« ZurückWeiter »
locks are 246 feet long and 36 feet wide, and have a depth of 8} feet over the sills, so that the canal will accommodate the largest boats plying on the Elbe, of 800 tons capacity; and a future increase in the bottom width and depth of the canal can be effected. The lock entrances will be built independently of each other; and where the foundation is suitable, the vertical sides of the lockchambers will be formed by arches abutting on double T-bars, the feet of which will be embedded in a continuous concrete foundation. The iron standards will be anchored back, and connected with one another by a continuous walling. The lock-chambers will have no inverts; and gates turning on horizontal axes will be used instead of vertical gates. The filling and emptying of the locks will be effected, in the case of vertical gates, by means of sluiceways in the lock-heads and gates; and in the case of horizontal gates, by culverts under the floor. Nearly all the bridges crossing the canal afford a clear width underneath of 85 feet. The estimated cost of the canal is £1,137,500, a third of which will be borne by Prussia, and two-thirds by Lübeck. The work was commenced in 1895, and it is hoped that the canal will be opened in 1899.
RIVER ODER IMPROVEMENT WORKS. ?
The Oder rises in Austria, 2,080 feet above the level of the Baltic; and it has a length of 587 miles to the mouth of the Swine at Swinemünde, 507 miles of which, with a fall of 672 feet, are in Germany. Its drainage area is 46,064 square miles. The importance of the Oder is due to it and its tributaries being navigable for 1,056 miles, and being connected with all the northeastern waterways of Germany from the Elbe to Memel. The most important of these waterways are the tributaries Warthe and Netze, the Finow Canal, and the Oder-Spree Canal. The Netze is connected with the Vistula by the Bromberg Canal, so that timber from Russia and Galicia can be floated to Stettin. The Finow Canal joins the Oder to the Havel, and is the most important connection between Berlin and Stettin. It was built by Frederick the Great in 1744–46, and, with an available depth of 4:1 feet to 4.9 feet, is used by vessels of from 150 tons to 170 tons. In 1890, 15,451 vessels passed through the Eberswalde lock on this canal.
i Zeitschrift für Bauwesen, 1896, Nos. vii.-xii.; of Centralblatt der Bauverwaltung, 1894, Nos. i. and ii.; 1898, No. i.; Denkschrift über die Ströme Memel, Weichsel, Oder, Elbe, Weser, und Rhein, Berlin, 1888.
To secure a better connection between the middle Oder and the Upper Spree at Berlin, the Oder-Spree Canal, for vessels up to 400 tons, was built in 1887-91. The locks on this canal have an entrance width of 281 feet, a chamber width of 31} feet, a depth of water over the sills of 8} feet, and an available length of 180 feet. The canal itself, with a depth of 6 feet, has a width of 76 feet at the water-level and 46 feet at the bottom. The canal is so constructed that it can be enlarged in the future to admit the passage of Elbe boats of 500 tons, 203 feet long, 26 feet wide, and 5 feet draught. Its cost was about £650,000. This canal has materially increased the traffic between Hamburg and Silesia.
Below Breslau, a low-water depth of 31 feet has been obtained on the Oder by regulation; and above Breslau, that river has to carry the important traffic from the Upper Silesian coalfields and manufacturing districts. An improvement in the waterway to meet the increased requirements was urgently needed; and this section of the river, especially the upper part, was improved by canalisation. From Cosel, where the goods, mainly coals, are transferred from rail to the river boats, and where there is a considerable port, down to the mouth of the Neisse, there are, on a length of 15 miles, twelve needle weirs having a total fall of 88 feet, Fig. 23, Plate 6. The fall of the weirs varies from 52 feet to 84 feet. The locks are placed near the weirs, the entrance channels being separated from the current by dams. The locks have an available length of 180 feet, a width of 314 feet, and a depth of water of 6 feet over the sills. Near these locks, which admit boats up to 400 tons capacity, space is left for the construction, when required, of locks, 426 feet long, capable of containing a tug and two 400-ton vessels. The length of the river also has been shortened 4 miles by various cuts. Between the mouth of the Neisse and Breslau there are two weirs on the Oder, at Brieg and Ohlau, with adjacent locks, formerly only large enough for vessels of 175 tons, which have been rebuilt to admit vessels of 400 tons.
In Breslau itself, many new works were needed to deal with the traffic of the larger vessels. Immediately above Breslau, the Oder divides itself into two arms, one of which, in passing through the town, is dammed up at two places to provide power for manufactories. The fall at one weir is 33 feet, and at the other 8 feet. Vessels pass these weirs through locks, one of which has an available length of 144 feet, and the other 178 feet, while both have a width of 17} feet, so that these locks are too small to accommodate boats of 400 tons. Since there were various difficulties
in the way of building larger locks near these, the new waterway for large boats is carried round the town, following for a part of the way the second arm, or Old Oder. The Old Oder, at its upper junction with the main stream, is dammed up by a fixed weir, and serves only during intermediate and high-water levels. About 547 yards below this weir, the channel for large boats branches off from the navigable Oder. The upper lock is at the entrance, and passing through it the boats gain the lower harbour and the Old Oder which serves them for 11 miles. From this point, a canal has been cut, having a bottom width of 59 feet, near to and following the direction of the Old Oder. It is over 1 mile long, and serves in winter as a lying-up place for several hundred boats. A sufficient depth of water is maintained in the upper part of the Old Oder and in the canal by a needle weir, about 547 yards below the junction of the canal with the Old Oder. Near the lower end of the canal is the old lock; and 546 yards below, the canal again enters the Old Oder. The length of this channel is 43 miles; and the locks have an available length of 180 feet, and a width of 311 feet. The canal is protected from floods by embankments; and there is a flood-gate at the upper end which ordinarily stands open, but is shut during floods by a sliding door. This gate not only protects the canal from flood-waters, but also maintains the normal water-level in the canal when the weir is lowered. The lower lock is provided with flood-gates to protect the canal from the entry of flood-water. Pumps at the lower lock replenish the loss of water, and maintain the normal level in the canal when the needle weir is lowered in winter. The foregoing works were mostly opened in 1895, and those in Breslau in 1897. The cost of the works was estimated at £1,150,000.
THE REGULATION OF THE ESTUARY OF THE VISTULA." The Vistula rises in the northern range of the Carpathian Hills, near the Jablunka Pass, in the principality of Teschen, at a height of 2,132 feet above the level of the Baltic. It is 700 miles long, 211 miles of which lie in Austria, 345 miles in Russia, and 144 miles in Germany. The fall of the Vistula, from its entry into Prussia to the Baltic, is about 128 feet; and the river drains an area of 76,510 square miles, 12,860 square miles of which are in Prussia.
The regulation of the German part of the Vistula was commenced in 1880; and extensive works have been undertaken in the estuary,
1 Denkschrift über die Ströme Memel, Weichsel, Oder, Elbe, und Rhein · Berlin, 1888; Centralblatt der Bauverwaltung, 1895, pp. 133, 365, and 369.
where the conditions were very unfavourable. Near Montan Point, 28 miles from the sea, the Nogat branches off from the Vistula, and flows in a north-easterly direction, eventually emptying itself through several shallow mouths into the Frische Haff, Fig. 24, Plate 6. From this branch, the Vistula flows nearly due north for 25 miles, where it separates into the Elbing and the Dantzig Vistula. The Elbing Vistula, after flowing 16 miles in an easterly direction, empties itself by a number of shallow arms into the Frische Haff. The Dantzig Vistula flows west, and up to 1810 passed by Dantzig; but that year, during a heavy flood, it broke through the sand dunes at Neufähr, and formed a new mouth, by which its course was shortened 9 miles. The estuary of the Vistula is embanked, and the surrounding land is fruitful and thickly populated.
The flood-waters of the Vistula have a maximum discharge of 353,000 cubic feet per second, 76,800 cubic feet to 95,300 cubic feet flow down the Nogat, and the remaining 276,200 cubic feet to 257,700 cubic feet through the Elbing and Dantzig Vistula. In spring, when ice commences to come down the main stream, the Frische Haff is mostly frozen over; and if the ice in the Lower Vistula could not get away, the greater part of the ice from the undivided Vistula often passed down the Nogat. Since this ice found no passage through the frozen shallow mouths of the Nogat, it formed dams which pent up the waters of the river, causing them to overflow and break through the embankments. Thus the shallow mouths of the Nogat and the Elbing Vistula were often unable to discharge harmlessly the flood-waters accompanying the ice. Those interested in the Nogat marshes had urged that the Nogat might be closed at the upper end, and all flood-waters forced to pass down the Lower Vistula. The inhabitants of Königsberg, which lies on the Frische Haff, and is connected with the sea by the Pillau Gut, objected strongly to this; and the Government Commission reported that the maintenance of the depth of water was largely due to the discharge of the Nogat, and a shoaling up was to be feared if the scouring action of the waters from the Frische Haff were weakened by a reduction in the flow of the Nogat. Consequently, the Government determined to retain the Nogat as an arm of the Vistula, and to prevent the flooding of the lowlands by the construction of a cut to the Baltic, 4; miles long, starting below the point where the Elbing Vistula branches off, which shortened the channel by 6} miles.
The normal breadth of this cut is 820 feet at its upper end, increasing to 1,312 feet at its mouth. The flood-water section
between the embankments has a breadth of 2,953 feet. The embankments have a top width of 33 feet, and are formed with material taken from the cut. While it was sufficient to construct a guiding cut, 164 feet wide, through the sand dunes, and leave it to be enlarged to the full section by the scour of the current, the upper part of the cut had to be excavated to the full width, and to a depth of 6 feet below the future mean water-level, owing to the varied character of the ground, which consisted of loam, sand, and firm blue clay. The banks of the new channel, and especially the left bank, which, owing to the curvature, would be strongly attacked by ice and floods, were protected by fascines, and loose and packed stones. The excavation, which amounted to 9,417,750 cubic yards, was commenced in the summer of 1891, and completed in 3} years. The work was done in the dry; and at times, one Dutch and six Lübeck excavators, with an average daily output of 2,620 cubic yards, were in use. The transport of the material was effected by twenty-five locomotives and twenty trains of wagons. Including the pumping plant and two steam-cranes on the banks of the Vistula, there were forty-one steam-engines on the works. In November, 1894, the works were far enough advanced, with the exception of the guiding channel through the sand-hills, to be connected with the Vistula. To secure sufficient water in the Dantzig and Elbing Vistula mouths to carry off the ice, the new cut was not opened until after the ice had come down in the spring of 1895, when the dam at the entrance of the sandy cut was broken through, so that the flood-waters following the ice passed through the new channel. The dam was broken through in the afternoon of the 31st March, 1895; and by the morning of the 1st April, the guiding channel through the sand-hills had been widened from 164 feet to 984 feet, the current having removed 2,616,000 cubic yards in sixteen hours. Subsequently the Dantzig and Elbing Vistula were closed. Considerable additional excavation, costing £700,000, and other works have become necessary, since the closure of the Dantzig Vistula, in order to maintain the traffic from the east to Dantzig. These works, which commence about the middle of the cut, on the left bank, and reach the Dantzig Vistula at Einlage, consist of an outer basin of nearly 15 acres, from which a lock opens out, having an available length of 200 feet, a width of 41 feet, and an effective depth of 6 feet at the lowest water-level, Fig. 25, Plate 6. The lock is founded on concrete and strongly built; and the iron gates are double-skinned, with air-chambers up to the mean water-level on the lower side. The sluices are closed by doors turning on