As the coastal wetlands in the Yellow River estuary are experiencing intensifying degradation and water security challenges are becoming increasingly severe, this study aims to explore the response mechanisms of runoff evolution and extreme hydrological effects in the Yellow River estuary region under the context of climate change. Currently, the degradation of coastal wetlands and water security issues have attracted widespread attention, and understanding the runoff changes and their impacts in this region is of great significance for ecological protection and water resource management. In this study, a surface water model for the study area was established based on the SWAT distributed hydrological model. After parameter calibration and validation, the daily runoff time series from the Lijin Hydrological Station at the basin inlet on the Yellow River was used as the upstream inflow, and its runoff time series was kept unchanged. The evolution process of runoff in the study area under future climate change scenarios was then simulated. Furthermore, the research explored the response relationships between the regional surface hydrological cycle and meteorological factors, as well as the variation patterns of runoff under extreme precipitation conditions.The results showed that: (1) Runoff in the Yellow River Estuary Basin exhibited a positive correlation with precipitation and a nonlinear relationship with temperature. Specifically, runoff increased with rising temperature under constant or decreasing precipitation, but displayed an initial increase followed by a slight decrease with temperature elevation under increasing precipitation. Comparatively, runoff in the Yellow River and its tributaries demonstrated higher sensitivity to precipitation changes. (2) Under extreme precipitation scenarios, daily and monthly runoff variations showed significant fluctuation rates, while annual runoff changes remained relatively smaller.These findings suggest that there are complex relationships between runoff and meteorological factors in the Yellow River estuary region. The results provide critical data support and a scientific basis for rational water resource allocation in wetland ecosystems, facilitating effective protection of wetland environments under flood threats.

In order to forecast and prevent storm surge disasters caused by typhoon in Jiaozhou Bay, a two-dimensional nested wave-current coupling numerical model is established in Jiaozhou Bay and its adjacent sea area based on Delft3D numerical simulation software and mixed wind field model. Based on the coupling model, the influence of the extreme value of wave-current coupling surge on the storm surge and Jiaozhou Bay during the influence of Typhoon Winnie on Jiaozhou Bay was simulated and analyzed. The temporal and spatial variation characteristics of the surface flow field of pure wind-driven current and the contribution of wave surge to storm surge surge surge are explored. The results indicate that the astronomical tide level is dominant in the storm surge water level caused by typhoon 9711 in Jiaozhou Bay. The extreme value of wave-current coupling increases with the decrease of superimposed astronomical tide level, and the comprehensive water level decreases with the decrease of astronomical tide level. The maximum increase of wave-current coupling and the high tide level of astronomical tide aggravate the risk of forming an inundation at the northwest of Jiaozhou Bay. In addition, the wave surge in the shallow water area of Jiaozhou Bay is more significant than that in the deep water area.