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With global warming and the increase in extreme precipitation events, floods are becoming more frequent in mountainous areas, and the safety of lives and property of people is seriously threatened. However, understanding of the flooding process in uninformative mountainous areas is limited due to the lack of high-quality hydrometeorological data. Hence, this study adopts the MIKE21 model to simulate flood inundation in the Shadai River basin in the Qilian Mountain region of the northern Tibetan Plateau as an example. This validates the modelsimulated flow and inundation extent using the flow data obtained from the calculation of the flood trace points, extent of inundation, and high-resolution remote sensing images. The results show that the flash flood inundation mainly occurs at 12:00-01:00 AM on 18 August 2022, and the simulated and actual maximum inundation areas are 7.9 and 9.5 km², respectively. The fitted F-statistic value is 0.81, and the relative error between the calculated flow rate of the flood trace point and the model-simulated flow rate is 8%, indicating good consistency. Furthermore, an in-depth exploration of the model parameter sensitivity reveals that the use of distributed Manning's roughness coefficient value has higher simulation accuracy. [ABSTRACT FROM AUTHOR]

In the face of depleting fossil energy and the imperative of sustainable development, there is a compelling drive towards advancing renewable energies. In this context, sustainable and predictable alternatives, like marine energy, gain prominence. Marine energy presents a cleaner option devoid of the adverse effects associated with fossil fuels, playing a crucial role in environmental sustainability by safeguarding coastlines against erosion. This study focuses on Astara Port in the Caspian Sea, exploring the utilization of wave energy converters (WECs). The originality of this study's research lies in exploring WECs' dual role in energy generation and coastal protection. Using MIKE21 software simulations, the impact of number, location, arrangement, and orientation of WECs across various scenarios was investigated, including two WEC number scenarios (11 and 13), three structural placement scenarios (north, front, and south of the port), two structural arrangement scenarios (linear and staggered), two port layout scenarios (original layout and modified layout), and two orientation scenarios for the structures (facing north-east, which is the dominant wave direction, and facing southeast). The results show a remarkable decrease in the significant wave height behind WECs, notably with 13 staggered devices facing dominant waves (from northeast), reducing the significant wave height Hs by 23–25%. This setup also shows the highest wave height reduction, notably 36.26% during a storm event. However, linear WEC setup offers more extensive coastline protection, covering 47.88% of the model boundary during storms. Furthermore, the 11 staggered WECs facing southeast (SE) arrangement had the lowest sediment accumulation at 0.0358 m over one year, showing effective sedimentation mitigation potential. Conversely, the 13 linear WECs facing northeast (NE) had the highest accumulation at 0.1231 m. Finally, the proposed port design redirects high-velocity flow away from the port entrance and removes rotatory flow, reducing sediment accumulation near the harbor entrance. [ABSTRACT FROM AUTHOR]

The diffusion of offshore salt in inland rivers along with tidal waves has an important effect on the aquatic ecological environment of the estuary area.This paper,taking the Wanquan River Estuary as an example,used the Mike21 model to simulate the salinity distribution along the channel under different runoff and tidal levels and analyzed the change rules and leading factors.The results show that the river system and riverbed topography at the Wanquan River Estuary reduce the upward diffusion of salt propelled by the tide and that the salt is mainly distributed in the waters near the estuary.The salinity distribution along the upper reaches of the river decreases rapidly,and it basically remains unchanged when the tidal level increases by 0.1 m and 0.3 m,respectively.A sudden increase in salinity occurs where a curved or narrow channel changes the local water flow and salt accumulates.The upward diffusion range of salt is mainly affected by runoff. When the runoff reaches 106 m3/s and 148 m3/s,the tidal level needs to increase by 0.1 m and 0.3 m respectively before it has an impact.Different degrees of change in runoff and tidal level have different effects on salinity distribution at the estuary,and channel conditions play a key role.