Cross-Scale Baroclinic Simulation of the Effect of Channel Dredging in an Estuarine Setting

• Main Authors: Fei Ye, Yinglong J. Zhang, Harry V. Wang, Hai Huang, Zhengui Wang, Zhuo Liu, Xiaonan Li
• Format: Article
• Language: English
• Published: MDPI AG 2018-02-01
• Series: Water
• Subjects: cross-scale; baroclinic simulation; SCHISM; estuary and coastal ocean; channel deepening
• Online Access: http://www.mdpi.com/2073-4441/10/2/163

Holistic simulation approaches are often required to assess human impacts on a river-estuary-coastal system, due to the intrinsically linked processes of contrasting spatial scales. In this paper, a Semi-implicit Cross-scale Hydroscience Integrated System Model (SCHISM) is applied in quantifying the impact of a proposed hydraulic engineering project on the estuarine hydrodynamics. The project involves channel dredging and land expansion that traverse several spatial scales on an ocean-estuary-river-tributary axis. SCHISM is suitable for this undertaking due to its flexible horizontal and vertical grid design and, more importantly, its efficient high-order implicit schemes applied in both the momentum and transport calculations. These techniques and their advantages are briefly described along with the model setup. The model features a mixed horizontal grid with quadrangles following the shipping channels and triangles resolving complex geometries elsewhere. The grid resolution ranges from ~6.3 km in the coastal ocean to 15 m in the project area. Even with this kind of extreme scale contrast, the baroclinic model still runs stably and accurately at a time step of 2 min, courtesy of the implicit schemes. We highlight that the implicit transport solver alone reduces the total computational cost by 82%, as compared to its explicit counterpart. The base model is shown to be well calibrated, then it is applied in simulating the proposed project scenario. The project-induced modifications on salinity intrusion, gravitational circulation, and transient events are quantified and analyzed.