Flood Risk Myths

Living in a low-risk area means that you do not have as much of a risk from flooding of rivers, lakes, or other bodies of water. However, homes in low-risk areas can still flood due to flash floods or water main breaks. A flash flood is a flood that can happen within minutes or hours of heavy rainfall, a dam or levee failure, or city drains overflowing.

Characteristics of a specific home, such as land sloping downward toward the base of the home, also can contribute to flood risk. Many of these home-specific risks can be corrected.

It also is important to understand that an extreme weather event can affect anyone. When Hurricane Harvey caused widespread flooding in the Houston area in 2017, more than half of the homes damaged were in areas classified as low risk, the Houston Chronicle reported. The same thing happened during a Houston-area flood in 2016.

The identification of flood risk is often based on maps the Federal Emergency Management Agency produces. These maps divide areas into different zones that are based on their level of risk.

These flood maps and their zones are largely developed based on known sources of flooding, such as rivers, streams, creeks, and lakes. However, those same maps are not able to measure the flood risk associated with a flash flooding event caused by torrential rainfall. Flash flooding can occur anywhere at any time, everywhere in the United States. Current flood maps also do not measure or predict the potential for increased risk in the future.

The Federal Emergency Management Agency (FEMA) designation of an area being at moderate risk for flooding is based on many factors. The risk calculation is based on known sources of flooding, such as rivers, streams, creeks, and lakes. It does not take into account the flood risk associated with a flash flooding event caused by torrential rainfall. Flash flooding can occur anywhere at any time.

In addition to flooding from rivers, streams, and lakes, flooding can result from poor drainage systems, snowmelt, and broken water mains.

A designation of “moderate risk” means the location’s estimated risk for major flooding in any given year is between 1 in 100 and 1 in 500. This risk may seem insignificant, but it is a real risk.

FEMA explains those 1-in-100 odds this way: Imagine a roulette wheel with 100 slots. During each spin, the ball has an equal chance of falling into each slot. Similarly, a “100-year flood” could happen in any year. It could and has happened two years in a row in the same area, or several times within 10 years. For example, the greater Houston area experienced a “500-year flood” in both 2015 and 2016 and a “1,000-year flood” in 2017.

It also is important to understand that the 1-in-500 risk refers to the chance of only the most severe flooding. Lesser but still damaging flooding is more likely to occur. For a sense of the frequency, consider how often Iowa residents have dealt with flooding over the past three decades. A University of Iowa study found that major flooding has affected every Iowa county multiple times between 1988 and 2016. Many counties have experienced major flooding more than a dozen times.

Flood-related events such as hurricanes and severe storms accounted for more than 7 out of 10 presidential disaster declarations from 2008 to 2017, according to a Pew Charitable Trusts analysis of Federal Emergency Management Agency records. That study also found that major flooding has been more common in landlocked states — such as Arkansas, Iowa, Missouri, Nebraska, and Oklahoma — than on the coast.

Since 1958:

• The amount of precipitation falling during heavy rainstorms has increased by 27 percent in the Southeast, the Environmental Protection Agency (EPA) reported. That includes Arkansas.
• Average annual precipitation in most of the Midwest — which includes Iowa, Missouri, and Nebraska — has increased by 5 to 10 percent. Rainfall during the four wettest days of the year has increased by about 35 percent. The amount of water in most streams during the worst flood of the year has increased by more than 20 percent.
• The amount of rain falling during the wettest four days of the year has increased by about 15 percent in the Great Plains, which includes Oklahoma. Over the next several decades in Oklahoma, the amount of rainfall during the wettest days of the year is likely to continue to increase, according to the EPA.

As the U.S. Geological Survey explains it, the term “100-year flood” is misleading because it leads people to believe that it happens only once every 100 years. The truth is that an uncommonly big flood can happen any year.

The term “100-year flood” better describes the size of the flood than how often it might occur in a single 100-year period. In fact, there is a 1-in-100 chance that a flood this size will happen during any year. Perhaps a better term would be the “1-in-100 chance flood.”

It also is important to keep in mind that the 1-in-100 risk refers only to the chance of flooding that is close to the worst-case scenario. Lesser amounts of flooding can and do occur more often. In fact, the Federal Emergency Management Agency notes that the majority of floods consist of what some people refer to as 1-year, 5-year, or 10-year floods. These floods also can cause major damage.

That’s why it is best to be prepared for flooding every year.

The NFIP’s Preferred Risk Policy is a lower-cost flood insurance policy available from insurance companies in most moderate- and low-risk areas.

You do not want to leave your home and family unprotected. In the North and South Carolina counties impacted by Hurricane Florence in 2018, there are estimates that only 10 percent of households have flood insurance. That will make it more difficult for them to rebuild their homes and lives. As reported by The Washington Post, “A key issue with Hurricane Florence [in 2018] and Hurricane Harvey last year is that some of the worst flooding occurred inland, sometimes in areas that were not FEMA-designated flood hazard zones.”

It is important to remember that NFIP flood insurance is available for purchase only if your home is in a community that participates in the program. But more than 22,000 cities and counties across the country do participate, so flood insurance is widely available.

Even if your community is not an NFIP participant, you still might be able to buy flood insurance. That’s because private flood insurance is available in some communities. You can find more information on this in our guide to flood insurance.

There are many factors that influence the cost of flood insurance, such as flood risk, year of construction, type of building, number of floors, and the location and type of items you own. Talk to an insurance provider to understand the cost of insuring your home against flood damage.

As a renter, you might be able to buy flood insurance for less than $200 a year if you live in an area at low or moderate risk for flooding. Costs are higher if you are a homeowner or if you live in a high-risk area. Read our Renters’ Guide to Flood Insurance and Homeowners’ Guide to Flood Insurance for more information on the costs of plans.

If you live in a Special Flood Hazard Area, the amount of flood insurance coverage required by law is the lowest dollar amount of the following:

• The maximum amount of NFIP coverage available for the property type
• The outstanding principal balance of the loan
• The insurable value of the structure

For example, assume that the following numbers are true:

• The maximum amount of NFIP coverage available for your property type is $250,000.
• You still owe the mortgage company $160,000 for the loan you received to buy your home.
• The insurable value of the structure is $200,000.

This means that you must buy coverage of at least $160,000 for flood damage.

The waiting period exists because insurance companies would lose money if most people bought flood insurance policies right before a big storm that could cause flooding.

However, there are some situations in which the policy can go into effect in less than 30 days. These rare exceptions include the following:

• If you buy flood insurance within 13 months of your home’s location being newly designated as a Special Flood Hazard Area (high risk for flooding). In that situation, there is typically a one-day waiting period before your policy goes into effect.
• If you purchase flood insurance in connection with getting, increasing, extending, or renewing your mortgage loan. The flood insurance is effective as soon as you close on the loan.
• If you choose to increase flood insurance coverage when you renew your existing policy. There is no waiting period for the higher coverage, which begins on the renewal date.
• If the flooding that damaged your home is caused or worsened by wildfire-related conditions on federal lands. Your coverage may go into effect immediately if you purchased the insurance before the fire was contained or within 60 days of a government agency declaring that the fire is 100 percent contained. The Federal Emergency Management Agency makes this exception because the fire’s destruction of vegetation can make the ground unable to absorb water, resulting in increased flood risks.