An optimal waterline approach for studying tidal flat morphological changes using remote sensing data: A case of the northern coast of Vietnam

Tong, Si Son; Deroin, Jean-Paul; Pham, Thi Lan

doi:10.1016/j.ecss.2020.106613

Cited by 43 publications

(25 citation statements)

References 22 publications

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“…Silty mudflats have different states under different tidal conditions, and the accurate extraction of information on silty mudflats under various scenarios is critical to the correct extraction of coastlines. Ryu et al [23] used the red band density partitioning to extract the water-line of silty mudflats in Gomso Bay, Korea, with an average deviation of less than 60 m. Tong et al [39] explored the NDWI and ratio of the green band to short-wave infrared band 1 in different seasons to extract the shoreline of silty mudflats in northern Vietnam. The results showed that different uses of the green band divided by short-wave infrared band 1 with coefficients of variation of 13% in the dry season and 25% in the rainy season was the optimal shoreline extraction method.…”

Section: Discussionmentioning

confidence: 99%

Improved Spectral Water Index Combined with Otsu Algorithm to Extract Muddy Coastline Data

Tang

Zhao

Lin

et al. 2022

Water

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Based on the spectral reflection characteristics analysis of the muddy coastline in Jiangsu, an improved spectral water index (IWI) combined with the Otsu algorithm is proposed to extract muddy coastlines from Landsat Operational Land Imager (OLI) images. The IWI-extracted coastline results are compared with those extracted by the modified normalized difference water index (MNDWI), normalized difference water index (NDWI), enhanced water index (EWI), revised normalized different water index (RNDWI) and automated water extraction index (AWEI). The results show that the IWI is not affected by tidal conditions or sand content in the water, can reduce the “salt-and-pepper” phenomenon in the Otsu algorithm classification, can accurately identify water boundaries and can extract silty mudflats and marine buildings with high accuracy. It can also significantly increase the degree of automation of coastline extraction. The IWI combined with the Otsu algorithm demonstrates high accuracy of over 84% in the extraction muddy coastline data with one-pixel tolerance, which is twice as accurate as other indices. The accuracy of extraction for all other types of coastlines is over 81%. Therefore, the IWI index combined with the Otsu algorithm is reliable for studies of sea–land processes and coastline evolutions.

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Section: Discussionmentioning

confidence: 99%

Improved Spectral Water Index Combined with Otsu Algorithm to Extract Muddy Coastline Data

Tang

Zhao

Lin

et al. 2022

Water

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“…The method proposed here is similar to the "water line" method [28][29][30][31]50] to map topography in the ITZ. However, instead of mapping the topography by associating single satellite observations to tidal gauge height observations, we mapped the percentage of atmospheric exposure only on the basis of a statistical analysis of temporally consistent long time series of Sentinel-1 radar imagery.…”

Section: Discussionmentioning

confidence: 99%

“…On a local scale, the atmospheric exposure is directly linked to the topography of the ITZ via the tidal range. The "water-line" method [28] has been used extensively to map the topography in the ITZ [29,30]. It is based on extracting the water line in single satellite images and associating them with observed tidal gauge height measurements.…”

Section: Introductionmentioning

confidence: 99%

Mapping Atmospheric Exposure of the Intertidal Zone with Sentinel-1 CSAR in Northern Norway

Haarpaintner

Davids

2021

Remote Sensing

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The intertidal zone (ITZ) is a highly dynamic and diverse coastal ecosystem under pressure that provides important eco-services. Being periodically under water makes it challenging to monitor, and the only possibility to map it in all tidal stages is by using dense time series of observations. At high latitudes, the Sentinel-1 (S1) constellation of the European Copernicus Program consistently provides radar imagery at fixed times on a near-daily basis, independently of cloud cover and sunlight. As tides have a period of 12 h 25.2 min, 1–2 year long S1 time series are therefore able to sample the whole tidal range and, thus, map the percentage of atmospheric exposure of the ITZ, which is an important environmental parameter. Tidal reference levels of mean high/low water at spring, mean and neap tide correspond each to specific percentiles of tidal heights and inversely correspond to atmospheric exposure. The presented method maps atmospheric exposure on the basis of purely statistical analyses of Sentinel-1 time series without the need for any tidal gauge data, by extracting water lines via simple thresholding of radar backscatter percentiles images. The individual thresholds for the second, fifth, 25th, 50th, 75th, 95th, and 98th percentile image were determined by fitting the threshold contour lines to in situ water line GPS tracks collected at corresponding tidal reference levels at five locations around Tromsø in Northern Norway. They inversely correspond to atmospheric exposures of 98%, 95%, 75%, 50%, 25%, 5%, and 2%, respectively. The method was applied to the whole Tromsø Municipality resulting in an ITZ atmospheric exposure map. The validation shows that the mean low water lines at neap, mid, and spring tide were mapped with accuracies of 93%, 84%, and 64%, respectively. The overall approach should be applicable worldwide.

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“…The manually digitized waterlines were then assembled to construct DEMs, which proved to be in good agreement with the observations with a height accuracy of 35 to 38 cm. Recent studies based on the waterline method commonly reported height accuracies ranging from 10 to 40 cm [28,[36][37][38][39]. The accuracy of the resulting DEM depends mainly on the well-distributed sampling of the tidal range, which implies a large variety of waterlines.…”

Section: Relevance Of Satellite-derived Topography Modelsmentioning

confidence: 99%

Satellite-Derived Topography and Morphological Evolution around Authie Macrotidal Estuary (France)

Bagot

Huybrechts

Sergent

2021

JMSE

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The wide spatial and temporal coverage of remotely sensing images is an essential asset to analyze the morphological behaviour of fast-changing coastal environments such as estuarine systems. This paper investigates the reliability of intertidal topography mapping around the Authie Bay, a macrotidal estuarine system located on the northern coast of France. A Satellite-Derived Topography technique is developed by relating the green band reflectance of Sentinel-2 images to rapid variations in topography. This method is well suited to small sedimentary structures of the coastal zone with a 0.30 to 0.35 m height accuracy of the constructed Digital Elevation Model (DEM). For the more complex estuarine configuration, the waterline method was applied and resulted in the construction of DEMs with a height accuracy of 0.35 to 0.38 m. Video animations and records of Authie meander positions along transects are created from Sentinel-2 and Landsat satellite archives (1984–2020). These materials allow to highlight a sedimentation phase at the east side of the spit since 2015. It constrains the main channel towards the eastern bank, thus promoting coastal erosion. The monitoring of a severe erosion phase throughout 2019 shows a 130 m retreat of the coastline. Topographic map differentiation led to the detection of a sedimentation anomaly upstream of the bay, probably linked to this erosion event.

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An optimal waterline approach for studying tidal flat morphological changes using remote sensing data: A case of the northern coast of Vietnam

Cited by 43 publications

References 22 publications

Improved Spectral Water Index Combined with Otsu Algorithm to Extract Muddy Coastline Data

Improved Spectral Water Index Combined with Otsu Algorithm to Extract Muddy Coastline Data

Mapping Atmospheric Exposure of the Intertidal Zone with Sentinel-1 CSAR in Northern Norway

Satellite-Derived Topography and Morphological Evolution around Authie Macrotidal Estuary (France)

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