73 to 80l incised channel. The lower reach of the drainageway below Morrison Road is an incised channel choked with vegetation, The channel meanders across the The flood hazards in this reach consist of erosion, debris removal high point of an alluvial fan and is crossed by several privately owned drainage structures with capacities less than the 10 year flood peak, The results are a broad expanse of sheet flow flooding. The channel falls at 2,0% in this reach. and cleaning, and a low to moderate life hazard due to the high velocity flow, 2, Station 76+00 to 0+00, Upstream Study Limits to Confluence with Drainageway K (Sheets 70 to 72) The channel in this reach, designated Drainageway K-l, is tributary to Drainageway K at Station 77+80. The channel varies from a broad V-shaped to a deeply incised trapezoidal section. The average slope below Welch Street is about 2.2% and above Welch Street, the slope steepens to about 5%. The channel is crossed by the Ward Canal, Welch Street, and Jewell Avenue. Portions of the channel in the vicinity of Jewell Avenue are currently being replaced by a 48" RCP storm sewer. Several near vertical natural drops in the channel have been created by erosion of the invert. The Welch Street crossing of Drainageway K-1 forms a flood detention The reach above Morrison Road to approximately Station 60+00 is a wide parabolic channel with a low capacity trickle channel. The flows are contained within the major channel which slopes at 2,0% to 2.4% in this reach. The reach from Station 60+00 to Wright Street becomes increasingly incised and narrow, The entire length of the drainageway is very incised above Wright Street with adequate capacity to convey the 100 year flood. All street crossings above and including Wright Street within the recently developed subdivisions serve as flood detention reservoirs with flood reservoir which results in a significant reduction in the flood peaks, storage depths ranging from 8 to 20 feet. Each structure has an RCP outlet (36" to 66") with an impact stilling basin. The effect of these large detention basins is to significantly reduce the major storm runoff The water is stored to a depth of 21 feet deep and the 48 inch RCP outlet has an impact stilling basin to dissipate energy, The flood hazards in this reach consist of erosion, debris removal and cleaning, and a moderate to high life hazard due to the steep incised channel and high yelocity flow, peaks, The culvert at the Wright Street Crossing has the capacity for conveying approximately a 50 year flood before overtopping the roadway. 21