Measuring instruments for rivers

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This article is a summary of sub-section 5.3.2 of the Manual Sediment Transport Measurements in Rivers, Estuaries and Coastal Seas[1]. This article describes which instruments can be used to measure bed load, suspended load, particle size and fall velocities in rivers.

Instruments for rivers

Table 1, 2 and 3 present the available instruments (and accuracies involved) for measuring:

  • bed load transport,
  • suspended sediment concentrations and transport rates,
  • particle sizes and fall velocities,

The order of preference is based on the overall sampling accuracy.

Simple mechanical instruments such as the bottle-type, the trap-type and the pump-type samplers are still very attractive because of their robustness and easy handling, particularly when used at isolated field sites (see also pump samplers; bottle and trap samplers). The accuracy of the measured parameters involved can be increased by increasing the number of samples collected. Analysis costs of all samples involved may be critical with respect to the available budget. Optical and acoustic instruments are attractive when large numbers of data have to be collected (see also General principles of optical and acoustical instruments). As calibration is involved, the accuracy strongly depends on the quality/reliability of the calibration curves. Hence, many calibration samples are required using a pump sampler with the nozzle as close as possible to the optical/acoustic sensor.

A major technological advance for measuring suspended load transport is the in-situ Laser diffraction instrument (LISST) (see also Optical Laser diffraction instruments (LISST)). This instrument can measure the particle size distribution and sediment concentration simultaneously. An attractive solution is the LISST-ST, which includes a streamlined body to improve sampling accuracy and is equipped with a pressure sensor and current meter for measuring the sampling height above the bed and the ambient velocity. The velocity data are used to control pump sampling (isokinetic sampling) across the internal Laser arrangement. The velocity and concentration data are used to compute fluxes for up to 32 particle size classes at points, verticals, or in the entire stream cross-section. All data are transmitted via a cable to the survey vessel (on-line measurement). Limitations (related to light penetration) are the maximum concentration ranges of about 150 mg/l for fines (mud/silt) and 500 mg/l for sand particles. Hence, the instrument cannot be used in high-concentration conditions (close to bed; upper flow regime).

Table 1 and 2 Instruments for bed load and suspended load
Table 3 Instruments for particle size and fall velocity


See also

Summaries of the manual

Other internal links

External links

References

  1. Rijn, L. C. van (1986). Manual sediment transport measurements. Delft, The Netherlands: Delft Hydraulics Laboratory
The main author of this article is Rijn, Leo van
Please note that others may also have edited the contents of this article.


The main author of this article is Roberti, Hans
Please note that others may also have edited the contents of this article.