L-Band Polarimetric Target Decomposition of Mangroves of the Rufiji Delta, Tanzania

Abstract

Abstract:The mangroves of the Rufiji Delta are an important habitat and resource. The mangrove forest reserve is home to an indigenous population and has been under pressure from an influx of migrants from the landward side of the delta. Timely and effective forest management is needed to preserve the delta and mangrove forest. Here, we investigate the potential of polarimetric target decomposition for mangrove forest monitoring and analysis. Using three ALOS PALSAR images, we show that L-band polarimetry is capable of mapping mangrove dynamics and is sensitive to stand structure and the hydro-geomorphology of stands. Entropy-alpha-anisotropy and incoherent target decompositions provided valuable measures of scattering behavior related to forest structure. Little difference was found between Yamaguchi and Arii decompositions, despite the conceptual differences between these models. Using these models, we were able to differentiate the scattering behavior of the four main species found in the delta, though classification was impractical due to the lack of pure stands. Scattering differences related to season were attributed primarily to differences in ground moisture or inundation. This is the first time mangrove species have been identified by their scattering behavior in L-band polarimetric data. These results suggest higher resolution L-band quad-polarized imagery, such as from PALSAR-2, may be a powerful tool for mangrove species mapping.

Mangrove cover change detection in the Rufiji Delta in Tanzania

“…For local management purposes, the delta has been divided in three major blocks: northern; central; and southern blocks (Semesi, 1989). The northern block contains about 46% of the total mangrove coverage, and is characterized by more freshwater input, is more accessible, and therefore more frequently utilized for local and commercial interests than the other blocks (Brown et al, 2016). The Rufiji mangrove forest was the first to be declared a forest reserve in Tanzania in 1898 during the German colonial period (Sunseri, 2007).…”

Inter‐annual hydroclimatic variability in coastal Tanzania

“…Therefore, strategies for improved conservation in this region have been proposed (Hansen et al, 2010). Such strategies include not only coastal areas, but also large watersheds (e.g., Rufiji basin) that control the structure and productivity of mangrove wetlands, where water availability shows major inter-annual and decadal fluctuations (Armanios and Fisher, 2014;Brown et al, 2016;Hirvonen, 2016).…”

Combining of the H/A/Alpha and Freeman–Durden Polarization Decomposition Methods for Soil Moisture Retrieval from Full-Polarization Radarsat-2 Data

“…H/A/Alpha is a polarization decomposition method based on eigen decomposition of polarized SAR data [18]. e biggest advantage of eigen decomposition is that it is not limited by the specific scattering mechanism employed; the eigenvalues do not change with transformation of the antenna coordinate system [25]. erefore, the method is associated with invariance in the basis, including rotation invariance, rendering the data more reliable.…”