Takahiro Nishi, Charles Lemckert, Kentaro Hayashi, Fumihiko Yamada


The in-situ Lagrangian-Acoustic Drogue (LAD) presented by Schacht and Lemckert (2007) for monitoring the temporal and spatial distributions of both the current and the suspended sediment concentration within the estuary environments has been modified to operate in the shallow water intertidal regions. The new drogue, called the LAD for Inter-Tidal environments (LAD-IT), is equipped with a Global Positioning System (GPS), a small Acoustic Doppler Current Profiler (ADCP) and nephelometer. The small ADCP, which did not have a bottom tracking facility, was used to maximize the range of depths the LAD-IT could operate over. The accuracy of a vertical current profile measured using the LAD-IT was examined through the laboratory experiments conducted at an outdoor stream pool in Kumamoto, Japan, with uni-directional flow conditions, and through the field experiments conducted within an intertidal zone of Ariake Sound in Kumamot, Japan, with multi-directional flow conditions. Under uni- directional flow conditions the current profile was measured within 7% accuracy by summing the surface current velocity calculated using GPS tracking and the relative current profile measured using ADCP. Under multi-directional flow conditions, such as those of tide and wind-induced wave fields, the current profile agreed within 5% accuracy. This was partly because both Eulerian and Lagrangian mass transport velocities under these conditions were on the order of 1cm/s, and thus the error value was very small. The temporal and spatial distributions of both the current velocity and the suspended sediment concentration were also measured using the LAD-IT on the Brisbane River, Australia under uni-directional flow conditions. The field observation results support the conventional concept of the suspended sediment as a vertical balance between downward suspended sediment settling and upward turbulent diffusion fluxes. The results indicate the LAD-IT is adequate for estimating the sediment settling velocity in the field.


Lagrangian measurements; water tracking ability; settling velocity

Full Text:



Dyer, K.R., Comelisse, J., Dearnaley. M.P., Fennessy, M.J., Jones, S.E., Kappenberg, J., McCave, I.N., Pejrup, M., Puls, W., Leussen, W.V. and Wolfstein, K. 1996. A comparision of in situ techniques for estuarine floc settling velocity measurements, J of Sea Research, 36, 15-29.

Eyer, B., Hossain, S. and McKee, L. 1998. A suspended sediment budget for the modified subtropical Brisbane River estuary, Estuarine, Coastal and Shelf Science, 47, 513-522.

Fugate, D.C. and Friendrichs, C.T. 2002. Determining concentration and fall velocity of estuarine particle populations using ADV, OBS and LISST, Continental Shelf Research, 22, 1867-1886.

Gartner, J.W., Cheng, R.T., Wang, P.F. and Richter, K. 2001. Laboratory and field of the LISST-100 instrument for suspended particle size determinations, Marine Geology, 175, 199-219

Geyer, W.R., Hill, P.S. and Kineke, G.C. 2004. The transport, transformation and dispersal of sediment by coastal flows, Continental Shelf Research, 24, 927-946.

Guichard, F., Levin, S.A., Hastings, A. and Siegel, D. 2004. Toward a dynamic metacommunity approach to marine reserve theory, Bioscience, 54, 1003-1011.[1003:TADMAT]2.0.CO;2

Hill, D.C., Jones, S.E. and Prandle, D. 2003. Derication of sediment resuspension rates from acoustic backscatter time-series in tidal waters, Continental Shelf Research, 23, 19-40.

Holdaway., G.P., Thorne, P.D., Flatt, D., Jones, S.E. and Prandle, D. 1999. Comparison between ADCP and transmissiometer measurements of suspended sediment concentration, Continental Shelf Research, 19, 421-441.

Hossain, S., Eyer, B.D. and McKee, L.J. 2004. Impacts of dredging on dry season suspended sediment concentration in the Brisbane River estuary, Queensland, Australia. Estuarine, Coastal and Shelf Science, 61, 539-545.

Johnson, D. and Pattiaratchi, C. 2004. Application modeling and validation of surfzone drifters, J. of Coastal Engineering, 51, 455-471.

Mehta, A.J. 1986. Characterization of cohesive sediment properties and transport processes in estuaries, Lecture Notes on Coastal and Estuarine, 14, 290-325.

Mikkelsen, O.A. and Pejrup, M. 2000. In situ particle size spectra and density particle aggregates in a dredging plume, Marine Geology, 170, 443-459.

Mikkelsen, O.A., Hill, P.S. and Milligan, T.G. 2006. Single-grain, microfloc volume variations observed with a LISST-100 and a digital floc camera, J. of Sea Research, 55, 87-102.

Naudin, J.J., Gauwet, G., Chretiennot-Dinet, M.J., Deniaux, B., Devenon, J.L. and Pauc, H. 1997. River discharge and wind influence upon particulate transfer at the land-ocean interaction, case study of the Rhone River plume, Estuarine, Coastal and Shelf Science, 45, 303-316.

Niller, P.P., Sybrandy, A.S., Bi, K., Poilain, P.M. and Bitterman, D. 1995. Measurement of the water following capability of holey-sock and TRISTAR drifters, Deep-Sea Research, I, 42, 1951-1964.

Nishi, T., Lemckert, C. and Yamada, F. 2007. Eulerian-Lagrangian measurements for estimating the sediment transport parameters in estuary, Annual L. of Coastal Engineering in Japan, 54, 1421-1425 (In Japanese with English abstract).

Righi, D.D. and Strub, P.T. 2001. The use of simulated drifters to estimate velocity, J. of Marine Systems, 29, 125-140.

Schacht, C. and Lemckert, C. 2007. A new Lagrangian-Acoustic Drogue (LAD) for monitoring flow dynamics in an estuary a quantification of its water-trackin ability, J. of Coastal Research, SI50, 420-426.

Schmidt, W.E., Woodward, B.T., Millikan, K.S., Guza, R.T., Raubenheimer, B., Elger, S. 2003.A GPS-tracked surf zone drifter, J. of Atmospheric and Ocean Technology, 20, 1069-1075.

Schmidt, W.E., Guza, R.T. and Slinn, D.N. 2005. Surf zone currents over irregular bathymetry: Drifter observations and numerical simulations, J. of Geophysical Research, 110, 1-19.

Siegel, D.A., Kinlan, B.P., Gaylord, B. and Gaines, S.D. 2003. Lagrangian descriptions of marine larval dispersion, Marine Ecology Progress Series, 260, 83-96.

Sternberg, R.W., Berhane, I. and Ogston, A.S. 1999. Measurement of size and settling velocity of suspended aggregates on the northern California continental shelf, Marine Geology, 154, 43-53.

Tamaki, A., Nakaoka, A., Maekawa, H. and Yamada. F. 2008. Spatial partitioning between species of the phytoplankton-feeding guild on an estuarine intertidal sandflat and its implication on habitant carrying capacity, Estuarine, Coastal and Shelf Science, 78, 727-738.

Van Leussen, W. 1999. The variability of settling velocities of suspended fine-grained sediment in the Ems estuary, J. of Sea Research, 36, 77-81.

Voulgaris, G. and Meyers, S.T. 2004. Temporal variability of hydrodynamics, sediment concentration and sediment settling velocity in a tidal creek, Continental Shelf Research, 24, 1659-4683.

Winterwerp, J.C. 2002. On the flocculation and settling velocity of estuarine mud, Continental Shelf Research, 22, 1339-1360.

Winterwerp, J.C., Manning, A.J., Martens, C., de Mulder, T. and Vanlede, J. 2006. A heuristic formula turbulence-induced flocculation of cohesive sediment, Estuarine, Coastal and Shelf Science, 68, 195-207.

Yamada, F. and Kobayashi, N. 2004. Annual variations of tide level and mudflat profile, J. of Waterway, Port, Coastal and Ocean Engineering, 130, 119-126.

Yamada, F., Kobayashi, N., Sakanishi, Y. and Tamaki, A. 2009. Phase averaged suspended sediment fluxes on intertidal mudflat adjacent to river mouth, J. of Coastal Research, 25, 350-358.