After several intense rain storms this month, water levels in Lake Monona and Mendota remain high. As a result, the city is providing Madison residents free sand and bags to protect their property in flood prone areas.
According to Dane County, as of Friday morning the water level in Lake Monona was 846.9 feet above sea level. The 100-year level for Monona is 847.7. Mendota is at 851.21, compared to a 100-year level of 852.8.
As of Tuesday, the county's lake level website said: "Flow out of Lake Mendota has been reduced below seasonable rates in order to allow downstream lake levels to decline. Aquatic plant harvesters are located in the Yahara River from Stoughton Dam to Lake Waubesa to remove aquatic plants impeding flow."
The county has also instituted "slow-no-wake" rules on Lakes Monona, Waubesa and Kegonsa. Lakefront property owners with piers are advised to raise them to avoid the risk of having them float away.
Many areas in the city that drain to Lake Monona and Starkweather Creek have a ground elevation approximately three feet higher than the current lake level on Lake Monona. As Lake Monona rises, the underground storm sewer system will not function efficiently as lake water inundates the system. Rising water will impact the storm sewer’s ability to drain water away and if the water is too high, flooding and standing water may occur.
According to John Reimer, assistant director of land and water resources, the county had to get emergency permits to move weed cutters to the rivers.
Last week, Dane County Executive Joe Parisi said the county is providing money to municipalities to invest in retention ponds. A retention pond is an artificial lake designed to manage storm water and reduce flooding. These ponds hold water and improve the quality of the water if it has to be dispersed in other locations.
According to Parisi, a significant number of wetlands in the county have been filled, so the county is targeting the remaining wetlands to try to preserve them.
There have been some areas that have been impacted more severely, because of the “extreme rainfall.”
“The west side of Madison has been hit hard. They received five inches of rainfall and all that flows into Lake Mendota,” Reimer said.
The county has worked with UW-Madison to try to project the impact of climate change in Dane county, and Parisi said the modeling predicted these floods and weather changes were coming.
“What we’re seeing right now is climate change,” Parisi said.
John Young of the State Climatology Office agreed an increase in flooding frequency is a result of climate change.
“There is an increase in frequency in 100 years old flood; they’re becoming more like 75 year old floods. The trends seem to be trending upward and almost certainly due to global warming,” Young said.
According to Young, residents should expect an increase in summer flooding.
“There will be dry months and there will be some years when the rain is not so heavy, but the trends are upward," he said.