The purpose of this report is to provide information on the extent , depth, and frequency of flooding of the lower Yahara River in Dane County, Wis.

The report contains discharge-frequency data for flood peaks, flood–frequency profiles, and the regional flood– (100-year flood) inundation limits for the lower Yahara River. The study reach is in southern Dane County extending from part of the shoreline of Lake Waubesa downstream through Lake Kegonsa to the Dane-Rock County line. Specifically the parts of the shoreline of Lake Waubesa included are those in and south of section 8, T. 6 N., R. 10 E. on the west shore and the south half of section 3, , T. 7 N., R. 10 E. on the east shore. (See figure 2.) The reach is 21 river miles (31 km) long.

The Wisconsin Legislature has enacted flood–plain–Zoning legislation (1965) to encourage economic use of flood plains and to minimize flood losses. This act gave counties, cities, and villages the responsibility of enacting, administering, and enforcing reasonable and effective flood-plain regulations.

This report is a sequel to earlier reports by Lawrence and Holmstrom (1971) and Holmstrom and Lawrence (1971). The earlier reports provided much of the same information, but the scale of the maps defining limits of flooding was much smaller. This report , using Orthophotographs at a scale of 1 in - 100 ft., provides greater detail.

The report is based on conditions existing in 1971. All elevations are referenced to mean sea level, datum of 1929.