project sedimentology

Channel bed morphology is mapped using a 130° swath coverage, RESON SeaBat 7125, multi-beam echo-sounder (MBES). The MBES can yield a vertical resolution of ~3 mm and three-dimensional bathymetric information at centimetre resolutions. MBES surveys from deeper waters (>2 m) is supplemented by shallow water, single-beam echo sounder (SBES) and bar-edge dGPS surveys.

Bedforms near Port Westward imaged using a MBES.  Data courtesy of NOAA.

National Oceanic and Atmospheric Administration MBES data collected in 2009 near Port Westward.

The bathymetric survey of the TIFZ extends from Port Westward (formerly Beaver Army Terminal) to Tongue Point gathering necessary modelling boundary conditions using SBES in the channels and integrating with geo-referenced LiDAR of exposed bartops. MBES surveys are conducted at the beginning and the other towards the end of the project to provide Digital Elevation Models (DEMs) of morphological change. Additionally, repeat surveys at key localities before/after flood and ebb tides in individual field seasons are quantifying bedform and bar migration patterns and rates.

Example Output

The alluvial architecture of bars in the TIFZ are quantified using Ground Penetrating Radar (GPR) and a Parametric Echo-Sounder (PES). A Sensors and Software Pulse EkkoPro GPR and 'Smart Cart' is used to collect data across exposed bars in the TIFZ. GPR surveys are undertaken at tidal ebb flows in the summer river low flows. Penetration depths are ~10 m with a vertical resolution that can decipher decimetre-scale bedforms and sedimentary structures.

Setting up the GPR and dGPS equipment prior to starting surveying

Setting up the GPR and dGPS equipment prior to starting surveying.

The GPR is ground-truthed using an extensive coring programme that provides information on the internal structure at much higher mm- resolution. Cores are taken using 'suction coring', vibracoring and deep cores using a Geoprobe. Cores are mostly to about 5 m depth though the Geoprobe has retrieved core to 20 m below the channel base. All cores are sliced, preserved, logged and quantitative data abstracted on bedform type, set thickness, grain size and vertical trends and trace fossils present. The PES is being used to quantify the primary subsurface structures up to 10 m below the river bed.

NERC

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