Floodedequivalent

Floodedequivalent is a modeling construct used in hydrology and flood risk assessment to summarize the severity of a flood event at a site by reducing spatially variable damage potential to a single, equivalent flood depth under a specified vulnerability model.

Definition and calculation: The concept relies on a depth-damage function D(h) that gives expected damage per unit area as a function of flood depth h. For a study area divided into n cells with depths h_i and areas A_i, total expected damage is D_total = sum_i D(h_i) * A_i. The flooded equivalent depth h_eq is defined as the depth for the whole area that would produce the same total damage, i.e., D(h_eq) * sum_i A_i = D_total. In probabilistic or duration-weighted formulations, duration, peak discharge, and flood return period may be incorporated by modifying the damage function or by using expected damage over a flood hydrograph.

Applications: Floodedequivalent is used to compare different flood scenarios, to communicate risk to stakeholders, and to calibrate models where only limited site-wide damage data are available. It provides a compact summary metric that is agnostic to the detailed spatial pattern of flooding.

Limitations: The flooded equivalent depends heavily on the chosen depth-damage function, the spatial aggregation, and whether duration, debris, or defenses in place are included. It does not capture local extremes or the timing of inundation, and different vulnerability models can yield different h_eq values for the same event.

Origin and terminology: The term appears in certain risk assessment studies as a descriptive modeling construct; it is not a universally defined physical quantity. Floodedequivalent should be understood as a summary metric rather than a direct measurement of water depth.