サロベツ湿原における湿地溝の形成 : カレックスモデルを用いた検証

概要

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A bog rill is a small channel formed on the surface of particular bog mire. The shapes in plan of bog rills are dendritic in pattern, its cross-sectional profiles are variegated. Various micro-topographies exist in mires, but no other micro-topographies form along the main inclination direction. In Hokkaido, bog rills are found only at Sarobetsu Mire. The bog rills have been used to be the cause of erosion empirically, though the inclination of the ground level of the headwater region in bog rills is extremely small. Hence, it should be assumed that erosion cannot function as geomorphic agents and cause bog rills. This study presents the results of recent researches related to the study of the bog rills in Sarobetsu Mire. In this study, on the basis of the characteristic features of bogs, the origin of bog rills is assumed and verified using the Carex model (Okada, 2008). Carex model, which based on the growth processes of bog vegetation, can simulate changes in peat layers and thus predicts the formation of the diverse micro-topographies of mires. As a result, bog rills are not formed on mires containing isotropic peat layer. It is assumed that bog rills are formed along the main inclination direction, where the peat layers lead to convergent flow. There could be various factors influencing this result. That is the inclination of a bog surface in a direction other than the main slope direction, the variation in the water permeability inside a peat layer, and others. In Sarobetsu Mire, a river meandered in an old age, however it is buried under the layer of peat presently. The high permeability of the buried river compared to surrounding peat, induces the groundwater flows in a direction other than the main inclination of the mire is assumed to be the reason behind the formation of the bog rills in Sarobetsu Mire.
2009-04-25

著者

岡田操
(株)水工リサーチ

サロベツ湿原における湿地溝の形成 : カレックスモデルを用いた検証

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