Description of project

In the United States the National Hurricane Center (NHC) monitors all storm developments on the Atlantic Ocean during Hurricane season. After a tropical storm develops, the NHC issues forecasts of air pressure, storm size (diameter), forward speed, wind speeds and the expected storm track every 6 hours. 24 to 36 hours prior to landfall, the National Weather Service (NWS) uses these parameters in to forecast maximum water levels based on their SLOSH (Sea, Lake and Overland Surges from Hurricanes) computer model. Besides SLOSH the USACE also uses the results of a modified version of the ADCIRC (ADvanced CIRCulation) model to forecast surge levels. The numeric model computes water levels based on predicted wind speeds, air pressure, bathymetry and surface roughness of an area. This information is used to make decisions for the operation of USACE structures.
The Hurricane Surge atlas was developed by using more than 300 different “Hypothetical” Hurricanes that make landfall in the State of Louisiana. The presented water levels in this atlas are the results from existing model runs done with a high resolution computational model. Although advanced, such a model is also computational intensive and thereby time consuming. The big advantage of the Hurricane Surge Atlas is that it allows for a very quick first estimate of maximum surge levels, wave heights if the forecasted track is matched to one of the 300 storms in The Hurricane Surge Atlas.

Future developments
The inherent nature of working with forecasts is that they contain uncertainty. In order to take uncertainties into account a methodology is being developed to select multiple storms from the hypothetical storm database. Based on maximum water levels in the selected set of storms it would subsequently be possible to calculate the standard deviation for example. In this way it is possible to quickly visualize and analyze best/worst case scenarios and provide the user a confidence level in combination with the predicted surge levels.

In addition to this improvement it is planned to use The Hurricane Surge Atlas to identify sites with possible damages to levees. By spatially combining the maximum water levels, wave heights from the atlas with up to date levee and floodwall height information it would be possible to assess the chance that a typical stretch of levee is overtopped. The results from this assessment could than be used to plan levee damage inspections in the wake of a storm.