Discussion of 'Discharge through a Permeable Rubble Mound Weir' by Kohji Michioku, Shiro Maeno, Takaaki Furusawa, and Masanori Haneda

摘要

The discusser congratulates the writers for their valuable contribution to flow through permeable weirs, including rubble mound weir, rockfill structures, and some timber weirs. Their combined theoretical and physical modeling approach yields convincing results, and prototype tests could be a nice complement. The following comments are aimed to complement the findings. Related applications of rubble mound weir include the in-built spillway dam and the stepped weir. The former design has been used in Australia since the 1950s (Fig. 1). Lawson (1987) described several prototype experiences. The latter design is commonly used for soil retention, storm-water system, and irrigation structures (e.g., Fig. 2). Chanson (2001) presented a wide range of applications. With both in-built spillway embankment and stepped weir, the shape of the downstream embankment face may have some influence on the seepage discharge. For example, in Fig. 2(b), the seepage outflow increases toward the downstream weir toe. It would be valuable if the authors could comment on the effect of the weir shape and the implications.