Southeast Oahu Coastal Hydrodynamic Modeling with ADCIRC and STWAVE

This study provides the Honolulu District (POH) with numerical modeling tools for understanding nearshore circulation and sediment transport for Southeast Oahu (SEO). Circulation and wave models are developed and validated for this region and can be applied to assess sediment transport potential for various forcing conditions and to determine the likelihood of accretional and erosional areas within the model domain. Application of a wave model includes the generation of a wave climate. In the wave climate development technique, nearshore conditions are extracted from the wave model results for each simulation. A transformation correlation between the offshore and nearshore condition is then determined for each simulation. By applying the appropriate transfer function to each wave condition in the offshore time series, a long-term nearshore time series is generated. The nearshore time series demonstrates that there is a reduction in wave height from the offshore location to the nearshore location, landward of the extensive reef system as expected. The technique of developing a nearshore wave climate by applying the wave model for a range of offshore wave conditions provides a permanent "look up" table of nearshore wave conditions at any location in the Honolulu District (POH) with numerical computational domain and can be applied to any time period for which offshore data are available, provided that bathymetric conditions within the model domain remain similar. POH is applying the database-generated time series to develop sediment transport potential estimates in the project area. Development of a bottom friction capability in the wave model was completed for application extensive reefs in the SEO study area. It is shown that bottom friction is extremely important and has a pronounced effect on modeling transformation over reefs, decreasing wave heights from the without-friction condition by 71-76% for a constant JONSWAP bottom friction value of 0.05.

The original document contains color images. All DTIC reproductions will be in black and white.