耕作ステージの異なるパイナップル圃場での赤土砂流出特性

概要

論文の詳細を見る
The major sources of red sediment discharged from mountainous areas of Okinawa Prefecture are pineapple fields. The authors prepared hydrological observation fields representing different cultivation stages in the upstream of the Furushima river in Higashi-son. The following are the major findings.1) The major period of red sediment outflow from pineapple fields ranges from 1 month to 1 year following the plowing-in performed to renew a field.2) Excluding the times of large rainfalls in excess of 200 mm, the volume of sediment discharged per unit field surface where erosion is possible is almost identical at every cultivation stage.3) Turbid water discharged from pineapple fields contains a large clay content that remains between 67% and 70% regardless of the cultivation stage.4) The mean value of the discharge rate during a continuous rainfall of 30 mm or more -rainfall that increases the discharge of red sediment- is about 0.25. From 100 mm to 200 mm, it is about 0.2, but when the rainfall is higher, it is about 0.4.5) When no rain falls for 200 hours or longer, the critical rainfall for red sediment outflow on a pineapple field is about 10 mm of cumulative rainfall. The critical rainfall intensity for red sediment discharge is between 0.3 and 0.6 mm/5 min.6) The mean red sediment erosion depth caused by a continuous rainfall where the ground surface is exposed in a field is a maximum of several millimeters.
社団法人砂防学会の論文