Abstract
The hydrological quantities governing the generation of riverbed waves
(formed spontaneously on the bottoms of rivers) have been elucidated
through geomorphological methods, laboratory experiments, stability
analyses, numerical analyses, and other research methods.Recently,
numerical analysis was performed with a fine spatial resolution.However,
numerical analysis cannot always describe the real phenomena because it
is based on assumptions.Therefore, understanding the physical phenomena
by measurements with the same resolution as the numerical analysis is
necessary.Measurement data with high resolution enable the construction
of a duplicate of the measurement target on a computer, called a
“digital twin”.To construct a digital twin of the process of riverbed
wave generation and development, the geometries of the water surface and
the river bottom must be measured simultaneously.We developed and
verified a measurement method for the construction of a digital twin
during the generation and development of riverbed waves.The measurement
system uses two cameras and a line laser to simultaneously measure the
water surface and river bottom.Accurate refraction correction at the
water surface is possible by acquiring the shape of the water surface,
allowing the bottom shape to be determined by geometric processing.The
method provides submillimeter-accurate measurements of the water surface
and bottom with a spatial resolution of 0.95 cm longitudinally and 0.038
cm transversely in a 12 m $\times$ 0.45 m channel and
takes only one minute per measurement.This method can provide
measurement results that contribute to the understanding of the
formation and development of riverbed waves.