Small inner marsh area delimitation using remote sensing spectral indexes and decision tree method in southern Brazil

Revista oficial de la Asociación Española de Teledetección[EN] Vast small inner marsh (SIM) areas have been lost in the past few decades through the conversion to agricultural, urban and industrial lands. The remaining marshes face several threats such as drainage for agriculture, construction of roads and port facilities, waste disposal, among others. This study integrates 17 remote sensing spectral indexes and decision tree (DT) method to map SIM areas using Sentinel 2A images from Summer and Winter seasons. Our results showed that remote sensing indexes, although not developed specifically for wetland delimitation, presented satisfactory results in order to classify these ecosystems. The indexes that showed to be more useful for marshes classification by DT techniques in the study area were NDTI, BI, NDPI and BI_2, with 25.9%, 17.7%, 11.1% and 0.8%, respectively. In general, the Proportion Correct (PC) found was 95.9% and 77.9% for the Summer and Winter images respectively. We hypothetize that this significant PC variation is related to the rice-planting period in the Summer and/or to the water level oscillation period in the Winter. For future studies, we recommend the use of active remote sensors (e.g., radar) and soil maps in addition to the remote sensing spectral indexes in order to obtain better results in the delimitation of small inner marsh areas.[ES] En las últimas décadas se han perdido grandes áreas de pequeñas marismas interiores (SIM) a través de la conversión a tierras agrícolas, urbanas e industriales. Las marismas restantes enfrentan varias amenazas, como el drenaje para la agricultura, la construcción de carreteras e instalaciones portuarias, la eliminación de residuos, entre otras. Este estudio integra 17 índices espectrales de teledetección y un método basado en árboles de decisión (DT) para cartografiar áreas de pequeñas marismas interiores utilizando imágenes del satélite Sentinel 2A de verano e invierno. Los resultados muestran que los índices de teledetección, aunque no han sido desarrollados específicamente para la delimitación de marismas, presentan resultados satisfactorios para clasificar estos ecosistemas. Los índices que demostraron ser más útiles para la clasificación de marismas mediante técnicas de DT en el área de estudio fueron el NDTI, BI, NDPI y BI_2, con 25.9%, 17.7%, 11.1% y 0.8%, respectivamente. En general, la proporción correcta encontrada fue de 95.9% y 77.9% para las imágenes de verano e invierno, respectivamente. Nuestra hipótesis es que esta variación significativa de la proporción correcta está relacionada con el período de siembra del arroz en verano y/o con el período de oscilación del nivel del agua en invierno. Para futuras investigaciones, recomendamos el uso de sensores remotos activos (por ejemplo, radar) y mapas de suelo además de los índices espectrales de teledetección para obtener mejores resultados en la delimitación de pequeñas áreas de marismas interiores.João Paulo Delapasse Simioni thanks the CAPES agency for providing a doctoral fellowship. The au-thors acknowledge the Center for Remote Sensing and Meteorology (CEPSRM) at the Federal University of Rio Grande do Sul (UFRGS) for the support provided for this research.Simioni, JPD.; Guasselli, LA.; Ruiz, LFC.; Nascimento, VF.; De Oliveira, G. (2018). Delimitación de pequeñas marismas interiores mediante índices espectrales y árboles de decisión en el sur de Brasil. Revista de Teledetección. (52):55-66. doi:10.4995/raet.2018.10366SWORD556652Artigas, F. J., Yang, J. 2006. Spectral discrimination of marsh vegetation types in the New Jersey Meadowlands, USA. 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