Remote Sensing Is Changing Our View of the Coast: Insights from 40 Years of Monitoring at Narrabeen-Collaroy, Australia

Abstract

Narrabeen-Collaroy Beach, located on the Northern Beaches of Sydney along the Pacific coast of southeast Australia, is one of the longest continuously monitored beaches in the world. This paper provides an overview of the evolution and international scientific impact of this long-term beach monitoring program, from its humble beginnings over 40 years ago using the rod and tape measure Emery field survey method; to today, where the application of remote sensing data collection including drones, satellites and crowd-sourced smartphone images, are now core aspects of this continuing and much expanded monitoring effort. Commenced in 1976, surveying at this beach for the first 30 years focused on in-situ methods, whereby the growing database of monthly beach profile surveys informed the coastal science community about fundamental processes such as beach state evolution and the role of cross-shore and alongshore sediment transport in embayment morphodynamics. In the mid-2000s, continuous (hourly) video-based monitoring was the first application of routine remote sensing at the site, providing much greater spatial and temporal resolution over the traditional monthly surveys. This implementation of video as the first of a now rapidly expanding range of remote sensing tools and techniques also facilitated much wider access by the international research community to the continuing data collection program at Narrabeen-Collaroy. In the past decade the video-based data streams have formed the basis of deeper understanding into storm to multi-year response of the shoreline to changing wave conditions and also contributed to progress in the understanding of estuary entrance dynamics. More recently, 'opportunistic' remote sensing platforms such as surf cameras and smartphones have also been used for image-based shoreline data collection. Commencing in 2011, a significant new focus for the Narrabeen-Collaroy monitoring program shifted to include airborne lidar (and later Unmanned Aerial Vehicles (UAVs)), in an enhanced effort to quantify the morphological impacts of individual storm events, understand key drivers of erosion, and the placing of these observations within their broader regional context. A fixed continuous scanning lidar installed in 2014 again improved the spatial and temporal resolution of the remote-sensed data collection, providing new insight into swash dynamics and the often-overlooked processes of post-storm beach recovery. The use of satellite data that is now readily available to all coastal researchers via Google Earth Engine continues to expand the routine data collection program and provide key insight into multi-decadal shoreline variability. As new and expanding remote sensing technologies continue to emerge, a key lesson from the long-term monitoring at Narrabeen-Collaroy is the importance of a regular re-evaluation of what data is most needed to progress the science.

Corridor Mapping of Sandy Coastal Foredunes with UAS Photogrammetry and Mobile Laser Scanning

“…On the other hand, coastal scientists ask for ever more frequent observations of sand and shoreline displacements to better understand the underlying physics and to improve the accuracy of prediction tools. Demand will likely increase with rising sea level and changing storm patterns [2,3], which has fostered the development and application of new surveying methods [4][5][6], and the so-called Blue Economy [7] is a chance to contribute to this effort.…”

“…This study opens the gate for exploring longer (hundreds of kilometers) shoreline dynamics with ground-control-point-free air and ground mapping techniques.coverage [11]. Indeed, spatial coverage of airborne LiDAR is unmatched [4]. Nonetheless, it involves technological, operational and logistic costs that prevent fast acquisition of pre-and post-storm data for instance.…”

“…coverage [11]. Indeed, spatial coverage of airborne LiDAR is unmatched [4]. Nonetheless, it involves technological, operational and logistic costs that prevent fast acquisition of pre-and post-storm data for instance.…”

Examining the utility of Simultaneous Localisation and Mapping (SLAM) LiDAR on a low-altitude unmanned aerial vehicle (UAV) across environments of various composition and dynamic complexity

“…4-1a), the advent of civilian use GPS (1983) enabled the use of airborne LiDAR in topographic and environmental research [5,6] followed by use as a standard survey and mapping tool by the later 1990's [7]. Such advancements in remote sensing research are often linked with such technological development [8][9][10] and, in recent years, several incremental developments in technology have resulted in lower cost and lighter weight components yielding increased affordability and accessibility of remotely piloted unmanned aerial vehicles (UAVs) ( Fig. 4-1b).…”

“…flight Pattern, Speed and Altitude (independent variables) onHovermap point cloud Density, Ground Sample Distance (GSD) and accuracy (response variables), a total of 24 flights were conducted using a full factorial experimental design including two patterns ('single-flight', 'cross-flight'), three speeds (1.5, 2.5, 3.5m s -1 ) and four altitudes(10,20,40, 80m AGL). Here, a focus on lower altitudes (<50m) were applied based on the previous work of Wallace et al[44], speeds were similar to that of Tulldahl et al[49] and the 'cross-flight' patterns discussed by Gerke and Przybilla[69].Each flight was planned using a geo-referenced LiDAR data of the study area previously collected with a Phoenix AL3-32 (Phoenix LiDAR Systems, U.S.A) and Global Mapper (v.18.2, Blue Marble Geographics, U.S.A.) software.…”