Abstract
In order to clarify changes of runoff characteristics of pipeflow, measurements of precipitation and pipeflow were conducted at a forested watershed situated in the paleozoic-mesozoic hills for three years. Similar changes in runoff characteristics were observed for two pipes ; the maximum discharge rate of pipeflow increased, the recession hydrograph of pipeflow became steep, and the duration of pipeflow discharge became short. However, the changes of runoff characteristics had no significant effect on relationships between total rainfall and total discharge from pipes. Based on observations of sediment yield from soil pipes, it was suggested that the pipe structure changes caused the changes of runoff characteristics of pipeflow.
