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🛰 Satellite(s)

ASTER (Advanced Spaceborne Thermal Emission and Reflection radiometer), ALOS AVNIR-2 (Advanced Land Observing Satellite, Advanced Visible and Near-Infrared Radiometer type 2), and Sentinel-2.

📊 Monitoring element

Land surface reflectance, SAR backscatter.

🧰 Description technique

The Nguyen Hao and Takewaka (2021) used Normalized Difference Water Index (NDWI) was used to distinguish water from land. The land-sea boundary was delineated using isocluster unsupervised classification.
The shoreline position was determined from removing the effect of tidal level on the waterline. The amount of retreat was calculated by subtracting the mean shoreline position estimated from the images acquired before the earthquake from the mean shoreline position estimated after the earthquake.

📏 Accuracy / Resolution

Spatial resolution: 10-15 m.

🗺 Case study

Nguyen Hao and Takewaka (2021) assessed the influence of the Great East Japan Earthquake (which occurred on 11 March 2011) on the shoreline of the northern Ibaraki Coast.

Tip

Benefits

The method demonstrated a fairly good agreement between the survey results and shoreline position within the scatter range of spatial resolution of satellite images.

Note

Limitations

  • Cloud cover can limit imagery availability at the moment of the event.

  • Complex sediment transport processes can affect shoreline evolution and need to be sufficiently characterised to be able to distinguish impacts related to earthquake.

Info

Applicability for Northland

Yes.

Limitations could come from the availability of good quality imagery at the time of a potential event.

Techniques applying optical data will be limited in coverage and temporal granularity by the persistent cloud cover in the region, particularly during the winter months. Mature cloud-masking techniques are directly available for open access multispectral data (e.g. Landsat and Sentinel-2). When using commercial data, care must be taken to ensure that there is sufficiently cloud free imagery available, as cloud masking is not as mature, and ordering a large volume of imagery to ensure complete cloud free coverage between multiple observations can become cost prohibitive.

Publication references

📚 Nguyen Hao Q, Takewaka S. 2021. Shoreline Changes along Northern Ibaraki Coast after the Great East Japan Earthquake of 2011. Remote Sensing. 13(7):1399.

🔗 https://www.mdpi.com/2072-4292/13/7/1399

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