木津川における底生動物生息場としての瀬の形態の歴史的変遷

Abstract

To understand qualitative and quantitative changes of riffles as habitat for invertebrates associated with channel degradation, field surveys of riffles and aerial photo analyses were conducted in the Kizu River. We classified 4 types of riffles based on geomorphologic characteristics. Taxonomic richness and biomass of invertebrates differ largely among the 4 types, and they were greater for the types with coarser bed materials, which provide sufficient stability and interstices for invertebrates. Aerial photo analysis suggests that despite the decrease of total riffle area since 1948, invertebrate biomass and taxonomic richness at reach-scale have recently increased in the Kizu River.