This Risk Compute Exercise involves simple exercises to demonstrate how flood risk (expected annual damage) and other risk metrics are computed. 

Part 1: Calculate Expected Annual Damage and Annual Exceedance Probability

Calculate expected annual damage and the annual exceedance probability for the without-project condition. For calculations of AEP, the stage at which significant damage begins is 369ft. 

Hydrology

Below is a simple graphical peak unregulated discharge-frequency function with 5 coordinates. These 5 coordinates are chosen for ease of calculation on paper, which results in loss of some nonlinearity. Typically, graphical frequency functions used in HEC-FDA should have several more coordinates and should span the probability domain. 

Hydraulics

Below is an example stage-discharge function, which transforms the peak discharge to stage of the river, also known as river elevation. 

Consequences

The consequences of flooding are modeled for many levels of flooding, from which we derive a relationship between peak stage and the consequences of flood inundation damage, as in the below example.