Tracing of
Sediments in Coastal Waters by
Fluorescent Materials
PER BRUUN .Head
Coastal Engineering Laboratory
University of Florida
Gainesville, Florida
The introduction of tracing technique into the sediment transport science
of coastal engineering technology opened new possibilities for progress in this
field. What researchers have tried to do for decades with little or no success
now became possible. The immediate results included some surprises, as
e.g. evidence that some material dredged and dumped at a "safe place"
returned shortly to the place from where it was dredged. Other results included facts on migration rates of the top layer of sand material along
beaches. These rates were up to two miles per hr according to recent experiments in the U.S.S.R. and Poland.
Furthermore, a very complex migration pattern in the nearshore zone
has been recorded revealing that the direction of sand travel may depend upon
the absolute size of the sand grains. During certain wave action the finer
grains may move shoreward or alongshore while the coarse grains move in an
offshore direction, thanks to undertow. It was also found that with oblique
waves the net drift was always down coast; the waves with different fractions
of sand advancing at different speeds.
Many other interesting results have come to light. The reader who wants
to familiarize himself with details is referred to Proceedings of the XXth
Permanent International Navigation Congress in Baltimore, 1961, Section II,
Subject V. These proceedings include articles on radioactive tracing experiments in Britain, Denmark, France, Germany, India, Japan, Netherlands,
Portugal and the U. S., and on tracing with luminescent materials in Britain,
Poland, and the U.S.S.R. Other publications include papers and reports
from the Institute of Oceanology in Moscow (U.S.S.R.), The Hydraulic Experiment Station at Wallingford, Berkshire, England; The Rijkswaterstaat,
Netherlands; Laboratorio Nacional, Portugal; The Port of Calcutta, India; the
University of California, Berkeley; and Scripps Institution of Oceanography,
La Jolla.
It is not the intention to review the present knowledge but rather to present a general overlook of the present trend of progress in this field. So far,
most results have been of descriptive or qualitative nature only, apart from
the results of some tests on pebble beaches in England using concrete pebble,
including fluorescent substances. Furthermore attempts have been made by
the Hydraulics Experiment Station at Wallingford, England, to measure sand
transport in a laboratory flume and to develop a statistical theory for same.
Coastal engineers are, needless to say, mainly concerned with material
transport problems on seashores which are extremely important to the main-
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