The use of multispectral video remote sensing to monitor suspended sediment concentrations.

Abstract

Detailed knowledge of suspended sediment concentration and sediment transport rates is one of the most important and, most elusive goals of data collection for studies involving stream channel morphology and water quality monitoring. Reliable, continuous data on the suspended sediment load of streams are virtually nonexistent. Although it is relatively easy to obtain information on the water discharge through an open channel, it is far more difficult to sample the sediment load of a stream. Suspended sediment concentration is highly variable with time, cumbersome and costly to sample even for short duration periods, and largely independent of other stream flow characteristics such as discharge. This study explored the potential of using ground-based multispectral video remote sensing to monitor suspended sediment concentrations. Data were collected during seven sampling episodes at two test sites in northern Arizona. Two different video systems were employed. The Xybion system recorded reflectance data in four bandwidths for three dates while the Bi-spectral system recorded data in two spectral bands for the remaining four episodes. Video imagery was acquired simultaneously with water samples containing suspended sediment. Digital numbers (DNs) for the two and four band imagery were extracted from 5 by 5 pixel arrays and the average value computed. Water samples were analyzed to determine sediment concentration. Relationships between DNs and reflectance were explored through the use of simple and multiple linear and non-linear regression. Models were generated for the best single and multiple band combinations for both the single date and multidate data sets. Correlation coefficients for the models were comparable or superior to similar models generated from orbital and airborne data. The results of the study indicate that the ground-based technique has great promise for providing suspended sediment data of high spatial and temporal resolution to supplement existing measurement techniques. Recommendations for future work to help improve the basic technique are included.