UA Researchers Provide U.S. Drought Vulnerability Rankings

  • September 18th, 2020
A color-coded map of the United States based on risk of drought effects.
The maps by UA researchers show vulnerability to drought, top, based on factors of sensitivity, exposure and ability to adapt to droughts.

If asked where in the United States is most vulnerable to drought, those states in the West currently suffering under hot and dry conditions and raging wildfires might come first to mind. However, according to research led by The University of Alabama, what makes a state vulnerable is driven by more than just a lack of rain.

According to the new NOAA-funded assessment done by UA researchers, drought vulnerability comes from a combination of how susceptible a state is to drought and whether it’s prepared for impacts. The most and least vulnerable states could surprise.

These maps show each state’s overall drought vulnerability in red and how it ranks in the three individual categories that make up the score:  sensitivity in blue, exposure in yellow-orange and ability to adapt in purple. Darker colors show higher overall drought vulnerability and a greater degree of factors that increase the state’s vulnerability.

Sensitivity is the likelihood of negative economic impacts, which is based on the percentage of agricultural land, number of cattle, how much the state relies on hydropower, and recreational lakes. The exposure score reflects how often a state experiences drought and what assets, like the number of people and freshwater ecosystems, are at risk when it occurs. The ability to adapt score ranks how well the state can cope with and recover from drought, which depends on whether the state has a drought plan, how equipped it is to irrigate its land, and whether it is financially strong overall.

By this scoring system, the most vulnerable states are Oklahoma, Montana and Iowa, while Delaware, Massachusetts, Connecticut and California are least vulnerable to drought. Oklahoma gets its high vulnerability score from having an outdated drought plan and limited irrigation, a low ability to adapt, as well as extensive agricultural activities and cattle ranching, a high sensitivity. Despite facing recurring multi-year droughts, meaning relatively high exposure, California ranks low in drought vulnerability. Thanks to a strong economy and well-developed adaptation measures, it’s better prepared for an extreme drought when it occurs than most other states.

On the east coast, the region is generally less vulnerable than other areas, given its wetter climate and lack of farming – except for New Jersey. As the most densely populated state in the country, meaning very high exposure, it gets the region’s highest vulnerability score.

By breaking down drought vulnerability into three components, this assessment can help decision makers identify what makes their state vulnerable for better planning. And, as the study shows, even states that receive lots of rain can still be vulnerable.

Though drought is one of the costliest natural hazards in the United States, there are actions states can take to become more resilient.

This research was led by Dr. Johanna Engström, former postdoctoral researcher at the UA Center for Complex Hydrosystems Research, Dr. Keighobad Jafarzadegan, postdoctoral researcher at the center, and Dr. Hamid Moradkhani, the Alton N. Scott Chair Professor of Civil and Environmental Engineering and director of the center.

The work was funded in part by NOAA’s Climate Program Office through its Modeling, Analysis, Predictions, and Projection program. The MAPP Program enhances understanding, predicting, and projecting variability and long-term changes in Earth’s climate system.

This was adapted from an article by Alison Stevens with NOAA and posted on

The University of Alabama, the state’s oldest and largest public institution of higher education, is a student-centered research university that draws the best and brightest to an academic community committed to providing a premier undergraduate and graduate education. UA is dedicated to achieving excellence in scholarship, collaboration and intellectual engagement; providing public outreach and service to the state of Alabama and the nation; and nurturing a campus environment that fosters collegiality, respect and inclusivity.