Cost-effective erosion monitoring of coastal cliffs

Westoby, Matthew; Lim, Michael; Hogg, Michelle; Pound, Matthew J.; Dunlop, Lesley; Woodward, John

doi:10.1016/j.coastaleng.2018.04.008

Cited by 81 publications

(50 citation statements)

References 65 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Several studies have compared close-range photogrammetry and UAV-based SfM products with LiDAR, RTK-GNSS, and total station surveys [2][3][4][30][31][32]. Compared to terrestrial LiDAR, UAV surveys have a clear advantage in terms of low-cost equipment, rapid survey time, ease of deployment, and fewer limitations for field survey [2,30]. The resolution and accuracy of SfM are comparable to terrestrial LiDAR in general, and both techniques exhibit a good degree of agreement with GNSS ground truths [2,3].…”

Section: Related Workmentioning

confidence: 99%

Evaluation of UAV LiDAR for Mapping Coastal Environments

et al. 2019

View full text Add to dashboard Cite

Unmanned Aerial Vehicle (UAV)-based remote sensing techniques have demonstrated great potential for monitoring rapid shoreline changes. With image-based approaches utilizing Structure from Motion (SfM), high-resolution Digital Surface Models (DSM), and orthophotos can be generated efficiently using UAV imagery. However, image-based mapping yields relatively poor results in low textured areas as compared to those from LiDAR. This study demonstrates the applicability of UAV LiDAR for mapping coastal environments. A custom-built UAV-based mobile mapping system is used to simultaneously collect LiDAR and imagery data. The quality of LiDAR, as well as image-based point clouds, are investigated and compared over different geomorphic environments in terms of their point density, relative and absolute accuracy, and area coverage. The results suggest that both UAV LiDAR and image-based techniques provide high-resolution and high-quality topographic data, and the point clouds generated by both techniques are compatible within a 5 to 10 cm range. UAV LiDAR has a clear advantage in terms of large and uniform ground coverage over different geomorphic environments, higher point density, and ability to penetrate through vegetation to capture points below the canopy. Furthermore, UAV LiDAR-based data acquisitions are assessed for their applicability in monitoring shoreline changes over two actively eroding sandy beaches along southern Lake Michigan, Dune Acres, and Beverly Shores, through repeated field surveys. The results indicate a considerable volume loss and ridge point retreat over an extended period of one year (May 2018 to May 2019) as well as a short storm-induced period of one month (November 2018 to December 2018). The foredune ridge recession ranges from 0 m to 9 m. The average volume loss at Dune Acres is 18.2 cubic meters per meter and 12.2 cubic meters per meter within the one-year period and storm-induced period, respectively, highlighting the importance of episodic events in coastline changes. The average volume loss at Beverly Shores is 2.8 cubic meters per meter and 2.6 cubic meters per meter within the survey period and storm-induced period, respectively.

show abstract

Section: Related Workmentioning

confidence: 99%

Evaluation of UAV LiDAR for Mapping Coastal Environments

et al. 2019

View full text Add to dashboard Cite

show abstract

“…Far-range remote sensing could be a solution in the future, but for now, satellite and aerial data do not enable to observe subtle changes because their resolution is not sufficient and because they generally capture only the cliff top [4]. Thus, considering their high spatial and temporal resolution, their low cost and their operational flexibility, near-range remote sensing methods (land-based or using UAVs) are increasingly used for the cliff face monitoring [4][5][6][7][8].…”

mentioning

confidence: 99%

UAV survey of a coastal cliff face – Selection of the best imaging angle

et al. 2019

View full text Add to dashboard Cite

UAVs are relevant for monitoring cliff faces. In this study, several flights are performed with various imaging angles (nadir, 20°, 30° and 40° off-nadir) to assess the impact of the imaging angle on the 3D cliff face reconstruction. Occlusions issues arising with sub-vertical cliffs make nadir surveys nearly irrelevant. The results obtained with 20°, 30° and 40° off-nadir imaging angles are satisfactory regarding texture restitution and accuracy with respectively 5.5 cm, 5.9 cm and 4.9 cm of error, higher tilting angles yielding better reconstructions on sub-vertical or overhanging parts of the cliff. This article also investigates other parameters affecting tiepoint detection on the cliff face, as the effective overlap, the UAV-cliff face distance and the cliff face illumination. Guidelines are provided for UAV survey parameterization, aiming at capturing the whole cliff face with a good trade-off between distance to the cliff, flight height and spatial resolution of the photographs. Highlights Impact of the UAV camera tilting angle on the 3D cliff face reconstruction  Because of occlusions, irrelevance of nadir pointing camera for sub-vertical cliffs  Satisfying accuracy and texture for both 20°, 30° and 40° off-nadir imaging angles  Other parameters impacting tiepoint detection in the reconstruction process

show abstract

“…Our approach also shows that specific areas (i.e., foredune) can be specifically analysed to aid in the understanding of change in specific parts of dune systems. This work develops that of [19,[58][59][60] but takes a more robust quantitative approach to multi-temporal monitoring by accounting for many forms of uncertainty with the M3C2-PM methodology.…”

Section: Discussionmentioning

confidence: 99%

“…From commercial satellite systems, relatively fine spatial (0.61 m panchromatic) resolution data such as those delivered by Quickbird, we argue, are poorly suited for cost-effective monitoring of dynamic systems such as those found in coastal environments. This is because dune systems are highly dynamic and repeat surveys are often required to gain understanding of the processes at work in the coastal zone, necessitating the purchase of multiple data sets, which can become very costly, sometimes prohibitively so for long-term monitoring programs [18,19]. Furthermore, despite their fine spatial resolution, issues such as mixed pixels can still arise in dune environments due to a high degree of habitat heterogeneity and mixtures of vegetation and sand [20].…”

Section: Introductionmentioning

confidence: 99%

Tracking Fine-Scale Structural Changes in Coastal Dune Morphology Using Kite Aerial Photography and Uncertainty-Assessed Structure-from-Motion Photogrammetry

et al. 2018

View full text Add to dashboard Cite

Coastal dunes are globally-distributed dynamic ecosystems that occur at the land-sea interface. They are sensitive to disturbance both from natural forces and anthropogenic stressors, and therefore require regular monitoring to track changes in their form and function ultimately informing management decisions. Existing techniques employing satellite or airborne data lack the temporal or spatial resolution to resolve fine-scale changes in these environments, both temporally and spatially whilst fine-scale in-situ monitoring (e.g., terrestrial laser scanning) can be costly and is therefore confined to relatively small areas. The rise of proximal sensing-based Structure-from-Motion Multi-View Stereo (SfM-MVS) photogrammetric techniques for land surface surveying offers an alternative, scale-appropriate method for spatially distributed surveying of dune systems. Here we present the results of an inter- and intra-annual experiment which utilised a low-cost and highly portable kite aerial photography (KAP) and SfM-MVS workflow to track sub-decimetre spatial scale changes in dune morphology over timescales of between 3 and 12 months. We also compare KAP and drone surveys undertaken at near-coincident times of the same dune system to test the KAP reproducibility. Using a Monte Carlo based change detection approach (Multiscale Model to Model Cloud Comparison (M3C2)) which quantifies and accounts for survey uncertainty, we show that the KAP-based survey technique, whilst exhibiting higher x, y, z uncertainties than the equivalent drone methodology, is capable of delivering data describing dune system topographical change. Significant change (according to M3C2); both positive (accretion) and negative (erosion) was detected across 3, 6 and 12 months timescales with the majority of change detected below 500 mm. Significant topographic changes as small as ~20 mm were detected between surveys. We demonstrate that portable, low-cost consumer-grade KAP survey techniques, which have been employed for decades for hobbyist aerial photography, can now deliver science-grade data, and we argue that kites are well-suited to coastal survey where winds and sediment might otherwise impede surveys by other proximal sensing platforms, such as drones.

show abstract

Cost-effective erosion monitoring of coastal cliffs

Cited by 81 publications

References 65 publications

Evaluation of UAV LiDAR for Mapping Coastal Environments

Evaluation of UAV LiDAR for Mapping Coastal Environments

UAV survey of a coastal cliff face – Selection of the best imaging angle

Tracking Fine-Scale Structural Changes in Coastal Dune Morphology Using Kite Aerial Photography and Uncertainty-Assessed Structure-from-Motion Photogrammetry

Contact Info

Product

Resources

About