Gurudeo Anand Tularam

Reducing the impact of acid sulphate soils at a site in Shoalhaven Floodplain of New South Wales, Australia

Oxidation of sulphide minerals in acid sulphate soils has acidified a substantial part of the low-lying coastal land in Australia. Such sulphides, including pyrite (FeS2) formed thousands of years ago during saline inundation of soils rich in iron. They do not pose a serious concern when submerged by the water table, because this prevents atmospheric oxygen reacting with the pyritic layer. However, flood protection of low-lying coastal land through the installation of deep surface drains has caused a general lowering of the water table elevation, that in turn has exposed the pyritic layers to atmospheric oxygen. High rainfall following droughts causes acid pollution of the surrounding flood mitigation drains, creeks and river systems. Large ground areas are affected by the transport of acid constituents during seepage. One way of controlling new acid production is through the installation of weirs in the flood mitigation drains in order to raise the water table elevation. In this paper, the acid pollution in New South Wales is reviewed, and the effect of groundwater elevation is examined. Relationship between acid production and groundwater table is examined. Mathematical models are developed to simulate acid production and transport, and two groundwater management regimes are examined. Weir based control of the groundwater table is shown to be successful in controlling acid production.

Salinity intrusion in coastal flood mitigation drains and creeks

This paper reports on mathematical model developed to simulate salinity intrusion in coastal waterways in the south eastern coastlands of the Gold Coast (Australia) to neutralize acidity caused by pyrite oxidation. The model was used to predict the effect of salinity intrusion upstream of existing floodgates. Predictions of the model compared favourably with the field results. Instrusion of saline water can increase the pH of the upland water from 2.4 to 6.5, while the salt levels remain low enough so that it is not of concern to the landholders. Based on the computer predictions and experimental observations, it was concluded that the Nerang river flood mitigation system ought to be redesigned to allow for controlled tidal water intrusion upland of the floodgates to neutralize acid leached from groundwater. Such a structure would have to be constructed and installed in the creeks replacing existing one way floodgates thereby allowing the flow of saline water upland during inland tidal periods. In this manner, the saline creek water can neutralize much of the acidic water stored upland of the floodgates thereby reducing the ill-effect on fish and other estuarine communities and their habitats downstream following heavy rainfalls. Dear Colleague, All papers published in the Wessex Institute of Technology conference proceedings are subject to peer review. This review process is carried out by the conference chairmen and members of the International Scientific Advisory Committee (ISAC). The names of the ISAC are published in the front of each conference book and the names and affiliations of the committee for each conference are published on our website, www.wessex.ac.uk. The review process takes place at the abstract stage and again at the final paper stage. At either stage the authors may be required to alter his/her paper in accordance with the reviewers comments and any alterations are also subject to review. Coverage of WIT conference proceedings appears regularly in a number of publications, including Applied Mechanics Reviews (AMR); Engineering Index and related publications from Elsevier Engineering Information Inc; INSPEC (IEE); Mathematical Reviews: Scitech Book News; ISIs Index to Scientific and Technical Proceedings, Index of Scientific Book Contents, Index to Social Science and Humanities Proceedings and Current Contents; and Various Cambridge Scientific Abstracts publications. Proceedings are also listed in the Directory of Published Proceedings. Kind regards Rachel Rachel Green Senior Conference Co-ordinator Email: rgreen@wessex.ac.uk Tel: +44 (0) 238 029 3223 Fax: +44 (0) 238 029 2853 ---------------------------- WESSEX INSTITUTE on the Web - http://www.wessex.ac.uk See our conference programme at: http://www.wessex.ac.uk/conferences/2005/index.html