Five putative barrages within Tamar estuary in Tasmania are assessed for morphological, ecological and hydrological impacts.

Modelling of morphological impacts shows that detrimental effects increase as the barrage position nears the coast.

Similarly ecological and hydrological impacts follow that trend.

Findings are supported by evidence from existing barrage installations.

Benefits of barrage installation are outweighed by the trade-offs and none of the putative barrages could be recommended.