Kapa’a Beach Erosion Evaluation

On the island of Kaua‘i, Sea Engineering was contracted to perform an erosion study for Kapa‘a Beach. Primary objectives were as follows:

• Survey beach profiles throughout the year to capture seasonal shifts in beach sand distribution.
• Measurement of waves and currents offshore and inshore throughout the year using in situ oceanographic instruments in order to relate forcing conditions with beach response.
• Survey offshore sand deposits using side scan sonar and sub-bottom profiling to identify significant offshore sand deposits.
• Numerical wave models driven by offshore wave gage data were used to quantify the level of wave energy propagating over the reefs to the shoreline along the entire stretch of Kapa‘a Beach.
• Investigation of improvement alternatives, which included development of oceanographic design criteria at the site, such as design wave heights and water levels, conceptual alternatives for beach erosion mitigation systems with representative plan maps and cross sections, and an evaluation of offshore sand deposits for suitability as borrow sites to nourish Kapa‘a Beach

Additionally, a baseline water quality and marine biological survey was conducted, which characterized typical conditions in the project area and identified any important resources and marine environmental issues.