The rapid economic development in coastal regions has threatened ecosystem functions and services of tidal flats. For coastal management, a high precision map of tidal flats is needed. 

The biggest difficulty in tidal flats mapping using optical satellite images lies in the uncertainty of tidal level. Coastal mudflat patches are only briefly exposed in the period of the lowest tide due to the periodic inundation of tides.  

In a recent study published in Remote Sensing of Environment, a research team led by Prof. WANG Zongming from the Northeast Institute of Geography and Agroecology (IGA) of the Chinese Academy of Sciences proposed an automatic method to extract coastal mudflat based on remote sensing big data and Google Earth Engine (GEE) cloud platform. 

The researchers developed a rapid, robust, and automated approach, named MSIC-OA approach, to map tidal flats from time series Sentinel-2 imagery. The innovative design of the proposed mapping method is that this method does not rely on auxiliary data, manual intervention thresholds, and before and after processing. 

With the complete storage of Sentinel-2 images and computing power of GEE platform, the MSIC-OA approach succeeded in producing a 10-meter spatial resolution map of China's tidal flat distribution (CTF) for the first time.   

The dense temporal resolution Sentinel-2 images with revisit interval of 2–5 days offers a great opportunity to capture the lowest and highest tides, which is vital to conduct accurate and robust delineation of tidal flats.   

According to the point-to-point (including ground samples and edge-points) and polygon-to-image accuracy assessments, the CTF map achieved high overall accuracies (95%) and F1 scores (0.93), and highly consistent with sub-meter resolution images. 

The results illustrated that the total area of China's coastal tidal flats was 858,784 ha in 2020, of which Jiangsu Province has the most abundant coastal tidal flats. 

The CTF map can provide reliable information for tidal flats management, sustainable development of coastal zones, Sustainable Development Goals (SDGs), and scientific research. 

Contact:

JIA Mingming

Northeast Institute of Geography and Agroecology

Tel: 86-431-85542362

E-mail: jiamingming@iga.ac.cn

Web:http://english.iga.cas.cn/