General studies : November, 1967 / by John C. Ayers, Joseph C. K. Huang.

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natural river plumes inversely as the mean depths along their
lines of flow.
From the charts we have taken 20 feet as the mean depth along
the flow paths of the plumes of the Grand and St. Joseph when
these run parallel to shore. We have estimated the mean depth
between the beach and the outer sand bar to be eight feet. It is
deemed reasonable in this first approximation to take all other
conditions as being equal.
Using the maximum observed river plume length as three miles
and multiplying by the inverse depth factor, 20/8 or 2.5, we
obtain an approximated length of effluent plume of 7.5 miles.
Another rough first approximation can be made from the flowcontent of natural plumes and topographic conditions at the plant
site.
Taking 0.2 mph as a mean "worst condition" light-wind current
speed at a quarter mile from shore, as was found in the drogue
runs off Palisades Park described above, we may divide into the
three-mile maximum river plume and obtain the estimate that the
maximum natural plume contains about 15 hours of river flow.
Taking the outer sand bar to lie at 1000 feet from shore, and
estimating the mean depth between the outer bar and shore at
eight feet, we obtain an approximate 8000 square feet as the crosssection available to effluent flow along shore. Dividing into 4000
cfs outflow, we obtain 0.5 feet per second as the indicated plume
speed near the outfall under light-wind conditions. Assuming
further that bottom friction will decrease the flow velocity along
the length of the effluent plume to the natural 0.2 ft/sec (mean