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<br />Flood Routing Criteria - The Successive-Averagc.Lag method was used to route floods. <br /> <br />Standard Project Flood (SPF) - The SPF was developed by the Corps in accordance with <br />their procedures. Both Wild Horse Creek and the Arkansas River standard project flood were <br />developed using one-half the probable maximum precipitation critically located over the drainage <br />areas. <br /> <br />Coincident Flow Study - A regression was used by the Corps to determine coincident flow <br />on the Arkansas River when peak flows occur on Wild Horse Cf(~ek. Vice versa, a regression <br />showed no significant correlation of coincident flow on Wild Horse Creek when peak flows occur <br />on the Arkansas River. <br /> <br />Frequency - Flood frequencies were developed by the Corps (except as noted) for Wild <br />Horse Creek, the Arkansas River, and coincident flow in the Arkansas River. Table 1 <br />summarizes the flood frequencies. <br /> <br />Methodology - The Corps developed peak frequency curves at locations along the <br />Arkansas River between John Martin Dam and Great Bend, Kansas. These peak frequency curves <br />were correlated and regionalized and then used to develop a peak frequency curve for the <br />Arkansas River at Holly. The Corps developed peak discharges for Wild Horse Creek using <br />frequency development procedures documented in "Design Memorandum No.1, Hydrology, Great <br />Bend Local Protection Project, Great Bend Kansas and Vicinity", dated, April 1973. <br /> <br />J-lvdraulic Analvsis <br /> <br />The Corps carried out detailed hydraulic studies in SUPPOlt of the Holly Flood Control <br />Project. These studies meet the Board's require:ments for detailed floodplain infOlmation. <br />Hydraulic information is summarized in the following paragraphs. <br /> <br />Roughness Coefficients - The following roughness coefficients were assigned to three parts <br />of the floodplain channel: <br />Channel areas <br />Overbank areas <br />Town of Holly <br /> <br />n = 0.035, <br />n = 0.06, <br />n = 0.1. <br /> <br />Project Design Flood - The Corps used the SPF for design of the levees and structures. <br />The design of the Wild Horse Creek levee (from the point of beginning about 1.0 mile north of <br />the Town, extending south [downstream] 9735 feet to AT&SF Railroad bridg(~ west of Town) <br />was based on the Wild Horse Creek SPF flow of 62,000 c.f.s. plus the coincident flow in the <br />Arkansas River of 14,700 c.f.s., totaling 76,700 c.f.s. Design for the Arkansas River levee <br />(extending south 2225 feet from the AT&SF Railroad bridge to 1he confluence of Wild Horse <br />Creek and then east [downstream] 10,200 feet along the Arkansas River to the end of the levee) <br />was based on the Arkansas River SPF flow of 160,000 c.f.s. <br /> <br />8 <br />