Hāpua are a type of non-estuarine river mouth lagoon, common in New Zealand, which form where gravel-bed rivers emerge onto high wave energy micro/meso-tidal coasts. Hāpua are separated from the ocean by a mixed sand and gravel beach barrier, through which a highly dynamic outlet channel generally flows. Hāpua outlet channel rapidly change in length, width and position in response to sediment transport by fluvial flows and waves.

HapuaMod is a morphodynamic model of hāpua evolution. The model is driven by timeseries inputs of river flow, wave conditions and sea level (i.e. tides).

HapuaMod is being developed by Richard Measures, as part of PhD research funded by NIWA's Environmental Flows research program.

For information about the model, how it works, how to use it, and how to contribute to its development, see the wiki