Intensity of Extreme Rainfall Events Over Minnesota

Project summary:

The design of drainage projects depends on estimates of rainfall intensity and frequency at a variety of time scales depending on the type of project. Road surface drainage projects, for example, require estimates of rainfall intensities for durations of 5 to 120 minutes. Designers may also be interested in rainfall intensities at recurrence intervals of 1 to over 100 years. The required information is usually obtained from standard published sources or from local rainfall observations that are analyzed by the designer. There are two interrelated problems. First, the published sources are based on widely spaced data that may not adequately represent that actual intensity of precipitation observed. Second, the designer does typically not know the quality of local data available. The purpose of phase I am to test the feasibility of improving the estimates of the extreme precipitation amounts by using the unique high spatial density precipitation measurement network that has existed in Minnesota since the late 1970's. The East Central climatological division will be site of this feasibility study. The result will be more realistic time series of annual 24-hour extreme precipitation amounts. From these time series more realistic estimates of rainfall intensities from 5 minutes to 24 hours and for return periods of one year to one hundred years will be calculated. If Phase I is successful, the study will be extended to the entire State of Minnesota.