Hydraulic analysis of U.S. Highway 75 crossing of the Fall River at Neodesha, Southeast Kansas

A hydraulic analysis of the Fall River inthe vicinity of the existing U.S. Highway 75 crossing at Neodesha, southeast Kansas, was conducted using a combination of step-backwater (WSPRO) and culvert (CAP) analysis program. Hydraulic data for these programs were determined fromonsite inspections and surveys, and from previously conducted Flood Insurance Studies (FIS).Discharge values with their appropriate recurrence intervals also were obtained fromthe previous FIS. The computation of water-surface elevations using step-backwater and culvert analyses indicate that free flow occurs through all drainage structures for all discharges equal to or less than those having a 100-year recurrence interval (400,000 cubic feet per second_ an the water-surface elevations are lower than the lowest point on the roadway. The total capacity of the three drainage-structure openings is sufficient at the 500-year recurrence- interval discharge (55,000 cubic feet per second) to prevent flow over the roadway. Flow over the roadway begins when total discharge exceeds about 58,000 cubic feet per second.