Impacts of Tidal Barriers on the Ecology of Flood Mitigation Drain Fish Assemblages

Floodgates and drainage networks, in addition to natural channels and tributaries, have been developed extensively throughout agricultural lands on the estuarine floodplains of NSW for drainage of agricultural fields and pastures. A characteristic and unfortunate consequence of draining and exposing previously waterlogged floodplains to oxygen, is the oxidation of reduced pyritic soils to produce sulfuric acid. Mass fish kills and poor water quality are dramatic and well documented effects of floodgate and drain management of floodplains in northern NSW, following intensive rain and high flush events that release stored reservoirs of acidic water from upstream of floodgates.