Surf Zone Studies - Tairua and Cooks Beach

This data was collected in a series of field experiments in the surf zone. Data was collected on a longshore-uniform beach (Cooks Beach) and a beach with strong horizontal rip-cell circulation (Tairua Ocean Beach). The experiments were targetted at measuring variations of set-up, mean circulation, currents and turbulence across the surf zone, incoming wave parameters and wave transformation. Sediment trapping experiments were undertaken to investigate the use of traps in wave-dominated turbulent environments at locations ranging from the surf zone to the shore-face/inner shelf. Sediment trapping experiments were undertaken across the surf zone at Cooks Beach and northern Tairua Beach. Trap calibration experiments (using a calibrated pump sampler) were also undertaken in conditions similar to those encountered during the trapping studies. The study found that cylindrical traps in wave-dominated turbulent environments such as surf zones of low to moderate wave energy provided good estimates of sediment deposition, time-averaged suspended sediment concentrations at various positions across the surf zone and inner shelf, as well as different elevations above the bed. Traps also provide sediment samples from which textural analyses can be undertaken. A range of techniques were used, including the construction of a instrumented sled ("RUDOLF") for winching through the surf zone, the use of a jet ski for bathymetry surveying and instrument deployments, the development of a portable depth sounding system for operation from teh jet ski and establishmetn of a shore-based data acquisition sytem including real-time video images of the sea bed. Purpose: This work is part of FoRST funded broader project: "Wave and Sediment Dynamics in Coastal and Estuarine Systems" - Objective 2: Hydrodynamics. The data was collected to quantify hydrodynamics and horizontal transformations of waves within and beyond the surf zone in order to more accurately model wave-driven circulation and understand hydrodynamic mechanisms that control open coast and estuarine morphodynamics.

Data as described below.

Tairua Ocean Beach and Cooks Beach, Coromandel Peninsula.

November - December 1996

Different instrument set-up each day. Beach surveys undertaken. Instrument frame with current meters (S4s and/or ADVs), DOBIE pressure sensors, sediment traps, capacitance wave wires, "Neilson" set-up measuring tubes, ADPs, suspended sediment sensors (OBSs) and sub-aerial video (Cam-era). Additional instrumentation mounted on mobile sled "RUDOLF". Sediment samples across beach and surf zone. Grain size and fall velocity distributions calculated. Subtidal bathymetry measured by jetski. 3-dimensional current meter around the vicinity of the trap aperture. Turbulence measured using a sontec acoustic Doppler velocimeter (ADV). Particle size analyses results from University of Waikato’s Rapid Sediment Analyser (RSA). Also settling velocity analysis from RSA. Trap calibration undertaken with an S4 adjacent to the traps. Traps, pump inlet and S4 all 1.2 m above the bed. Frequency of collection: One-off four week intensive data collection period. Instruments deployed and retreived daily.

Data quality: See publications. Completeness: One-off experiment.

Detailed printed appendices of all data included in reports. Digital Format: Available in .pdf format from NIWA library (electronically available through NIWA website www.niwa.co.nz)

Reported in internal NIWA reports.

See NIWA Sensitivity/Confidentiality: Unknown.

Complete

Related information: Later work was undertaken with NIWA and VIMS (Virginian Institute of Marine Sciences) - see linked database record below.