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<br />Type of Structure <br /> <br />Return Period <br />(yeaL;il <br /> <br />PMF <br /> <br />Highway culverts <br />Low traffic <br />Intermediate traffic <br />High traffic <br />Railroad culverts <br />Highway bridges <br />Secondary system <br />Primary system <br />Farm drainage <br />Culverts <br />Ditches <br />Urban Drainage <br />Storm sewers in small cities <br />Storm sewers in large cities <br />Airfields <br />Low traffic <br />Intermediate traffic <br />High traffic <br />Levees <br />On farms <br />Around cities <br />Dams with no likelihood of <br />loss of life (low hazard) <br />Small dams <br />Intermediate dams <br />Large dams <br />Dams with probable loss of life <br />(significant hazard) <br />Small dams <br />Intermediate dams <br />Large dams <br />Dams with high likelihood of <br />considerable loss of life (high hazard) <br />Small dams <br />Intermediate dams <br />Large dams <br /> <br />5-10 <br />10-25 <br />50-100 <br />50-100 <br /> <br />10-50 <br />50-100 <br /> <br />5-50 <br />5-50 <br /> <br />2-25 <br />2-50 <br /> <br />5-10 <br />10-25 <br />50-100 <br /> <br />2-50 <br />50-200 <br /> <br />50-100 <br />100+ <br /> <br />50-100% <br /> <br />50% <br />50-100% <br />100% <br /> <br />50-100% <br />100% <br />100% <br /> <br />6.3.3 Data Availability. Data availability also affects which hydrologic method to use. In general, more <br />complex methods require a greater amount of data.. The general data requirements for the various <br />hydrologic methods are shown below. <br /> <br />6.3.3.1 Simplified Methods. Simplified methods such as the rational method have relatively <br />small data requirements of: (1) landuse, (2) site specific rainfall intensity -duration curve, and (3) <br />drainage area. <br /> <br />Colorado Flood <br />Hydrology Manual <br /> <br />6.8 <br /> <br />DRAFr <br />