Mapping changes in coastlines and tidal flats in developing islands using the full time series of Landsat images

Authors: Wenting Cao*, Zhejiang University; Iowa State University, Yuyu Zhou, Iowa State University, Rui Li, Zhejiang University , Xuecao Li, Iowa State University
Topics: Remote Sensing, Coastal and Marine, China
Keywords: Full time series; Change detection; East China, Island; Google Earth Engine; Land reclamation
Session Type: Paper
Day: 4/5/2019
Start / End Time: 8:00 AM / 9:40 AM
Room: Roosevelt 6, Marriott, Exhibition Level
Presentation File: No File Uploaded

Insights into the dynamics of coastlines and tidal flats at fine spatial and temporal resolutions are essential for sustainable development. Previous studies were generally conducted at relatively coarse temporal intervals, which hardly captured detailed coastal dynamics, especially in rapidly developing islands. This study developed a new method to map the monthly changes in coastlines and tidal flats in the Zhoushan Archipelago during 1985-2017 using the full time series of Landsat images based on the Google Earth Engine (GEE) platform. First, we built the full time series of the Modified Normalized Difference Water Index (MNDWI). Second, we derived temporal segments of MNDWI using a binary segmentation algorithm. Third, we classified the corresponding coastal cover types (i.e., water, tidal flats, and land) for each temporal segment. Finally, we identified the change information including conversion types, and turning years and months. Results indicate that the proposed method can well identify turning years with an overall accuracy of 90% and map coastal cover types with overall accuracies within 89-94% in 1985 and 87-92% in 2017. Significant coastline expansions and declines in tidal flats were found. The areas of water and tidal flats decreased by 6% and 10%, respectively, while the land area increased by 18%. The change was accelerated in the recent decade and mainly occurred on the medium-large islands, their surrounding small islands, and the islands close to the mainland. The derived coastal dynamics are useful for environmental management and ecological studies.

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