The Indus Civilization c5.53

c5.53

As the level of a street rose, it was also necessary to raise the level of its drain. At first this was done without much expense by heightening the walls of the channel, but this process could not go on for any length of time, as the channel would then become too deep in proportion to its width. When the bed of a drain ultimately was too low down to be properly inspected and cleared, an entirely new channel was constructed on top of the old one; in many cases, however, all the bricks of the old drain were removed and re-used to build the new one.