To determine the relative risk of spring flooding, numerous factors are considered including snow cover, soil moisture, and current river conditions. A significant snow cover with high water content can increase the chances of flooding once warmer weather melts the snow. Elevated soil moisture conditions reduce the amount of rainfall that is soaked up by the ground and increase the amount of water that then runs off into area streams. Above average river levels reduce the river rise required to reach flood stage, while below average river levels would require an increased amount of river rise to reach flood stage.
Here is a general overview of spring flood risk factors across northeast Illinois and northwest Indiana river basins.
Risk Factor | Has effect on... | Current Condition | Effect on Flood Risk |
Fall/Winter River Levels |
Space in river for additional streamflow. | Below Average to Above Average | Decrease/Increase |
Fall/Winter Soil Moisture |
Space in soil for additional infiltration. | Below Average to Above Average | Decrease/Increase |
Winter Precipitation | Snow cover, the amount of water available for spring melt. | Below Average to Near Average | Decrease/No effect |
Winter Temperatures |
Frost depth, the possibility that infiltration could be blocked by frozen ground. | Near Average | No effect |
Spring Precipitation |
Amount of water headed to area rivers. | - | - |
Spring Temperatures | Rate of melt for snow cover. | - | No effect Most snow cover is melted, so temperatures will not play a major role. |
Valid March 10, 2022.
Modeled snow cover across area river basins ranges from 0 to 2 inches across the area, which contains 0 inches to 0.25 inches of water equivalent. The deepest snow cover is in northwest Illinois and southern Wisconsin. Snow cover is low enough that it will not be a major factor in spring flood risk.
Valid March 9, 2022. Click here for the latest snow cover information.
Modeled soil moisture values across the area range from below average to near average. Values are the lowest in northern Illinois, at the 5th to 10th percentile for this time of year.
Frost depth ranges from 0 to 25 inches across area river basins, with the deepest frost depth values reported in isolated parts of southern Wisconsin. Even areas with relatively deep frost depth have several inches of near-surface thaw, which will limit the impact of frozen ground on spring flood risk.
Valid March 9, 2022. Click here for the latest soil moisture information from the Climate Prediction Center.
River streamflow across the area ranges from near average to above average. Streamflow has generally decreased across the area since the last outlook, and will have only a limited impact on spring flood risk.
River ice spotters, river gauges, and satellite imagery indicates that area rivers are generally ice free. There is little-to-no risk of additional ice jam flooding this spring.
Valid March 9, 2022. Graphics update daily. Click here for the latest streamflow conditions from the USGS. Click here for the latest river ice spotter reports.
The long term (next couple months) outlook from the Climate Prediction Center indicates generally near average temperatures favored during March. The outlook indicates above average precipitation is slightly favored for March, especially in northwest Indiana.
Although snow cover, soil moisture, and recent river levels can provide some indication of the relative risk of spring flooding, any weather system that produces heavy rainfall could cause flooding. Spring flood outlooks are not able to assess the risk of flooding due to heavy rainfall more than a week or so in advance.
Relative flood risk for river forecast locations can be viewed on the Advanced Hydrologic Prediction Service (AHPS) page for our area.
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