霞ヶ浦における植生帯と砂浜の消失要因の検討

概要

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In Lake Kasumigaura, lakeshore vegetations and sandy beaches have been rapidly decreased in recent years, resulting in the extension of artificial shoreline. Hirai (1993, 1995a, 1998, 2006) studied the change in lowland and lake use, and the artificial land alteration in Lake Kasumigaura. He concluded that the anthropogenic factors such as the construction of fishing port, aquaculture facility and sand mining account for 45% of all the artificial land alteration, causing loss of appropriate growth zone of the lakeshore vegetation. In addition to these factors related to artificial land alteration, there are other important factors; direct effect of wind waves and indirect effect associated with littoral transport along the lakeshore. This study aims at investigating these factors; the effect of waves reflected from the exposed seawall to the disappearance of lakeshore vegetation, obstruction of longshore sand transport by structures and removal of sand out of the littoral zone by dredging to the disappearance of sandy beaches. Aerial photographs and beach survey data were compared to investigate these causes.
2008-04-25