Intertidal morphodynamics at Narrowneck Reef

摘要: As part of the Beach Protection Strategy (ICM, 1997) a submerged reef was constructed at Narrowneck (Gold Coast, Australia). This has to act as shoreline control point and provide improved surfing conditions. The construction completed in January 2001, but adjustments design are still possible depending on its functioning. critical question designing whether salient would form or tombolo. In order monitor changes Northern Gold an ARGUS coastal imaging system installed 1999. first objective this study is apply new image analysis technique Coast assess performance technique. developed Delft Hydraulics enables quantitatively intertidal beach variability. A second determine effectiveness structure carrying out intra-annual mapping. third goal predict long-term response result different wave transmissions over find criteria, which indicate enhance stabilise beach. one-line model GENESIS used applying updated mapped survey data (giving information about position dimensions constructed). (Intertidal Mapping) put into operation for site setting up pre- post-processing routines. resulted Plan Operation indicating how can best be operated. Validation given insight sensitivity site-related luminance colour characteristics. It further shows that accuracy very acceptable quantify volume Intertidal Beach: Typical mean errors quantified variability 15 30 %. From mapping (January 2000 - April 2001) two dominating features could discerned: storm-based erosion events migration nourishment northwards. able identify follow morphological beachfront. Shoreline modelling number plots showing extent transmissions. An effective transmission 70% seems desirable. Evaluation results suggests simulated accretion / upper limits. More dispersion expected (considering interaction range 3-D physical processes) smoothing changes. main conclusions concerning Reef: So far (April 2001), not been detected Argus video images. However, cumulative lee (relative July 2000) may initial stage formation. Predictive numerical show formation will increase width approximately 1000 m south Narrowneck. most important recommendations near future: * Continue monitoring well prevention scientific purposes.) Measure response. Then, cost-benefit made decide crest level should raised. Facilitate mode with e.g. standard routines user-manual. Investigate character consistency (alongshore) relation varying characteristics