Experimental study on discharge process regulation to debris flow with open-type check dams
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Hao Sun I Yong You I Jinfeng Liu I Guangze Zhang I Tao Feng I Dong Wang
Experimental study on discharge process regulation to debris flow with open-type check dams
Abstract Open-type check dams are widely used to mitigate debris-flow hazards in mountainous areas. However, the regulation function of dams is a non-trivial and still open issue. With the aim to better understand the process regulation of open-type check dam against debris flow, in this study, a series of specially designed flume experiments are conducted as well as contrast tests of closed-type dam. The effects of the debris-flow bulk density, opening form, and dam size are considered. Analysis of the flow patterns, discharge process, peak discharge, and flow duration give an insight into regulating detail. Results reveal that the regulation characteristics depend on the blocking performance of open structure. There are differences in the debris-flow hydrography after passing through an open-type or closed-type dam, and the temporary blocking phenomenon is found to play an important role in regulating the discharge process. Moreover, open-type dams produce a reduction and time lag in the peak discharge, and more effectively regulate the travel time of debris flow downstream than closed-type dam. The reduction ratio of peak discharge for narrow openings is similar to that of closed-type dam and decreases as the relative opening becomes wider. Finally, based on these regulation characteristics, the application of open-type dams for a novel form of debris flow mitigation is discussed from the perspective of balancing interception and regulation of sediment. Keywords Debris flow . Open-type check dams . Process regulation . Temporary blocking Introduction As a key countermeasure to control debris flow movement, check dams are widely used for debris-flow hazards mitigation (Ikeya 1989; Jakob and Hungr 2005; Mizuyama 2008). The main purposes of such dams are to decrease the debris-flow momentum, raise the erosion base, and enhance the gully bed stability. Check dams can generally be divided into open-type dams and closed-type dams according to their structural form (Fei and Shu 2004) and functional purpose (Armanini et al. 2006). One of the most important functions of a dam is to trap and regulate debris flow and sediment transport. Open-type dams can discharge part of the debris flow through their open structure while intercepting sediment. Figure 1 shows some open-type check dams in mountainous areas of Southwest China. In recent decades, a considerable number of studies have investigated various functions, including interception, regulation, deposition, and self-cleaning. In terms of interception, You (2001) examined a beam dam, Shrestha et al. (2008), Takahara and Matsumura (2008), and Shima et al. (2016) investigated grid dams, Fei et al. (2013) and Silva et al. (2015, 2016) considered piles groups, and Wendeler and Volkwein (2015), Ferrero et al. (2015), and Huo et al. (2017) studied flexible barriers. In addition, D’Agostino et al. (2000), Nakatani e
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