Advances and Challenges in Real-Time Flash Flood Warning Worldwide

Far ahead of all other types of floods, flash floods account for the majority of loss of lives. In China, for example, it is reported that flash floods account for over 80% of losses of lives and recent events world-wide underline this fact. The challenge has been to provide flash flood guidance in real-time with a systematic, science-based approach that requires minimum investments as compared to other conventional flash flood warning systems, is affordable also in the context of developing countries, and allows use of local data and forecaster experience to be overall reliable to keep false alarms at a minimum. The Hydrologic Research Center in partnership with the World Meteorological Organization, the U.S. Agency for International Development and the National Oceanic and Atmospheric Administration has begun implementation of such real time flash flood warning systems for diverse regions around the world, with more system implementations including in South Asia and South East Europe under way. Implemented systems include those in Southern Africa, Central America, Black Sea and Middle East region, Mekong Basin countries and several country implementations. These systems are based on methodologies that (a) utilize remotely sensed and on-site data to produce estimates of precipitation over small basins, soil moisture models and geomorphologic relationships to produce diagnostic indices for flash flood occurrence; and (b) allow forecaster intervention and adjustments in real time prior to warning generation. They have regional and local components and are supported by global databases and, where available, by refined local databases (e.g., spatial data for soil types, land use and land cover, stream network topology, terrain elevation, and others). The presentation discusses the design fundamentals for these systems, how they can be useful tools for real time forecasters and the various components that allow satellite precipitation information to be used as viable input to the system land surface models. Issues of education and training for regional and country forecasters in the hydrometeorology of flash floods and in the effective use of the systems are also outlined. The talk also highlights challenges associated with the design and deployment of systems supporting real time flash flood warning operations worldwide.