Drones and Crowdsourced Science Aid Great Lakes Data Collection

Important data collection can aid coastal monitoring and management.

Citizen-Science with off-the-shelf UAV for Coastal Monitoring

Accurate and repetitive observation and quantification of the shoreline position and the coastal feature are essential aspects of coastal management and planning. Commonly, the dataset associated with coastal observation and quantification is obtained with in-situ coastal surveys. The current methods are mostly quite expensive, time-consuming, and require trained individuals to do the task. With the availability of the off-the-shelf low cost, lightweight, and reliable Unmanned Aerial Vehicle (UAV) with the advances of the algorithms such as structure-from-motion (SfM), UAV-based measurement becomes a promising tool. Open SfM initiative, open topographical database, and UAV communities are the enablers that make it possible to collect accurate and frequent coastal monitoring and democratize data. This paper provides a review and discussions that highlight the possibility of conducting scientific coastal monitoring or collaborating with the public. Literature was examined for the advances in coastal monitoring, challenges, and recommendations. We identified and proposed the use of UAV along with the strategies and systems to encourage citizen-led UAV observation for coastal monitoring while attaining the quality.

ICESat-2 Marine Bathymetry: Extraction, Refraction Adjustment and Vertical Accuracy as a Function of Depth in Mid-Latitude Temperate Contexts

Nearshore bathymetric data are used in many coastal monitoring applications, but acquisition conditions can be challenging. Shipborne surveys are prone to the risk of grounding in shallow waters, and scheduled airborne surveys often fail to coincide with optimal atmospheric and water conditions. As an alternative, since its launch in 2018, ICESat-2 satellite laser profile altimetry data provide free and readily available data on a 91-day repeat cycle, which may contain incidental bathymetric returns when suitable environmental conditions prevail. In this paper, the vertical accuracy of extracted, refraction-adjusted ICESat-2 nearshore marine bathymetric data is evaluated at four test sites in a Northern hemisphere, temperate latitude location. Multiple ICEsat-2 bathymetric values that occurred in close horizontal proximity to one another were averaged at a spatial scale of 1 m and compared with Multibeam Echosounder bathymetric survey data and Global Navigation Satellite System reference data. Mean absolute errors of less than 0.15 m were observed up to depths of 5 m, with errors of less than 0.24 m (to 6 m), 0.39 m (to 7 m) and 0.52 m (to 10 m). The occurrence of larger bathymetric errors with depth, which increase to 0.54 m at maximum photon depths of 11 m, appears to be primarily related to reduced numbers of geolocated photons with depth. The accuracies achieved up to 6 m suggest that the manual extraction, refraction adjustment and bathymetric filtering steps were effective. Overall, the results suggest that ICESat-2 bathymetric data accuracy may be sufficient to be considered for use in nearshore coastal monitoring applications where shipborne and airborne bathymetric data might otherwise be applied.

Beach Response to a Shoreface Nourishment (Aveiro, Portugal)

In Aveiro (NW coast of Portugal), a coastal monitoring programme was carried out in sequence of a shoreface nourishment intervention (over than 2 M m3) performed in 2020. In this programme, almost one year of biweekly subaerial topographies and quarterly bathymetric surveys have been collected along a 10 km coastal stretch between June 2020 and June 2021. In this study, topographic and bathymetric surveys were analysed to assess the expectation that if the shoreface nourishment is located in sufficiently shallow water depths, its landward movement will feed adjacent beaches and, consequently, increase the subaerial beach volume. Results show that the subaerial beach volume is well correlated with the 1.05 m (above MSL) isoline displacement through time. While the seaward limit of the shoreface nourishment moved landwards about 200 m, the shoreline proxy (isoline of 1.05 m) displayed a maximum seaward displacement of 60 m. The displacement of the shoreline proxy was highly variable in space, along the 10 km coastal stretch, and also in time, during storm events. During such events, both landward and seawards displacement of the shoreline proxy took place, depending on the spatial position. Moreover, while beaches close to the initial shoreface nourishment intervention displayed faster accretion patterns than those located farther away, the well-defined onshore movement of the shoreface nourishment did not result in a considerable beach volume increase. The achieved results were also compared against case studies of shoreface nourishments with similar volumes performed worldwide.

Mapping of Coastline Changes in Athens Riviera over the Past 76 Year’s Measurements

Mapping of coastline changes assists in coastal development and monitoring. Athens Riviera, located in the southwestern coastal zone in Attica in central Greece, has undergone major and radical changes generated by human interference during the last decades. The aim of this paper is to map record and measure the coastline changes in Athens Riviera over the past 76 years. Aerial photographs and satellite images from 1945 to 2021 as well as geographic information system (GIS) techniques were used to depict the spatial and temporal variations of the coastline. The results show that 60% of the total length of the coastline is artificial coast, while 29% is rocky coast and 12% beach. The study of seven subareas showed that human interventions caused significant coastline changes in Faliro Bay, Alimos and Glyfada. The adjacent coastal regions to Athens metropolitan area illustrate the highest modifications in the coastline. The main changes in the coastlines are recorded from 1960 to 1987, while the rate of changes in coastline slowed down from 1987 to 2021. The total changes in the coastline of Athens Riviera demonstrate that, during the past 76 years, the coastline was enhanced by 40% while land reclaimed to the sea area approaches 2.67 km2. The applied method is effective and rapid and may utilize in the coastal monitoring and management.

Evaluation of PAZ satellite imagery for the assessment of intra-seasonal dynamics of permafrost coasts (Beaufort Sea, Canada)

<p>Arctic permafrost coasts represent about 34% of the Earth’s coastline, with long sections affected by high erosion rates, increasingly threatening coastal communities. Year-round reduction in Arctic sea ice is forecasted and by the end of the 21st century, models indicate a decrease in sea ice area from 43 to 94% in September and from 8 to 34% in February (IPCC, 2014). An increase of the ice-free season leads to a longer exposure to wave action. Monitoring the Arctic coasts is limited by remoteness, climate harshness and difficulty of access for direct surveying, but also, when using satellite remote sensing, by frequent high cloudiness conditions and by illumination. In order to overcome these limitations, three sites at the Beaufort Sea Coast (Clarence lagoon, Hopper Island and Qikiqtaruk/Herschel Island) have been selected for monitoring using very high-resolution microwave X-band spotlight PAZ imagery from Hisdesat. Bluff top, thaw-slump headwalls and water lines were digitised from images acquired during the ice-free seasons of 2019 and 2020 at sub-monthly time-steps. The effects of coastal exposure on delineation accuracy in relation to satellite overpass geometry have been assessed and coastal changes have been quantified and compared to meteorological and tide-gauge data. The results show that PAZ imagery allow for monitoring and quantifying coastal changes at sub-monthly intervals and following the evolution of coastal features, such as small mud-flow fans and retrogressive thaw slumps. This shows that high resolution microwave imagery has a strong potential for significantly advancing coastal monitoring in remote Arctic areas. This research is part of project Nunataryuk funded under the European Union's Horizon 2020 Research and Innovation Programme (grant agreement no. 773421) and of Hisdesat project Coastal Monitoring for Permafrost Research in the Beaufort Sea Coast (Canada). </p>

Novel approach to enhance coastal habitat and biotope mapping with drone aerial imagery analysis

Understanding the complex factors and mechanisms driving the functioning of coastal ecosystems is vital towards assessing how organisms, ecosystems, and ultimately human populations will cope with the ecological consequences of natural and anthropogenic impacts. Towards this goal, coastal monitoring programs and studies must deliver information on a range of variables and factors, from taxonomic/functional diversity and spatial distribution of habitats, to anthropogenic stress indicators such as land use, fisheries use, and pollution. Effective monitoring programs must therefore integrate observations from different sources and spatial scales to provide a comprehensive view to managers. Here we explore integrating aerial surveys from a low-cost Remotely Piloted Aircraft System (RPAS) with concurrent underwater surveys to deliver a novel approach to coastal monitoring. We: (i) map depth and substrate of shallow rocky habitats, and; (ii) classify the major biotopes associated with these environmental axes; and (iii) combine data from i and ii to assess the likely distribution of common sessile organismal assemblages over the survey area. Finally, we propose a general workflow that can be adapted to different needs and aerial platforms, which can be used as blueprints for further integration of remote-sensing with in situ surveys to produce spatially-explicit biotope maps.