Investigation of the performance of artificial surfing reefs

Artificial surfing reefs are emerging as a favoured coastal structure in specific regions where improved shoreline protection and subsequent beach widening, along with enhanced surfing conditions, are desired. With relatively few design studies completed to date and only one successful implemented prototype, there exists an opportunity to learn more about the performance of artificial surfing reefs. Past studies have been limited to a small range of design variables tested over a common beach slope.; This thesis presents the results of an extensive 3-D testing program of an artificial surfing reef for Orewa Beach, New Zealand. Orewa Beach experiences an annual loss of beach material resulting in a severely eroded shoreline and is therefore being considered for an artificial surfing reef. The site is an ideal candidate for this study due to its relatively small wave climate and gradual 1:200 beach slope---previously unexplored conditions for implementation of an artificial surfing reef. The performance of the reef was evaluated based on test results using a suite of variables: four reef alternatives, three water levels, five incident wave directions and up to seven incident wave heights. A total of 361 tests were performed. Although these tests were specific to Orewa Beach, they are general enough to form the basis of guidelines for successful reef implementation.; Results from the 3-D tests were assessed using six parameters to evaluate improved shoreline protection and enhanced surfing conditions. Wave height attenuation was realized primarily in the lagoon area immediately shoreward of the reef. Closer to the shoreline, wave height attenuation was limited and only occurred for a small number of tests. The artificial surfing reef was found to improve the shape---as opposed to the size---of waves for the purpose of surfing. Favourable crest front steepness values, Iribarren numbers and peel angles were realized and showed a significant improvement over existing conditions. Significant wave height amplification was not consistently recorded at the reef location.