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I I I I I I I I I I I I I I I I I I I lined channel was not feasible due to excessive velocities (10 fps at 100-year flood flows); therefore, riprap lining is recommended. The estimated cost of modifying this reach to contain the 100-year flood proved the scheme to be economical compared to the high damage potential. Very little maintenance will be required in this reach except for cleaning out debris which collects on the baffle blocks of the drop structure. Explorador Calle Crossing The existing bridge opening has a discharge capacity of 880 cfs which is less than the 10-year flood flow of 1,250 cfs. Raising the bridge to increase dis- charge capacity would be difficult and expensive. Examination of construction drawings of the existing bridge indicated that the channel beneath the bridge could be widened to increase the discharge capacity to 1,900 cfs. This would result in sheet flow over the bridge during a 100-year flood; however, almost all of the overflow wi II return to the channe I. Explorador Calle to Washington Street - Plates 111-5 and 111-6 Channel Design The channel in this reach is contained in a corridor known as the Coronado Parkway, bounded by Coronado Parkway on the north and East S3rd Drive on the south. The existing chonnel is concrete lined for a height of 3.5 feet above the channel invert. The channel drops approximately 28 feet in a length of 2,980 feet or 9.5 percent. The existing channel shows no apparent sign of damage due to the /lky 5, 1973 flood. The land adjacent to the creek in this reach is fully developed with single- and multi-family dwellings except for a 900-foot reach to the south of the creek immediately east of Washington Street. 111-6