Multiple Flood Source Expected Annual Damage Computations

Abstract

For flood damage reduction analysis, the standard for measuring risk is expected annual damage. This index represents a long-term average annual flood damage for a given structure or area. We compute this index by integrating a probability-damage function. In practice, we develop the required function by developing a water level (stage)-probability function and an elevation-damage relationship. The analysis becomes complex when the stage-probability function is dependent upon multiple flooding sources. For example, this occurs when an area is protected by multiple leveed reaches or can be flooded from more than one stream. Here we propose alternative analysis frameworks for computing expected annual damage considering this complicating factor. An example illustrates that appropriate methods depend on the alternatives evaluated, the correlation of discharges, and the number of levee reaches.