The flood index is an internally calculated algorithm that is designed to display the area of the coastline most likely to experience the highest flooding due to storm surge and wind driven water.  In the case of "Actual" analysis it displays the actual flood index for an area of the coastline (as shown in the graphic below).  The index  is an index and does not equate to any specific level of flooding.

The flood index's main component is the strength and duration of the onshore wind flow.  It does NOT take into account the bathymetry of the ocean floor nor any possible funneling situations, such as a strong SW flow into Tampa Bay.  For this data you should refer to the SLOSH Data charts.

In addition, you should not focus on the exact location of the forecasted maximum flood index since small changes in the storm's path will dramatically affect the area with the highest storm surge.  It is best to use this data only within a few hours of landfall and in conjunction with the SLOSH information.

An example of a plotted flood index is shown below: