Author(s): Shoji Fukuoka, Yoshiharu Takemura

Linked Author(s): Shoji Fukuoka

Keywords: Mountain streams; Boulders; Flood flows; Water surface profiles; Q3D-FEBS;

Abstract: The value of the Manning’s roughness coefficients (= n) for mountain streams varies considerably in time and space due to the complex riverbed geometry including boulders and rocks. It reduces the reliability of the flood flow analysis in mountain streams. In this paper, the 2017 flood of the Takiyama River is analyzed by using 2D flow model and Q3D-FEBS based on observed water surface profiles for the reach where the detailed riverbed geometry including the shapes of boulders and rocks was measured. The results show that the value of n can be almost invariably determined from the flood flows and channel geometry by taking account of the three-dimensional flow velocities and non-hydrostatic pressure distributions around the boulders and rocks by using Q3D-FEBS. This makes it possible to estimate flood discharge hydrographs and flow structures from the reliable flood flow analysis in mountain streams.

DOI: https://doi.org/10.3850/38WC092019-1618

Year: 2019