Diving into equity: Examining flood-related road closures in Virginia

Written by Dr. P. J. Ruess

Virginia is no stranger to flooding – it is Virginia’s second most costly natural disaster after drought, with most flood deaths in Virginia attributed to driving through flooded roadways. Maybe you’ve had a personal experience with flooding, like flood damaging your home or your car hydroplaning. We are all impacted by flooding, which is why it is so important to understand these impacts.

Flooding also tends to unequally impact different groups of people, and this will become worse in the future. Racial minorities and lower income groups are often hit hardest by flood events, and these very same communities often have insufficient access to resources to protect their assets or rebuild. Documenting and comparing flood risk and exposure across different socio-economic groups and different geographies has consequently become increasingly vital as we strive for a more equitable future.

To address this, in the Virginia Climate Center’s recent study we prioritized assessing flood risk on Virginia’s roads and how this impacts Virginians of different socio-economic groupings across different parts of the state. We first collected flood-related road closure data for all available years (2020-2023) from the Virginia Department of Transportation’s SmarterRoads portal (Fig. 1). This data contains the locations of all reported road closures as well as their start and end times. Note that this dataset does not include all flooded roads, instead it only shows road closures that were reported.

Figure 1: All VDOT reported road closures (smaller gray points, total 99,017 points), highlighting flood-specific closures (larger blue points, 6,144 total points) between 2020 and 2023.

We then collected data describing race and poverty for all census tracts throughout Virginia (Fig. 2). These social vulnerability variables (fraction of population that is non-white, and fraction of population living under the poverty line) were then compared against flood-related road closure data to search for any trends and relationships between them.

Figure 2: Social vulnerability data considered in this study, including (A) Fraction of the population experiencing poverty in 2022, and (B) Fraction of the population that is non-white in 2022. Values are plotted on a scale of 0 to 1 such that 0 denotes no social vulnerability while 1 denotes significant social vulnerability. Both maps show data processed from publicly available US Census Bureau data.

Finally, we differentiated counties as coastal vs. inland and rural vs. urban based on formal definitions (Fig. 3), allowing us to split our analysis over different regions and see how our results changed. Looking at all of Virginia, we find that flood-related road closures are largely reported in census tracts whose residents are predominantly white and living above the poverty line.

Figure 3: Coastal and Inland areas in Virginia, separated by Urban vs. Rural Census Tracts. Coastal areas are defined from Virginia Department of Environmental Quality Coastal Zone Management areas while inland areas represent all remaining non-coastal Virginia census tracts. Urban areas are defined by Census Bureau reported ‘‘Urban Areas’’ census blocks while rural areas are all remaining non-urban Virginia census tracts.

Splitting our results into coastal vs. inland regions we see clearer trends, with most flood-related road closures reported inland and in predominantly white regions, while coastal closures occurred in more racially diverse areas. When considering poverty, we see more geographical similarities as coastal communities experiencing flood-related road closures seem to be relatively wealthier, though slightly more closures are reported inland for impoverished regions.

Analyzing rural vs. urban trends, rural areas uniformly experienced more flood-related road closures than urban areas. Furthermore, coastal rural areas observed increased flood-related road closures in areas with racial diversity, whereas inland rural areas instead reported more closures where populations were primarily white.

In summary, flood-related road closures are generally most reported in wealthy, predominantly white urban areas along the coasts and poorer, predominantly white rural areas inland. Coastal rural areas reporting flood-related road closures are generally more racially diverse. While this may seem counterintuitive, we emphasize that this analysis does not capture actual road flooding and instead captures reported events only, meaning that biases in reporting may significantly skew results.

 Overall, our findings show noticeable differences when considering flood-related road closures across different socio-economic factors and geographic delineations in the state of Virginia. This work has potentially wide-reaching implications for transportation infrastructure prioritization from a social justice lens, as historical reporting trends could better inform which communities are most at-risk of flood-related road closures. Furthermore, assessing these trends may allow identification of any biases built into reporting structures.

The full publication containing all calculations and figures is available online: https://doi.org/10.1016/j.ijdrr.2024.105123

 Author

Dr. P.J. Ruess

P. J. Ruess is a postdoctoral researcher with the Virginia Climate Center at George Mason University.