Real-Time Current and Flux Measurements for the Nearshore Sample Clauses

Real-Time Current and Flux Measurements for the Nearshore. Xxxxxx Xxxxxxxx 3rd Wave, tidal current, and wind generated flow vary locally and temporally in the nearshore influenced by-depth, local and offshore storms, and topography. These flows may move sediment shoreward, offshore, alongshore, or may build bars, erode structures, fill dredged channels, deposit or remove beaches and generally impact human occupation of the shore. Studies of the processes responsible for sediment flux require as input, forcing functions in the form of currents and waves. This in turn requires current sensors that work reliably and accurately in a near surface wave field. The sensor, MAVS (Modular Acoustic Velocity Sensor, developed under NSF support), is such a current meter, designed to have good cosine response in the vertical as well as excellent response characteristics for flow in 3 dimensions. Using magnetometers to rotate each instantaneous velocity measurement into earth coordinates and averaging these to reduce the noise of the magnetometers provides flow information useful to parameterize the conditions during sediment erosion or deposition. Coupled with an optical sensor of suspended sediment concentration, a flux measurement can be made to further provide information about conditions affecting erosion and deposition. Current flow and sediment flux measurements are needed during storms and during all stages of tide. Real time return of information during such events from sites as shallow as 2 meters to as far offshore as 10 km and as deep as 30 m can be used to trigger sampling on the beach or on a bar. Two routes to provide real time data from the MAVS current meter are being developed in another program: direct wire link ashore (shallow site) and SeaNet radio link from a surface buoy. In each case, the data link from the sensor to the transmitter is a cable with RS485 communications. The transmitter is a wireless LAN radio transmitter with receiver on one of four towers in the Nantucket Sound/Martha’s Vineyard area with return to WHOI for entry into a website. Thus the data are available in nearly real time via web. The elements of the research program that are new to this program are the physical coupling to the transmitters, the mooring or cable connection ashore, and the coupling to scientific users. Previous work will have solved the problem of getting the information from the transmitter to the website via wireless LAN transmitter. This program will deploy approximately seven MAVS current meters, three with OBS se...