Dimensionless attenuation of dam-breach flood wave propagating along a river

• Published in: Journal of hydrology (Amsterdam) Vol. 641; p. 131765
• Main Authors: Macchione, Francesco, Graziano, Andrea Antonella
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.2024
• Subjects: Dam failure; Dam-breach; Earthen dams; Flood wave attenuation; Flood wave propagation; Flood wave propagation; Dam failure; Flood wave attenuation; Earthen dams; Dam-breach
• ISSN: 0022-1694
• DOI: 10.1016/j.jhydrol.2024.131765

•The dam-breach wave propagation is studied through a dimensionless formulation.•The dimensionless hydrographs shape depends mainly on the reservoir morphology.•The wave downstream attenuation is governed by a key dimensionless parameter.•A quick assessment of the attenuation can be performed using the graphs presented. In the past, several authors have proposed methods to study the routing behaviour of a flood caused by a sudden dam failure (dam-break). As regards, instead, the progressive failure of earthen dams, defined as “dam-breach” in the literature, very few studies have been proposed in this scope. Furthermore, existing studies have limited validity, as they are often based on weighty simplifications and/or limited to a specific range of cases. Therefore, there is a need to study the dam-breach wave propagation phenomenon with a more comprehensive approach, in order to identify the essential key aspects related to the wave routing. In light of the above, in this work the generation and propagation of the dam-breach flood waves have been studied by means of an appropriate dimensional analysis that allowed for the identification of the parameters that have the major influence on the breach outflow hydrograph and the downstream attenuation of the flood wave. As for the generation, a parameter describing the morphology of the reservoir has been shown to control the shape of the dimensionless discharge hydrographs outflowing from the breach. As for the propagation, all the involved parameters (i.e., flood volume, peak discharge at the dam site, downstream longitudinal slope, and cross-sectional flow area and depth) have been collected in two dimensionless parameters that characterize the 1D full-momentum Shallow Water Equations in dimensionless form. One of them has been shown to be predominant in controlling the downstream attenuation of the flood wave. So just three graphs have been enough to cover much of the possible real-world variability. These graphs can also be used for the purposes of a quick assessment of the downstream attenuation of a flood generated by the hypothetical breaching of a real earthen dam. The proposed method has been shown to give satisfactory results through application to different case studies: the hypothetical failure of three real earthen dams, in which the results of the proposed method have been compared with the results of 2D full-momentum hydrodynamic simulations, and the Baige landslide dam-breach flood that occurred along the Jinsha River (China) in November 2018.