What Controls the Magnitude and the Shape of Landslide Dam-Breaching Flood Hydrograph? Case Studies of Emergent Forecasts for Outburst Floods of Jiala and Baige Barrier Lakes

Yuntian Song,Xudong Fu,Hongbo Ma,Chenge An,Yongpeng Lin

doi:10.3389/frwa.2022.834132

Abstract

Outburst floods released by failing barrier dams are likely to be catastrophic, posing high risk to downstream areas. However, emergent forecasting of the breaching process is still challenging due to the complex mechanisms as well as the lack of adequate data. During October and November 2018, four tremendous barrier lakes formed and breached on the Jinsha River and the Yarlung Zangbo River, China. In this paper, we present numerical simulations for three of these events (October 17 and October 29 at Jiala Village, Yarlung Zangbo; November 3 at Baige Village, Jinsha River), and investigate what factors control the magnitude and shape of the hydrograph of the outburst flood. A physically-based dam-breach model was established for the prediction. We first specified the model parameters based on the aerial images, DEM data and hydrological measurements during the emergency treatment. With these parameters, the model can successfully predict the breaching process of the two barrier dams in the Yarlung Zangpo, but underpredict the peak discharge of the outburst flood in the Jinsha River. The outburst flood in the Jinsha River, however, can be well-reproduced with refined information on dam height and grain size distribution. Moreover, both field data and our numerical simulation showed that the magnitude and shape of the outburst flood hydrograph can be affected by the dam morphology and the composition of dam material. Two patterns of outburst flood hydrographs with different symmetry characteristics were identified using statistical analysis. The approximately symmetrical breach hydrograph of the “November 3” Baige barrier lake could be partly attributed to the relatively fine grain size distribution of the dam material.

Highlights

As a consequence of tectonic movement and climate change, hazards caused by barrier lakes have hit mountain areas all around the world (Costa and Schuster, 1988; Miller and Cruden, 2002; Nicoletti and Parise, 2002; Abril and Knight, 2004; Korup and Tweed, 2007; Ruiz-Villanueva et al, 2017)
We discuss the reason for the underprediction of our model in the case of the “November 3” Baige barrier dam, Jinsha River, and explore whether the model performance could be improved with refined field information
The results indicate that for the emergency treatment of barrier dams, finer dam materials might lead to a larger and earlier outburst flood peak, and more people in the downstream region need to be resettled in advance to mitigate the flood hazard

Summary

Introduction

As a consequence of tectonic movement and climate change, hazards caused by barrier lakes have hit mountain areas all around the world (Costa and Schuster, 1988; Miller and Cruden, 2002; Nicoletti and Parise, 2002; Abril and Knight, 2004; Korup and Tweed, 2007; Ruiz-Villanueva et al, 2017). Only a few observation data of breach hydrographs of landslide dams are available due to the limitations of measurement time and accessibility (Balmforth et al, 2009; Dang et al, 2014). Studies on the breach process of landslide dams and their influential factors have been carried out mostly by laboratory experiments (Spinewine and Zech, 2003), which show that the magnitude and shape of dam-breaching flood hydrograph are influenced by dam material, dam geometry, upstream inflow conditions, as well as artificial intervention (Balmforth et al, 2009; Schmocker and Hager, 2009; Gregoretti et al, 2010; Cao et al, 2011a; Chen et al, 2015, 2020). As it is difficult to scale both the actual sizes and material composition of natural landslide dams in laboratories, the conclusions obtained from experiments still need further validation (Schmocker and Hager, 2009; Cao et al, 2011b)

Methods

Discussion

Conclusion