Articles | Volume 4, issue 3
Nat. Hazards Earth Syst. Sci., 4, 469–474, 2004

Special issue: Monitoring and modeling of landslides and debris flows

Nat. Hazards Earth Syst. Sci., 4, 469–474, 2004

  02 Aug 2004

02 Aug 2004

Critical conditions of bed sediment entrainment due to debris flow

M. Papa1, S. Egashira2, and T. Itoh2 M. Papa et al.
  • 1Department of Civil Engineering, Salerno University, Italy
  • 2Department of Civil and Environmental Systems Engineering, College of Science and Engineering, Ritsumeikan Univ., Japan

Abstract. The present study describes entrainment characteristics of bed material into debris flow, based on flume tests, numerical and dimensional analyses. Flume tests are conducted to investigate influences of bed sediment size on erosion rate by supplying debris flows having unsaturated sediment concentration over erodible beds. Experimental results show that the erosion rate decreases monotonically with increase of sediment size, although erosion rate changes with sediment concentration of debris flow body.

In order to evaluate critical condition of bed sediment entrainment, a length scale which measures an effective bed shear stress is introduced. The effective bed shear stress is defined as total shear stress minus yield stress on the bed surface. The results show that critical entrainment conditions can be evaluated well in terms of Shields curve using the effective bed shear stress instead of a usual bed shear stress.