When it comes to compounding natural hazards like landslides, wildfires, flooding and extreme heat, where you live makes all the difference according to new research.

A study by a team at Portland State University found that in Portland, the areas most vulnerable to multiple climate hazards are historically underinvested neighbourhoods marked by lower median incomes, lower education levels and higher racial diversity.

The research – led by Justin Huber, a doctoral student in the Earth, Environment & Society program, and Heejun Chang, a professor of geography – mapped where hazards are most likely to hit across Portland and how those risks align with factors like income, education, tree cover, wetlands and access to critical services.

By examining social, ecological and technological variables, the researchers sought to better understand how natural hazards interact with the complex dynamics of urban systems.

“We’re not just people experiencing natural hazards, but we’re in a system that interacts with the natural hazards and the things we do also influence the potential for those hazards,” Huber said. “If we cut down a bunch of trees, that may increase the likelihood of landslides but decrease the likelihood of forest fires.”

Looking at individual hazards, flood and heat risks were more common in flat East Portland, while wildfire and landslide risks were more concentrated in the hilly terrain of West Portland.

When these threats overlap, though, East Portland emerges as the city’s multi-hazard hotspot, with neighbourhoods along Interstate-205 scoring among the highest for all four hazard risks. These areas are home to a higher proportion of non-white residents, lower median incomes and lower educational attainment, according to the study. The inverse is often true of Central and West Portland, where overall hazard exposure is much lower.

The high-risk areas are the same areas that have dealt with chronic underinvestment, the researchers said. Most of East Portland near present-day I-205 was labelled “definitely declining” – the second lowest rating – on the 1938 Home Owners’ Loan Corporation maps that institutionalised redlining. In recent decades, as historically redlined but lower-risk neighbourhoods in North/Northeast Portland underwent redevelopment, rising housing costs forced residents out to the more hazard-prone neighbourhoods of East Portland.

“It’s important to see how people move when these other two things – ecological and technological variables – change,” Huber said. “You don’t want to inadvertently cause people to move.”

The study found:

• Roughly 5% of Portland residents live in neighbourhoods facing the highest risk from three or more hazards.
• Compared with the citywide average, those 18 census block groups — neighbourhood-level areas typically home to 600 to 3,000 residents each — have lower median incomes, lower educational attainment, fewer wetlands and longer distances to hospitals.

“Even though the city is trying to do some equity work, we have a long way to go,” Chang said. “These hazard hotspots are the areas where the city can do better in creating more green and blue spaces and invest in infrastructure to make them more resilient to future hazards.”

The researchers say the study can be replicated in other cities facing similar hazards from climate change and land development – not only for city managers to be better informed, but for residents living in those high-risk areas to be educated and empowered to advocate for better environmental infrastructure.

Accounting for overlapping hazards can dramatically improve emergency planning, the researchers said. For example, cities could use multi-hazard maps to better position evacuation routes and ensure critical infrastructure like hospitals is built in lower-risk areas so they can remain operational during a disaster.