PROPERTIES OF EXTREME POINT RAINFALL .2. PARAMETRIC DATA INTERPRETATION AND REGIONAL UNCERTAINTY ASSESSMENT

As an alternative to the traditional non-parametric method the partial duration series approach with exponentially distributed exceedances i s used to model extreme values of depth and maximum 10 min intensity p er rainfall event, measured at gauges placed at different locations in Denmark. A statistically significant regional variation is documented and shown to be of importance to engineering application. The apparen t variability is divided into sampling uncertainty and uncertainty cau sed by true regional variability. Further, a method for assessing the total inherent design uncertainty, taking into account a possible inte rsite dependence structure, is developed. Adding one total design stan dard deviation to the regionally averaged T-year events yields increas ed design values between 5 and 17%. This result brings up a number of questions with respect to application of historical rainfall data in u rban storm drainage design and analysis.