The hydrology and hydrometeorology of flash floods are examined through experimental and numerical modeling studies for urban watersheds in the eastern US. Analyses focus on: 1) the role of urban infrastructure in controlling hydrologic and hydraulic properties of flood response in urban watersheds, 2) the scale-dependent flood response of urban watersheds, 3) the space-time variability of rainfall for flash flood producing storms, and 4) radar rainfall estimation for flash flood producing storms. Analyses are presented for urban watersheds in the Charlotte NC, Baltimore MD, and New York City metropolitan regions. These analyses will be used to synthesize key enhancements that are needed for flash flood forecasting systems in urban environments.