Tidal-forcing groundwater dynamics in a restored coastal wetland: implications of saline intrusion
Australian Journal of Earth Sciences
A bstract: Tidal restoration projects are currently being undertaken throughout coastal A ustralia w ithout a full understanding o f the influence o f tidal forcing on groundw ater salinity. To determ ine th e im pact o f restoring tidal flow s on groundw ater salinity levels, field investigations w ere undertaken at a study site near Berry, NSW. Fluctuations in groundw ater and surface w ater chem istry (soluble chloride, pH, electrical conductivity) and hydrodynamics w ere measured over a
... measured over a 12-week period using m ultilevel peizom eters and subm ersible data loggers spaced at discrete distances from a flood mitigation drain. Additional param eters, including saturated hydraulic conductivity (K sat), were undertaken to determ ine baseline conditions and to provide initialisation d ata for a 3dim ensional finite element model. The finite elem ent nodel w as calibrated w ithin ±5% o f field data and developed to sim ulate saline intrusion during a 'w orse-case' scenario. R esults from the m odel sim ulations indicate that saline intrusion at the site is limited even under extreme conditions. To quantify the influ en ce o f Ksat(h) levels on saline intrusion, material properties w ithin the numerical model w ere altered to represent 1, 10 and 20 m/day. Model sim ulations showed that Kjat(h) values >10m /day perm itted saline intrusion in excess o f A N ZECC (1992) criteria. B ased on the model findings a series o f m anagem ent criteria are proposed that detail acid sulfate soil remediation techniques, including tidal restoration, dependent on K^h ) values. The proposed m anagem ent criteria suggest that tidal restoration projects are m ost suited in sites w here the K sat(h)values are <10m /day.