Coastal Model Applications and Field Measurements- Advances in Instrumentation

Science Center Objects

Ongoing acquisition of new instruments and development of analytical methods provides us with the means to make better observations of coastal ocean processes. The measurements provide us with insight and data for critical evaluation of model performance. Advances in a range of measurement capabilities, including bottom stress, sediment erodibility, water properties and nutrient concentrations, optical properties, and acoustic backscatter calibration have been conducted under this project. New methods for measuring the orientation of instruments on bottom platforms and processing platform-mounted sonar data have been developed. A novel method for measuring profiles of optical properties in the bottom boundary layer has been developed. Tests and applications of sediment-camera methods have been incorporated into several field efforts. A low-cost autonomous boat is under development for use as a platform for repeated transect measurements of currents or surface water properties, and for shallow-water surveying. These advances are the result of collaboration among researchers and technical staff across USGS coastal science centers.

Profiling Arm

A specially modified tripod with a moving arm was developed to measure profiles of optical and acoustic properties near the sea floor by moving instruments vertically in the bottom boundary layer, between the bottom and about 2 meters above the sea floor The profiling arm was designed, built, and tested during spring and summer 2011 as part of the OASIS project. To accommodate power requirements and the large data files recorded by some of the optical instruments, the tripod was connected via underwater cable to the Martha's Vineyard Coastal Observatory, operated by the Woods Hole Oceanographic Institution (WHOI). This afforded real-time Internet communication with the embedded computers aboard the tripod. Instruments were mounted on the profiling arm, and additional instruments were mounted elsewhere on the tripod and nearby on the sea floor The details of the data recorded during the experiment and the location of files containing the best basic version of the data are described in an Open-File Report.

Illustration of the NIMBBLE (New instrument for making bottom boundary layer evaluations)

Illustration of the the NIMBBLE (New instrument for making bottom boundary layer evaluations). The NIMBBLE is a low-profile platform with two acoustic Doppler velocimeters and an upward-looking acoustic Doppler profilers.

NIMBBLEs - New Instruments for Making Bottom Boundary Layer Evaluations

The NIMBBLEs were designed to measure bottom stress in the presence of waves and currents. They are low-profile, relocatable bottom platforms with two acoustic Doppler velocimeters located about 1.5 m apart, measuring three components of near-bottom current velocities about 0.45 m above the sea floor. Theory suggests that turbulence eddies scale with distance from the sea floor, so turbulent motions at the two sensors should be uncorrelated. Larger-scale motions (waves, tides, mean flow) should be identical, so the differences in rapidly-sampled velocities at the two sensors provides a measurement of near-bed turbulence and hence bottom stress. The USGS developed the NIMBBLEs with help from WHOI engineers and is testing them near MVCO with in conjunction with the NSF Bottom Stress project.

Flying Eyeball - Underwater Sediment Camera Systems

Photo of sand on the bottom of the Connecticut River

Photo of sand on the bottom of the Connecticut River taken by the flying eyeball in Autumn 2013. The flying eyeball and its cousin, the poking eyeball, are prototype underwater camera systems developed by U.S. Geological Survey (USGS) scientists

The flying eyeball and its cousin, the poking eyeball, are prototype underwater camera systems developed by U.S. Geological Survey (USGS) scientists. The poking eyeball was designed to take repetitive microscopic images of the seabed from a tripod on the sea floor. The images record changes in seabed sediment over time, and are used in studies of how changes in sediment grain size influence rates of sediment movement. The camera system was developed as part of the multinational EuroStrataform Project, a program funded by the Office of Naval Research to understand geologic processes on the continental shelf and slope that form sedimentary strata over a continuum of scales. The poking eyeball consists of five major components: a power pack, water pump, digital camera, electronic controller, and a mini winch, all designed to be mounted on a tripod that sits on the sea floor. (see Rubin et al., 2007).

The poking eyeball system builds on a previous the “flying eyeball” that used low-resolution video technology to capture underwater black-and-white microscopic images of sand on a seabed or riverbed. The flying eyeball has been particularly successful in recording changes in sand sizes along the Colorado River bed. Several new flying eyeball systems were built in 2010, and are maintained by the USGS in Woods Hole and Santa Cruz. WHCMSC scientists tested the camera in the Connecticut River (sample image) in Autumn 2013, and are working to incorporate it onto the Sea Floor Mapping Groups miniSeaBoss sled.          

Jetyak - Autonomous Kayak

Photograph of a jetyak

The jetyak at Pier 6 on the East River, New York. Water-jet drive (black) is visible on the stern, at bottom right. Red pole near bow supports a radio antenna; mounted silver brackets support instruments for measuring depth (Hummingbird sidescan sonar, an inexpensive commercial unit marketed to recreational fishermen) and currents (Teledyne/RDI acoustic Doppler current profiler). 

The jetyak is an unmanned, gasoline-powered kayak that can be driven by radio or run autonomously using on-board navigation software. It was developed by Hanumant Singh and Peter Traykovski in the Applied Ocean Physics and Engineering Department at WHOI.  The prototype jetyak was used to measure freshwater flow (with an acoustic Doppler current profiler; ADCP) at the front of calving glaciers in Greenland in July 2013.  A second-generation jetyak was built in summer 2013 with help from Sara Goheen, a USGS WHOI Summer Student Fellow, co-advised by Traykovski and USGS oceanographer Chris Sherwood.  The jetyak is ideal for work in areas that would be dangerous for humans, for repetitive and (or) protracted surveys that can be performed more precisely by autonomous systems than by human operators; and for data collection that increases the efficiency of field scientists conducting complementary tasks as they monitor the jetyak.  The device is programmed using Google Earth images in the Mission Planner software or by remote control, and has a generous capacity for batteries and scientific equipment.

Scientists from the U.S. Geological Survey (USGS) Woods Hole Coastal and Marine Science Center in Woods Hole, Massachusetts, and their partners from the Woods Hole Oceanographic Institution (WHOI) used the jetyak in August, 2013, to map the floor of a shallow cove in the Connecticut River estuary with both downward-looking and sidescan sonar and to measure current profiles (current velocities at various heights about the sea floor) with ADCP.   During the August survey of Hamburg Cove in the Connecticut River estuary, both the jetyak and the R/V Knob (a 14-ft skiff with outboard) were equipped with relatively inexpensive sidescan sonars with integrated GPS, and thus the team had dual-vessel survey capability that could be conducted by two people.

The core of the jetyak is a commercially sold gas-powered kayak built in upstate New York and marketed mostly to fishermen and hunters. It has a roto-molded polyethylene hull and an air-cooled 7-horsepower four-stroke engine. It is propelled and steered by means of a water-drive. The stock boat costs about $5,000, is 11 feet long, weighs 165 pounds, draws 3 inches, and has a payload of 360 pounds. Full speed is around 20 miles per hour, and the boat will run for 8 to 10 hours on 3 gallons of gas at survey speeds of 2 to 6 knots. Newer versions of the stock boat break into three pieces that nest together and can be transported inside an SUV or float plane.

Tilt Current Meters

Photograph of USGS tilt current meter (white cylinder) in overwash channel in the Sandwich Town Beach

USGS tilt current meter (white cylinder) in overwash channel in the Sandwich Town Beach flooded during a Nor'Easter in March 2014

(Public domain.)

The USGS is working with Lowell Instruments LLC to develop inexpensive current meters for long-term deployments. They are small (0.3-m long) buoys housing recording tilt sensors. They stand upright in still water, and tilt at increasing angles as current speed increases. Our objective is to develop a sensor for measuring storm surges washing over barrier islands.