Snowmelt Flooding
In terms of area, property damage and deaths, eight of the most significant floods in the 20th century were snowmelt-related. Several factors contribute to snowmelt flooding:
- High soil moisture content: Soil that is saturated with water in late fall may not have time to drain and dry out before it freezes, resulting in deep ground frost and frozen soil.
- Ground frost or frozen soil: Deep frozen soil or ground frost prevents snowmelt from soaking into the soil.
- Heavy winter snow: More snow means that more water will be released when snow melts. When snow melts very rapidly, the risk for flooding increases.
- Rain: Heavy rain during the snowmelt period can increase the risk for flooding. Rainfall can warm snowpack, causing it to melt more quickly that it otherwise would.
- Ice jams: When river ice breaks up and flows downstream, it may pile up at narrow passes or near bridges and dams. Ice jams act like dams and can result in river flooding, especially when water is running high due to snowmelt.
Viewer Tip: There are simple steps you can take to protect your home from damage related to snowmelt flooding:
- Shovel snow away from doors and your home foundation. Remove snow from window wells.
- When snow begins to melt, water may still seep into some basements. Protect your belongings by clearing basement floors and moving shelves and furniture away from basement walls.
- Look for moisture coming through ceilings. This may indicate that ice dams are blocking gutters.
- Don’t climb on your roof or high areas of your home to clear ice and snow away or clean gutters. Stay safe by asking a professional contractor to do the job.
Season: Winter
(Sources: NOAA National Weather Service. Flood Safety: Snowmelt Flooding. http://www.floodsafety.noaa.gov/snowmelt.shtml; Institute for Business and Home Safety. Disaster Safety Blog: Winter Storm Damage Can be Prevented. http://disastersafety.typepad.com/disaster_safety_blog/)
