Model of a simple kauri dam used by timber loggers in Katikati, New Zealand. During the days of the early logging industry, there was no easy way to get the logs to saw mills or ports. Logs were therefore dragged by horses to a nearby stream bed with steep sides and a Kauri Dam was constructed of wood with a "trapdoor" near the bottom, large enough for the logs to pass through. When the dam filled, which could take weeks or months, the trapdoor was opened and logs floating above the dam were sucked through the hole and swept down to the sea.