Applicability of the local inertial approximation of the shallow water equations to flood modeling

Recent studies have demonstrated the improved computational performance of a computer algorithm based on a simplification of the shallow water equationsthe so-called local inertial approximationwhich has been observed to provide results comparable to the full set of equations in a range of flood flow problems. This study presents an extended view on the local inertial system, shedding light on those key elements necessary to understand its applicability to flows of practical interest. First, the properties of the simplified system with potential impact on the accuracy of the solutions are described and compared to the corresponding full-dynamic counterparts. In light of this discussion, the behavior of the solutions is then analyzed through a set of rigorously designed test cases in which analytical solutions to the shallow water system are available. Results show a general good agreement between the local inertial and full-dynamic models, especially in the lower range of subcritical flows (Fr