Journal of the Japan Society of Erosion Control Engineering, Vol.58,No.1,2005
Numerical simulation on a debris flow in a mountainous river with a Sabo
dam
Yoshifumi SATOFUKA Takahisa MIZUYAMA
Abstract
Numerical simulation model that can reproduce the riverbed variation caused by
a debris flow in a mountainous river is proposed. In the model, the sediment material
is composed of two grain]size classes and the one]dimensional governing equations
for a stony debris flow are employed. The governing equations are discretized
according to the staggard scheme. The influence of a sabo dam upon the debris
flow is built in the model by changing the outflow condition at the concerned
point where the flow velocity, flow discharge and sediment discharge are calculated.
The rapid deposition phenomena at the upstream of the sabo dam can not be represented
by former models in which the deposition velocity equation is used. The calculated
deposition velocity by such equation is too small in the upstream area of the
dam, because it is proportional to the flow velocity. Usual deposition velocity
equation was developed under the condition where the riverbed gradient changes
gradually, therefore it is not applicable for the area where the flow depth and
velocity suddenly change. In the present model, the rapid separation of sediment
from the flow at the upstream of the sabo dam is taken into account, consequently
the larger deposition velocity can be estimated. We try to calculate a long distance
runoff process of a debris flow by the present model, and investigate the influence
of the characteristics of sediment on the hydrograph.
Key words:debris flow, one]dimensional numerical simulation, influence of a sabo
dam on bed variation
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