Flooding

Risk Assessment

We experience no significant additional flood risk due to the current lake levels. Recall typically 1 inch of rain in the Yahara Watershed typically gets you a 3-inch rise in the elevation of Lake Monona.

Lake Mendota Today

Elevation = 850.68 feet
Change from one week ago = down 0.01 feet
Change from one month ago = 0 feet
Above/below summer maximum: Above by 0.58 feet
Above or below 100 year elevation: Down 2.12 feet

Lake Mendota Statistics

Surface Area = 9,842 surface area acres
Summer Min = 849.6 feet
Summer Max = 850.1 feet
100-Year Record = 852.8 feet

Lake Monona Today

Elevation = 846.69 feet
Change from one week ago = up 0.14 feet
Change from one month ago = up 0.23 feet
Above/below summer maximum: above by 1.49 feet
Above or below 100 year elevation: down 1.01 feet

Lake Monona Statistics

Surface Area = 3,274 surface area acres
Summer Min = 844.7 feet
Summer Max = 845.2 feet
100-Year Record = 847.7 feet

Further description of numbers above:

Mendota is at 850.68, which is down from 850.69 last week. The summer max by WDNR order is 850.10 (so we are approximately 7 inches over summer max). The 100-year elevation is 852.8, but we can only currently effectively rise to approximately 852.0.

Monona is at 846.69 up from 846.55 last week. The summer max by WDNR order is 845.20 (so we are approximately 1 foot, 6 inches over). The 100-year is 847.7.

The problem low ground elevations in the Isthmus area are at about elevation 848.0-849.00. These areas drain to Lake Monona and/or the Yahara River mostly at East Washington. The closer Monona rises to 847.00, the more ineffective our drainage system in these low areas becomes at addressing high intensity summer storms (1" per hour).