IPET Report 3 Vol VIII

Wave Setup Relative to Maximum Wave Setup
1.0
0.8
0.6
0.4
0.2
0.0
0.0 0.2 0.4 0.6 0.8 1.0
Depth Relative to Breaking Depth
Figure 16. Proportion of Maximum Wave Setup that has Occurred versus a Proportion of the Breaking
Depth
Determination of Hurricane Frequencies
Each storm considered in the MR1 ADCIRC simulation set is envisioned to represent all
possible storms with similar values of radius, central pressure, and so forth. Accordingly, a rate
of occurrence is assigned to each storm, representing the total rate of occurrence of all similar
storms.
The controlling factors are the overall density of storms in space and time – λ0 – and the
fractional occurrence rates of each of a storm’s several defining parameters. These are the central
pressure deficit, ΔP, the radius to maximum winds, Rmax, the forward translation speed of the
storm, V, the shoreline crossing angle, θ, and the crossing location, X. The fractional occurrence
rates for the parameters are derived from the cumulative probability distribution functions for
each, by dividing the CDF into segments centered on each selected parameter value.
For example, crossing angles of -60, -30, 0, 30, and 60 degrees clockwise from north were
selected for simulation. The fraction of all storms represented by the discrete value 30, say, is
equal to the total probability mass for all angles between 15 and 45 degrees. This is simply the
difference between the angle-CDF values at 15 and 45 degrees. This is the approach used for
angle, forward speed, radius, and central pressure, although some adjustment of the pressure
Volume VIII Engineering and Operational Risk and Reliability Analysis VIII-41
This is a preliminary report subject to revision; it does not contain final conclusions of the United States Army Corps of Engineers.