South Boulder Creek Flood Mapping Study: What Happens When Citizen-Based Demands Push the Technological Envelope?

The South Boulder Creek watershed has long had a known, but unmapped flood hazard. The Boulder community demanded that the uncertainty be resolved through a flood mapping study that employed state of the art methodologies to assure scientifically defensible results. A mapping study was undertaken that included an unprecedented level of public involvement to assure process transparency, an extensive climatological evaluation to determine basin specific design rainfall events, a detailed hydrologic modeling effort supported by extensive calibration, and a hydraulic simulation that combined both 1D and 2D representations. While the technical work products produced the desired level of scientific accuracy, they identified a number of issues that posed challenges to the study team and will continue to pose challenges to those faced with future administration of the floodplain. Some of these issues and how the team resolved them are described.