Dane County continues to experience groundwater related flooding one year after a historic storm dropped nearly 15 inches of rain on parts of the area, County Executive Joe Parisi announced Aug. 19.
Parisi, along with the Director of Emergency Management and others, held a briefing in the county’s Emergency Operations Center, nearly a year after record rains caused over $154 million in damage across the county.
The floods predominately damaged homes, businesses, and roads in the western half of the county and resulted in the unfortunate loss of a man’s life on Madison’s west side.
Approximately 60 percent of the damage claims filed with the Federal Emergency Management Agency (FEMA) came from properties that experienced flooding from Black Earth Creek – residences in Mazomanie, Black Earth, and Cross Plains.
The other significant concentration of damage was on the west side of Madison, Middleton, and Shorewood as a result of rapid stormwater runoff.
While lake levels in the Yahara Chain rose in the days subsequent to the heavy rainfall, quick collaboration by the county, communities, and responders on sandbagging efforts resulted in only 3 percent of the total FEMA claims coming from the Yahara River watershed. To date, FEMA has awarded $3.8 million in claims to 917 Dane County households.
While the visible effects of those damaging rains remain 12 months later, the subsequent impact on the area’s groundwater table has caused millions in additional losses this year in agricultural production and brought water into basements of homes.
“Nearly one of every 10 acres of cropland in this county went unplanted this year because areas that were forever farm fields had small lakes in them well into the early part of this summer,” Parisi said.
The county executive cited statistics from the USDA’s Farm Service Agency showing nearly 32,000 acres of farmland were not planted this spring. That’s roughly 50 square miles of land that had so much water this year it was unusable.
In past years, typically only 1 or 2 percent of Dane County farm lands are left unplanted.
“Because of the extreme rains last August, we finished 2018 with almost 18 more inches of precipitation than we typically see,” Parisi said. “The ground and surface water can take a certain amount of that runoff before the sponge gets saturated and the result is the standing water we saw in tens of thousands of acres of some of the most productive farmland in the state.”
Historic precipitation amounts have resulted in high groundwater tables in certain areas in Dane County where the groundwater is unable to drain quickly. As a result, the high groundwater table is causing surface flooding in low-lying topographic depressions such as agriculture fields.
Also, the higher water table is resulting in increased reports of basement flooding in areas where flooding hasn’t been problematic in the past. Homes may be built on ground that is dry the vast majority of the time, but in periods like this in which groundwater is high residences can be more prone to basement flooding.
There are a myriad of factors that make some homes and businesses more vulnerable during periods of high groundwater, including the soil type and historic drainage patterns that may have been impacted during development.
“We’ve heard reports this year of people saying they’ve never seen water in their basements before,” Emergency Management Director Charles Tubbs said.
“They may think the problem is lakes or rivers but actually it’s the water in the ground coming up because it has no place left to go,” Tubbs added. “That’s why we’re encouraging all homeowners to look into flood insurance policies and consider other household preparations – like not storing sensitive documents downstairs – in the event water starts coming in.”
In addition, Tubbs mentioned many homeowners report sump pumps running more frequently than ever before Homeowners should make sure their system is functioning and should consider installing backup pumps and batteries.
Dane County Emergency Management and Dane County Planning and Development are currently doing an analysis to evaluate the flooding risk for homes that may not fall within FEMA’s floodplain designation, but could be susceptible to water damage in the wake of climate change rain events.
Together, they’re reviewing damage reports from last year combined with topography and soil types to compile an assessment of which areas may be most affected by future high volume storm water runoff or subsequent elevated groundwater tables.
When complete, the county will use that analysis to inform potential affected homeowners of any additional risk they may face either as a result of rapid rainfall run-off or high groundwater levels.
In response to last summer’s flooding, Parisi included more than $18 million in his 2019 budget to improve Dane County’s flood readiness and take steps to mitigate the impacts of future flooding events.
Earlier this summer, Parisi announced the acquisition of 160 acres of land – otherwise slated for development – in the Lake Mendota watershed adjacent to Pheasant Branch Conservancy to prevent more than 5 million gallons of stormwater run-off that would have otherwise occurred had the property been developed.