Laserfiche WebLink
<br />flood volume is part of a probability spectrum and has some <br />fini te probability of being exceedecl. The concE:pt of probabilis- <br />tic design is unique to water resources engineering. other civil <br />engineering disciplines do not seek to establish a probabilistic <br />relationship for design criteria. For example, the structural <br />designer of a building is concerned only with analysis of dead <br />loads and live loads that are in compliance wi1:h thE' applicable <br />building codes and has no concern with the probability of these <br />loads being exceeded. The probabilistic analysis and design <br />concept give!; rise to terms such as "exceedance probability" and <br />"recurrence inteJ:val" or "return pE'!riod." ~'hese terms are de- <br />fined as follows: <br /> <br />Exceedance probability - The probability of exceeding a given <br />flood descriptor such as peak discharge or flood volume in any <br />given year. <br /> <br />Return Period or Recurrence Interval Both of these terms have <br />the same meaning and refer to thE! average time interval in years <br />between the occur-rence of a flood having a givem peak discharge <br />or flood volume. The lOa-year flood peak disc:harge, for example, <br />is the peak discharge that would bE! excE:ed c,n the a''lerage once <br />every 100 years. Sometimes it is incorrectly inferred that the <br />lOa-year flood oc';urs every 100 years. <br /> <br />The relationship between return period or recurr,ence interval and <br />exceedance probability is defined by the following relationship. <br /> <br />RP= 1/El' <br /> <br />where RP= Return Period or Recurrence Interval <br /> <br />EP = Exceedance Probability <br /> <br />~ <br /> <br />2 <br />