Comparison of recording current meters used for measuring velocities in shallow waters of San Francisco Bay, California

Abstract

A P s m c r Several recording current meters were field tested in south San Francisco Bay, California to determine their effectiveness for use in s h d l l a w (tidally effezkd) waters urder the influence of the meters incluped a horizontal-axis d u c t d impeller (ErKieco-174 ), vertical-axis rotor (Aanderaa , i n c l i n C a n e t e r ( G e n e r d l o c e a n i s 6011 MKtI), and electrmaqnetic sensor (Interocean systems 54) .Meters were deploy& from June to S e p t e r k r 1984 at 1.2 m abwe bottcw using b o tplatforms and a taut-wire mring. Water depth r a n g d between 2.0 and 5.1 m during the study.Cnmpdson of velocity records shawed that nearslackwaterwhenwindspeedwasabout5m/sor greater and water depth was about 3.5 m or less, Aanderaa and Generdl oceanics meters recorded higher current speeds than did Meco and Interocean meters. EMfXm and Interocean meters recorded speeds that approached zero near slack water regardless of wind and water depth. Hcxlrever, as current speeds imreasd after slack water, speeds recorded by the lnterocean meter were 20 to 50 prcent higher than those reconled by the WECO meter. m i n g law wind periods or when water depth exceeded abaut 3.5 m, speed readings fram Meco and Aanderaa meters &med close agreemnt even at slack water. At higher current speeds, InteroOean hiam speeds than did the Meco or Aanderaa metem.Directional data differences were insignificant. whersx the ErKieco and rnterocean meters (as tested) appear suitable for measuring law velocities in the wind wave zone, further testing is -to determine which meter type records more accurately at higher current speeds.wird-generated waves. speed sensors e m p l a y e d by and Generdl oceanics meters record63 consistently INTR3IXJCl'ION Numeraus aquatic s+xdies have been and are being condtuded in the sari Francisco ~a y estuarine system in order to better understard the camplicatd relations among @ysicdl, chemical and b s e of trade name in this reprt is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey. Richard N. 01-U.S. Geological survey 2800 Cottage Way Sarramento, Ca 95825 biological processes. Other goals of these s u e s are to estimate haw chaqes in freshwater inflm W i t y and quantity effect the relations as well as p r d i c t what effects future changes might have on the eC0SyStem. Achievement of these goals depenas in part on an M e r d x d i q of the hydrodtyd c prcrxses in the bay,a ccnrrplicated interaction of tides, winds, salinity, freshwater inflaws, and h t t m topgra@~y. In turn, a clearer urdemtanding of the hydroaynamic processes deperxk i n part on collection of long term Current-meter (velocity) and stage (water level) data and the use of these data in cdlibration and verification of mathem3ticdl models.Much water-level and velocity data were collected i n San Francisco Bay i n 1979 and 1980 (Cheng and Garber, 1984), kut the vast majority of the velocity data were collected in areas where water depth is 6 m or greater (referenced to MLW).EIpproxima...

Activities of the Water Resources Division, California District, in the 1986 fiscal year

“…Reports: Gartner, J.W., and Oltmann, R.N., 1985 Problem: The planning and management of coastal resources require information about coastal processes such as beach formation and destruction, longshore transport of beach material, and the contributions of sediment from coastal streams and cliff retreat. The California Department of Boating and Waterways has undertaken the development of a management plan for beaches along the California coast.…”