2D flood model design fundamentals

What 2D mesh resolution is necessary if flood design modelling?

Flood modellers

Flood modelling is the analytical tool used to inform all aspects of floodplain management. Flood mitigation assessments, land use planning controls, infrastructure design and even flood insurance classifications are all directly impacted by the precision and accuracy of the flood modeling on which they are based.  With this in mind it is prudent that our flood estimates are accurate.

Selection of the 2D mesh resolution (also referred to as the 2D cell size) is a fundamental decision that is made at the start of all modeling projects. The importance of this decision is sometimes not fully appreciated, and in some cases, based entirely on simulation run-time assumptions without consideration of the implications it can have on the overall accuracy of the flood modeling estimations. One size does not fit all! Result sensitivity to mesh resolution is a function of numerous aspects, including: topographic scale considerations, geometric complexity, flow regime and software assumptions. To further complicate matters, what is considered fit for purpose is also influenced by the desired end use of model results. For example, the level of accuracy required for a detail design study is different to what is necessary for a broad scale first pass feasibility assessment.

This presentation uses a suite of case study examples to highlight how the above factors influence what should be considered an appropriate 2D mesh resolution for a range of catchment scenarios. In doing so it also demonstrates a best practice methodology that should be used by all practitioners at the start of a modeling project when deciding what 2D mesh resolution is necessary.

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