Investigation of bedload transport with seismometers and with hydrophones

SCHEME: CORE

CALL: 2011

DOMAIN: SR - Water Resources under Change

FIRST NAME: Andreas

LAST NAME: Krein

INDUSTRY PARTNERSHIP / PPP: No

INDUSTRY / PPP PARTNER:

HOST INSTITUTION: LIST

KEYWORDS: Bedload transport, erosion, hydroacoustic signals, seismic signals, river bottom sediment, new measurement techniques, sensor development

START: 2012-09-01

END: 2015-02-28

WEBSITE: https://www.list.lu/

Submitted Abstract

A great portion of the mass transport in rivers during floods is eroded and mobilised bed material. This so-called bedload poses a number of problems, like the silting of reservoirs or the disturbance of local biological habitats that make it necessary to study the dynamics of this kind of material transport. Existing bedload measuring techniques have limited possibilities for sediment studies in high temporal resolutions. Optical systems are usually not applicable because of the turbidity of the suspended sediment transported in flood waves. Sediment traps or bedload samplers that are periodically lowered to the river bottom for measurements yield only summative information on bedload transport in low temporal resolution. An alternative bedload measuring technique is the parallel use of hydro-acoustic and seismological systems. The potential advantages of acoustic and seismic techniques are a high temporal resolution in real time, the possibility to register the bedload transport during high turbidity, a chance to measure materials down to the sand fraction, and the observation of material transport under undisturbed conditions. The prime research question that we wish to answer with this BEDLOAD project is what information can be derived, using state-of-the-art signal processing techniques, on the bedload transport (sediments, gravel, etc.) during flood events in fluvial systems from seismological measurements in the immediate vicinity of the considered test area. With modern digital data processing and time-frequency analysis techniques, our aim is to extract these signals and use them, in comparison with the hydro-acoustic and sediment trap data, to investigate how these signals scale with the quantity of the transported material as well as its composition. Hydrophones, two different seismometers and bedload traps will be installed in – or next to (seismometers) – two small gravel-bed rivers in Luxembourg. Discharge is measured via recording stream gauges. The parallel recording of hydrophone noise and seismometer vibration with a trapping and an analysis of selected bedload material describes the highly time-resolved kinetics of transported material, guarantees the description of the mode of transport, and enables a characterisation of the material that caused the acoustic or seismic signals. We expect an improved and deeper understanding of bedload transport with new complementary measurement techniques. From the analysis we expect to identify significant relations between the geophysical data and the properties of the trapped materials and the mode of transport under various flow conditions (Froude number). New denoising methods for seismic and acoustic datasets will improve the significance of the methods.

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