Medicion de la concentracion de sedimentos en suspension mediante dispositivos opticos y acusticos: aplicacion en sistemas tropicales (Delta del rio Mira, Colombia)

Abstract

RESUMEN.En los últimos años, la utilización de dispositivos ópticos (e.g. Optical Backscatter Sensor, OBS) y acústicos (e.g. Acoustic Doppler Current Profiler-ADCP) ha permitido monitorear con mayor resolución la variabilidad temporal y espacial de la concentración de sedimentos en suspensión (CSS) en ambientes costeros y estuarinos. Sin embargo, la aplicación de estas técnicas en ambientes tropicales ha tenido un desarrollo incipiente. En el presente trabajo se implementó un procedimiento de calibración para un dispositivo OBS-3A, tomando como patrón de calibración sedimento seco y desagregado de la zona de estudio. Además, se presentan las correcciones a las que se debe someter la señal de respuesta del ADCP, debido a la dispersión geométrica, la atenuación del sonido por el agua y las partículas en suspensión, para que sea útil en la estimación de CSS. El ADCP y el OBS-3A se utilizaron para realizar mediciones de CSS en el sistema deltaico del río Mira (isla del Morro y desembocadura principal), ubicado sobre la costa del Pacífico colombiano, un ambiente costero tropical donde algunos factores oceanográficos y estuarinos son determinantes en la señal de respuesta de los equipos. Palabras clave: sedimento en suspensión, transporte de sedimento, instrumentos ópticos (OBS), equipo acústico (ADCP), deltas tropicales, Colombia. Measurement of suspended sediment concentration using optical and acoustic devices: application in tropical systems (Mira River Delta, Colombia)ABSTRACT. In recent years, the use of optical (Optical Backscatter Sensor, OBS) and acoustic (Acoustic Current Doppler Profiler, ADCP) instruments has allowed monitoring the temporal and spatial variation of the suspended sediment concentration (SSC) in coastal and estuarine environments with greater resolution. However, the development of the application of those techniques in tropical environments is incipient. For this study, an OBS-3A calibration procedure was implemented, taking dry and desegregated sediment from the study zone as a calibrating pattern. Moreover, we present the corrections required for the ADCP signal to be useful in the estimation of SSC due to geometrical spreading, the attenuation of sound by water, and the particles in suspension. The ADCP and OBS-3A were used to measure SSC in the Mira River delta system (Morro Island and principal river mouth), located on the Pacific coast of Colombia, a coastal tropical environment where some oceanographic and estuarine factors determine the signal response of the instruments.

Measuring and modeling vertical gradients in suspended sediments in the Solimões/Amazon River

“…Turbidity can be measured by a turbidity meter, whose sensor detects the portion of light that is scattered by suspended particles (Anderson, 2004). Turbidity is an optical measurement technique used to estimate [C] without interfering with the sediment (Bunt, Larcombe, & Jago, 1999;Pavanelli & Bigi, 2005;Restrepo & Pierini, 2012;Landers, 2011). One of its main advantages is that it allows values to be obtained at high frequency with portable probes.…”

Tsunami hazard assessment in the southern Colombian Pacific basin and a proposal to regenerate a previous barrier island as protection

“…The latter could be the result of the combined effects of the tidal range, littoral drift, sedimentary contributions of the Mira River, and differential displacements of tectonic blocks (e.g. Correa, 1996;Otero and Restrepo, 2008;Restrepo and López, 2008;Restrepo et al, 2008a). The Mira River delta is characterised by a semidiurnal tide and mesotidal tide range; the tidal range is 1.1 m during quadrature and during syzygy rises to 2.7 and 2.9 m in the southern and northern portions of the delta, respectively (Otero and Restrepo, 2008).…”