Flood hazard mapping in the coastal zone: accounting for multiple drivers of flood risk

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Adam Luke, Jochen E. Schubert, Timu W. Gallien, Amir AghaKouchak, Richard A. Matthew, Brett F. Sanders

Tuesday 30 june 2015

9:45 - 10:00h at South America (level 0)

Themes: (T) Flood risk management and adaptation, (ST) Flooding along in rivers and coasts

Parallel session: 4J. Floodrisk – Flooding

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Delineating flood zones in systems that are susceptible to flooding from a single mechanism is a relatively well-defined procedure with specific guidance from government agencies such as the Federal Emergency Management Agency (FEMA) and the United States Army Corps of Engineers (USACE) in the USA. However, there is relatively little guidance in delineating flood zones associated with multiple mechanisms such as storm surge, high tides, and riverine discharge. Deterministic hydraulic modeling simulations involving the coincidence of multiple extremes can be used to identify possible flood hazards, but deciding which scenarios to simulate is challenging due to the infinite number of events that are possible when considering multiple drivers of flooding. Moreover, deterministic modeling ignores the uncertainty associated within the modeling process, which is especially significant in the context of inundation mapping due to the large amount of uncertainty in the magnitude of extreme events. This study presents a stochastic modeling framework for generating annual exceedance probability (AEP) maps which considers the uncertainty in the model boundary forcing and the joint occurrence of flooding mechanisms. The methodology will be applied to Tijuana, Mexico and the produced AEP map will be compared to: (1) an inundation map depicting contours of the “canonical” flooding events, ignoring uncertainty in boundary forcing and joint occurrences of extremes, and (2) an AEP map which considers only uncertainty in the boundary forcing but not the joint occurrence of extremes. Results will demonstrate how the consideration of uncertainty and multiple drivers of flooding can affect the predictions of flood hazards in the coastal zone