AUTHOR=Al Assi Ayat , Mostafiz Rubayet Bin , Friedland Carol J. , Rohli Robert V. , Rahim Md Adilur 

TITLE=Homeowner flood risk and risk reduction from home elevation between the limits of the 100- and 500-year floodplains

JOURNAL=Frontiers in Earth Science

VOLUME=11

YEAR=2023

URL=https://www.frontiersin.org/journals/earth-science/articles/10.3389/feart.2023.1051546

DOI=10.3389/feart.2023.1051546

ISSN=2296-6463

ABSTRACT=<p>Floods inflict significant damage even outside the 100-year floodplain. Thus, restricting flood risk analysis to the 100-year floodplain (Special Flood Hazard Area (SFHA) in the United States of America) is misleading. Flood risk outside the SFHA is often underestimated because of minimal flood-related insurance requirements and regulations and sparse flood depth data. This study proposes a systematic approach to predict flood risk for a single-family home using average annual loss (AAL) in the shaded X Zone–the area immediately outside the SFHA (i.e., the 500-year floodplain), which lies between the limits of the 1.0- and 0.2-percent annual flood probability. To further inform flood mitigation strategy, annual flood risk reduction with additional elevation above an initial first-floor height (<inline-formula id="inf1"><mml:math id="m1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mrow><mml:mi>F</mml:mi><mml:mi>F</mml:mi><mml:mi>H</mml:mi></mml:mrow><mml:mn>0</mml:mn></mml:msub></mml:mrow></mml:math></inline-formula>) is estimated. The proposed approach generates synthetic flood parameters, quantifies AAL for a hypothetical slab-on–grade, single-family home with varying attributes and scenarios above the slab-on-grade elevation, and compares flood risk for two areas using the synthetic flood parameters vs existing spatial interpolation-estimated flood parameters. Results reveal a median AAL in the shaded X Zone of 0.13 and 0.17 percent of replacement cost value (<inline-formula id="inf2"><mml:math id="m2" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>V</mml:mi><mml:mi>R</mml:mi></mml:msub></mml:mrow></mml:math></inline-formula>) for a one-story, single-family home without and with basement, respectively, at <inline-formula id="inf3"><mml:math id="m3" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mrow><mml:mi>F</mml:mi><mml:mi>F</mml:mi><mml:mi>H</mml:mi></mml:mrow><mml:mn>0</mml:mn></mml:msub></mml:mrow></mml:math></inline-formula> and 500-year flood depth &lt;1 foot. Elevating homes one and four feet above <inline-formula id="inf4"><mml:math id="m4" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mrow><mml:mi>F</mml:mi><mml:mi>F</mml:mi><mml:mi>H</mml:mi></mml:mrow><mml:mn>0</mml:mn></mml:msub></mml:mrow></mml:math></inline-formula> substantially mitigates this risk, generating savings of 0.07–0.18 and 0.09–0.23 percent of <inline-formula id="inf5"><mml:math id="m5" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>V</mml:mi><mml:mi>R</mml:mi></mml:msub></mml:mrow></mml:math></inline-formula> for a one-story, single-family home without and with basement, respectively. These results enhance understanding of flood risk and the benefits of elevating homes above <inline-formula id="inf6"><mml:math id="m6" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mrow><mml:mi>F</mml:mi><mml:mi>F</mml:mi><mml:mi>H</mml:mi></mml:mrow><mml:mn>0</mml:mn></mml:msub></mml:mrow></mml:math></inline-formula> in the shaded X Zone.</p>