Flash Flood Forecasting in Urban Drainage Basins

Urban drainage basins present a major challenge for flash flood forecasting because of the concentrated threat to life and property and the difficulties in monitoring and modeling the relevant hydraulic, hydrologic and meteorological processes. Measuring rainfall accurately at the time and space scales required for flash flood forecasting in small urban drainage basins remains a fundamental problem in many settings. Recent advances and promising technologies and procedures for rainfall estimation will be examined. Hydrologic modeling in urban environments is complicated by alterations of the land surface that accompany urbanization. Readily available land surface data sets provide an important resource for advancing capabilities for hydrologic modeling in urban catchments. Urban infrastructure also has a profound impact on the hydraulics of urban rivers. High-resolution topographic data sets provide the potential for marked advances in inundation forecasting in urban drainage basins. The hydrologic, hydraulic and hydrometeorological problems that arise in flash flood forecasting are illustrated through case study examples from the Baltimore metropolitan region.