Warmer spring temperatures, while pleasant, can also be a danger in parts of the world, causing floods when large amounts of winter snow melts.
Flooding from snow can cause the top layer of ice on frozen rivers to break, sending water over the riverbanks and putting lives and property at risk. These ice jams can be a danger in the New England region of the United States, but they also have occurred in areas as disparate as Ohio, Alaska, and Austria.
Knowing that flooding from snowmelt, northeast ice melt and ice jam can happen motivates those in flood-prone areas to prepare and mitigate flooding from the snow.
What are Ice Jams?
Ice jams happen when rising temperatures melt snow. The runoff from the frozen snow combined with heavy spring rains causes rivers to overflow. Once this water hits a frozen river, it will break the top layer of ice on the river into large chunks.
These large ice slabs floating can jam narrow passages, causing flooding in the area and upriver. Once the ice jam breaks, it can cause flooding downstream as well.
What Conditions Lead to Ice Jams?
If you’re wondering just how snow can cause rivers to flood, spring rains and higher temperatures can show you. The conditions that lead to ice jams happen over months, starting with heavy winter snowfalls and weather cold enough for rivers to freeze. This snow combined with spring rains and a rise in temperatures results in ice breaking loose from frozen rivers and waterways.
How Fast Do Ice Jams Form When Weather Changes Quickly?
Rapid rises in temperature bring on snowmelt, northeast ice melt and ice jams, so these could form within as little as three to five days. A slower rise in temperatures will melt snow more slowly and is less likely to break ice in frozen rivers.
Where Geographically are Ice Jams Most Commonly Occurring in the U.S.?
The New England states of Massachusetts, New Hampshire, Connecticut, Rhode Island, Maine, and Vermont are prone to flooding from ice jams and northeast snowmelt, but other regions of the United States can also experience conditions that can cause ice jam-related flooding. These include Michigan, Minnesota, Iowa, Ohio, Montana, North Dakota, and Alaska, among others.
Internationally, ice jam flooding occurs in the countries of eastern and central Europe, Scandinavia, and Canada, among other areas throughout the world.
What are the Effects of an Ice Jam?
Whether in the U.S. or overseas, ice jams can be more destructive and can occur more rapidly than open-water flooding. Americans suffer more than $125 million in losses due to ice jam damage each year. Aside from flooding, ice jams can interfere with shipping and can cause industrial facilities and hydroelectric plants to shut down.
Ice jam flooding can be mitigated by developing land-use plans, observing building codes in flood-prone areas, and offering incentives for hazard mitigation.
Purchasing flood insurance from the National Flood Insurance Program is another way homeowners can manage the risk of flooding from snowmelt and ice jams. Comprehensive coverage auto insurance will cover flood damage to your vehicle.
What is Snowmelt?
The snowmelt definition may seem obvious among weather terminology. High levels of moisture in soil prior to warmer temperatures melting snow can lead to snowmelt damage and flooding. While snow and precipitation have similar weights, snow becomes heavier when it is rained on, sending it downriver quickly.
Slight temperature differences can create very different situations. With 40-degree weather, an inch of rain will create just a 10th of an inch of additional water through snowmelt. At 50 degrees, about 2 to 4 inches of snow can melt in three days.
Snowmelt can be an aggravation or a hazard when it hits your garage, so make sure any garage drains are clear. A sump pump will help in removing water from melted snow.
What Conditions Lead to Heavy Amounts of Snowmelt?
Heavy snow on top of soil that is saturated with moisture will cause heavy amounts of snowmelt when unseasonably warm spring temperatures occur. Heavy spring rains also contribute to snowmelt flowing downriver to cause ice jams and flooding. These warning signs of heavy snowmelt shouldn’t be ignored.
What are the Effects of Snowmelt?
Each year, millions of dollars in damage is caused by flooding from snow. Shipping can be blocked by ice jams, and hydroelectric plants can be forced to shut down.
Ice dam formation can cause damage to homes or businesses by pulling shingles and even gutters down with the weight of rain-soaked snow and melting ice. Gutters that are full of snow and ice can create a dam that will hold large amounts of frozen precipitation until the ice dam breaks.
Where buildings are placed and how they are built can help mitigate snowmelt and ice jam flooding.
Flood-prone areas near river tributaries may be left undeveloped to increase the amount of water that can be absorbed by the soil.
How Do Snowmelt and Ice Jams Each Cause Flooding?
Snowmelt, through the volume of water released during melting, can cause flooding on its own, especially when spring rains speed water flow downriver. The volume of water is more than can be absorbed or accommodated by waterways, so the snowmelt spills over riverbanks and onto roads and property.
This snowmelt, when it hits a thawing river, can cause the top layer of ice on the river to break into large pieces. These pieces cause flooding when they clog small tributaries, blocking the flow of water and sending rivers over their banks.
What is the Best Response to Flooding from Snowmelt and Ice Jams?
After an ice jam has formed, it will clog waterways until the weather becomes warm enough to melt the chunks of ice or until boats are sent to create a jam break. In severe cases away from populated areas, ice jams can be blasted with dynamite to break them apart.
An ice jam can be prevented by drilling holes in the ice before a break or by dusting it with sand. In areas where ice jam and flooding from snow are common, flood barriers are often installed to hold waters back from property. Another option is to install cement pillars across a waterway to catch large pieces of ice before they do any damage.
If you live near a waterway and an ice jam might be imminent, monitor ice conditions and water levels as well as emergency management notifications.
Plan an escape route and pack an emergency kit including water, food, blankets, cell phone charger, and dry clothes. Be ready to move quickly, since ice jam floods can happen with little warning. Shut off water, natural gas, and appliances if flooding is predicted.
Once it is safe for you to return to your home, check for damages to your house and utilities. Take photos to document any damages and share them with your insurance company.
Boil water before drinking, washing, or cooking with it, and wear rubber gloves when removing debris.
Be Prepared for Snowmelt and Ice Jam Flooding
Knowing that snowmelt, and the ice jams that may follow, can cause catastrophic flooding, being aware of weather conditions including heavy snowfalls as well as unseasonably warm temperatures will help in protecting lives and property.
If your area is prone to snowmelt and ice jam flooding, be prepared to evacuate and mitigate your risks by adhering to building codes and by making sure your home and vehicles are properly insured against flood damage.
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