A benefit–cost analysis of floodplain land acquisition for US flood damage reduction


Flooding is the costliest form of natural disaster and impacts are expected to increase, in part, due to exposure of new development to flooding. However, these costs could be reduced through the acquisition and conservation of natural land in floodplains. Here we quantify the benefits and costs of reducing future flood damages in the United States by avoiding development in floodplains. We find that by 2070, cumulative avoided future flood damages exceed the costs of land acquisition for more than one-third of the unprotected natural lands in the 100-yr floodplain (areas with a 1% chance of flooding annually). Large areas have an even higher benefit–cost ratio: for 54,433 km2 of floodplain, avoided damages exceed land acquisition costs by a factor of at least five to one. Strategic conservation of floodplains would avoid unnecessarily increasing the economic and human costs of flooding while simultaneously providing multiple ecosystem services.

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Fig. 1: Costs to acquire unprotected natural floodplain areas and avoided future damages.
Fig. 2: The area of each additional return period acquisition zone that exceeds a certain BCR.
Fig. 3: Map of counties and associated BCRs.
Fig. 4: Maps of selected counties showing the 1% AEP floodplain, unprotected natural floodplain land and areas projected to be developed by 2070 within it, with grid lines spaced 0.5 degrees apart.

Map data ©2019 Google

Fig. 5: Costs to acquire unprotected natural floodplain areas and avoided future damages.

Data availability

Publicly available data are available online as follows: USGS National Elevation Dataset (http://www.ned.usgs.gov); HydroSHEDS (http://www.hydrosheds.org); USACE National Levee Database (http://www.nld.usace.army.mil); FEMA National Structure Inventory (http://data.femadata.com/FIMA/NSI_2010); MRLC National Land Cover Database (http://www.mrlc.gov/nlcd2011.php); USGS PADUS (http://gapanalysis.usgs.gov/padus); Theobold (2014) National Land-Use Dataset (http://csp-inc.org/public/NLUD2010_20140326.zip); EPA ICLUS scenarios (http://www.epa.gov/iclus); FAO Harmonized World Soil Database (http://www.fao.org/soils-portal/soil-survey/soil-maps-and-databases/harmonized-world-soil-database-v12/en); NOAA Intensity–Duration–Frequency curves (http://hdsc.nws.noaa.gov/hdsc/pfds); Elvidge et al. (2007) satellite luminosity data (http://www.ngdc.noaa.gov/eog); USDA Census of Agriculture (https://www.nass.usda.gov/Quick_Stats/index.php); and FHFA residential land price data (https://www.fhfa.gov/PolicyProgramsResearch/Research/Pages/wp1901.aspx). Data available for non-commercial academic research purposes are available as follows: flood hazard data can be acquired by contacting Christopher Sampson at Fathom (c.sampson@fathom.global); the hydraulic model can be found at LISFLOOD-FP (http://www.bristol.ac.uk/geography/research/hydrology/models/lisflood/downloads/); and Global Runoff Data Center discharge data can be found at http://www.bafg.de/GRDC/EN/01_GRDC/12_plcy/data_policy_node.html.


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This study was made possible by funding for the Nature Conservancy from the Kresge Foundation. P.B. was supported by a Leverhulme Research Fellowship and a Wolfson Research Merit Award from the Royal Society in the United Kingdom. We thank Philip Morefield for providing the ICLUS data. W.D.L contributed to this research in his personal capacity and not as part of his official duties at the Federal Housing Finance Agency. The analysis and conclusions are those of the authors alone and should not be represented or interpreted as conveying an official Federal Housing Finance Agency position, policy, analysis, opinion or endorsement. Any errors or omissions are the sole responsibility of the authors.

Author information

K.A.J., O.W., P.B., J.F., T.K., C.S. and A.S. designed the research. O.W., T.K., W.L., J.F. and K.A.J. completed the analyses. K.A.J. drafted the manuscript. All authors discussed the results and edited and commented on the manuscript.

Correspondence to Kris A. Johnson or Oliver E. J. Wing.

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Competing interests

K.A.J., J.F, T.K. and W.D.L. have no competing interests. O.W., P.B., C.S. and A.S. have an interest in or are employed by Fathom, a flood analytics company based in the United Kingdom.

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Supplementary Information

Supplementary Discussion, Methods, Figs. 1–5 and Tables 1–4.

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Johnson, K.A., Wing, O.E.J., Bates, P.D. et al. A benefit–cost analysis of floodplain land acquisition for US flood damage reduction. Nat Sustain 3, 56–62 (2020). https://doi.org/10.1038/s41893-019-0437-5

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