Water level within wetlands marshes using SAR instruments and Electromagnetic models

KARSZENBAUM HAYDEE; GRINGS, FRANCISCO MATIAS; SALVIA, MARÍA MERCEDES; KANDUS, PATRICIA; PERNA, PABLO

Centro de Convençoes, Florianópolis, Santa Catarina, Brasil

Simposio; XIII Simpósio Brasileiro de Sensoriamento Remoto; 2007

Sociedade de Especialistas Latino-Americanos de Percepción Remota

The general goal of our current studies in radar remote sensing of wetlands is to better understand how variations in climate and anthropogenic factors influence the hydrologic condition of coastal wetland and to develop tools to improve the capability to map and monitor these ecosystems through the use of C and L band spaceborne imaging radars. The final objective is to contribute with reliable information for hydrologic process modeling. Imaging radars have distinct characteristics which make them of significant value for monitoring and mapping wetland conditions. The microwave energy transmitted by the radar penetrates the vegetation canopy, and the backscattered energy detected is mainly the result of electromagnetic interactions of a combination of vegetation structure and soil condition. The presence or absence of water in wetlands (which have a much higher dielectric constant than dry or wet soil) significantly alters the signal detected from these areas. The ability of radar observations to provide information about vegetation structure and soil condition (water level below the canopy) has driven the current research on the use of radar instruments and techniques for wetland mapping and monitoring The present work addresses the lower delta of the Paraná river, a vast wetland macro-mosaic located at the terminal area of that river in Argentina. It stretches through the final 300 km of the Paraná basin, covering approximately 17,500 km2, and is located between 32º05’S, 60º48’W, and 34º29’S, 58º30’W, close to Buenos Aires City. It has a complex hydrological regime determined by the influence of the Paraná and Uruguay rivers and the Del Plata estuary. The latter is primarily responsible for the regular flooding of the downstream portion of the region. The combined effects of wind and tide result in frequent but short (hours-long or day-long) floods.Two types of marshes, junco and cortadera, occupy 50% of the lower delta (Kandus et al., 2006). They are the main cause of the water buffer effect on this wetland, a key phenomenon for flood control and a key argument in wetlands conservation policies. In order to fully understand this buffer effect, water storage capacity needs to be monitored at regional scale.This paper presents the analysis, interpretation and modeling of a multitemporal set of ENVISAT ASAR alternated polarization beam mode data acquired over the lower Paraná Delta. This presentation discusses whether it is possible to determine the amount of water below vegetation, and which environmental conditions and instrument characteristics (polarization and incidence angles) are required.