Future Heavy Rainfall and Flood Risks for Native Americans under Climate and Demographic Changes: A Case Study in Oklahoma

Abstract

Abstract Climate change has posed inequitable risks to different communities. Among communities of color in the United States, Native Americans stand out because 1) they desire resources to sustain resilient nations and 2) they have developed nature-based solutions through experiences with local climate-related challenges, which can provide deep insight for the whole society. Projection of climate risks for Native Americans is essential to assess future risks and support their climate-ready nations, yet there has been lack of useable information. In this study, we projected three climate hazards—heavy rainfall, 2-yr floods, and flash floods—for tribal nations in Oklahoma. To break down into tribal jurisdictions, we utilize a coupled regional climate model at 4 km and flash-flood forecast model at 1 km. A hazard–exposure–vulnerability risk framework is applied to integrate both climate and demographic changes in a high-emissions scenario. It is found that 1) Indigenous people are the most vulnerable community in Oklahoma; 2) heavy rainfall and 2-yr floods have marked increases in risks at 501.1% and 632.6%, respectively, while flash floods have a moderate increase (296.4%); 3) Native Americans bear 68.0%, 64.3%, and 64.0% higher risks in heavy rainfall, 2-yr flooding, and flash flooding, respectively, than the general population in Oklahoma; 4) in comparing climate and demographic changes, it is seen that population growth leads to greater climate hazard risks than does climate change; and 5) emerging tribal nations are projected to have 10 times as much population, resulting in great exposures to climate extremes. This study can raise awareness of the impact of climate changes and draw attention to address climate injustice issues for minoritized communities. Significance Statement This study examines the impact of climate change on a marginalized community—Native Americans in Oklahoma, home to 39 federally recognized tribal nations. We utilized the high-resolution climate simulation at 4-km resolution and hydrologic simulation at 1-km resolution to aggregate three climate extremes to tribal jurisdictions. We find that climate and demographic changes disproportionately put many Native Americans at risk. The heavy rainfall, 2-yr floods, and flash floods are all projected to have increased risks by 501.1%, 632.6%, and 296.4%, respectively. Those risks are 68.0%, 64.3%, and 64.0% higher than the state average for the general population, respectively. We urge proper attention to tribal nations to address climate injustice issues as a whole with the acknowledgment of their distinct relationships to their homelands as sovereign peoples.