Abstract
Seasonal inundation is an important effect that governs the distribution of ecosystems in the tropics. In the Amazon Basin, the seasonal flood pulse causes a difference in high and low water levels that can exceed 15 m. The associated flood duration and extent play an important role in land-atmosphere carbon exchange and affect the ecosystem’s carbon pool that originates from organic matter transported from upland and flooded forests. Studies of wetlands inundation across the Amazon Basin have utilized dual season mosaics from JERS-1 and wide-swath ScanSAR data from ALOS PALSAR to characterize inundation across the basin. This study builds upon past efforts with JERS-1 and ALOS PALSAR and uses ALOS-2 PALSAR-2 ScanSAR data to generate annual maximum and minimum inundation extent maps over the full Amazon Basin for the period spanning November 2014–October 2017. The study uses decision tree classification to create a maximum and a minimum inundation extent map for each year over this time period. The results show that a generalized algorithm that fits the entire basin has an 86% overall accuracy compared with a classification made for a local region from the same PALSAR-2 datasets. Comparisons with previous full-basin inundation maps by other L-band radars shows similar results for inundated areas during maximum inundation. The maps derived previously from JERS-1 and ALOS PALSAR show 7.3% and 6.9% inundated vegetation, respectively, and this study using PALSAR-2 shows values ranging between 5.5% and 7.0% across the three study years. Comparisons between the stage data across the basin and acquisition dates/periods for JERS-1 and PALSAR-2 show that the sensors capture the nature of the maximum and minimum flooding across the basins but have not successfully captured the exact maximum and minimum flood levels that have been recorded in the stage data. The inundation maps are publicly available under a Creative Commons (CC BY 4.0) licensefrom the Alaska Satellite Facility.
Highlights
The Amazon Basin covers an area of approximately six million km2 and is a host two evtalastnwdse,tlcaonmdsp,lexes and biodive complexes and biodiversity richness with the meandering of rivers creating a mosaic ohf ahbaibtiattast.s.RRiviverermeandering and meandering and its effects on flood regimes and water and soil qualities result in varyivnagrdyinstgribduisttiroinbsutions of species a of species and habitat composition
Comparisons with existing local and basin-wide inundation maps generated by L-band Synthetic aperture radar (SAR) indicate comparable results for inundated areas during the maximum inundation conditions, and uniquely low estimates of minimum inundation extents
Some available ancillary datasets may differ across regions, the general technique should be transferable to other flood pulse-dominated wetlands, albeit with corresponding adjustments made to the region-specific thresholds supporting implementation of the decision tree
Summary
The Amazon Basin coversThe Amazon Basin covers an area of approximately six million km and is a host two evtalastnwdse,tlcaonmdsp,lexes and biodive complexes and biodiversity richness with the meandering of rivers creating a mosaic ohf ahbaibtiattast.s.RRiviverermeandering and meandering and its effects on flood regimes and water and soil qualities result in varyivnagrdyinstgribduisttiroinbsutions of species a of species and habitat composition. The biotic interactions in river-floodplain systems wsyisttheimn tshwe ibtahsiinn the basin are driv are driven primarily by the seasonal flood pulse phenomenon [1,2] This annual pualsnenmuaolvpeuslfsreomoves from the we the west in the Andes eastward to the Amazon delta over the course of several monthssevaenrdalremsuolntsthins and results in lar Remote Sens. Accurate and consistent geospatial datasets of inundation extent and dynamics across the Amazon Basin are needed to support study of this globally crucial tropical complex [2]. Such data records support characterizing seasonal inundation processes so that current state and future changes related to both natural and anthropogenic factors can be monitored, and associated impacts addressed. L-band SAR is currently the only spaceborne remote sensing system that can provide geospatially explicit mappings of inundation extents in forested wetlands
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