Mountain streams are generally characterized by the high Froude number of the flow and the largescale roughness of the river-bed. The hydraulic characteristics of flow in these streams have not yet been understood well.
The purpose of the study in this experiment is to investigate the resistance of flow by discussing the location of the reference bed surface in the steep open channel flow on the bed with large roughness elements.
The results are summarized as follows:
1) The location of the reference bed surface is related with the subflow discharge flowing under the top of roughness elements.
2) In the flow in which the bed slope and the void of roughness elements cover a wide range, it seems better for the datum to be treated in shifting.
3) The location of the reference bed surface is expressed as a function of the bed slope and the void of roughness elements. The datum shifts below the roughness elements as these parameters increase.
4) The resistance equation is expressed as a function of
Rb/kg and
u*b2/g·kg in a logarithmic form.
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