Laserfiche WebLink
<br />~ <br /> <br />frequency of a 10,000 c,f,s. flood may be 10 times in 100 years, The same <br /> <br /> <br />frequency can also be expressed as an exceedance probability, ,1, or a <br /> <br /> <br />flood with 10% chance of occurring in any particular year, Most often, <br /> <br /> <br />the discharge-frequency relationship is expressed by its recurrence <br /> <br /> <br />interval, which in this case would be a 10-year event. <br /> <br /> <br />~ Frequency relationships are the key element in the criteria for <br /> <br /> <br />establishing the magnitude of flood damage, No estimate of damage can be <br /> <br /> <br />determined without first estimating how often any particular flood is <br /> <br />expected to occur, Discharge-frequency relationships can be combined with <br /> <br /> <br />discharge-elevation to establish the probability of each flood reaching a <br /> <br /> <br />given elevation in any particular year. Figure V-4 is an example of a <br /> <br /> <br />discharge-frequency relationship, <br /> <br />Procedure. The discharge-frequency relationship is estimated from <br /> <br /> <br />three sources: 1) streamflow records, which give the maximum daily figure <br /> <br /> <br />readings at stream gage sites for the period of record; 2) data from <br /> <br /> <br />similar watersheds, which are used to identify patterns for unusual events <br /> <br /> <br />and the reasonableness of estimates for the study area; and, <br /> <br />3) precipitation data, which are used to verify probability estimates. <br /> <br />The accuracy of damage. frequency relationships can vary with the <br /> <br />variability and understanding of climatic trends, randomness of the <br /> <br />events, physical changes within the watershed, mixed combinations of <br /> <br />rainstorms, snowmelt, and hurricanes, and the reliability of streamflow <br /> <br />estimates. <br /> <br />V,12 <br />