Narrow Waterways Research Articles

Chemical investigations on the hydrographical system of Cananéia lagoon

Periodical observations were made in 1958 in the hydrographical system of Cananéia lagoon State of São Paulo. The present paper reports the general characteristics of the regional distribution of chemical constituents in the water of the lagoon as observed on the February 11, 1958. The outer sea water (34 ‰ salinity, 4.5 ml/l O2, pH 8.4, 0.1 µg-atoms-nitrate-N/l, 0.3 µg-atoms-phosphate-P/l and 4 µg-atoms-silicate-Si/l) flows into the lagoon at flood tide through the Barra de Cananéia. The major portion of the inflowing sea water moves westward through the Baía de Trapandé pushing the inner lagoon water toward the northern sheltered region, while a smaller portion enters along the eastern waterway called Mar de Cananéia, but is apparently blocked in its flow because of the narrow passage. In the sheltered inner region the rise of the water level apparently depends upon an accumulation on the water of the tributaries which is blocked by the outer tidal wave. The lowering of the water level of the open sea during the ebb sucks out the lagoon water, and a high velocity of the outflow through the narrow waterway of the Mar de Cananéia is then usually observed. In the inner region of the lagoon when the horizontal movement of the water due to the tides is weakened, a reduction state is likely to develop in the bottom layer on account of active decomposition by bacteria of the deposited organic materials. Accordingly, considerable lowering of the oxygen tension is observed in the water overlying the bottom. In the surface water at the same station the amount of dissolved oxygen is near saturation point. The decomposing activity of the bacteria is very important for the lagoon's metabolism. The return of nutrients into the water undoubtedly contributes efficiently to enrich the phytoplankton crop.

GEOPHYSICAL EXPLORATION IN TORRES STRAIT

Torres Strait is the narrow waterway on the Continental Shelf which connects the Arafura Sea to the Coral Sea and separates the Cape York Peninsula from South-western Papua. Within Torres Strait and the Arafura Sea the marine seismic survey area specifically discussed here covers the north-western part of Authority to Prospect 104P held by Marathon Petroleum Australia Ltd. Except for a few small islands this area is covered by a shallow tropical sea not more than 160 feet deep which is studded with coral reefs.Four regional structural features influence the area. These are the Cape York-Oriomo Ridge to the east, the Carpentaria Basin to the south and the Morehead and Papuan Basins to the north. These features are indicated by regional geology and have been confirmed by the combined interpretations of reconnaissance geophysical surveys conducted by various exploration organisations during the past 30 years.The A.T.P. 104P (West) Marine Seismic Survey, consisting of 618 miles of subsurface coverage, was carried out for Marathon between November 8 and November 28, 1964.Several operational problems prevented completion of the survey as originally planned. Shallow water and reefing prevented shooting in the north-east portion of the proposed area.Shooting 300 per cent subsurface coverage commenced in the south-eastern part of the survey area, but, due to shallow basement at less than one second, multiple coverage was not feasible. Production shooting which gave 100 per cent subsurface coverage on the short spreads was continued throughout the remainder of the survey.Two reflection horizons and a resultant isochron were mapped in the area. A "deep" reflector is interpreted as originating from granitic basement, while a "shallow" reflector is tentatively correlated with a horizon in the Cretaceous section.The "shallow" horizon mapped is essentially conformable with the "deep" horizon. Both show a regional west dip with thinning of section to the east. Some north and south components of the regional west dip are established. The resultant isochron comparisons based on this work appear too limited in scope to establish any definite local structural control of deposition.

Sand Waves in Kesennuma Harbour

Kesennuma harbour suffered a great damage caused by the Chilean Tsunami of May 24, 1960. Erosion caused by the Tsunami in this harbour was remarkable at the narrow water-way near Hatigasaki in particular. There are sand waves aligning transverse to the direction of the narrow water-way in the eroded area, according to the results of detailed survey which was made just after the Tsunami. The length of sand wave near Hatigasaki attained 20 meters, and amplitudes 1.5 meters. The group on the shallow sea bottom to the southeast of Hachigasaki was less than 5 meters in length and 0.5 meters in amplitude. It is likely that the sand waves were formed by the secondary current of the Tsunami which flowed west to east near bottom and were caused by the curvature of the narrow water-way.

Grundtvigs sysler og interesser i første halvdel af 1831

Grundtvigs sysler og interesser i første halvdel af 1831

Steel tower economics

Partly from theoretical considerations, but mainly from practical data, an empirical formula is derived giving the approximate weight of any tower in terms of its height and maximum working overturning moment at the base. The tower weight above ground line is shown to be satisfactorily represented by kH√M tons, where H is the overall tower height above ground line, in feet; M is the overturning moment at ground line, in thousand lb-ft; and k is a “constant” which varies within an extreme range of about 0.0014 to 0.0029 throughout the whole series of towers; most towers have k values well within this range.The towers investigated covered ranges of about 16 to 1 in height, 3 000 to 1 in overturning moment, and 1 200 to 1 in tower weight.Design factors which explain variations in the “constant” k are discussed at some length on a qualitative basis.It is shown that an economic value for the base width of any tower is in the neighbourhood of 0.5√M ft.On the assumption that, for any given general type of tower, the total erected cost may be regarded as proportional to the aboveground weight, the tower-weight formula, kH√M, can be used with convenience and reasonable accuracy for a wide field of cost estimations, especially those involving comparisons of a number of alternatives of a generally similar nature.Such investigations include the following:Ordinary transmission lines: (a) Economic span lengths. (b) Relative costs of lines for different voltages, conductor sizes and conductor materials. (c) Number of circuits. (d) Number and height of earth conductors. (e) Abnormal wind and ice loading assumptions and/or actors of safety. (f) Different clearances between conductors and ground. (g) Suspended auxiliary cables. (h) Hypothetical “dogleg” lines. (j) Hypothetical “super e.h.v.” lines.Navigable river crossings: (a) General layout. (b) Clearance to high water; Air Ministry height restrictions. (c) Span lengths and river bank configuration. (d) Foundation conditions. (e) Number of circuits. (f) Long spans; economic conductor. (g) Narrow waterways; economic number of towers. (h) Terminal-type crossing towers; economic conductor tension.