Inundation Mapping Over Tonle Sap Lake Region in Cambodia Using C-band Sentinel-1 Data in 2017 to support WEF Nexus Assessment
Abstract
Tonle Sap lake located in the lower Mekong Basin in Cambodia, is a seasonally inundated ecosystem consisting of very high natural productivity. Monitoring its inundation status over time is of paramount importance to understand the ecosystem services and functions provided to the region. Active Synthetic Aperture Radar (SAR) with long wavelengths working day and night in all weather conditions is more valuable than passive optical sensors in this frequently cloud covered region. Single Look Complex (SLC) C-band Sentinel-1 Interferometric Wide Swath (IW) data with a revisit time of 12 days with similar geometry was used to assess Tonle Sap inundation dynamics to understand inundation fluxes. A total of 54 images covering the lake region acquired in 2017 are pre-processed using open access software ("XAR") developed at Applied Geosolutions to calibrate and geocode the VV and VH polarizations as well as to generate coherence maps between adjacent observations. Time-series gamma naught of the VV and VH polarizations are used for the land cover mapping under the classical unsupervised K-Mean method, which achieves very high accuracy compared with the ground truth. Then, histograms of the large area coherence maps over time are used to determine spatiotemporal soil moisture patterns. Together with the classification map, both VV and VH of each land class are analyzed in dry and wet seasons to construct a decision tree for inundation mapping over time. Comparison with the rainfall data estimated from the Climate Hazards Group InfraRed Precipitation with Station data (CHIPRS) shows strong correspondence. Further, cross calibration against JASON 2/3 and Mekong gauge data provides a mechanism to assess inundation at moderate spatial scales that is critical for understanding tradeoffs among water-energy-food nexus.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.H13A..06T
- Keywords:
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- 1622 Earth system modeling;
- GLOBAL CHANGEDE: 1834 Human impacts;
- HYDROLOGYDE: 1836 Hydrological cycles and budgets;
- HYDROLOGYDE: 1855 Remote sensing;
- HYDROLOGY