Winter Flooding: Every region in the United
States is at risk for winter flooding. While many people focus
primarily on ice and snow during this time of year, it is important to
also consider winter flood risks.
Ice Jams: Long
cold spells can cause the surface of rivers to freeze, leading to ice
jams. When a rise in the water level or a thaw breaks the ice into large
chunks, these chunks can become jammed at man made and natural
obstructions, resulting in severe flooding.
Snowmelt: A
sudden thaw can produce large amounts of runoff in a short period of
time. Because the ground is hard and frozen, water cannot be reabsorbed.
The water then runs off the surface and flows into lakes, streams, and
rivers, at faster rate causing excess water to spill over their banks.
Log/Debris Jams
Rivers and streams can carry many things downstream. From trees and
vegetation to sediment. While much of this stream load is part of the
natural riverine function, these items and this load can a/so be
dramatically increased during flooding events. Floating objects and
debris can be very dangerous and can cause damage, but this debris and
sediment can a/so begin to deposit and begin accumulating in areas. This
accumulation can change channel paths, depths, and compromise urbanized
infrastructure.