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. | Near Average to Above Average | No effect/Increase |
Winter Temperatures |
Frost depth, the possibility that infiltration could be blocked by frozen ground. | Above Average | Decrease |
Spring Precipitation |
Amount of water headed to area rivers. | - | - |
Spring Temperatures | Rate of melt for snow cover. | - | - |
Valid March 8, 2023.
Modeled snow cover across area river basins was generally a few inches or less, which contains 0 inches to 0.25 inches of water equivalent. The deepest snow cover is in central Wisconsin. The majority of the area has no snow cover.
Valid March 8, 2023. Click here for the latest snow cover information.
Modeled soil moisture values across the area range from near average to much above average. Values are the lowest in northern Indiana, at the 30th to 70th percentile for this time of year. Values are highest in southern Wisconsin, exceeding the 95th percentile.
Frost depth is near 0 inches across area river basins.
Valid March 8, 2023. Click here for the latest soil moisture information from the Climate Prediction Center.
River streamflow across the area ranges from near average to much above average.
River ice spotters, river gauges, and satellite imagery indicate that little-to-no river ice exists on area rivers.
Valid March 8, 2023. 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 below average temperatures slightly favored through at least early to mid March. The outlook indicates above average precipitation is slightly favored by the end of 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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