Diverging Kinematic Wave Flow

Abstract

The governing equation for kinematic wave (KW) flow on a diverging alluvial fan is derived and presented with comparison with observed data. The key factors to describe a diverging KW flow are found to be the angle of apex, radius of alluvial fan area, ground surface slope, and rainfall intensity. The sensitivity tests indicate that under a specified condition, the rectangular KW flow is the enveloping curve for all diverging KW flows. The wider the angle of apex, the closer the diverging KW flow becomes similar to the rectangular KW flow. The analytical solution derived in this study provides the time to equilibrium and the peak flow on the diverging KW hydrograph. Both parameters are important for peak flow predictions. The new equation derived in this study offers a deterministic approach to define the base flood flow and the corresponding floodplain boundaries on the alluvial fan. It is believed that the approach outlined in this paper presents a significant improvement to the current practice on alluvial floodplain hydrology and hydraulics.