Symmetric and asymmetric enlargements of block ramp stilling basins

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Stefano Pagliara, Michele Palermo

Friday 3 july 2015

11:00 - 11:15h at Asia (level 0)

Themes: (T) Hydro-environment, (ST) Ecohydraulics and ecohydrology, (ST) River and coastal engineering

Parallel session: 15C. Engineering - Industrial

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Block ramps can reduce the impact of anthropic river restoration structures on the river eco-systems. The correct assessment of their effects on the river system in which they are located is depending on several factors. Among others, the most relevant are: the hydraulic and geometric parameters characterizing the river branch and the geometry of the stilling basin. In particular, this last aspect is of fundamental importance as the downstream stilling basin has a significant role both for the structure stability and for the dissipative process. Nevertheless, the stilling basin geometry is a key parameter for scour morphology characteristics. The aim of the present paper is to compare the morphological characteristics of the scour hole in basins characterized by different geometries downstream of block ramps. Namely, the analysis of scour hole profiles and characteristics were conducted for stilling basins with the same width of the upstream ramp and compared with those occurring in symmetrically and asymmetrically enlarged basins, in order to highlight similitudes and differences. The comparison of scour typologies occurring under different stilling basin configurations was discussed and analyzed. The results of the analysis put in evidence the prominent effect of the stilling basin configurations on both scour hole dimensions and flow features. In particular, the knowledge of different scour typologies occurring in the tested stilling basins could be extremely beneficial for a correct design of the structure. Furthermore, this paper aims to furnish practical criteria which could be useful to design more suitable riparian zones for fish species.