Case Study: Roughened Channel Hydraulic Characteristics

This presentation discusses the measured hydraulic characteristics of a constructed roughened channel measured using mobile Large Scale Particle Image Velocimetry (LSPIV) methods and an Acoustic Doppler Velocimeter (ADV).  The roughened channel was constructed in October of 2011 as part of an irrigation diversion screen facility.  The roughened channel slopes at about 4 percent and is about 70 feet long.  It is composed of large rock buttresses spaced at about 25 feet with engineered stream bed material between buttresses.  The objectives of monitoring hydraulic characteristics along the roughened channel include quantification of spatial variability of velocity, depth, and turbulence; comparison of microhydraulic characteristics with numerical model estimates; and assessment of microhydraulics as they relate to California Department of Fish and Game (CDFG) fish passage criteria.

 LSPIV and ADV measurements were collected concurrently at the site during winter flows.  LSPIV provided surface velocity measurements at many points in an area, while the ADV provided detailed velocity measurements at particular points and depths.  NHC compared the LSPIV measurements with the ADV measurements to assess the ability of LSPIV to characterize the velocity field.  Using the LSPIV measurements, NHC calculated the average velocity at specific cross sections and compared the cross section average velocity with velocities measured at discreet locations along the cross section.   Results from one and two-dimensional models were compared with the measured velocities and differences between the computed and measured velocities were documented.  The measured and modeled hydraulic characteristics were used to compute the energy dissipation factor (EDF), a proxy for turbulence.  Measured and modeled velocities, depths, and EDF were compared with CDFG fish passage criteria.