Abstract
The massive development of floating plants in floodplain lakes and wetlands in the upper Middle Paraná river in the La Plata basin is environmentally and socioeconomically important. Every year aquatic plant detachments drift downstream arriving in small amounts to the Río de la Plata, but huge temporary invasions have been observed every 10 or 15 years associated to massive floods. From late December 2015, heavy rains driven by a strong El Niño increased river levels, provoking a large temporary invasion of aquatic plants from January to May 2016. This event caused significant disruption of human activities via clogging of drinking water intakes in the estuary, blocking of ports and marinas and introducing dangerous animals from faraway wetlands into the city. In this study, we developed a scheme to map floating vegetation in turbid waters using high-resolution imagery, like Sentinel-2/SMI (MultiSpectral Imager), Landsat-8/OLI (Operational Land Imager), and Aqua/MODIS (MODerate resolution Imager Spectroradiometer)-250 m. A combination of the Floating Algal Index (that make use of the strong signal in the NIR part of the spectrum), plus conditions set on the RED band (to avoid misclassifying highly turbid waters) and on the CIE La*b* color space coordinates (to confirm the visually “green” pixels as floating vegetation) were used. A time-series of multisensor high resolution imagery was analyzed to study the temporal variability, covered area and distribution of the unusual floating macroalgae invasion that started in January 2016 in the Río de la Plata estuary.
Highlights
Water hyacinth (Eichhornia crassipes) is a free-floating macrophyte native to Lower Amazonia, Brazil, that forms dense mats on the surface of slow-moving waterways and backwaters
The proposed methodology allows identifying and mapping the floating aquatic hyacinth (Eichhornia crassipes) invasion in the highly turbid RdP waters that started in January 2016
Combination of the floating algal index (FAI) index, plus conditions set on the RED band and on the La*b* color space coordinates were used
Summary
Water hyacinth (Eichhornia crassipes) is a free-floating macrophyte native to Lower Amazonia, Brazil, that forms dense mats on the surface of slow-moving waterways and backwaters. 2018, 10, 1140; doi:10.3390/rs10071140 www.mdpi.com/journal/remotesensing the Río Grande River [3], and in California’s Sacramento–San Joaquin River Delta [4] in the United States. Mapping of aquatic plants and estimation of their surface extent are crucial to the efficient management and implementation of mitigation measures. This information can be derived accurately with10,fine. 2018, 1140resolution remote sensing products like the high resolution imagery provided by Sentinel-2/MSI (10 m) and Landsat-8/OLI (30 m) systems, but their low observation frequency and narrow swath hinder their ability to continuously monitor and quantify the extent of floating processes of freshwater ecosystems, like in lake Victoria in East. Remote Sens. 2018, 1140resolution remote sensing products like the high resolution imagery provided by Sentinel-2/MSI (10 m) and Landsat-8/OLI (30 m) systems, but their low observation frequency and narrow swath hinder their ability to continuously monitor and quantify the extent of floating processes of freshwater ecosystems, like in lake Victoria in East
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