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States with the most homes at risk of coastal flooding

  • States with the most homes at risk of coastal flooding

    While it’s difficult to attribute any specific storm to climate change, scientists agree that overall, extreme weather events are increasing in frequency and intensity because of the Earth’s changing climate. There have already been five category-5 hurricanes in the Atlantic Ocean in the past four hurricane seasons, and many others that were category 4 or 3 by the time they hit land in the United States.

    This increase in extreme weather events has caused flooding, especially in U.S. coastal states. However, despite flooding increases, building in some states is increasing in flood-prone areas. According to a joint report conducted in July 2019 by Climate Central and Zillow, new homes are being built in Connecticut 3.5 times faster in risk zones than in safer locations. In Delaware, Mississippi, New Jersey, and Rhode Island, the rate is twice as fast as other, more safe areas. Also, Florida, New Jersey, and North Carolina combined have built more than 9,000 homes in risk zones since 2010.

    The report, “Ocean at the Door: New Homes and the Rising Sea,” determined which states have the most homes at risk of coastal flooding using the metric of how many homes they would build in a 10-year flood zone by 2050. A 10-year flood zone refers to an area that has a 10% chance of flooding annually. These zones were determined based on a moderate greenhouse-gas emissions scenario with a Representative Concentration Pathway of 4.5, meaning that, under this projection, emissions would peak in 2040 and then decline.

    Using data from the report, Stacker has ranked 24 states impacted by America's coastlines, plus Washington D.C., and ranked them based on how many homes each will have in a 10-year flood zone by 2050. This list also includes information about which states are building the most homes in these risky areas, which are trying to curb new building, and which already have experienced unprecedented flooding.

    To determine the states with the most homes at risk of coastal flooding, Stacker worked with the Climate Central and Zillow joint July 2019 report, “Ocean at the Door: New Homes and the Rising Sea.” Climate Central investigated 24 states and the District of Columbia, all located on or close to America's coastlines, to determine how many homes would be located in 10-year flood zones in 2050 under the Representative Concentration Pathway of 4.5, a moderate greenhouse emissions scenario. Then, Zillow attached property values to these homes. The states are ranked here based on how many total homes will be at risk. This story also includes new homes that will be located in 10-year flood zones; new homes refers to dwellings built between 2010 and 2017 for most states, or between 2010 and 2016 in Alabama, Florida, Mississippi, and New York. Ten-year flood zones refer to areas that have a 10% chance of flooding annually.

    Read on to discover which states have the most homes threatened by coastal flood risk.

    You may also like: 50 common weather terms, explained

  • #25. District of Columbia

    - Homes in 10-year flood zones by 2050: 8 (0% of all homes, $7 million in property value)
    - Homes built since 2010 in flood zones by 2050: data not available
    - Most threatened counties:
    --- District of Columbia (8 homes threatened, 0% of all homes in the county, $7 million in property value)

    Of the United States’ 25 coastal states or areas, Washington D.C. has the fewest homes in danger of flooding. By 2050, it is estimated that only eight homes will be in 10-year flood zones, totaling $7 million in real estate value. That doesn’t mean that the District is safe. D.C. is still vulnerable to three types of flooding: interior, which is when drainage systems can’t keep up with heavy rainfall, riverine, and tidal, the latter two caused by rivers but from different directions.

  • #24. Alaska

    - Homes in 10-year flood zones by 2050: 23 (0.01% of all homes, $16 million in property value)
    - Homes built since 2010 in flood zones by 2050: data not available
    - Most threatened counties:
    --- Juneau City and Borough (23 homes threatened, 0.26% of all homes in the county, $16 million in property value)

    In Alaska, 23 of the state’s homes will be in 10-year flood zones by 2050. The most threatened area is Juneau (city and borough) where just over 32,000 people live. The 23 homes under threat make up 0.26% of Juneau’s total homes. In early October 2019, Juneau experienced heavy rains, which caused mudslides and flooding.

  • #23. Pennsylvania

    - Homes in 10-year flood zones by 2050: 1,221 (0.03% of all homes, $332 million in property value)
    - Homes built since 2010 in flood zones by 2050: 0
    - Most threatened counties:
    --- Philadelphia County (958 homes threatened, 0.21% of all homes in the county, $288 million in property value)
    --- Delaware County (146 homes threatened, 0.08% of all homes, $17 million in property value)
    --- Bucks County (117 homes threatened, 0.06% of all homes, $27 million in property value)

    The county most at risk in Pennsylvania is Philadelphia County, where nearly 1,000 homes will be threatened, representing $288 million in property value. Already, $90 million worth of property is destroyed each year by floods in the state, and a big storm in Philadelphia in July gave residents a preview of what could be to come.

    Note: Although Pennsylvania is not a coastal state, it is in danger of coastal flooding because the tidal influence of the Delaware River extends through densely populated areas, including Philadelphia. Climate Central and Zillow included it in their study as a result.

  • #22. Hawaii

    - Homes in 10-year flood zones by 2050: 1,701 (0.41% of all homes, $1.3 billion in property value)
    - Homes built since 2010 in flood zones by 2050: 16 (0.26% of all new homes, $9 million in property value)
    - Most threatened counties:
    --- Maui County (1,187 homes threatened, 2.21% of all homes in the county, $531 million in property value)
    --- Honolulu County (359 homes threatened, 0.13% of all homes, $585 million in property value)
    --- Kauai County (126 homes threatened, 0.47% of all homes, $160 million in property value)

    Hawaii’s most threatened counties are Maui, Honolulu, and Kauai: This can be a problem for homeowners in hurricane zones, who might find that their insurance won’t fully cover their losses. “Unlike most homeowners’ insurance in other states, policies in Hawaii generally exclude hurricanes from coverage,” according to CNBC personal finance writer Sarah O’Brien.

  • #21. Oregon

    - Homes in 10-year flood zones by 2050: 2,011 (0.15% of all homes, $418 million in property value)
    - Homes built since 2010 in flood zones by 2050: 14 (0.08% of all new homes, $3 million in property value)
    - Most threatened counties:
    --- Clatsop County (1,307 homes threatened, 6.99% of all homes in the county, $266 million in property value)
    --- Coos County (233 homes threatened, 1.04% of all homes, $39 million in property value)
    --- Lincoln County (219 homes threatened, 0.81% of all homes, $43 million in property value)

    The counties with the most homes at risk in Oregon are Clatsop, Coos, and Lincoln. Already, Coos County had to declare a state of local emergency in February after snow, along with 5 to 7 inches of rain, hit the western side of the state. Coos County will have 233 homes in a 10-year flood zone in 2050.

  • #20. Maine

    - Homes in 10-year flood zones by 2050: 2,107 (0.54% of all homes, $1.1 billion in property value)
    - Homes built since 2010 in flood zones by 2050: 72 (0.71% of all new homes, $62 million in property value)
    - Most threatened counties:
    --- York County (1,657 homes threatened, 2% of all homes in the county, $946 million in property value)
    --- Cumberland County (144 homes threatened, 0.15% of all homes, $93 million in property value)
    --- Sagadahoc County (143 homes threatened, 1.11% of all homes, $45 million in property value)

    Maine will have 2,107 homes in a 10-year flood zone by 2050, 72 of which were built in the past decade. These homes represent $1.1 billion in property value. A study in January 2019 by Columbia University and the First Street Foundation showed that between 2005 and 2017, $69.9 million was lost in Maine because of flooding.

  • #19. Rhode Island

    - Homes in 10-year flood zones by 2050: 2,209 (0.70% of all homes, $1.4 billion in property value)
    - Homes built since 2010 in flood zones by 2050: 78 (1.56% of all new homes, $74 million in property value)
    - Most threatened counties:
    --- Washington County (1,144 homes threatened, 2.11% of all homes in the county, $844 million in property value)
    --- Newport County (486 homes threatened, 1.52% of all homes, $307 million in property value)
    --- Bristol County (322 homes threatened, 1.98% of all homes, $147 million in property value)

    By 2050, Rhode Island’s Washington County will have 1,144 homes, 2.11% of the state’s total, in a 10-year flood zone, totaling $1.4 billion in property value. However, while scientists have seen the writing on the wall, the real estate industry has not. Lint Barrage, an assistant professor of economics and environmental studies at Brown University found that people with homes in federally designated flood zones underestimate their risk of being flooded. Of the aforementioned 1,144 homes, 78 were built between 2010 and 2017.

  • #18. New Hampshire

    - Homes in 10-year flood zones by 2050: 2,767 (0.55% of all homes, $935 million in property value)
    - Homes built since 2010 in flood zones by 2050: 50 (0.38% of all new homes, $39 million in property value)
    - Most threatened counties:
    --- Rockingham County (2,754 homes threatened, 2.45% of all homes in the county, $929 million in property value)
    --- Strafford County (13 homes threatened, 0.03% of all homes, $6 million in property value)

    New Hampshire is projected to have 2,767 homes in a 10-year flood zone by 2050. This makes up 0.55% of all homes in the state and $935 million in property value. Of these, 50 have been built since 2010, representing 0.38% of all new homes built and $39 million in property value. The state is trying to raise citizen awareness about flooding dangers by creating New Hampshire Flood Safety Awareness Week, which took place in March this year. The website links to resources about flood preparation and flood insurance.

  • #17. Mississippi

    - Homes in 10-year flood zones by 2050: 4,617 (0.54% of all homes, $877 million in property value)
    - Homes built since 2010 in flood zones by 2050: 333 (1.32% of all new homes, $84 million in property value)
    - Most threatened counties:
    --- Hancock County (2,158 homes threatened, 11.7% of all homes in the county, $373 million in property value)
    --- Jackson County (1,340 homes threatened, 2.57% of all homes, $239 million in property value)
    --- Harrison County (1,119 homes threatened, 1.63% of all homes, $266 million in property value)

    Of the southern states, Mississippi, with a population of nearly 3 million, will have the fewest homes in a 10-year flood zone by 2050, with 4,617 homes (0.54% of the state’s total) and $877 million in property value under threat. All told, 333 of these dwellings have been built since 2010, which is 1.32% of all new homes and $84 million in property value. The state already experienced a loss in real estate values of over $260 million between 2005 and 2017, according to a First Street Foundation study.

  • #16. Alabama

    - Homes in 10-year flood zones by 2050: 7,290 (0.46% of all homes, $2.8 billion in property value)
    - Homes built since 2010 in flood zones by 2050: 167 (0.36% of all new homes, $89 million in property value)
    - Most threatened counties:
    --- Baldwin County (5,237 homes threatened, 5.29% of all homes in the county, $2.2 billion in property value)
    --- Mobile County (2,053 homes threatened, 1.49% of all homes, $581 million in property value)
    --- Clarke County (homes threatened, 0% of all homes, $ million in property value)

    Alabama will have 7,290 homes, 0.46% of the state’s total, in a 10-year flood zone by 2050, making up $2.8 billion in property value. Of these over 7,000 properties, 167 have been built since 2010. The two most threatened counties are Baldwin and Mobile, which in September 2019 experienced flash flooding and sewage overflows.

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