In the development of rainfall frequency and volume data for Minnesota, the Minnesota Stormwater Manual Sub-Committee conducted an analysis of rainfall distribution for several locations in Minnesota. The methodology and results of this analysis are described in Issue Paper B. Frequency-volume graphs were developed for several locations in the state and are illustrated below.

In viewing these graphs, note that the volume represents the percent volume captured for a particular size storm and not the cumulative volume. For example, consider a BMP designed to capture the first inch of precipitation. A 1 inch storm captures about 90 percent of all rainfall events at Minneapolis-St. Paul International Airport. Storms up to 1 inch represent about 60 percent of the total volume. However, for storms exceeding 1 inch in depth, the first inch will be captured by the BMP. Thus, the annual volume captured by the BMP is much greater than 60 percent. For a B soil, the annual volume captured by the BMP will be about 90 percent.

map showing rainfall frequency and volume percentiles as a function of precipitation depth for Cloquet map showing rainfall frequency and volume percentiles as a function of precipitation depth for Fargo map showing rainfall frequency and volume percentiles as a function of precipitation depth for Grand Forks map showing rainfall frequency and volume percentiles as a function of precipitation depth for Grand Marais map showing rainfall frequency and volume percentiles as a function of precipitation depth for Itasca map showing rainfall frequency and volume percentiles as a function of precipitation depth for Lamberton map showing rainfall frequency and volume percentiles as a function of precipitation depth for Minneapolis and St. Paul map showing rainfall frequency and volume percentiles as a function of precipitation depth for Rochester map showing rainfall frequency and volume percentiles as a function of precipitation depth for St. Cloud map showing rainfall frequency and volume percentiles as a function of precipitation depth for Thief River Falls