stanch

…developed with the construction of stanches, or flash locks, in the weirs (dams) of water mills and at intervals along the waterways. Such a lock could be opened suddenly, releasing a torrent that carried a vessel over a shallow place. The commercially advanced and level Low Countries developed a system…

…made navigable about 1340 using flash locks, a primitive and dangerous type of lock that used boards, or paddles, supported by horizontal timbers, that could be removed to allow a temporary “flash” of water into a lock. In 1390 permission was granted for a canal to be built in order…