R. Birch

Bio: R. Birch is an academic researcher. The author has contributed to research in topics: Tripod (photography) & Data logger. The author has an hindex of 2, co-authored 2 publications receiving 8 citations.

A configurable multi-sensor tripod for the study of near-bottom ocean processes

Abstract: A cost effective and highly configurable scientific platform, dubbed Norton, has been developed for the scientific study of near-bottom ocean processes. The basic platform is a collapsible lightweight aluminum tripod that can be transported in the back of a pick-up truck, and is easily accommodated on most vessels. Ballast is supplied in the form of large ship anodes bolted to the base of each leg. The desired sensors are attached to the tripod legs and bracing. A typical deployment might utilize the following sensors: Acoustic Doppler Current Profiler for current profiles and directional wave data. Marsh McBirney electromagnetic flow sensor for measurements close to the bottom, supporting both wave orbital burst sampling and average current measurements. Optical Backscatter Sensors (OBS) for sediment concentration. Sector-scanning sonar to supply bed-form images; an Imagenex variable frequency scanning head has been integrated into a self-contained housing containing a control module, data logger and power supply. Other sensors can be added as desired. Norton is usually deployed by lowering with a line from the ship. An acoustic release is used to let go of the tripod once it is on bottom. A customized 'tilt-pinger' provides confirmation to the crew that the tripod is upright. Recovery can be via a pop-up buoy and/or a ground-line.

Assessing the site potential for underwater turbines in tidal channels using numerical modeling and advanced ocean current measurements

Abstract: A combination of advanced ocean current profiling measurements and high resolution 3D numerical models was used to assess site potential for underwater turbines in tidal channels of the inland waters off the coast of British Columbia, Canada. The measurements involved the use of ADCP transects through potential sites. Due to the very strong tidal currents of up to 10 knots or more, special procedures are required to generate accurate and reliable maps of the very strong ocean currents. The three-dimensional, coastal circulation model COCIRM was used to map these detailed flows under different scenarios and assess the potential at various sites for operation of underwater turbines after validated using available water elevation and ocean current data.

Scanners, targets, and methods for surveying

Abstract: Apparatus and methods useful in surveying to provide information rich models. In particular, information not readily or possibly provided by conventional survey techniques can be provided. In some versions targets provide reference for baseline positioning or improving position information otherwise acquired. Scanning may be carried out in multiple locations and merged to form a single image. Machine mounted and hand mounted scanning apparatus is disclosed.

Sediment Transport on Roberts Bank: A Sandy Intertidal Flat on the Fraser River Delta

Abstract: Waves and currents were monitored over a range of incident forcing between March 23 and April 24, 2003, on Roberts Bank, the sandy intertidal portion of the Fraser River Delta. A comparison of the dimensionless, current-induced skin friction with the critical skin friction for the initiation of sediment motion suggests that the currents are only capable of entraining sediment briefly with the ebbing tide or when enhanced by the wind. Since these wind-generated currents are associated with storm waves, which typically exceed the critical skin friction, they have a disproportionately large impact on the direction of the sediment transport. An energetics-based model, driven by locally measured near-bottom currents, is used to characterize the rate and direction of bedload and suspended load transport. The largest transport rates were predicted in response to storm waves and were initially directed onshore with weak oscillatory transport and alongshore by wind-generated currents that turned offshore ...

Energy potential metric for rapid macro-level resource assessment of tidal in-stream energy in the Philippines

Abstract: This paper presents preliminary efforts in developing a rapid evaluation tool for tidal in-stream energy (TISE) in the Philippines. We study the possibility of using an energy density metric based on the sea surface elevation (SSE) or tide height difference at the boundaries of a site of interest as a gauge for the TISE potential of that site. Results show good correlation with high potential sites and the proposed metric. Verde Island Passage was assessed, through a combination of DELFT3D simulation and Matlab-based power computations, to have four potential TISE sites with a total energy density of 271.90 kW-h /m2 in a month.

The capabilities of Doppler current profilers for directional wave measurements in coastal and nearshore waters

Abstract: The adaptation of Doppler current profilers to measure directional wave spectra has provided a new instrumentation approach to coastal and nearshore oceanographic studies Past studies have shown favorable comparisons between Doppler current profiler wave instruments with bottom mounted PUV (pressure-velocity) sensors sampling at wave frequencies and wave buoys In this paper, we examine the capabilities and limitations of two different Doppler current profilers for directional wave measurements in shallow coastal waters of 0-25 m water depth Data collection programs using Doppler current profilers for wave measurements have been conducted for one month long periods in the early spring of 2002, 2003 and 2004 on Roberts Bank in the Fraser River foreslope region of the Strait of Georgia, British Columbia, Canada In 2004, an RD Instrument ADCP along with the newly-released 1000 kHz Nortek AWAC current profiler and wave instrument were co-located in 7 m water depth at a different site on the edge of Roberts Bank Inter-comparisons between these bottom mounted instruments are used to examine the capabilities of the directional wave spectral parameters, in terms of: resolvable frequencies for directional and nondirectional wave spectra; wave directional resolution and reliability, and limitations arising from the use of linear wave theory For a preliminary assessment of the capability of Doppler wave spectra in deeper waters of 20-25 m depths, in particular for very long wave periods, some experiences derived from a long-term measurement program being conducted off the west coast of Africa are presented

3D Hydrodynamic Modeling of Sediment Dynamics on Roberts Bank, Fraser River Foreslope, Strait of Georgia, Canada

Abstract: A fully three-dimensional, nested grid, integrated circulation-wave-sedimentgeomorphology numerical model, COCIRM-SED, was developed to study sediment dynamics on Roberts Bank, Fraser River foreslope, Strait of Georgia, Canada. Roberts Bank is an extensive intertidal zone, located just south of where the main (South Arm) Fraser River channel enters the Strait of Georgia. The substrate of Roberts Bank is primarily silty sand, and a total of four grain size classes were considered in the model. The study area of interest is modeled using a fine grid size of 100 m by 100 m, and is nested within the much larger domain of the Strait of Georgia with a coarser grid size of 500 m by 500 m. These two model domains are solved together at every time step using a fully dynamic and two-way connection scheme. Following initial testing with idealized analytical cases, the COCIRM-SED modeled flows and suspended sediment concentration were calibrated and verified using the data obtained with a configurable multi-sensor tripod system on the Bank and at the edge of the Bank, respectively. These field data, including month-long ADCP current profiles, OBS sediment concentrations, and directional wave measurements, are used to examine the model performance. The preliminary model results provide improved understandings of the sediment dynamics on Roberts Bank.