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1. Recognizing flood exposure inequities across flood frequencies

   https://doi.org/10.1016/j.ancene.2023.100371  

   Selsor, Haley; Bledsoe, Brian P.; Lammers, Roderick (June 2023, Anthropocene)

   Urban flooding is a growing threat due to land use and climate change. Vulnerable populations tend to have greater exposure to flooding as a result of historical societal and institutional processes. Most flood vulnerability studies focus on a single large flood, neglecting the impact of small, frequent floods. Therefore, there is a need to investigate inequitable flood exposure across a range of event magnitudes and frequencies. To explore this question, we develop a novel score of inequitable flood risk by defining risk as a function of frequency, exposure, and vulnerability. This analysis combines high-resolution, parcel-scale compounded fluvial and pluvial flood data with census data at the census block group scale. We focus on six census tracts within Athens-Clarke County, Georgia that are highly developed with diverse populations. We define vulnerable populations as non-Hispanic Black, Hispanic, and households under the poverty level and use dasymetric mapping techniques to calculate the over-representation of these populations in flood zones. Inequitable risks at each census tract (approximately neighborhood scale) were estimated for multiple (e.g., 5-, 10-, 20-, 50-, and 100-year) flood return periods. Results show that the relatively greatest flood risk inequities occur for the 10-year flood and not at the largest event. We also found that the size of inequity is dynamic, depending on the flood magnitude. Therefore, addressing a range of events including smaller, more frequent floods can increase equity and reveal opportunities that may be missed if only one event is considered. 

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2. Divergent priorities in flood adaptation

   https://doi.org/10.1088/2752-5295/adecba  

   Niemann-Morris, Jennifer; Siders, AR; Hino, Miyuki; Kraan, Carolien; Agopian, Armen; Samoray, Christopher; Mach, Katharine_J (July 2025, Environmental Research: Climate)

   Abstract Actions to reduce flood risk often appear to run counter to other societal goals, and resolving these conflicts is important as flood adaptations increasingly transform settlements and societies. Here, we evaluate the tensions between flood risk reduction and other priorities in the context of voluntary buyouts of flood-prone properties in the United States—a controversial flood response to restore land to open space, but with trade-offs. We apply a nation-wide systematic review (133 literature references, 1983–2023) to assess goals stated for buyouts and combine it with a comprehensive media analysis (281 media articles, 1993–2023) to compare those goals to the experiences and results perceived by buyout implementers, residents, and other practitioner groups. Across the systematic-review literature, flood risk reduction dominates goals expressed for buyouts (62.6% of documented goals), and local government predominates in this goal setting (61.7% of documented goals). However, involved and affected actors—especially residents—perceive outcomes beyond flood risk reduction, most notably in the experiences of buyout implementation itself (35.5% of documented resident perceptions) and in results impacting social and economic priorities (49.5%). Despite the difficulties of buyouts, the systematic-review literature largely reflects positive perceived outcomes (79.4% of outcome sentiments, weighing each buyout location equally), but nonprofit organizations and residents perceive largely negative outcomes. Media coverage related to buyouts is more negative than positive but with improved sentiments through time. Our findings point to the importance of designing, implementing, and evaluating flood adaptations not just as flood control measures given their consequences for other societal objectives. The uneven documentation on buyouts also implies opportunities to learn from contexts where buyouts have been integrated into everyday life with little fanfare, through mechanisms either novel or perhaps routine, yielding insights into making ambitious climate adaptations a common, more ordinary, and increasingly imperative occurrence. 

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3. Process-based flood frequency analysis in an agricultural watershed exhibiting nonstationary flood seasonality

   https://doi.org/10.5194/hess-23-2225-2019  

   Yu, Guo; Wright, Daniel B.; Zhu, Zhihua; Smith, Cassia; Holman, Kathleen D. (January 2019, Hydrology and Earth System Sciences)

   Abstract. Floods are the product of complex interactions among processes includingprecipitation, soil moisture, and watershed morphology. Conventional floodfrequency analysis (FFA) methods such as design storms and discharge-basedstatistical methods offer few insights into these process interactions andhow they “shape” the probability distributions of floods. Understanding andprojecting flood frequency in conditions of nonstationary hydroclimate andland use require deeper understanding of these processes, some or all ofwhich may be changing in ways that will be undersampled in observationalrecords. This study presents an alternative “process-based” FFA approachthat uses stochastic storm transposition to generate large numbers ofrealistic rainstorm “scenarios” based on relatively short rainfall remotesensing records. Long-term continuous hydrologic model simulations are usedto derive seasonally varying distributions of watershed antecedentconditions. We couple rainstorm scenarios with seasonally appropriateantecedent conditions to simulate flood frequency. The methodology is appliedto the 4002 km2 Turkey River watershed in the Midwestern United States,which is undergoing significant climatic and hydrologic change. We show that,using only 15 years of rainfall records, our methodology can produce accurateestimates of “present-day” flood frequency. We found that shifts in theseasonality of soil moisture, snow, and extreme rainfall in the Turkey Riverexert important controls on flood frequency. We also demonstrate thatprocess-based techniques may be prone to errors due to inadequaterepresentation of specific seasonal processes within hydrologic models. Ifsuch mistakes are avoided, however, process-based approaches can provide auseful pathway toward understanding current and future flood frequency innonstationary conditions and thus be valuable for supplementing existing FFApractices. 

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4. Framing the Problem of Flood Risk and Flood Management in Metropolitan Los Angeles

   https://doi.org/10.1175/WCAS-D-22-0013.1  

   Ulibarri, Nicola; Valencia-Uribe, Claudia; Sanders, Brett F.; Schubert, Jochen; Matthew, Richard; Forman, Fonna; Allaire, Maura; Brady, David (January 2023, Weather, Climate, and Society)

   Abstract This paper develops the concept of flood problem framing to understand decision-makers’ priorities in flood risk management in the Los Angeles Metropolitan Region in California (LA Metro). Problem frames shape an individual’s preferences for particular management strategies and their future behaviors. While flooding is a complex, multifaceted problem, with multiple causes and multiple impacts, a decision-maker is most likely to manage only those dimensions of flooding about which they are aware or concerned. To evaluate flood decision-makers’ primary concerns related to flood exposure, vulnerability, and management in the LA Metro, we draw on focus groups with flood control districts, city planners, nonprofit organizations, and other flood-related decision-makers. We identify numerous concerns, including concerns about specific types of floods (e.g., fluvial vs pluvial) and impacts to diverse infrastructure and communities. Our analyses demonstrate that flood concerns aggregate into three problem frames: one concerned with large fluvial floods exacerbated by climate change and their housing, economic, and infrastructure impacts; one concerned with pluvial nuisance flooding, pollution, and historic underinvestment in communities; and one concerned with coastal and fluvial flooding’s ecosystem impacts. While each individual typically articulated concerns that overlapped with only one problem frame, each problem frame was discussed by numerous organization types, suggesting low barriers to cross-organizational coordination in flood planning and response. This paper also advances our understanding of flood risk perception in a region that does not face frequent large floods. Significance StatementThis paper investigates the primary concerns that planners, flood managers, and other decision-makers have about flooding in Southern California. This is important because the way that decision-makers understand flooding shapes the way that they will plan for and respond to flood events. We find that some decision-makers are primarily concerned with large floods affecting large swaths of infrastructure and housing; others are concerned with frequent, small floods that mobilize pollution in low-income areas; and others are concerned with protecting coastal ecosystems during sea level rise. Our results also highlight key priorities for research and practice, including the need for flexible and accessible flood data and education about how to evacuate. 

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5. Quantifying Social Inequalities in Flood Risk

   https://doi.org/10.1061/AOMJAH.AOENG-0017  

   Sanders, Brett F; Brady, David; Schubert, Jochen E; Martin, Eva-Marie H; Davis, Steven J; Mach, Katharine J (April 2024, ASCE OPEN: Multidisciplinary Journal of Civil Engineering)