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I I I . I I I I I I I I I I I I I I I Drawing No. SG-2 The channel reach covered by this sheet is to be regulated under a stringent. flood plaln zoning ordinance. The 100-year flood plain has been delineated on the map. The channel through the railroad and Rio Grande Street rights-of-way should be lined with rip rap at points upstream of Rio Grande Street and both upstream and downstream of the AT&SF railroad tracks. These areas will experience high veloci- ties during high flood flow events and as a result could see extensive damage resulting from local scour around the structure abutments. Upstream of the railroad tracks, the average maximum velocity is on the order of 6.1 fps with peak maximum velocities on the order of 9 feet in the area of the confluence with the south tributary. With velocities in this range for the 100 year flood event, for natural conditions, it is not recommended that any structural improve- ments be made through the reach. If the area is to be developed as a park, it would be appropriate that the exist- ing low flow channel be stabilized and steep banks flattened to control scour resulting from regular low flows. In this reach, the City Ditch crosses Slaughterhouse Gulch in an open flume. Sufficient separation is provided between the flume and the 100 year storm water flood profile. A waste-way from City Ditch exists on the south side of the Gulch through a l2inch corrugated metal pipe. The dirt ditch below the pipe should be stabilized and lined with rock to stop the erosion, characteristic of this small ditch. There is also a flume drain in the middle of the metal flume. The use of this drain should be limited. If excessive use is made of the drain, some type of splash block or lining should be provided in the channel area to minimize the erosive effects on the channel. With the future development of this area into a city park, access should be provided for the continued maintenance of the low flow channel and major channel. The maintenance access can also be incorporated into a hiker/biker trail which could extend from Windermere Street on the east, along the major channel and through the railroad underpasses, by easement, to Rio Grande Street and tie into the trail system proposed for the channel west of Rio Grande Street. Drawing No. SG-3 This drawing covers the reach from Station 30+00, just down- stream of Windermere Street to Station 45+00, downstream of Elmwood Street. From the match line at Station 30+00 to Windermere Street, the plan proposes the perpetuation of the existing natural conditions which adequately carry the 100 year flood flows, while generating no damages other than localized scour and vegetative deterioration. From Windermere Street upstream, storm sewers have been installed having limited capacity. VIII-5