Flooding

Risk Assessment

We experience no significant additional flood risk due to the current lake levels, Lake Monona is dropping slowly. We had approximately 1.25” of rain on Thursday. The Engineering Division expects the following elevations will creep up the next few days.

Recall typically 1” of rain in the Mendota watershed gets you a 3” rise in the elevation of Lake Mendota.

Lake Mendota Today

Elevation = 850.68 feet

Change from one week ago = down 0.06 feet

Change from one month ago = up 0.4 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 = 846.46 feet

Change from one week ago = down 0.06 feet

Change from one month ago = up 0.3 feet

Above/below summer maximum: above by 1.26 feet

Above or below 100 year elevation: down 1.24 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

The problem low ground elevations in the isthmus area are at about elevation 848.5 to 849.00.  These areas drain to Lake Monona and/or the Yahara River downstream of the Tenney Locks. The closer Monona rises to 847.00 the more ineffective our drainage system in these low areas becomes.