Response of Multi-Incidence Angle Polarimetric RADARSAT-2 Data to Herbaceous Vegetation Features in the Lower Paraná River Floodplain, Argentina

GRINGS, FRANCISCO MATÍAS; BRISCO, BRIAN; BARBER, MATÍAS ERNESTO; KANDUS, PATRICIA; MORANDEIRA, NATALIA SOLEDAD; AHERN, FRANK

Remote Sensing

MDPI

Año: 2021 vol. 13 p. 1 - 17

Wetland ecosystems play a key role in hydrological and biogeochemical cycles. In emergentvegetation targets, the occurrence of double-bounce scatter is indicative of the presence of water andcan be valuable for hydrological monitoring. Double-bounce scatter would lead to an increase ofσ0HH over σ0VV and a non-zero co-polarized phase difference (CPD). In the Lower Paraná Riverfloodplain, a total of 11 full polarimetric RADARSAT-2 scenes from a wide range of incidence angleswere acquired during a month. Flooded targets dominated by two herbaceous species were sampled:Schoenoplectus californicus (four sites, Bulrush marshes) and Ludwigia peruviana (three sites, Broadleafmarshes). As a general trend, σ0HH was higher than σ0VV, especially at the steeper incidence angles.By modeling CPD with maximum likelihood estimations, we found results consistent with doublebounce scatter in two Ludwigia plots, at certain scene incidence angles. Incidence angle accounted formost of the variation on σ0HH, whereas emergent green biomass was the main feature influencingσ0HV. Multivariate models explaining backscattering variation included the incidence angle andat least two of these variables: emergent plant height, stem diameter, number of green stems, andemergent green biomass. This study provides an example of using CPD to decide on the contributionof double-bounce scatter and highlights the influence of vegetation biomass on radar response. Evenwith the presence of water below vegetation, the contribution of double-bounce scatter to C-bandbackscattering depends on scene incidence angles and may be negligible in dense herbaceous targets.