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<br />I <br /> <br />21 <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />playgrounds and bike paths, A subdivision is planned in the upper portion <br /> <br /> <br />of the basin and preliminary drainage plans indicate that management of <br /> <br /> <br />increased runoff will be provided for by utilization of the existing dry <br /> <br /> <br />pond located just downstream from the Community Ditch, The culverts located <br /> <br /> <br />at Daphne Street, Miramonte Boulevard, and Main Street are unable to handle <br /> <br /> <br />the IDO-year flow and consequently are overtopped. <br /> <br />I <br /> <br />Just downstream from Main Street, the North Tributary enters the main <br /> <br />channel from the north. The area drained by the North Tributary (Sheet 13) <br /> <br /> <br />is largely undeveloped at present, but primarily zoned as single-family <br /> <br /> <br />residential. The existing channel flows into Nissen Reservoir, which spill- <br /> <br /> <br />way directs outflows southward across a golf course to join the main channel <br /> <br /> <br />east of Main Street, <br /> <br />Downstream from 10th Avenue, the channel flows through a farm pond and <br /> <br /> <br />then across a large open field to East 7th Avenue in the form of a large <br /> <br /> <br />swale with no defined low flow channel, The channel is carried beneath <br /> <br /> <br />Ash Street and East 7th Avenue by a 24-inch diameter pipe, outfalling at <br /> <br /> <br />Birch Street (Sheet 15), The area between Birch Street and Midway Boulevard <br /> <br /> <br />has been developed as a single-family residential subdivision and a 100- <br /> <br /> <br />year capacity grass-lined channel has been constructed to carry flows to <br /> <br />Midway Boulevard (Sheet 16), A double 5-foot by 7-foot box culvert has <br /> <br /> <br />been installed at Midway Boulevard with a total capacity of approximately <br /> <br /> <br />600 cfs, compared to the 100-year flow of 1,450 cfs at this location. The <br /> <br /> <br />existing channel travels southward from Midway Boulevard in a natural channel <br /> <br /> <br />which jogs to parallel Sheridan Boulevard until it reaches the twin culvert <br /> <br /> <br />pipes carrying flows eastward beneath Sheridan Boulevard. <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br />I <br /> <br />At present, the only problems in this reach are the undersized culverts at <br /> <br /> <br />Country Club Road and the inadequate channel carrying flows into Nissen <br /> <br /> <br />Reservoir, The area is presently being developed, however, and preliminary <br /> <br /> <br />design information indicates that the existing drainage problems will be <br /> <br /> <br />corrected and stormwater detention measures implemented by onsite methods <br /> <br /> <br />and by routing flows through Nissen Reservoir. <br /> <br />I <br /> <br />In the central portion of the basin (Sheet 14) the channel traverses the <br /> <br /> <br />golf course to East 10th Avenue, flowing through two small ponds and cross- <br /> <br /> <br />ing the Equity Ditch. An 18-inch pipe carries the normal trickle outflows <br /> <br /> <br />from the golf course ponds. l1ajor flows would breach the pond embankments <br /> <br /> <br />and overtop East 10th Avenue where the existing culvert has the capacity <br /> <br /> <br />to handle less than a 2-year flood, <br /> <br />As indicated by Sheets 15 and 16, the obvious floodplain encroachment by <br /> <br /> <br />the development along East 7th Avenue is the most serious flood hazard <br /> <br /> <br />problem in the entire basin. During a major flood event, East 7th Avenue <br /> <br /> <br />becomes the main drainageway carrying flows at sufficient depths to affect <br /> <br /> <br />most of the residences along 7th Avenue and areas immediately adjacent. The <br /> <br /> <br />design for the channel downstream from Birch Street is sufficient to carry <br /> <br /> <br />100-year flows, but these flows will overtop Midway Boulevard. Upstream <br /> <br /> <br />from Sheridan Boulevard, 100-year flows will spread out in a wide floodplain <br /> <br /> <br />due to the flat topography in the area, Low density single~family residential <br /> <br /> <br />development is currently underway for this area and a 100-year, grass-l ined <br /> <br /> <br />channel is planned to convey flows to Sheridan Boulevard, <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />The most serious effect of a major flood event in this area would be the <br /> <br /> <br />severing of a major east~west transportation route by a washout of the <br /> <br /> <br />road surface and embankment at East 10th Avenue, <br /> <br />Immediately downstream from Sheridan Boulevard (Sheets 16 and 17), the <br /> <br /> <br />channel is a large flat swale which travels across an open field, Subbasins <br /> <br /> <br />immediately tributary to this area are undeveloped and land use is agricul- <br /> <br /> <br />tural, A man-made channel carries flows southward between the mobile home <br /> <br /> <br />park and an existing waste pond embankment and then eastward along the park's <br /> <br /> <br />south property line, The Channe 1 then f lows through a sma 11 nursery pond <br /> <br /> <br />and continues to Perry Street (Sheet 18), <br /> <br />I <br /> <br />I <br /> <br />I <br />