Positive surge propagating in an asymmetrical canal.

• Positive surge translation in an asymmetrical canal is three-dimensional. • Detailed experiments performed in a 19 m long canal, with 1 V:5H transverse bed slope. • Geometry corresponded to a distorted scaling of natural channel with tidal bores. • Complicated transient secondary motion behind surge. • Leading edge of the surge arrived first in the shallow-water section. A positive surge is an unsteady open channel flow motion characterised by a sudden rise in water surface elevation. The literature is focused primarily on rectangular channels. Herein, the free-surface features of positive surges propagating upstream were investigated in an asymmetrical canal. The surge propagation was a three-dimensional unsteady flow motion, resulting in a complicated transient secondary motion compared to positive surge propagating in rectangular canals. The present results may be relevant to surge propagation in man-made trapezoidal canals and natural irregular-shaped channels. [ABSTRACT FROM AUTHOR]