GENERATION AND FLOATING BEHAVIOR OF SCUM IN AN URBAN TIDAL RIVER IN OSAKA, JAPAN

Abstract

In urban rivers where combined sewer overflows occur, scum appears several days after rainfall, causing bad odor and adverse effects on the landscape and ecosystem. To clarify the generation and floating behavior of scum, we conducted a detailed observations of scum using multiple fixed-point cameras and sediment surveys in the Hirano River, an urban tidal river in Osaka, Japan. Organic mud derived from sewage was deposited in two separate areas, of which the upstream was the main source of scum in the river. The floating behavior of scum was mainly dominated by tide, and scum accumulated at the stagnant point at rising tide. Scum was frequently observed at the bend of the river channel, suggesting that the local flow structure had a considerable influence on the behavior of scum over a wide area of the river.