結晶片岩地域で発生した崩壊地の源頭部に形成されたパイプの変遷とパイプ流の降雨応答特性

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Pipes formed by a small animal-activity, root decay and underground erosion exist frequently in the upper part of rain-induced collapse sites. These pipes affect significantly on water discharge and occurrences of hillside landslides in a watershed. Many hillside landslides occurred at Nishiiyayama village in Tokushima Prefecture, on June 29 th, 1999, due to heavy rainfall. In the upper part of C torrent of Tobinosu-valley, hillside landslides occurred, and several pipes appeared. Investigations in approximately 2 months later showed that discharge from these pipes still continued, in spite of little rain after the occurrence of collapses. Tobinosu-valley is adjacent to the west side of large crystalline schist landslides "Zentoku". After the occurrence of the collapse on June 29 th, these pipes repeated disappearance and revival by expansion of surface rupture and partial fall. In this study since 19 August 1999, situations at the upper part of a collapse site in C torrent, that is, appearance, disappearance and revival of pipes, were periodically observed, and the discharge from these pipes was measured. Based on the measured results, responses of the discharge from these pipes to rainfall were analyzed, and the discharge from these pipes was compared to the groundwater level in the "Zentoku" landslides. Furthermore, using the results from these investigations and water quality analyses, source of water supply to the upper part of the collapse site in C torrent was estimated. The following results were obtained from our investigations. (1) After the occurrence of collapse on June 29 th, 1999, pipes of the upper part of the collapse site in C torrent repeated disappearance and revival, and discharge from three of these pipes (pipe No: [3 + 3'], [4], [6']) still continue.(2) The total discharge from all pipes is more than 50 cc/sec, even in the duration of continuous drought. (3) No runoff from the pipes increases when rainfall is less than 50 mm/day. (4) Rainfall affects on pipe discharge during three days from the next day. (5) This study suggests groundwater supply from the "Zentoku" landslide area to C torrent in Tobinosu-valley.
2002-10-25

結晶片岩地域で発生した崩壊地の源頭部に形成されたパイプの変遷とパイプ流の降雨応答特性

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