## 4 Conclusions  
The type of flow model can be classified according to the number of spatial dimensions in the governing equations upon which their predictions are based. A 1D exact solution, a 3D SW model (MIKE 3 FM), and a RANS equation solution with a \(k\)-\(\epsilon\) turbulence model (Flow-3D) were tested on typical dam-break flows over dry and wet beds. The validity of the three methods was based on comparisons of the model-calculated results with the laboratory data from [PERSON] and [PERSON] [30] and [PERSON] et al. [39]. To better understand the tailwater level effects on the dam-break wave impact, numerical simulations were conducted for different water depth ratios.  
The RANS approach reproduced the free-surface profiles of the front wave during the initial stage reasonably well for dry- and wet-bed conditions while the wavefront modelled by the MIKE 3 FM model and 1D analytical solution for the wet-bed case was a bore (i.e., a rectangular jump rather than a curved surface). As time passed, the movement of the front of the flood wave was well simulated by the MIKE 3 FM model. The Flow-3D and MIKE 3 FM models were useful 3D numerical tools for forecasting the temporal variations in the water depth variations and the velocity variation over time for dry and wet beds. However, the 1D analytical solution had a limited practical scope for evaluating the variation in hydraulic features at the full stage of dam-break flow over the dry- and wet-bed and was only applicable during the steady stage. The Flow-3D and MIKE 3 FM numerical methods presented here are suitable for fully hydrodynamic simulations of 3D dam-break flows.  
Only idealized 1D dam-break flow cases are examined in this study, and the comparison made here between MIKE 3 FM and RANS models for simulating three-dimensional dam-break flood flows that can be addressed reveal their respective limitations within the dam-break problem. These two 3D models are able to provide complete and detailed information on the physical quantities of dam break flows over space and time that provide information on the dam-break flood evolution, especially in terms of the free surface profile, water depth and flow velocity. At approximately one order of magnitude greater in terms of computation time than the MIKE 3 FM model, the Flow-3D model is much more complicated and time-consuming to use. Therefore, the Flow-3D is more specifically suited  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Experimental** & \multicolumn{2}{c}{**No. of Grids**} & \multicolumn{2}{c}{**Computation Time (s)**} \\ \cline{2-5}
**Group** & **MIKE 3 FM** & **Flow-3D** & **MIKE 3 FM** & **Flow-3D** \\ \hline Test 1 (\(\alpha=0\)) & 267 & 106,800 & 5 min & 120 min \\ Test 2 (\(\alpha=0.1\)) & 267 & 106,800 & 5 min & 120 min \\ Test 3 (\(\alpha=0.4\)) & 267 & 106,800 & 5 min & 120 min \\ Test 4 (\(\alpha=0\)) & 2860 & 256,000 & 9 min & 480 min \\ Test 5 (\(\alpha=0.2\)) & 2860 &to small-scale simulations with a focus on details, and it could be used for the analyses of small areas when knowledge of the 3D structure of the flow is available. In spite of the shortcomings of the MIKE 3 FM approach when applied to dam break problems during the initial stage, this model is more suitable for the large computational domains used in actual problems.  
[PERSON] carried out the numerical simulations, analyze data and wrote the first draft of the manuscript. [PERSON] and [PERSON] conceived and supervised the study and edited the manuscript. All authors reviewed the manuscript.  
This research was supported financially by the State Key Laboratory Base of Eco-hydraulic Engineering in Arid Area, China (Grant No. 2017 ZZKT-5), the National Natural Science Foundation of China (Grant No. 51609197), CAS \"Light of West China\" Program (Grant No. XAB2016 AW06) and the Xian Science and Technology Program (Grant No. SF1335).  
The authors declare no conflict of interest.