Flooding Knows No Season
In much of the country, people think of spring through summer as the primary risk period for flooding, thanks to seasonal rainstorms and hurricanes. It’s logical to think, for example, that Alaska’s frigid temperatures mean scant chances for winter flooding. Yet, on December 1, 2020, heavy rains hit Southeast Alaska, causing nearly $30 million in damage.[1]
Flooding is a year-round threat, because many storm systems and other flooding risks are active throughout fall and winter. For starters, Atlantic hurricane season continues through November 30. According to the National Oceanic and Atmospheric Administration (NOAA), most tropical storm activity occurs between mid-August and mid-October, meaning hurricane risk is not yet behind us. It’s also important to realize that, while less common, hurricanes and tropical cyclones can and do occur off-season.[2]
Atmospheric rivers, huge bands of moist air that can bring extreme precipitation, are a frequent flooding risk in the West and Northwest. They are most common fall through spring, particularly from December through February. High-intensity atmospheric river storms can be as destructive as hurricanes. When they deliver torrential rain, flooding can occur almost immediately. When they bring heavy snowfall, flash flooding can follow when the snowpack melts quickly.
Nor’easters, which are most frequent and violent between September and April, can trigger storm surges affecting East Coast communities. They can also bring downpours that can move farther inland, and flash floods can happen throughout the winter, so long as temperatures are high enough.
Impermeable surfaces and parched soils can contribute to flooding even with lesser amounts of rain. This poses risks for communities with recent major development, desert areas, and regions experiencing significant drought.
Flood after fire is another serious threat, as charred soils and destroyed vegetation may create elevated flooding risk for five years or more following a fire. Moderate or heavy rain can quickly generate flash floods and mudflows in communities downstream from a burn scar.
Flooding can also result when ice jams cause streams or rivers to overflow. Heavy debris can cause waterways or stormwater drains to overflow any time of year.
Aging and inadequate flood control infrastructure also poses flood risk. Many dams and levees across the country are old and were not engineered for today’s more extreme storms, posing flash flood risk from structural failure or overflows.
The bottom line: Anywhere it can rain, it can flood … and any time it can rain, it can flood.
Remind clients and your community that there are many year-round flood risks, and flood insurance is the best way to protect the lives they’ve built from the financial effects of flood damage.
