Study on hydraulic resistance of erodible bed at the Chiyoda experimental flume

Abstract

The authors made erodible bed experiments under steady flow condition at the Chiyoda Experimental Flume, a large-scale facility constructed on the floodplain of the Tokachi River, and observed sand waves on the bed of the flume. In this study, the characteristics of the sand waves are examined along the longitudinal survey lines and confirmed to be dunes. Next, the authors estimated Manning's roughness coefficients from the observed hydraulic values and assumed that the rise of the coefficients attributed to the sand wave development. Finally, vertical flow distribution on the sand waves are examined, and observed velocity distribution on the crest of waves found to be explained by the logarithmic distribution theory.

Overtopping‐Induced Failure of Non–Cohesive Homogeneous Fluvial Dikes: Effect of Dike Geometry on Breach Discharge and Widening

“…Field-scale observations of fluvial dike breaching remain scarce, due to the difficulty in setting up largescale tests, controlling boundary conditions and recording accurate measurements. To our knowledge, only Kakinuma et al (2013) conducted four field tests of overtopping of 3 m high dikes made of sand and gravel. The dike composition, crest width, and inflow discharge in the main channel were varied.…”

“…The breaching of fluvial dikes exhibits distinct features than those involved in embankment dams (ASCE/EWRI Task Committee on Dam/Levee Breaching, 2011). This includes complex 3D flow structures involving spiral flow in the breach (Michelazzo et al., 2015), non‐symmetric breach expansion and impinging jet erosion (e.g., Elalfy et al., 2018; Kakinuma et al., 2013; Rifai et al., 2017).…”

“…To our knowledge, only Kakinuma et al. (2013) conducted four field tests of overtopping of 3 m high dikes made of sand and gravel. The dike composition, crest width, and inflow discharge in the main channel were varied.…”