For protecting the banks of the Indus it has been proposed (_Punjab Rivers and Works_, CHAP. IV.) to use trees in exactly the same manner as bushing, the trees being grown in several rows parallel to the river so that whenever the river, by eroding its bank, comes up to the lines of trees the first row will fall in. The first row would be chained to the second, which would take the place of the pegs used in bushing. The other rows would remain as a reserve. The Villa system of bed protection (CHAP. V., _Art. 6_) has also been successfully used for bank protection on the Scheldt, and on the Brussels-Ghent Canal, the prisms being about 10 × 10 × 4 inches, and having overlapping joints. The bands of prisms are placed in position by a boat, the bands unrolling over a drum. The boat is provided with an oscillating platform carrying rollers at its end. A thin layer of gravel is laid over the bank and is pressed down by the rollers before the prisms are laid on it (_Min. Proc. Inst. C.E._, vol. cxxxiv., and vol. clxxv.). In the case of the river mentioned in CHAP. XI., _Art. 3_, where extremely high velocities were met with, cylindrical rolls of wire-netting were made, each 50 feet long and 5 feet in diameter, and filled with boulders. These rolls can be used for bank protection. The netting was made by wires 6 inches apart, crossing each other at right angles and tied together at the crossings by short pieces of wire. [Illustration: FIG. 21.] On ship canals a berm (fig. 21) is frequently made a few feet below the water-level. It serves as a foundation for the pitching, which need not usually extend down to more than 5 feet below the water-level. Below that the wash has little or no effect on the banks. On ordinary navigation canals a similar berm is sometimes made--one or two feet in width and a foot or less below the water-level--and rushes are planted on it. Sometimes a bank has been protected by a kind of artificial weed, consisting of bushes or branches of trees attached to ropes. The end of the rope is fastened to the bank and the weeds float in the stream alongside the bank. To protect a bank from ice, which exercises an uplifting force on pitching, use has been made of a covering of a kind of reinforced concrete consisting of slabs of concrete with wires embedded in it, and fastened to the bank by wires, 20 inches long, running into the bank, these wires being embedded in mortar so as to act like stakes. [Illustration: FIG. 22.]