Abstract
When utilizing a finite volume method to predict outburst flood evolution in real geometry, the processing of wet-dry front and dry cells is an important step. In this paper, we propose a new approach to process wet-dry front and dry cells, including four steps: (1) estimating intercell properties; (2) modifying interface elevation; (3) calculating dry cell elevations by averaging intercell elevations; and (4) changing the value of the first term of slope limiter based on geometry in dry cells. The Harten, Lax, and van Leer with the contact wave restored (HLLC) scheme was implemented to calculate the flux. By combining the MUSCL (Monotone Upstream–centred Scheme for Conservation Laws)-Hancock method with the minmod slope limiter, we achieved second-order accuracy in space and time. This approach is able to keep the conservation property (C-property) and the mass conservation of complex bed geometry. The results of numerical tests in this study are consistent with experimental data, which verifies the effectiveness of the new approach. This method could be applied to acquire wetting and drying processes during flood evolution on structured meshes. Furthermore, a new settlement introduces few modification steps, so it could be easily applied to matrix calculations. The new method proposed in this study can facilitate the simulation of flood routing in real terrain.
Highlights
Glacier avalanche [1,2], debris flow [3,4,5], and landslide [6,7,8] in mountain areas could trigger the occurrence of river blocking [9,10,11,12]
In order to apply shallow water equations to a river with a complex geometry and avoid more elevation modifications, we propose processing dry cells by adopting the first term of the slope limiter function in dry cells to solve the wet-dry front problem and accomplish matrix simulation in the whole calculation area
We propose a new approach to process dry cells and wet-dry front cells via a Godunovtype finite volume prediction method of flood evolution
Summary
Glacier avalanche [1,2], debris flow [3,4,5], and landslide [6,7,8] in mountain areas could trigger the occurrence of river blocking [9,10,11,12]. Yigong Lake was blocked by catastrophic landslides in 1902 and 2000 [14] and formed outburst floods with peak discharges of around 18.9 × 104 m3 /s [15] and 12.4 × 104 m3 /s [8], respectively; the Yarlung Tsangpo gorge was blocked twice in 2018, with a peak discharge of 3.2 × 104 m3 /s in the second outburst flood [3,4]. Outburst floods may have significant geomorphic and geologic impacts; they have substantial erosive and transport capacity that can rapidly transform river channels and bedforms [17,18,19], and may even lead to climate change [20] and a global sea level decrease [21] Outburst floods and their impacts even appear in the myths and stories of many civilizations, such as the Bible and the Koran [22]
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