Experimental study of the influence of macro-roughnesses on vertical slot fishway flows
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Houille Blanche, ISSN: 0018-6368, Vol: 2017-April, Issue: 2, Page: 9-14
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- Environmental Science
The European Water Framework Directive (2000) has aimed to restore the ecological continuity of the river streams. One of its main objectives is to ensure the free circulation of aquatic species. In practice, many obstacles can be found across rivers that hinder this movement. Fish passage facilities (like vertical slot fishways, VSFs) are required to help fish to cross permanent obstructions and thus allowing their natural migration.To improve the fish passage of specific species, macro-roughnesses are often arranged on the bottom of each VSF pool to assist some species which move close to the bottom. However, the presence of macro-roughnesses is not yet taken into account during the VSF design. This paper presents results of experimental studies on the influence of evenly distributed macro-roughnesses on the discharge coefficient and on the flow topology in a VSF. By water depth and flow velocities measurement, the influence of macro-roughnesses on the flow features is highlighted. These experiments were carried out for two block densities and for a wide range of channel slopes, pool widths and flow discharges. Thus, discharge coefficient maps and flow topologies were produced. Moreover, a sensitivity analysis of the design parameters on the discharge coefficient and topology were performed. The results presented herein may be used to define a predictive law that would help engineers ensure the greatest effectiveness of VSFs with the presence of macro-roughnesses.