REPORTS AND DOCUMENTS RELATING TO THE LOCATION OF THE SEACOAST LINE WITH RELATION TO THE ESTUARY OF THE HAMILTON RIVER SYSTEM.
REPORT OF W. J. STEWART, CHIEF HYDROGRAPHER, CANADA,
ON THE DETERMINATION OF THE SLOPE OF THE NARROWS BETWEEN LAKE MELVILLE AND LESTER POINT.
Two Haskell automatic gauges, one a mile east of Lester Point (hereinafter referred to as the Lester Point gauge) in the outer part of the Narrows, the outlet from Lake Melville of the Hamilton River system, and the other at what may be called the lower end of Lake Melville, were maintained in operation continuously from August 5th to October 2nd, 1923, or for two complete lunar months.
The records were compiled from half-hourly readings taken to the nearest hundredth of a foot for height, and the time to the nearest minute.
The vertical scale of the gauge records was to inches to one foot, the hundredth of a foot on the record being represented to one and a quarter of a sixty-fourth of an inch, quite a measurable quantity.
Each gauge was referred to a bench mark in close proximity to it, and the two bench marks were connected by precise levels undertaken by the Geodetic Survey of Canada.
From the analysis of the records the following information was obtained :
At the Lester Point gauge the range of the tide was found to vary from 5.1 feet at springs to 2.02 feet at neaps, with a mean range of 3.46 feet.
At the lake Melville gauge, the range varied from 1.12 feet at springs to .54 of a foot at neaps, with, a mean range of .83 of a foot.
Thus in a distance of about 13 miles between the two gauge locations, 30 there is a decrease in range of about 75 per cent.
At Lake Melville, as an average, high water occurred 3 hours 33 minutes and low water 3 hours later than at Leslie Point, showing a considerable retardation in the progress of the tidal wave for so short a distance, the channel between these two points is deep and extends nearly the whole width of the inlet, so that this retardation cannot be ascribed to friction against a rapidly rising bed.
Mean tide level, obtained at each gauge location, from over 2,800 simultaneous half-hourly readings, shows a mean tide level slope of .419 of a foot or 5 inches, between the Jake Melville and the Lester Point gauges.
At each instant of time there is a definite slope of the surface of the water 10 between the two gauge points. The mean slope was calculated at springs and neaps and showed that at springs the outgoing mean slope was 40 per cent. or 6 inches greater than the incoming slope, its duration being one hour more.
At neaps when there is less influx from the sea, the difference is still more pronounced ; the outgoing slope being double or 8 inches more than the incoming slope, with throe hours more duration.
The inference to be drawn from this is that on the ebb there is a consider-ably greater volume of water discharging through the Narrows than can be accounted for by the influx of flood tide.
Apart from the actual mean tide slope found between the two gauges, the considerable retardation in progress of the wave through a deep channel in a short distance and the considerable reduction in range of the tide, are distinct characteristics that are most generally found in river tides.
(signed) WM. J. STEWART,
Department of Marine and Fisheries,