Federally Overlooked Flood Risk Inequities in Houston, Texas: Novel Insights Based on Dasymetric Mapping and State-of-the-Art Flood Modeling

Abstract

In the United States, the Federal Emergency Management Agency (FEMA) delineates 100-year flood zones to define risks, regulate flood insurance premiums, and inform flood management. Evidence indicates that FEMA flood maps are incomplete, calling much of our current knowledge of U.S. flood hazard inequities into question. We use a state-of-the-art flood hazard model and census tract-level dasymetrically mapped sociodemographic data to examine flood risk inequities in the Greater Houston area, where increasingly frequent and damaging flood events are occurring. We innovate by analyzing federally overlooked 100-year flood risks (100-year flood zones delineated by the flood hazard model that are outside of FEMA 100-year flood zones). Results indicate that nearly 1 million Greater Houston residents live in federally overlooked 100-year flood zones. Black and Asian neighborhoods experience disproportionate risk in federally overlooked pluvial and fluvial flood zones, and Hispanic neighborhoods experience disproportionate risk in all federally overlooked zones (coastal, pluvial, and fluvial). High flood risk and the relative lack of protective resources in federally overlooked 100-year flood zones doubly jeopardizes racial and ethnic minority communities. Our findings and recent flood disasters suggest that future flood impacts in Greater Houston will be catastrophic and unjust unless FEMA revises their risk mapping and management approach to promote long-term public safety and social equity.

美国联邦应急事务管理局（FEMA）制作了百年一遇洪水区划, 用于定义风险、监管洪水保险费、辅助洪水管理。有证据表明, FEMA的洪水地图并不完整, 使得我们对美国洪水灾害不公平现象的认识受到质疑。本文利用最先进的洪水灾害模型和人口普查区尺度的分区密度社会人口数据, 研究了破坏性洪水事件愈发频繁的大休斯顿地区的洪水风险不平等。本文的创新点, 是分析了被联邦政府忽视的百年一遇洪水风险, 即, 由洪水灾害模型划定的位于FEMA百年一遇洪水区域之外的百年一遇洪水区。结果表明, 大休斯顿地区近100万居民生活在被联邦政府忽视的百年一遇洪水区。在被联邦政府忽视的洪泛区和江河洪水区内的黑人和亚裔社区, 以及在被联邦政府忽视的沿海地区、洪泛区和江河区域的西裔社区, 都面临着不成比例的风险。在被联邦政府忽视的百年一遇洪水区, 洪水的高风险和保护资源的相对缺乏, 加倍危害了少数种族和族群社区。本文的结果和近期的洪水灾害表明, 除非FEMA修改风险图和管理方法、促进长期的公共安全和社会公平, 大休斯顿地区未来洪水的影响将是灾难性的、不公平的。

La Agencia Federal para la Atención de Emergencias (FEMA) es la encargada de delinear en los Estados Unidos las zonas de inundación de 100 años, para definir los riesgos, regular las primas de los seguros de inundación e informar sobre el manejo de este fenómeno natural. Las evidencias indican que los mapas de inundaciones de la FEMA pecan de incompletos, lo cual pone en tela de juicio una gran parte de los actuales conocimientos sobre las desigualdades en materia de riesgos de inundación en este país. Usamos un modelo de avanzada sobre riesgo de inundación y datos sociodemográficos cartografiados dasimétricamente a nivel de tracto censal, para examinar las desigualdades de riesgo de inundación en el área de la Gran Houston, donde están ocurriendo eventos de inundación cada vez más frecuentes y devastadores. Innovamos analizando los riesgos de inundación en 100 años que se pasaron por alto en términos federales (zonas de inundación de 100 años delineadas por el modelo de peligro de inundación que están fuera de del esquema de los zonas de inundación de 100 años de la FEMA). Los resultados indican que alrededor de un millón de residentes de la Gran Houston viven en las zonas inundables de 100 años no tenidas en cuenta en el esquema federal. Los vecindarios negros y asiáticos están expuestos a un riesgo desproporcionado en las áreas de inundación pluvial y fluvial ignoradas en la previsión federal, y los barrios hispanos experimentan un riesgo fuera de proporción en todas las zonas ignoradas federalmente (costeras, pluviales y fluviales). El alto riesgo de inundación y la relativa falta de recursos protectores en las zonas de inundación ignoradas en el esquema federal de 100 años ponen en doble peligro a las comunidades de minorías étnicas y raciales. Nuestros descubrimientos y los desastres recientes por inundación permiten sugerir que los impactos futuros en la Gran Houston serán catastróficos e injustos, a menos que la FEMA revise sus mapas de riesgos y el enfoque de manejo del fenómeno para promover a largo plazo la seguridad pública y la equidad social.

Key Words:

• dasymetric mapping
• environmental justice
• FEMA
• flood risk
• Houston
• race/ethnicity

关键词：:

• 分区密度制图
• 环境正义
• FEMA
• 洪水风险
• 休斯顿
• 种族/族群。

Palabras clave::

• FEMA
• Houston
• justicia ambiental
• mapeo dasimétrico
• raza/etnicidad
• riesgo de inundación

Supplemental Material

Supplemental data for this article can be accessed on the publisher’s site at: http://dx.doi.org/10.1080/24694452.2022.2085656. Materials include bivariate correlations, maps of analysis variables, and results from an exploratory supplemental analysis in which we introduced the independent variables in four stages using a stepwise approach.

Additional information

Notes on contributors

Aaron B. Flores

AARON B. FLORES is a Postdoctoral Research Scholar in the School of Geographical Sciences and Urban Planning at Arizona State University, Tempe, AZ 85287. E-mail: [email protected]. His research interests include social vulnerability, environmental justice, and health disparities in the context of hazards and disasters.

Timothy W. Collins

TIMOTHY W. COLLINS is Co-Director of the Center for Natural and Technological Hazards and a Professor in the Department of Geography and Environmental & Sustainability Studies Program at the University of Utah, Salt Lake City, UT 84112. E-mail: [email protected]. His research interests include environmental justice, health disparities, and social vulnerability to risks, hazards, and disasters.

Sara E. Grineski

SARA E. GRINESKI is Co-Director of the Center for Natural and Technological Hazards and a Professor in the Department of Sociology and the Environmental & Sustainability Studies Program at the University of Utah, Salt Lake City, UT 84112. E-mail: [email protected]. Her research interests include environmental injustice and environmental health disparities.

Mike Amodeo

MIKE AMODEO is the Head of Data Science at the First Street Foundation, Brooklyn, NY 11201. E-mail: [email protected]. He is also a licensed civil engineer with a deep background in sustainable water resource management, including flooding.

Jeremy R. Porter

JEREMY R. PORTER is the Chief Research Officer at the First Street Foundation and a Professor of Quantitative Methods and Director of the Quantitative Methods in the Social Sciences program at the City University of New York’s Graduate Center and Brooklyn College, New York, NY 10016. E-mail: [email protected]. His research focuses on the economic and social implications of climate change, spatial analysis, location, and quantitative methods, generally.

Christopher C. Sampson

CHRISTOPHER C. SAMPSON is the Chief Technology Officer at Fathom (Bristol, UK) and an Honorary Researcher in the Hydrology Group, University of Bristol, Bristol, UK. E-mail: [email protected]. His research focuses on large-scale hydraulic model frameworks to assess flood hazard and risk at national to global scales.

Oliver Wing

OLIVER WING is the Chief Research Officer at Fathom (Bristol, UK) and an Honorary Research Fellow in the Hydrology Group, University of Bristol, Bristol, UK. E-mail: [email protected]. His research focuses on the development and application of national- to global-scale flood risk models.