Application of the wavelet transform to sediment grain sizes analysis with an impact plate for bedload monitoring in sediment bypass tunnels

Takahiro Koshiba,Tetsuya Sumi

doi:10.1051/e3sconf/20184004022

Abstract

An impact plate (IP) is a bedload transport monitoring device developed for a part of the sediment bypass tunnels management. In the measurement, the impact produced by bedload is recorded as the number of impulses (Ip) which is widely used in Japan. Ip, however, has several shortcomings attributed to the insufficient raw signal denoising. In this study, the discrete wavelet transform (DWT), an advanced signal processing technique especially for noisy, non-periodical, and transient signals, was introduced to devise an improved Ip count system solving the problems in the original signal denoising process. The presented results revealed that the DWT is useful for water noise reduction, signal overlap reduction, and mitigating Ip saturation at grain sizes Ds = 50 and 100 mm compared to the original Ip counting system.

Highlights

A crucial issue in the long term use of dams is reservoir sedimentation caused by incoming sediment from the upstream reaches, and the sediment bypass tunnel (SBT) is an effective measure to mitigate the problem
We applied discrete wavelet transform (DWT) for denoising sediment impact signals recorded by impact plate (IP) to develop improved impulse count system
Results revealed that the DWT denoising was useful for water noise reduction, signal overlap reduction, and mitigating Ip saturation at Ds = 50 and 100 mm compared to the original Ip count system

Summary

Introduction

A crucial issue in the long term use of dams is reservoir sedimentation caused by incoming sediment from the upstream reaches, and the sediment bypass tunnel (SBT) is an effective measure to mitigate the problem. The accurate abrasion estimation is desired for the better management and operation of SBTs. For the use of existing abrasion prediction models, the amount and grain sizes of the impacted sediment onto the invert are essential [2]. An impact plate (IP) is one of the surrogate bedload monitoring systems developed for sediment monitoring in SBTs. In general, the surrogate bedload monitoring systems observe the oscillation or acoustic energy caused by sediment impact onto the device placed in the river bed to estimate bedload movement with this.

Methods

Discussion

Conclusion