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<br />CHAPTER 6 <br />APPROACHES TO FLOOD HYDROLOGY <br /> <br />There are a variety of approaches to flood hydrology. This chapter summarizes the <br />approaches, while Chapter 7 describes them in detail. These approaches can be classified <br />into either standard or non-standard categories. Standard approaches, as the name <br />implies, are methods commonly used for flood hydrology estimates. These methods can <br />be considered "tried and somewhat true" methods for flood hydrology estimates. Non- <br />standard methods, though, are not so commonly used techniques or relatively new <br />techniques that have not been used on a regular basis, but show promise and may be <br />increasingly used in future analysis. <br /> <br />6.1 Standard Approaches. Standard approaches to flood hydrology can be categorized <br />under three methods: <br /> <br />(1) Simplified methods <br /> <br />(2) Frequency analysis of streamflow data <br /> <br />(3) Rainfall-runoff analysis of storm events <br /> <br />6.1.1 Slmolified Method. Simplified methods may involve U8El of relatively simple <br />equations such as the rational formula. previously developed regression equations. etc. <br />.. Depending on time and resources, these methods can be used as stand-alone estimates, <br />or more preferably, should be usild for providing an Independent check on estimates <br />developed by other, poten~11y more a~rate methods. <br />. .' <br /> <br />Advantaaes <br /> <br />Disadvantaaes <br /> <br />1. Simplicity. <br /> <br />1. Due to assumptions of homogeneity, <br />method is only for small areas (< 1 mi"). <br /> <br />2. Widely used, particularly for sewer <br />design. <br /> <br />2. Assumes rainfall intensity is constant <br />during storm duration. <br /> <br />3. Only defines peak discharge. <br /> <br />6.1.2 Freauencv Analvsis of Streamflow Data. Where adequate streamflow data are <br />available, frequency analysis of such data can be performed to develop exceedance <br />frequency estimates. Frequency analysis is a method to infer the probability of <br />exceedance of all possible discharge values from observed discharge values, This <br />process is accomplished by selecting a statistical model that describes the distribution of <br />discharges of the parent population, The parameters of the statistical model are estimated <br /> <br />Colorado Flood <br />Hydrology Manual <br /> <br />6.1 <br /> <br />[FW=f <br />