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I I I I I I I I I I I I I I I I I I I 5 plain and vegetative cover were determined from aerial photography and field survey. 48-inch diameter pipe east of Harlan, the channel is well defined, and the maximum lOa-year flood plain width is only about 50 feet. A 48-inch diameter pipe discharges about 200 feet east of Harlan Street, carrying flow from Villa Italia Shopping Center, and flow from a 27-inch diameter pipe located under Nevada Avenue between Harlan and Pierce Streets. The area between Harlan and Pierce is all residential development. Channel and Flood Plain The 1st Avenue Tributary flood plain between Sheridan Boulevard and Weir Gulch is completely developed. Stormwater is conveyed by underground pipes 42 inches to 54 inches in diameter or box culverts. Sections of open channel, heavily overgrown and poorly maintained, are located between stretches of pipe. A 24- inch diameter corrugated metal pipe extends from west of Benton Street to Sheridan Boulevard, discharging into a 34-inch by 53-inch eliptical concrete pipe which discharges into an open channel east of Sheridan Boulevard. No development in the flood plain is observed between Chase Street and Harlan Street. Here, the lOa-year flood plain is between 50 - 80 feet wide on the average. Between Harlan Street and Hay Street, no residences are located within the flood plain itself, and the culverts are partially or fully clogged.4 West of Jay Street, two residences are located in the flood plain. Fro~ Jay Street west to the study limit at Teller Street, the flood plain is located along the northerly limit of a park located immediately south of 2nd Avenue. In the north-south direction, the flood plain extends from south of Nevada PI ace to the south edge of Alameda Avenue. The Vi 11 a Ita 1 i a Shoppi ng Center is fully developed with an internal drainage system and parking lot detention facility. That portion of the drainage basin located south and west of Villa Italia Shopping Center is presently undeveloped, flat, and overgrown with natural grass, weeds, and brush. Commercial development with greenbelts is anticipated, but no specific planning details are available. Roughness Coefficients Friction factors used ranged from .035 for channels and flood plains with medium growth to .080 for areas with heavy growth and residential develop- ment. The n-factors were selected on the basis of experience on similar pro- jects, and the recommendations given in Chow's "Open Channel Hydraulics". The flood plain of the Dakota Avenue Tributary east of Sheridan Boulevard is fully developed with residential structures. Property along the north side of Alaska Place between Yates and Xavier Streets is low lying and subject to flooding at regular intervals. Between Sheridan Boulevard and Depew Street, the flood plain follows a well defined channel. The flood plain itself has only sparse vegetation and is easily erodible. About half-way between Sheridan Boulevard and Depew Street, an old dam exists which causes some ponding. A 42- inch diameter pipe is located between Depew and Eaton Streets. The flood plain between Depew and Eaton Streets is between 70 and 150 feet wide, and three residences are located in that section. From Eaton Street to the outlet of a 4For the hydraulic analy,is. it was assumed the culverts would be properly maintained. Water Surface Profile Computations For the purpose of IIJJater surface profile computations, it was assumed that all culverts were in good operating condition when diameter, type of culvert, and invert elevations could be determined. The culvert crossing Ingall Street on 1st Avenue Tributary could not be identified and was assumed not existing. The Corps of Engineers computer program HEC-2 was utilizec to calculate the water sur- face profile for the 1st Avenue Tributary ilnd the Dakota Avenue Tributary.