Flood
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flood
a rising and overflowing of a body of water especially onto normally dry land
Floods are the nation's most common natural disaster. Flooding can happen in every state but not all floods are alike. A flood occurs when water overflows or inundates land that is normally dry. This can happen in a multitude of ways. Most floods develop slowly over an extended period time giving residents time to prepare or evacuate while others can occur quickly without any sign of rain. It's important to be prepared no matter where you live but it's especially important to be prepared f you are in a low-lying area near water or downstream from a damn.
Types of Flood
All floods are not the same and flooding can happen in a multitude of ways. The most common flooding is when rivers or streams overflow their banks due to an extended period of rain or after a warming trend has melted heavy snow. Along with excessive rain, a ruptured dam or levee or even an unfortunately placed beaver dam can overwhelm a river and create a flood. Even a small stream or dry creek bed can overflow if the conditions are right. Flash floods can occur quickly without any visible sign of rain. These often have a dangerous wall of roaring water that carries rock, mud and other debris. This wall can sweep away things in its path as large as an automobile. Flash floods can be extremely dangerous. Coastal flooding occurs when a large storm or tsunami causes the sea to surge inland. Flooding can also develop due to torrential rains from decaying hurricanes or other tropical systems as they push inland.
- Flood (commonly called river flood) - is a high flow or overflow of water from a river or similar body of water, occurring over a period of time too long to be considered a flash flood.
- Flash Floods - quick-rising floods usually occurring as the result of heavy rains over a short period of time, often only several hours or even less.
They can be can caused by winter or spring thaw or a damn break. The influx of water that flows is powerful enough to sweep vehicles, roll boulders, uproot trees, level buildings and even drag bridges off their piers.
- Coastal Flooding - occurs when strong onshore winds push water from an ocean, bay or inlet onto land.
Normally associated with tropical storms or hurricanes, they can also be associated with tsunamis and Nor'easters.
Frequent Causes of Flooding
Tropical Storms and Hurricanes
Hurricanes have a triple threat - high winds, soaking rain and flying debris They cause storm surges to coastal areas and can bring heavy rainfall which in turn causes flooding hundreds of miles inland. While all coastal areas are at risk, certain cities are particularly vulnerable and could have losses similar to or even greater than those caused by the 2005 hurricane, Katrina, in New Orleans and Mississippi.
A tropical storm is weaker than a hurricane but they can generate rainfall and flooding especially if it is a slow moving storm. In 2001, Tropical Storm Allison produced more than 30 inches of rainfall in Houston in just a few days, flooding over 70,000 houses and destroying 2,744 homes.
Spring Thaw
Each cubic foot of compacted snow contains gallons of water and once the snow melts, it can result in flooding of streams, rivers and lakes.
Heavy Rains
Many areas of the country are at heightened risk for flooding due to heavy rains in a short period of time. The Northwest is at high risk due to La Niña conditions, which include: snow melts, heavy rains, and recent wildfires. And the Northeast is at high risk due to heavy rains produced from Nor'easters. This excessive amount of rainfall can happen throughout the year, putting your property at risk.
West Coast Threats
The rainy season on the West Coast is from November to April. It brings heavy flooding and an increase flood risk. Flooding can happen at anytime. A string of large wildfires have dramatically changed the landscape and ground conditions. The fire-scorched land has a tendency to become mudflows under heavy rain. Experts predict it will be years before vegetation will return to stabilize the area. The West Coast also has thousands of miles of levees, which are meant to help protect homes and their land in case of a flood. However, levees can erode, weaken, or overtop when waters rise, often causing catastrophic results.
Levees & Dams
Levees are designed to protect against a certain level of flooding. Levees can decay over time and if they are maintained they can be overtopped or even fail during large floods.
Experience has shown that this can create more damage than if the levee wasn't there. Because of the escalating flood risks in areas with levees, especially in the mid-west, FEMA strongly recommends flood insurance for all homeowners in these areas.
Flash Floods
Flash floods are the #1 weather-related killer in the U.S. They can roll boulders, tear out trees, and destroy buildings and bridges. A flash flood, a rapid flooding of low-lying areas in less than six hours, is caused by intense rainfall from a thunderstorm or several thunderstorms. Flash floods can also occur from the collapse of a man-made structure or ice dam.
New Development
Construction and development can change the natural drainage and create brand new flood risks. That's because new buildings, parking lots, and roads mean less land to absorb excess precipitation from heavy rains, hurricanes, and tropical storms.
When the Floodwaters Recede
When the floodwaters finally receded, the affected areas are often blanketed in silt and mud and the area can be contaminated with hazardous materials.
Sharp debris, pesticides, fuel, along with untreated sewage present dangers that everyone needs to be aware of as they return home.
Potentially dangerous mold blooms can quickly overwhelm water-soaked structures. The residents of the flooded areas are often left without power and clean drinking water. Outbreaks of diseases like typhoid, hepatitis A, and cholera are common. Residents that are returning home should take the necessary precautions to remain healthy and safe.
Flood Destruction
Most flood destruction is attributed to our desire to live near coastlines and along rivers. Developers tend to backfill and build on wetlands that would normally act as a natural buffer to flooding. Many governments mandate that residents of flood-prone areas purchase flood insurance and build flood-resistant structures. Massive efforts are being made to mitigate and redirect the inevitable floods but as the residents of New Orlean's learned flood waters can be an incredibly destructive force.
Facts about Flooding
- Since 1900, floods have taken more than 10,000 lives in the United States alone.
- 66-percent of flood deaths occur in vehicles, and most happen when drivers make a single, fatal mistake trying to navigate through flood waters.
- Just 6 inches of rapidly moving flood water can knock a person down.
- A mere 2 feet of water can float a large vehicle even a bus.
- One-third of flooded roads and bridges are so damaged by water that any vehicle trying to cross stands only a 50% chance of making it to the other side.
- The great Mississippi River Flood of 1993 covered an area 500 miles long and 200 miles wide. More than 50,000 homes were damaged, and 12,000 miles of farmland were washed out.
- The Big Thompson Canyon (Colorado) Flood, which killed 140 people in 1976, proved a tragic illustration of a sobering statistic 95% of those killed in a flash flood try to outrun the waters along their path rather than climbing rocks or going uphill to higher grounds.