Flood Safety

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Reading about the flood in San Antonio that took the life of 2 women, I realized that I hadn’t written an article about flood safety, other than discussing storm surges during hurricanes.  Yet floods count among the disasters most responsible for loss of human life, both during the event and from the effects of the aftermath.

The definition of a flood is an overflow of water that submerges land, which is normally dry.  Flooding may occur as an overflow of water from water bodies, such as a seacoast, river or lake, in which the water runs over or breaks levees, resulting in the escape of large amounts of water into populated areas. It may also occur due to an accumulation of rainwater on saturated ground.

Some floods develop slowly, while others (called “flash” floods), can develop in a very short time and affect areas where it wasn’t even raining.  As a result, it often catches the population downriver by surprise, causing severe damage and loss of life

There are several types of floods:

Areal

Floods can happen on flat or low-lying areas when the ground is saturated and water cannot run off quickly enough to stop accumulating. This may be followed by a river flood as water moves into local waterways. Floods related to rainfall can also occur if water falls on an impenetrable surface, such as concrete, asphalt paving or frozen ground, and cannot rapidly be absorbed into the ground.  In urban areas, it usually takes at least 1 inch (25 mm) of rainfall per hour to start significant ponding of water on impermeable surfaces.

Riverine

Floods happen in rivers when the flow rate exceeds the capacity of the river channel, particularly at bends in the waterway. These are some of the most dangerous, as people tend to live and work by rivers due to access to fertile soil, irrigation, and trade routes.

River flows may rise to floods levels at different rates, from a few minutes to several weeks, depending on channel width and the source of the increased flow.

Slow rising floods most commonly occur in large rivers, like the Mississippi, that have large catchment areas. The increase in flow may be the result of sustained rainfall, rapid snow melt, monsoons, or tropical storms.

Coastal

Flooding on the coast is commonly caused by a combination of sea tidal surges caused by winds and low barometric pressure. Coastal areas may be flooded by storm events, such as hurricanes, resulting in waves over-topping seawalls and levees.

johnstown-floodAftermath of dam collapse in Johnstown, Pennsylvania, 1889

Failures of infrastructure such as the collapse of a dam may cause catastrophic flooding, as in the
Johnstown, Pennsylvania event in 1889 that took 2,200 lives. Major flooding may also be caused by the effects of an earthquake or volcanic eruption. These events often occur at sea hundreds of miles from the area affected, but result in tidal wave floods called Tsunamis. The penetration of salt water causes widespread failure of fresh water delivery systems and may make farmland unusable, sometimes for many years.  More on tsunamis in a future article.

Flooding often causes a failure of the power grid. Once this happens, the aftermath
of the disaster may have more severe effects than the flood itself. These effects include loss of the water supply due to contamination by sewage. As a result, water-borne illness such as diarrheal disease may take a major toll on the population. Cholera and Typhoid are just some of the diarrheal/dysenteric diseases that may be life threatening. Other issues include the inability of aid to get to flooded areas and the inundation of farmland causing loss of entire crops.  Some industries may fail, leading to depression in the affected area. Once water and food shortage combine with the inability to receive help and/or make a living, economic collapse and civil unrest are likely to follow.

The scenario above is not purely hypothetical: Disasters related to flooding have sometimes caused millions of short- and long-term casualties. In both 1887 and 1931, major flooding of the Yangtze river in China ended up costing 1-2 and 3-4 million lives, respectively.  If you take out war, famine, and pandemics, flooding is, undeniably, the deadliest of human tragedies.

Most people have heard of hurricane or tornado watches and warnings, but the U.S. weather services also tries to warn the populace of flooding. A “flash flood watch” means that flash flooding is possible in the near future; a “flash flood warning” means that flooding is imminent in the area. Many people ignore these warnings at their own peril.

If you live in a low-lying area, especially near a dam or river, then you should heed warnings when they are given and be prepared to evacuate quickly. Rising flood waters could easily trap you in your home, and you don’t want to have to perch on your roof waiting for help.

Here are some flood safety tips:

Get Out Early

Make the decision to leave for higher ground before extensive ponding occurs.

Be Careful Walking Through Flowing Water

Drowning is the most common cause of death during a flood, especially a flash flood. Wilderness experts know that rapidly moving water can knock you off your feet even if not that deep.

Don’t Drive Through a Flooded Area

As many people drown in their cars as anywhere else. Cars stall and roads/bridges could easily be washed out. Try to figure out now if there is a “high road” to safety, before a flood occurs.

downed-power-lineBeware Of Downed Power Lines

Electrical current is easily conducted through water. Watch for downed power lines; you don’t have to touch them to be electrocuted, only step in the water they’re in.

Turn Off The Power

If you have reason to believe that water will get into your home, turn off the electricity. Don’t use appliances or motors that have gotten wet unless they have completely dried. You might have to take some apart to clean debris out of them.

Watch Out For Intruders

Critters that have been flooded out of their homes may seek shelter in yours. Snakes, raccoons, and other unfriendly creatures may decide your home is now their territory.  Human
intruders may also be interested in your property.

Look Before You Step

After a flood, watch where you step; there is debris everywhere. The floors of your home may be covered in mud, causing a slip-and-fall hazard.

Check for Gas Leaks

Don’t use candles, lanterns, stoves, or lighters unless you are sure that the gas has been turned off and the area has been well-ventilated.

Exhaust Fumes Can Kill!

Only use generators, camping stoves or charcoal grills outside. Their fumes can be deadly.

Clean Out Saturated Items Completely

Floodwaters are not clean! Don’t use floodwater as drinking water or to cook food unless you have thoroughly sterilized and filtered it. Make sure you have food storage in waterproof containers.

Floods are just one of the many natural disasters that can endanger your family.  Pay close attention to storm and flood warnings and you’ll have a head start on keeping them safe.

 

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