Search

A numerical study based on FVCOM model was carried out to investigate the storm surge behavior induced by Typhoon Mangkhut in and around Lingdingyang Bay, Pearl River Estuary. Through elaborate calibration, the simulation results matched well with the measurements on the tidal-gauge stations. The validated Typhoon Mangkhut simulation was used as a case to study temporal–spatial behavior of the storm surge. Specifically, hourly spatial distribution of surge evolvement before the landfall of Typhoon Mangkhut and the time series of the surge from the twelve points in and around Lingdingyang Bay were analyzed. Beyond that, a series of artificial typhoons were designed through revising some parameters of the original typhoon including the landfall time, central pressure deficit, landfall location and moving direction, to study the influence caused by typhoon uncertainties. Results show that the influence of landfall time is dominated by the rule of tide–surge interaction, namely the lowest surge on the high tidal level and vice versa. The results also illustrate that the response of the surge to the same shift of the pressure deficit for a typhoon is uneven in space. The response of surge is more sensitive near shallow coastal regions than that in deep sea. Through investigating the surge in response to the track for the original typhoon, we find that a west shift of the track makes the ascending surge advanced and an east shift of the track makes the receding surge delayed in Lingdingyang Bay. A decrease of the angle between the coast and the direction of movement enlarges the maximum surge and an increase of the angle induces the opposite result. This study could improve our understanding about how uncertainties of a northwesterly moving typhoon would induce the storm surge response along the coastal regions such like Lingdingyang Bay, in Pearl River Estuary.

Urban pluvial flash floods have become a matter of widespread concern, as they severely impact people’s lives in urban areas. Hydrological and hydraulic models have been widely used for urban flood management and urban planning. Traditionally, to reduce the complexity of urban flood modelling and simulations, simplification or generalization methods have been used; for example, some models focus on the simulation of overland water flow, and some models focus on the simulation of the water flow in sewer systems. However, the water flow of urban floods includes both overland flow and sewer system flow. The overland flow processes are impacted by many different geographical features in what is an extremely spatially heterogeneous environment. Therefore, this article is based on two widely used models (SWMM and ANUGA) that are coupled to develop a bi-directional method of simulating water flow processes in urban areas. The open source overland flow model uses the unstructured triangular as the spatial discretization scheme. The unstructured triangular-based hydraulic model can be better used to capture the spatial heterogeneity of the urban surfaces. So, the unstructured triangular-based model is an essential condition for heterogeneous feature-based urban flood simulation. The experiments indicate that the proposed coupled model in this article can accurately depict surface waterlogged areas and that the heterogeneous feature-based urban flood model can be used to determine different types of urban flow processes.

Under climate change, flood-induced inundation becomes frequent in low-lying coastal and riverine regions as a result of an increasing storm surge and sea-level rise. An efficient and robust inundation assessment model is necessary for flood control, coastal management and inundation evacuation. Due to the complexity and runtime consumption of hydrodynamic models, a series of rapid flood inundation methods (RFIMs) have been developed based on high-resolution digital elevation models (DEMs) and advanced geographic information system (GIS) technology. However, a shortage of hydrodynamic mechanisms restricts the application of the RFIM. This paper proposes a novel rapid flood inundation method based on a combination of GIS and hydrodynamics for application in coastal and riverine regions. In a common-sense approach, the tidal flood flow first propagates along the river network and then diffuses from the network to the floodplain. First GIS-based algorithms are used to extract hydrodynamic model parameters from the DEM. Specifically, it includes the extraction of the flow network and the cross section bottom level on each flow segment, and the discretization of the main terrain into a triangulated irregular network (TIN) and the division of the catchments. Next, a one-dimensional hydrodynamic network model is applied to calculate flood flow propagation on the complex network. The model solves the full hydrodynamic equations to capture the dynamic process of flooding wave propagation such as wave amplification and damping. Last, a simple elevation-determined and domain-connected algorithm on the triangulated irregular network is implemented to obtain the extent of the flood inundation. The results indicate that the proposed method can estimate a reasonable flooding extent with a good degree of agreement with that by the three-dimensional hydrodynamic model. However, the runtime of the proposed method is significantly reduced by orders of magnitude at the same resolution compared to the runtime of the hydrodynamic model. Moreover, the effect of the banks, which is a difficult problem for many hydrodynamic models, can also be solved without local refinement of the grids. Therefore, our main conclusion is that the proposed RFIM is a useful tool for estimating inundation processes in coastal and riverine regions with limited input data and low computational burden.

In order to ensure the safety of bridges and ships, non-navigable channel arresting facilities for ships have become an important part of cross-sea bridges, and the diffusion of suspended sediment caused by their implementation has an impact on seawater quality. Taking the Jintang bridge as an example, a two-dimensional tidal current and sediment numerical model was applied to predict the distribution of suspended sediment diffusion caused by the implementation of arresting facilities, in order to analyze seawater quality. We adopted a new formula for the equivalent roughness method, to generalize the bridge piers, and obtained good results. The results showed that the zone where the SSC (suspended sediment concentration) reached 10 mg/L was concentrated in the area from 4.5 km north to 6.5 km south of the arresting facility, when it was implemented near the western channel. The sea area by the main channel was concentrated within 500 m of the arresting facility. The impact of the implementation of the arresting facility on seawater quality was relatively limited. Only the protected marine area in the Zhenhai Section of the Hangzhou Bay Estuary Coastal Wetland was affected by the suspended sediment from the construction of the western channel.