RapidEye Imagery Used to Monitor Suspended Sediments in Tropical Rivers

The flow of suspended sediment—fine particles carried by the water column—varies widely in tropical rivers, and can influence water availability, silting of reservoirs and pollution. Monitoring sediment loads over large rivers can be difficult with ground stations, making remote sensing a preferred solution.

However, high spatial and temporal resolution are required to capture the wide variation in sediment loads through time, and deal with persistent clouds in tropical regions.

Francisco Jairo Soares Pereira, from the Federal University of Ceará led a team from the German Research Centre for Geosciences, and the University of Potsdam, to explore the use of RapidEye imagery to monitor suspended sediments in the Jaguaribe River in Ceará, Brazil. The 5-day revisit time of the RapidEye Constellation uniquely allowed Francisco and team to capture a variety of river velocities, discharge levels and sediment loads.

The authors evaluated nine different spectral techniques, leveraging four or five bands from the RapidEye data: “The results of this investigation show that images of the RapidEye satellite constellation can assess moderate (67–230 mg L−1) suspended sediment concentration (SSC) of an intermittent river, even when the discharge is low (2 m3 s−1).” The authors found that the RapidEye NIR band was the most sensitive to suspended sediment.

The authors identified the short-lived nature of high-sediment flows (which are typically accompanied by heavy cloud cover) as a key obstacle to scaling their work, but the ingestion of additional satellite data from other high temporal resolution sensors may support this effort.

RapidEye data were provided by the RapidEye Science Archive, sponsored by the German Aerospace Center (DLR). Read the full article at the International Journal of Applied Earth Observation and Geoinformation.

Suspended sediments in the Jaguaribe River, across various levels of precipitation, as estimated from RapidEye imagery.