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| # Floods                                                              |
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| A [flood]{.underline} occurs any time a body of water rises to cover  |
| what is usually dry land.                                             |
|                                                                       |
| Floods are the most frequent and costly natural disasters in terms of |
| human hardship and economic loss. As much as 90 percent of the damage |
| related to all natural disasters (excluding droughts) is associated   |
| with flooding.                                                        |
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| Floods have many causes:                                              |
|                                                                       |
| -   [Heavy rain]{.underline}, which may occur over several days or as |
|     intense rainfall over a short period of time.                     |
|                                                                       |
| -   [Spring snowmelt]{.underline} or ice or debris jams that cause a  |
|     river or stream to overflow its banks and flood the surrounding   |
|     area.                                                             |
|                                                                       |
| -   [Dam and levee failure]{.underline}. While dam and levee failure  |
|     occurs relatively infrequently, it can be a risk, especially      |
|     following prolonged heavy rain, such as occurred throughout the   |
|     Midwest in 1993.                                                  |
|                                                                       |
| -   [Low absorption or no soil percolation]{.underline}. As land is   |
|     converted from fields or woodlands to roads and parking lots, it  |
|     loses its ability to absorb rainfall. Urbanization increases      |
|     runoff two to six times over what would occur on natural terrain. |
|     In areas with rocky geology, rainfall or snowmelt cannot be       |
|     absorbed. The result can be flash flooding with little or no      |
|     warning.                                                          |
|                                                                       |
| Each of these causes can be factored to several key elements.         |
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| -   [Rainfall intensity]{.underline} is the rate of rainfall (in      |
|     inches per hour).                                                 |
|                                                                       |
| -   [Duration]{.underline} is how long the rain lasts.                |
|                                                                       |
| -   [Topography]{.underline} is the overall configuration of the of   |
|     the Earth's surface, including natural and manmade features.      |
|                                                                       |
| -   [Soil conditions]{.underline} include the type of soil, the       |
|     amount of moisture in the soil, and the amount of soil relative   |
|     to the amount of rock.                                            |
|                                                                       |
| -   [Ground cover]{.underline} includes vegetation as well as manmade |
|     covers. Ground that includes larger amounts of vegetation can     |
|     also absorb greater amounts of water. Ground that is paved or has |
|     structures on it will cause runoff.                               |
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| # Floods (Continued)                                                  |
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| The reasons floods pose such a risk are that:                         |
|                                                                       |
| -   Heavy rainfall can exacerbate problems with runoff, absorption,   |
|     and flood-control measures.                                       |
|                                                                       |
| -   Riverine flooding can potentially inundate a city or downstream   |
|     areas when protection fails.                                      |
|                                                                       |
| ```{=html}                                                            |
| <!-- -->                                                              |
| ```                                                                   |
| -   In rocky areas, lack of absorption can cause flash flooding.      |
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| Every major drainage basin in the United States has a floodplain      |
| surrounding it. Two areas where inundation is very likely are:        |
|                                                                       |
| -   Along the Mississippi River.                                      |
|                                                                       |
| -   The central valley of California.                                 |
|                                                                       |
| Most areas of the United States are subject to some degree of         |
| flooding.                                                             |
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| Floodplain areas are widespread in the South Atlantic, the Gulf       |
| Coast, and the Missouri and Arkansas River basins.                    |
|                                                                       |
| Note that there are almost 4,000 communities that are at risk of      |
| flooding, and more than 100 million people are exposed.               |
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| The costs associated with flooding are increasing as more development |
| occurs in coastal areas and floodplains. Each year, flood losses and  |
| damages reach into the billions of dollars. During the 10-year period |
| from 1992 to 2001, floods cost, on average, \$4.1 billion annually.   |
| The long-term (1971 to 2000) annual average lives lost is 127 per     |
| year, primarily as a result of flash floods.                          |
|                                                                       |
| Floods are measured according to the height that the waters reach.    |
| Their magnitude is based on the chances that water levels will equal  |
| or exceed a certain point on a recurring basis. Intervals of          |
| probability are classified into [hazard zones]{.underline}.           |
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| # Floods (Continued)                                                  |
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| ## Flood Preparedness                                                 |
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| It is important to:                                                   |
|                                                                       |
| -   [Know the flood risk in the area]{.underline}, including the      |
|     elevation above flood stage and the history of flooding in the    |
|     area.                                                             |
|                                                                       |
| -   [Prepare a flood evacuation plan]{.underline}, and practice the   |
|     route. Be aware of which roads become flooded and which remain    |
|     passable. The entire family should know where to go if they have  |
|     to evacuate.                                                      |
|                                                                       |
| -   [Obtain flood insurance]{.underline} if living in a floodplain    |
|     (Special Flood Hazard Area). [Homeowner's policies do not cover   |
|     flooding]{.underline}! Check with the city or county government   |
|     to review the Flood Insurance Rate Maps (FIRMs). Then, check with |
|     an insurance agent to obtain coverage under the National Flood    |
|     Insurance Program (NFIP).                                         |
|                                                                       |
| -   [Keep important documents in a water-proof box]{.underline}. Most |
|     documents can be replaced, but some are more difficult to replace |
|     than others. Protecting them in a water- (and fire-) proof        |
|     container is the safest plan of action.                           |
|                                                                       |
| -   [Check emergency messages]{.underline} using a portable radio.    |
|     NWS and local officials update watches and warnings as necessary. |
|     Listen often for up-to-date information.                          |
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| The best way to protect your property from flood damage is to avoid   |
| building in a flood plain unless the home is elevated and other flood |
| protection measures are taken. If an existing home is in a            |
| floodplain, there are some steps that can help reduce potential       |
| damage.                                                               |
|                                                                       |
| -   [Elevate the furnace, water heater, and electric                  |
|     panel]{.underline} to at least one foot above the level of the    |
|     floodplain (also called the [Base Flood Elevation]{.underline}).  |
|     In some areas, elevating these appliances and utilities may mean  |
|     relocating them to a higher floor or even to the attic.           |
|                                                                       |
| -   [Move furniture and other items to a higher level]{.underline}.   |
|     Even if the main floor of the home is flood damaged, moving       |
|     furniture and other items to a higher level will reduce flood     |
|     losses.                                                           |
|                                                                       |
| ```{=html}                                                            |
| <!-- -->                                                              |
| ```                                                                   |
| -   [Install check valves]{.underline} in plumbing to prevent flood   |
|     water from backing up into the drains of the home.                |
|                                                                       |
| -   [Waterproof the basement floor and walls]{.underline} to prevent  |
|     seepage through cracks.                                           |
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+-----------------------------------------------------------------------+
| # Floods (Continued)                                                  |
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| In some cases, even these suggestions will not be enough to prevent   |
| serious damage from flooding. If you live in a floodplain, consult    |
| building professionals to see if they think they need more elaborate  |
| mitigation measures (such as elevation).                              |
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| If you must evacuate, you should:                                     |
|                                                                       |
| -   [Not walk, swim, or drive through flood waters]{.underline}.      |
|     Learn and practice driving the local flood evacuation routes.     |
|     They have been selected because they are safe and provide the     |
|     best means of escaping flood waters. Flood waters move swiftly    |
|     and may carry debris that can cause injuries. Remember that 24    |
|     inches of water can wash a car away and six inches of fast moving |
|     water can knock a person off his or her feet.                     |
|                                                                       |
| -   [Stay off bridges over fast-moving water]{.underline}.            |
|     Fast-moving water can wash bridges away without warning,          |
|     especially if the water contains heavy debris.                    |
+-----------------------------------------------------------------------+
| -   [Keep away from waterways]{.underline}. If you are driving and    |
|     come upon rapidly rising waters, turn around and find another     |
|     route. Move to higher ground away from rivers, streams, and       |
|     creeks.                                                           |
|                                                                       |
| -   [Heed barricades]{.underline}. Local responders place barricades  |
|     to warn of flooding ahead or to direct traffic safely out of the  |
|     area. [Never]{.underline} drive around barricades.                |
|                                                                       |
| -   [Avoid storm drains and irrigation ditches]{.underline}. During a |
|     flood, storm drains and irrigation ditches fill quickly with      |
|     fast-moving water. Walking in or near storm drains or irrigation  |
|     ditches is nearly a sure way to drown.                            |
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+-----------------------------------------------------------------------+
| # Floods (Continued)                                                  |
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| Precautions to follow after a flood.                                  |
+-----------------------------------------------------------------------+
| -   [Stay out of flooded areas]{.underline}. Flooded areas remain     |
|     unsafe. Entering a flooded area places you---and the individuals  |
|     who may need to rescue you---at risk.                             |
|                                                                       |
| -   [Reserve the telephone for emergencies only]{.underline}.         |
|     Telecommunication lines (both land line and cellular) will be     |
|     busy following a flood. A nonemergency call may prevent an        |
|     emergency call from getting through. It is best not to use the    |
|     phone unless it is necessary.                                     |
|                                                                       |
| -   [Avoid driving]{.underline}, except in emergencies. Reserve the   |
|     roads for those who must evacuate and for emergency vehicles.     |
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