Title :
Geomagnetic Induction to Measure Strong Nearshore Flow Velocities
Author :
Flick, Reinhard E. ; Parker, Merle D.
Author_Institution :
Shore Processes Lab., Scripps Instn. of Oceanogr., La Jolla, CA, USA
Abstract :
Engineering and design criteria are given for two systems using geomagnetic induction to measure (1) tidal transport in a small lagoon entrance channel and (2) the longshore current in the surf zone. The electrical potentials measured are on the order of 40 microvolts per meter of cross flow distance per meter per second of flow speed. The salt-bridge instrumentation first used by Mangelsdorf (1962) and later refined by Sanford and Flick (1975) and Sanford (1977) for use over highly conducting bottoms has been adapted to settings of low bottom conductivity and strong flow speeds. The effects of strong unidirectional currents, cyclical wave loading, sand bottom erosion, kelp fouling and pressure signal changes are presented. Proto-type deployments are described in which the salt-bridge support system failed under persistent 4 meter high breaking waves and 3 meter per second longshore currents.
Keywords :
geomagnetism; geophysical fluid dynamics; ocean waves; tides; cross flow distance; cyclical wave loading; design criteria; electrical potentials; geomagnetic induction; high breaking waves; kelp fouling; longshore current; low bottom conductivity; pressure signal changes; prototype deployments; salt-bridge instrumentation; salt-bridge support system; sand bottom erosion; small lagoon entrance channel; strong flow speeds; strong nearshore flow velocities; strong unidirectional currents; surf zone; tidal transport; Bridge circuits; Conductivity; Current measurement; Electric variables measurement; Electrodes; Equivalent circuits; Fluid flow measurement; Geomagnetism; Magnetic field measurement; Sea measurements;
Conference_Titel :
OCEANS '80
Conference_Location :
Seattle, WA
DOI :
10.1109/OCEANS.1980.1151435
