The design, application, and assessment of rapid-response airborne lidar for monitoring of storm induced beach erosion

Abstract

A key limitation to further understanding of storm induced beach erosion and the development of accurate predictive coastal erosion models is the paucity of field scale data collected within a short period of time of an erosion event. The collection of this data is made difficult by the challenging coastal environment in addition to the episodic nature of coastal storms. This thesis introduces the method of rapid-response airborne lidar that was developed and tested in order to collect such data. A light aircraft mounted lidar system performed surveys with different flight configurations at the Narrabeen Embayment and the ability to resolve beach topography and derived coastal change were investigated. This was compared to the standard survey method of a GPS equipped ATV, with the airborne lidar surveys able to perform beach surveys at an accuracy on par with the ATV method, and able to derive a shoreline position and beach volume with a root means squared error of 0.94 m and 3.89 m3/ m when compared the ATV method. In order to reduce uncertainty as to the drivers of storm induced beach erosion, a nearshore spectral wave model was developed to transform the offshore deep water wave climate into a nearshore wave climate at 75 different locations within Narrabeen Embayment. This model was tested against nearshore wave observations taken from two wave rider buoys located within the embayment. The rapid-response airborne lidar capability was deployed immediately before, during and immediately after an East Coast Low storm event at the Narrabeen Embayment, representing an almost daily dataset of the rapidly evolving morphology. This survey data, which indicated considerable alongshore variation in the dune erosion response to the storm, was then combined with the measured and modelled hydrodynamic data to test several simple dune erosion models. The effect of forcing data resolution and alongshore averaging was also investigated. A modification to one of the models was presented, it showing modest improvement compared to the other models, being able to explain 67% of the observed dune erosion across the entire embayment.