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POSITION STATEMENT DRAFT

U.S. Flood Risk Management

GSA members are invited to submit comments and suggestions States, climate change is already altering the frequency, intensity,
regarding the following Position Statement draft by 15 June. Go to type, and seasonality of intense precipitation events and contribut-
https://www.geosociety.org/PositionStatements to learn more ing to sea-level rise. Combined with increases in impervious
and submit comments. cover, modifications to river floodways and shorelines, and devel-
opment of flood-prone land, many communities are experiencing
POSITION SUMMARY flood damages and risk greater than current assessments.
Across the United States and worldwide, flooding is the deadli- Not all flood risks are shown on flood maps. In urban areas, for
est and most costly natural disaster. The rising costs of flooding example, intense rainfall combined with inadequate storm-water
largely result from continued development of flood-prone land and drainage can cause widespread damage [8]. Behind levees, there
modifications to river and coastal systems, amplified by climate exists the “residual risk” of failure or levee overtopping even in
change. By most metrics, the U.S. is losing the fight to manage the communities with protection adequate for removal from FEMA’s
nation’s flood risk. Science provides tools for quantifying flood regulatory floodplain. Many residents in leveed areas are unaware
risk, estimating future conditions, balancing human uses of flood- of their residual risk [9]. Similarly, downstream of dams, residual
plains with ecosystem services, and identifying effective mitiga- risk is not universally mapped nor widely publicized.
tion strategies. The Geological Society of America recommends River and flood science are fundamentally geological sciences.
policies that move the U.S. toward long-term resilience, focusing Geoscientists collect data on the characteristics and causes of
on pathways toward sustainable floodplain management and flooding using field-based methods, modeling, and remote sens-
flood-risk reduction. ing. More broadly, geoscientists bring unique perspectives critical
to understanding, predicting, and mitigating flood hazards, includ-
RATIONALE ing how nature functions over long time scales and the variability
Flooding—including the inundation of inland waterways, and dynamics of natural systems. For example, paleoflood and
coasts, and urban areas—ranks among the costliest and most paleoclimate records supplement short instrumental records,
frequent type of natural disaster in the U.S. and worldwide. The better predict extreme events, and help to parse out natural and
economic consequences of flooding are growing rapidly, with human-caused shifts in flood hazard [10–12].
floods causing hundreds of billions of dollars in losses in the last
decade alone [1], displacing communities, and damaging liveli- CONCLUSIONS AND RECOMMENDATIONS
hoods. The rising economic and humanitarian costs of flooding The U.S. has experienced more than 250 weather- and climate-
are largely the result of continued development in watersheds and related disasters since 1980, with damages of $1 billion or more
floodplains and other modifications to river and coastal systems, (adjusted for inflation), and flooding contributing to nearly 70% of
amplified by climate change [2]. these events [13]. By most metrics, the U.S. is losing, not winning,
Responsibility for managing flood risks across the U.S. spans the fight to manage the nation’s flood risk. But tools are available
every level of government (federal, state, local, tribal, territorial) to chart a more sustainable path for the future. Science provides
and involves individuals, businesses, and other community stake- the best possible basis for estimating future conditions, informing
holders. Under the National Flood Insurance Program (NFIP), the hazard assessment, balancing human uses of floodplains with eco-
federal government underwrites insurance for more than 22,000 system services, and identifying effective mitigation strategies
participating communities in exchange for community adoption against future damages. Key recommendations are outlined below.
and enforcement of baseline land-use and construction require-
ments intended to mitigate losses associated with the base flood • Move U.S. flood policy toward long-term sustainability,
(1% annual chance or 100-year flood). As of September 2019, focusing on pathways to flood-risk reduction and resilience:
52% of NFIP participating communities have recognized the need Every disaster provides a window of opportunity to rebuild bet-
to go beyond the NFIP minimum standards, adopting more strin- ter. In the face of spiraling losses from flood damages, communities
gent requirements. Model building codes and standards [e.g., 3] across the U.S. and worldwide seek solutions to increase their resil-
require most buildings to be elevated above the NFIP minimum. ience—the ability to withstand a shock with minimal degradation
While individual federal agencies have adopted higher standards and restore function in a reasonable amount of time. Specific poli-
for planning and projects (e.g., [4]) or as conditions for financial cies, programs, and resources are needed that move away from
assistance (e.g., [5]), the base flood currently remains the mini- rebuilding “just in time for the next disaster” and toward mitigating,
mum federal flood standard nationwide. protecting, and adapting to reduce losses long term, improve eco-
Most current assessments of flood hazard assume that recent system services, and foster community safety and resilience.
conditions are representative of the future (i.e., flooding is “sta-
tionary”), but geoscientists have repeatedly demonstrated that • Invest in basic river and flood data and research:
flood hazard is highly sensitive to climatic, geomorphic, and Flood-risk management and investment decisions, involving
human-driven change and thus non-stationary [6–7]. In the United billions, and ultimately trillions of dollars, should be based on

58 GSA Today | May 2020