The Effect of Urban Density and Urban Form on Rainwater Capture Efficiency in Arlington, VA and Washington, DC

Rainwater harvesting is an increasingly important strategy for reducing dependence on imported water and managing urban flooding in growing cities and suburbs. However, limited city-wide research has compared rainwater capture efficiency across different building types, such as high-rises, rowhouses, and detached homes, under real-world usage scenarios in both Washington, DC and Arlington, VA.Therefore, this study investigates how differences in building density and form influence rainwater harvesting efficiency in Arlington, VA, compared to Washington, DC. Building data was obtained from official government websites for both regions and QGIS (Quantum GIS), which was used to quantify building footprint area, density, and distribution (Arlington County Government, 2025; District of Columbia Government, n.d.) Important aspects analyzed include roof coverage percentage, total annual rainwater capture, and per capita rainwater availability relative to average water demand. These metrics were used to evaluate which region demonstrates greater rainwater harvesting potential under similar climatic conditions to test the hypothesis that Arlington, VA would exhibit higher rainwater capture efficiency per inhabitant due to lower building density and greater roof area per inhabitant, although Washington, DC, may have a higher total capture volume due to its larger overall area. By providing a direct comparison between an urban and suburban environment with very similar climate characteristics, this study offers insights into how urban form influences water sustainability and landscaping for both urban and suburban environments to maximise rainwater capture.