The Mid-Atlantic region of the US has an area of more than 100K square miles, including five major river systems and large cities, and it houses one-fifth of the United States population. Over the past decade, the Mid-Atlantic region has experienced extreme rainfall events, periodic drought/wet conditions, and water quality issues. Climate change and population growth have disrupted precipitation patterns and streamflow peaks in the past decades, challenging urban planning and water resource management. Although some studies have analyzed the current state and future projections of hydrologic conditions in urban areas at local scales, regional scale studies are lacking, as limited by data availability at the regional scale. We address this issue by employing a semi-distributed, physically-based urban hydrologic modeling framework, Model for Scale Adaptive River Transport for Urban (MOSART-Urban), in the Mid-Atlantic region, especially the lower Delaware River Basin, where urbanization is generally higher. MOSART-Urban uses geospatial data such as street networks, land use/land cover, and topographic datasets that are readily available to estimate the below-ground urban drainage network. This unique feature of MOSART- Urban enables us to study the regional hydrological responses to climate and anthropogenic stressors in highly urbanized regions. We assess the vulnerability of the urban systems in the Mid-Atlantic region under the historical hydroclimatic conditions. Utilizing the MOSART-Urban's drainage network generator, we obtain multiple urban drainage network scenarios which will be used in combination with future hydroclimatic projections to study changes of vulnerability of urban areas in the future and the key drivers. This study advances our goal to improve science-based support for short- and long-term urban development and planning in the Mid-Atlantic region.