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Fieldwork

Bathymetric Data from Waverunners


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launching the waverunner
Project scientists launch a modified waverunner into the surf off Washington state. The GPS antenna can be seen at the rear of the boat on top of a yellow box that contains the computer. The computer screen on the handle bars aids the driver in navigation.
For the past six months, we have been building and testing a new system to collect bathymetric data in energetic, nearshore environments. Based on a system developed by Oregon State University, our system is comprised of a waverunner, which we have equipped with an echo sounder, GPS receiver and antenna, and onboard computer running navigation software. The waverunner is a Yamaha Wave Venture 700, which is large, powerful, and stable. The echo sounder is an Oceandata Bathy 500, from which we stripped the paper recorder and mounted the acquisition and processing boards in a waterproof box underneath the seat. For precise horizontal and vertical positioning, we operate a Trimble GPS receiver in Real-Time-Kinematic (RTK) mode. The GPS antenna is mounted on the waverunner directly above the echo sounder. The GPS receiver is enclosed in a waterproof box and stored underneath the seat. The GPS base station is set up on a benchmark on land to provide a land-based vertical datum. The GPS and echo-sounder data are delivered to the navigation software, Hypack, which is running on a Libretto laptop computer also stored beneath the seat.

A monitor is housed in a waterproof box and mounted above the handlebars, along with a waterproof keypad. The entire system is run by two 12-volt batteries, which are also housed in a waterproof box and attached to a mount on the back of the boat.

3D sea floor model
 
Three-dimensional model of nearshore sea floor off Oysterville, Washington, derived from data collected by the waverunner. Elevation is relative to North American Vertical Datum of 1988 in meters. Lateral distance is relative to North American Datum of 1983 in meters. Northing and easting are ways of describing latitudinal and longitudinal differences among data points, respectively.
A waverunner is the optimal boat for collecting nearshore bathymetry through the surf zone. The boats operate with a jet-propulsion system, so they are safer and have a shallower draft than a propeller-driven system. The boats are extremely maneuverable, and, best of all, they can be easily righted after they flip over (I know from personal experience!). The echo sounder operates at 8 Hz and the GPS at 5 Hz, so surface waves are easily resolved and accounted for in the data. Getting through the waves as they are breaking in the surf zone is another matter.

Many people helped assemble this new data-collection system. Jamie MacMahan, a Ph.D. student at the University of Florida working under a cooperative agreement with the USGS, was responsible for integrating all of the components of the new system. Jamie worked closely with Peter Ruggiero from the Washington Department of Ecology (DOE) and Guy Gelfenbaum from the Menlo Park office to design the system. We had lots of advice and even some help from Dave Wegener, Phil Thompson, Mark Hansen, Keith Ludwig, and Terry Kelley from the St. Petersburg Field Center, and Jessica Cote from the Woods Hole Field Center. Dave and Phil were also recruited as field operators to check the boats for safe operation.

After a three-day comparative test in South Carolina, the waverunners were delivered to the Washington coast for the summer field season. As part of the Southwest Washington Coastal Erosion Study, the waverunners have been working all summer collecting nearshore bathymetry across the 165-km-long Columbia River littoral cell. Peter Ruggiero is responsible for the data collection, and, along with Jamie MacMahan, has been assisted in the field this summer by Troy Warnick, Josh McInnis, and Emily Lindstrum from DOE, and by Guy Gelfenbaum and Britt Argow from Menlo Park. Bathymetric data are being collected in cross-shore profiles from mean sea level out to depths of 11 to 12 m. In selected areas within each sub-cell, profiles are spaced 200 m apart and are gridded to produce 3-D bathymetric surface maps. Between these surface maps, profiles are collected every 1 km. Thanks to small swell (1-2 m, 7-9 s) and light winds (< 20 knots), the field crew has collected over 125 profiles, and they are still going strong.


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Seeing the Bottom

Bathymetric Data: Waverunners

Research Sediment Database

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Staff & Center News Hein Elected IMMS President

Robbins Attends FWC Ceremony

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