Latest revision as of 11:59, 26 June 2020

Abstract

Doñana National Park wetlands, in South West Spain, undergo yearly cycles of inundation and drying out. During the hydrological year 2006–2007, 43 ASAR/Envisat images of Doñana, mostly in HH and VV polarizations, were acquired with the aim to monitor the flood extent evolution during an entire flooding cycle. The images were ordered in the seven ASAR incidence angles, also referred to as swaths, to achieve high observation frequency.

In this study, backscattering temporal signatures of the main land cover types in Doñana were obtained for the different incidence angles and polarizations. Plots showing the ${\displaystyle \sigma ^{0}HH/\sigma ^{0}VV}$ ratio behavior were also produced. The signatures were analyzed with the aid of miscellaneous site data in order to identify the effect of the flooding on the backscattering. Conclusions on the feasibility to discriminate emerged versus flooded land are derived for the different incidence angles, land cover types and phenological stages: intermediate incidence angles (ASAR IS3 and IS4) came up as the most appropriate single swaths to discriminate open water surface from smooth bare soil in the marshland deepest areas. Flood mapping in pasture lands, the most elevated regions, is feasible at steep to mid incidence angles (ASAR IS1 to IS4). In the medium elevation zones, colonized by large helophytes, shallow incidence angles (ASAR IS6 and IS7) enable more accurate flood delineation during the vegetation growing phase.

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