INVESTIGATING THE EFFECTS OF HISTORIC REDLINING ON ECOHYDROLOGICAL PROCESSES IN RICHMOND, VIRGINIA

Urbanization leads to increased impervious surface and decreased tree cover, which are known to cause higher temperatures and increased flooding in cities. However, impervious surface and green space are not equally distributed throughout a city, and one factor driving this inequity is historic redlining. In the 1930’s, the Home Owners Loan Corporation (HOLC) graded neighborhoods in cities based on their perceived riskiness for investment, which was primarily determined by the race of their residents. The lowest grade was outlined in red, and previous studies have shown that historically redlined neighborhoods still have more impervious surface and less tree cover than other neighborhoods in the same city. However, there is a knowledge gap about how this affects ecohydrological processes, such as vapor pressure deficit (VPD) and flood risk. This study aims to address this gap by investigating these processes in Richmond, VA. To study the VPD, a small weather station was attached to a car and driven through neighborhoods of each HOLC grade to measure the temperature and dew point, which were used to calculate VPD. Relative flood risk was determined using the Flow Accumulation tool in ArcGIS Pro’s Spatial Analyst toolbox, which uses elevation data to predict where runoff will accumulate. We found that the median VPD for redlined neighborhoods is about 4.5 mbars higher than that of greenlined neighborhoods (the highest HOLC grade). However, greenlined neighborhoods contained the highest flow accumulation values, followed by redlined neighborhoods, then bluelined and yellowlined. High VPDs mean that redlined neighborhoods are drier on average, which, combined with their higher temperatures, could increase the risk of dehydration among residents. Additionally, redlined neighborhoods have the second highest estimated flow accumulation along with more impervious surface and less trees, all of which indicate a potentially high flood risk. Overall, this research aims to further our understanding of urban ecohydrology in the context of redlining with a goal of informing future policies that alleviate these issues.