National Flood Safety Awareness Week

WEDNESDAY: FLOODS AND OTHER RELATED PHENOMENA

􀂃 Tropical Cyclone Inland Flooding – Heavy rainfall associated with hurricanes, typhoons, and tropical storms often causes more damage than high winds. As a matter of fact, nearly 60 percent of deaths associated with tropical cyclones in the U.S. since 1970 have been tied to inland flooding. Slow-moving storms can mean that heavy rains persist over one area, increasing the risk for flooding.

􀂃 Snowmelt Flooding – Snowpacks hold water, and when snow begins to melt, flooding can occur if the amount of snowmelt exceeds the capacity for soils and surface waters (rivers, lakes, streams) to store water. The Northeast, North Central and Western U.S. are particularly vulnerable to snowpack flooding, and eight of the most significant floods in the Twentieth Century were snowmelt related.

􀂃 Ice Jams – In northern parts of the U.S., ice covers many lakes and rivers during the winter. Sometimes, as ice breaks up and flows downstream, it can pile up at obstructed areas (such as narrow parts of the river or bridges) and cause upstream flooding. Montana and New York have reported the most ice jams, followed by Pennsylvania and Minnesota.

􀂃 Debris Flows – After a wildfire, debris flows (mud flows) can be a serious risk. When rain falls on burned slopes, water can pick up speed quickly, carrying soils and rocks along the way. Debris flows can damage bridges, roadways, culverts, and buildings, and can cause injuries and death.


􀂃 Flash Floods – Flash flooding usually happens when heavy, localized rainfall causes water to rise rapidly in a low lying area or stream. Flash floods can happen quickly and without warning, and are often the result of slowly moving thunderstorms or multiple storms occurring in a short amount of time.