A dike-groyne module is developed and implemented into the unstructured-grid, three
dimensional primitive equation Finite-Volume Coastal Ocean Model (FVCOM) for the study of
the hydrodynamics around human-made construction in the coastal area. The unstructured-grid
finite-volume flux discrete algorithm makes this module capable of realistically including
narrow-width dikes and groynes with free exchange in the upper column and solid blocking in
the lower column in a terrain-following coordinate system. This algorithm used in the module is
validated for idealized cases with emerged and/or submerged dikes and a coastal seawall where
either analytical solutions or laboratory experiments are available for comparison. As an
example, this module is applied to the Changjiang Estuary where a dike-groyne structure was
constructed in the Deep Waterway channel in the inner shelf of the East China Sea (ECS).
Driven by the same forcing under given initial and boundary conditions, a comparison was made
for model-predicted flow and salinity via observations between dike-groyne and bed-conforming
slope algorithms. The results show that with realistic resolution of water transport above and
below the dike-groyne structures, the new method provides more accurate results. FVCOM with
this MPI-architecture parallelized dike-groyne module provides a new tool for ocean engineering
and inundation applications in coastal regions with dike, seawall and/or dam structures.