Estuarine dynamics and acid sulfate soil discharge: Quantifying a conceptual model

Over 170,000 km(2) of Acid Sulfate Soils (ASS) have been identified worldwide, with 65,000 km2 in Asia; 45,000 km2 in Africa; 30,000 km2 in Australia; 30,000 km2 in South America; and a combined total of 10,000 km2 in Europe and North America. A state-of-the-science approach to remediate these soils is to encourage tidal buffering. This approach involves the removal of drainage infrastructure and the repurposing of agricultural land back to tidal wetlands. To date, remediation efforts have largely focused on individual locations at the farm plot scale. Remediation projects have commonly focused on onsite acidity levels, groundwater transport and impacts to agricultural infrastructure. This site-based approach provides detailed information on acid hotspots, but provides limited understanding of the overall issues affecting the broader coastal floodplain. A catchment-wide estuarine dynamics approach has been developed and field tested to overcome current limitations. The catchment-wide approach combines onsite investigations with large-scale studies of: (i) the fate/transport of acidic plumes, (ii) the coastal floodplain response dynamics to rainfall or flooding events, and (iii) the objective prioritisation of impacted landscapes for remediation. This paper provides a detailed description of the catchment-wide approach supported by conceptual processes and a detailed case study. The 20 km(2) case study site highlights the importance of local and catchment processes in guiding rehabilitation plans.