February 2025 Edition

Agriculture & Natural Resources
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Winter and Spring River Flooding
Dean Acheson, a politician and lawyer, once said, “You can’t argue with a river - it is going to flow. You can dam it up, put it to useful purposes, you can deflect it, but you can’t argue with it.” The further we head into the winter, rivers seem to become more “argumentative” as they swell and flood. So why do we typically see most of our river flooding in the winter and early spring here in Kentucky? There are several factors.

During the winter months, the lack of vegetation, and the cold and occasionally frozen ground make it unable to absorb as much water. This creates more runoff into area creeks and streams, and eventually into the riverways.
The winter also tends to bring more amplified/stronger storm systems, which can result in more widespread significant precipitation. Typically in the spring and summertime, heavy precipitation associated with thunderstorms is more localized, while in the winter, it can cover vast expanses, leading to more impacts on the rivers.
Jam - it isn’t just for bread! Ice floating down the river can get backed up and dam up the waterway, known as an ice jam. The water behind the jam will rise and flow out of the banks, leading to areal flooding. The jam will eventually release, sending large chunks of ice and pent up water down the river, leading to potential flooding and damage downstream. Ice jams typically occur farther north than Kentucky, where rivers are more likely to freeze over.
As we head into the early spring months, or even a warm spell after a large winter storm, rising temperatures begin to melt away at the snow and ice on the ground. If too much ice or snow melts at once, this creates a large amount of runoff into the waterways, leading to significant river rises. This gets amplified when heavy rains also fall on top of the melting ice and snow.
According to FEMA and the National Inventory of Dams (2007), there are more than 80,000 dams in the United States. Dam failure or levee breaches can occur with little warning. Failures and breaches can be slow, lasting from days to weeks, or can be very abrupt with profound, sudden impacts to locations downstream. Causes of dam failure vary from natural causes such as prolonged rainfall, landslides, earthquakes, or erosion -to human causes such as improper maintenance and design, and negligent operation.
In the last few months, the NWS launched nationwide Flood Inundation Mapping (FIM). These maps are available online and help decision makers, such as Emergency Management, show the extent of inundation at different river stage levels (both static and forecasted). FIM will help to better message the impacts for flooding events, with increasing accuracy and capability moving forward.