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Open AccessArticle

Implementation of a Surface Water Extent Model in Cambodia using Cloud-Based Remote Sensing

1
U.S. Geological Survey, Western Geographic Science Center, P.O. Box 158, Moffett Field, CA 94035, USA
2
U.S. Geological Survey, Western Geographic Science Center, Tucson, AZ 85719, USA
3
Contractor to the U.S. Geological Survey, Western Geographic Science Center, Tucson, AZ 85719, USA
*
Author to whom correspondence should be addressed.
Remote Sens. 2020, 12(6), 984; https://doi.org/10.3390/rs12060984
Received: 5 February 2020 / Revised: 6 March 2020 / Accepted: 9 March 2020 / Published: 19 March 2020
Mapping surface water over time provides the spatially explicit information essential for hydroclimatic research focused on droughts and flooding. Hazard risk assessments and water management planning also rely on accurate, long-term measurements describing hydrologic fluctuations. Stream gages are a common measurement tool used to better understand flow and inundation dynamics, but gage networks are incomplete or non-existent in many parts of the world. In such instances, satellite imagery may provide the only data available to monitor surface water changes over time. Here, we describe an effort to extend the applicability of the USGS Dynamic Surface Water Extent (DSWE) model to non-US regions. We leverage the multi-decadal archive of the Landsat satellite in the Google Earth Engine (GEE) cloud-based computing platform to produce and analyze 372 monthly composite maps and 31 annual maps (January 1988–December 2018) in Cambodia, a flood-prone country in Southeast Asia that lacks a comprehensive stream gage network. DSWE relies on a series of spectral water indices and elevation data to classify water into four categories of water inundation. We compared model outputs to existing surface water maps and independently assessed DSWE accuracy at discrete dates across the time series. Despite considerable cloud obstruction and missing imagery across the monthly time series, the overall accuracy exceeded 85% for all annual tests. The DSWE model consistently mapped open water with high accuracy, and areas classified as “high confidence” water correlate well to other available maps at the country scale. Results in Cambodia suggest that extending DSWE globally using a cloud computing framework may benefit scientists, managers, and planners in a wide array of applications across the globe. View Full-Text
Keywords: surface water; inundation; land change; remote sensing; Landsat; Google Earth Engine; Southeast Asia; Cambodia surface water; inundation; land change; remote sensing; Landsat; Google Earth Engine; Southeast Asia; Cambodia
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  • Externally hosted supplementary file 1
    Doi: https://doi.org/10.5066/P9LH9YYF
    Link: https://doi.org/10.5066/P9LH9YYF
    Description: A USGS data release including the data and code used for this research can be found on USGS ScienceBase.
MDPI and ACS Style

E. Soulard, C.; J. Walker, J.; E. Petrakis, R. Implementation of a Surface Water Extent Model in Cambodia using Cloud-Based Remote Sensing. Remote Sens. 2020, 12, 984.

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