Abstract
Abstract. The black duck population has decreased significantly due to loss of its breeding habitat. Wetlands are an important feature that relates to habitat management and requires monitoring. Synthetic Aperture Radar (SAR) systems are helpful to map the wetland as the microwave signals are sensitive to water content and can be used to map surface water extent, saturated soils, and flooded vegetation. In this study, RadarSat 2 Polarimetric data is employed to map surface water and track changes in extent over the years through image thresholding and reviewed different approaches of Polarimetric decompositions for detecting flooded vegetation. Also, object-based analysis associated with beaver activity is conducted with combined multispectral SPOT satellite imagery. Results show SAR data has proven ability to improve mapping open water areas and locate flooded vegetation areas.
Highlights
American black ducks (Anas rubripes) experienced a long-term decline between the 1950s and 1990s causing the population to be reduced by more than 50%. (Black Duck Joint Venture Management Board, 2015) It is important to locate and protect their breeding range habitat
RADARSAT-2 is a fully Polarimetric satellite system that transmits and receives energy in all four planes (HH, VV, HV and VH), such configuration can maintain the phase that makes mapping the different scattering mechanisms within a wetland possible. (Brisco et al, 2011) The Synthetic Aperture Radar (SAR) backscatter can be decomposed into four types: (1) specular scattering indicating smoother surfaces; (2) rough scattering indicating rough water; (3) volume scattering indicating vegetation canopies; and (4) double-bounce indicating vertical emergent vegetation is surrounded by a visible, smooth water surface
Flooded vegetation can be differentiated by a combination of doublebounce and volume backscattering. (Wdowinski et al, 2008, Brisco and Touzi, 2008, Brisco et al, 2013) Despite studies have shown that the polarimetric information significantly improves the wetland vegetation characterization, the classification has only been done at pixel levels. (Ghedira et al, 2000, Parmuchi, 2002, Kaya et al, 2004, Touzi et al, 2007, Brisco et al, 2013) This is due to the nature of the SAR data appearance that makes the process of segmenting into image objects difficult
Summary
American black ducks (Anas rubripes) experienced a long-term decline between the 1950s and 1990s causing the population to be reduced by more than 50%. (Black Duck Joint Venture Management Board, 2015) It is important to locate and protect their breeding range habitat. Water has strong specular microwave reflection that results to be appeared dark and homogeneous in the SAR imagery Such information is useful in detecting flooded areas and classifying wetlands (Hess et al, 2003, Touzi et al, 2007, Lane and D’Amico, 2010). Different target scattering decomposition methods are studied to derive unique parameters, such as alpha angle and entropy that optimize the characterization of wetland classes and establish the relationship between remote sensing (SAR) parameters and physical indicators of the back duck habitat. These indices will be used with available long-term waterfowl data for modeling the contribution of habitat to demographic variation in black ducks. Our findings will help identify the value of remote sensing products to support standardized monitoring of change in wetland habitat and integration into the existing monitoring-management framework
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