Evaluating the flood mitigation capacity of grey and green infrastructure in Baltimore, MD

Urban flooding in the city of Baltimore, MD is the product of short, intense rainfall events, extensive impervious surfaces, and inadequate infrastructure. This type of rainfall-driven pluvial flooding often results in property damage, flooded basements and inundated streets. Climate change has altered the frequency and intensity of rainfall events, elevating the risk posed by pluvial flooding. Given the complexity of urban flood patterns and uncertainty regarding the performance of Baltimore’s current green infrastructure, it is challenging to determine what further action is needed to address flooding. While traditional grey infrastructure can effectively reduce vulnerability to flooding, it often proves counterproductive as added impervious surface can increase flood risk. Conversely, Baltimore's planned green infrastructure has the potential to capture and store runoff, reducing maximum flow through the storm pipe network while also providing open space for community gathering and engagement. As part of a larger project, this study focused on the ability of proposed green infrastructure projects in the Broadway East neighborhood of Baltimore to address urban pluvial flooding. An EPA SWMM model was developed, incorporating subsurface pipe data and the City’s greening plan, to explore the impact of current and proposed green infrastructure on surface and subsurface flows. Flow rates through the storm pipe network were compared across three extreme rainfall events and across nonexistent, current, and proposed green infrastructure scenarios. Results of this study suggest proposed green infrastructure projects in Broadway East will alleviate pressure on the stormwater system, increasing the city of Baltimore’s flooding and climate resilience.