  The capability to accurately predict flood flows via numerical simulations is
a key component of contemporary flood risk management practice. However, modern
flood models lack the capacity to accurately model flow interactions with
linear features, or hydraulic structures like bridges and gates, which act as
partial barriers to flow. Presented within this paper is a new Riemann solver
which represents a novel approach to modelling fluid-structure interactions
within two-dimensional hydrodynamic models. The solution procedure models
obstacles as existing at the interface between neighbouring cells and uses a
combination of internal boundary conditions, different forms of the
conservation laws and vertical discretisation of the neighbouring cells to
resolve numerical fluxes across a partially obstructed interface. The
predictive capacity of the solver has been validated through comparisons with
experimental data collected from experiments conducted in a state-of-the-art
hydraulic flume. Since the solution procedure is local, only applying to the
cells within the immediate vicinity of a structure, the method is designed to
be compatible with existing two-dimensional hydrodynamic models which use a
finite volume scheme to solve the shallow water equations.
