Geomorphic landscape features and associated surface materials are fundamental to groundwater recharge processes as they form the first layer through which surface water passes before it becomes groundwater. Different surface materials exhibit different water-holding capacity and hence permeability characteristics. In the Broken Hill Managed Aquifer Recharge project, surface-materials mapping in conjunction with geomorphic mapping, has assisted hydrogeological investigations, including recharge predictions, salinity hazard and the identification of potential infiltration basins. Prior to landform identification, LiDAR DEM data was levelled using trend surfaces to eliminate regional slope (~20m). As a consequence of this, an ArcGIS interactive contour tool could be used to identify specific breaks in elevation associated with landform features. Multivariate image analysis of elevation, high resolution SPOT and Landsat-derived wetness further enhanced the contrast between geomorphic elements to confirm mapping boundaries. While specific landforms can be characterised by particular surface materials, these sediments can vary within a single geomorphic feature. Consequently, SPOT multispectral satellite imagery was used to identify surface materials using principal component analysis and unsupervised classification. This approach generated 20 classes; each assigned a preliminary cover/landform attribute using SPOT imagery. Field data (surface and borehole sample, and observations at shallow pits) were used to refine the classification approach. Interactive mapping using a de-trended DEM provided a rapid, effective and accurate alternative to time consuming manual landform digitisation. The combination of these two new products - surface-materials and geomorphic maps - has assisted in the identification of potential recharge sites and naturally occurring infiltration sites.

The 2004 Sumatra-Andaman Earthquake and Indian Ocean Tsunami shattered the paradigm that guided our understanding of giant subduction zone earthquakes: that massive, magnitude 9+ earthquakes occur only in subduction zones experiencing rapid subduction of young oceanic lithosphere. Although this paradigm forms the basis of discussion of subduction zone earthquakes in earth sciences textbooks, the 2004 earthquake was the final blow in an accumulating body of evidence showing that it was simply an artefact of a sparse and biased dataset (Okal, 2008). This has led to the realization that the only factor known to limit the size of megathrust earthquakes is subduction zone length. This new appreciation of subduction zone earthquake potential has important implications for the southern Asia-Pacific region. This region is transected by many thousands of km of active subduction, including the Tonga-Kermadec, Sunda Arc, and the Makran Subduction zone along the northern margin of the Arabian Sea. Judging from length alone, all of these subduction zones are capable of hosting megathrust earthquakes of magnitude greater than 8.5, and most could host earthquakes as large as the 2004 Sumatra-Andaman earthquake (Mw=9.3). Such events are without historical precedent for many countries bordering the Indian and Pacific Oceans, many of which have large coastal populations immediately proximate to subduction zones. This talk will summarize the current state of knowledge, and lack thereof, of the tsunami hazard in the southern Asia-Pacific region. I will show that 'worst case' scenarios threaten many lives in large coastal communities, but that in most cases the uncertainty in these scenarios is close to 100%. Is the tsunami risk in SE Asia and the SW Pacific really this dire as the worst-case scenarios predict? The answer to this question relies on our ability to extend the record of tsunamis beyond the historical time frame using paleotsunami research.

The Ord is one of the largest rivers in northern Australia and is located in the Kimberley region of Western Australia. In this study we show that the lower Ord landscape near Kununurra in Western Australia consists of a large scale ancient landscape, possibly pre-Cambrian, being exhumed from beneath flat-lying Cambrian to Carboniferous cover rocks. Additional post-Permian landscapes are being formed by this process. The Ord Valley alluvium is of late Pleistocene to Holocene in age and consts off upward fining gravels, sands and clays infilling an inset valley profile. The Ord River initially flowed to the sea via the keep River estuary, however a major avulsion, possibly due to sedimentatain topping a low point in the surrounding valley walls, occurred possibly as recently as 1,800 years ago. As a result to mouth of the Ord shifted some 100 km to the east, to Cambridge Gulf, its course through the former alluvial plain and along the new course across the coastal plain was incised, and a scabland formed across the low point of Tararar Bar. This association of very ancient (pre-Paleozoic) landscape elements and by thin, very young weathering profiles and young sedimentary accumulations in alluvial valleys is paradoxical in the broader Australian pattern where very ancient landscape elements are associated with ancient sedimentary infill and weathering profiles.

On 23 March 2012, at 09:25 GMT, a MW 5.4 earthquake occurred in the eastern Musgrave Ranges region of north-central South Australia, near the community of Ernabella (Pukatja). Several small communities in this remote part of central Australia reported the tremor, but there were no reports of injury or significant damage. This was the largest earthquake to be recorded on mainland Australia for the past 15 years and resulted in the formation of a 1.6 km-long surface deformation zone comprising reverse fault scarps with a maximum vertical displacement of over 0.5 m, extensive ground cracking, and numerous rock falls. The maximum ground-shaking is estimated to have been in the order of MMI VI. The earthquake occurred in non-extended Stable Continental Region (SCR) cratonic crust, over 1900 km from the nearest plate boundary. Fewer than fifteen historic earthquakes worldwide are documented to have produced co-seismic surface deformation (i.e. faulting or folding) in the SCR setting. The record of surface deformation relating to the Ernabella earthquake therefore provides an important constraint on models relating surface rupture length to earthquake magnitude. Such models may be employed to better interpret Australia's rich prehistoric record of seismicity, and contribute to improved estimates of seismic hazard.

The Lower Darling Valley (LDV) Cenozoic sequence contains Paleogene and Neogene shallow marine and shoreline as well as fluvial and shoreline sediments overlain by Quaternary lacustrine, aeolian and fluvial units. Recent investigations in the LDV using multiple datasets have provided new insights into the nature of post-Blanchetown Clay Quaternary fluvial deposition which differs to the Mallee and Riverine Plain regions elsewhere in the Murray Basin. In the LDV Quaternary fluvial sequence, multiple scroll-plain tracts are incised into higher, older and more featureless floodplain terrain. Prior to this study, these were respectively correlated to the Coonambidgal and Shepparton Formations of the Riverine Plain in the eastern Murray Basin. These formations were originally associated with the subsequently discarded Prior Stream/Ancestral River chronosequence of different climatically controlled depositional styles. In contrast to that suggestion, we ascribe all LDV Quaternary fluvial deposition to lateral-migration depositional phases of one style, though with variable stream discharges and channel and meander-scroll dimensions. Successively higher overbank-mud deposition through time obscures scroll traces and provides the main ongoing morphologic difference. A new morphostratigraphic unit, the Menindee Formation, refers to mostly older and higher floodplain sediments, where scroll traces are obscured by overbank mud which continues to be deposited by the highest modern floods. Younger inset scroll-plain tracts, with visible scroll-plain traces, are still referred to as the Coonambidgal Formation. Another new stratigraphic unit, the Willotia beds, refers to even older fluvial sediments, now above modern floodplain levels and mostly covered by aeolian sediments.

Faults of the Lapstone Structural Complex (LSC) underlie 100 km, and perhaps as much as 160 km, of the eastern range front of the Blue Mountains, west of Sydney. More than a dozen major faults and monoclinal flexures have been mapped along its extent. The Lapstone Monocline is the most prominent of the flexures, and accounts for more than three quarters of the deformation across the complex at its northern end. Opinion varies as to whether recent tectonism, or erosional exhumation of a pre-existing structure, better accounts for the deeply dissected Blue Mountains plateau that we see today. Geomorphic features such as the abandoned meanders at Thirlmere Lakes illustrate the antiquity of the landscape and favour an erosional exhumation model. According to this model, over-steepened reaches developed in easterly flowing streams at the Lapstone Monocline when down-cutting through shale reached more resistant sandstone on the western side of the LSC. These over-steepened reaches drove headward (westerly) knick point retreat, ultimately dissecting the plateau. However, a series of swamps and lakes occurring where small easterly flowing streams cross the westernmost faults of the LSC, coupled with over-steepened reaches 'pinned' to the fault zones in nearby larger streams, imply that tectonism plays a continuing role in the development of this landscape. We present preliminary results from an ongoing investigation of Mountain Lagoon, a small fault-bound basin bordering the Kurrajong Fault in the northern part of the LSC.

Several different techniques have recently been developed to rapidly map and characterise surface landforms and materials for groundwater recharge studies in Australia. In this example, in the Darling Floodplain of western New South Wales, regional landform mapping was carried out primarily using Google Earth imagery with hill-shaded LiDAR DEM and SPOT images as visual guide and some field validation. A second, more detailed map (compiled: 1:25,000; final usable scale: 1:30,000) included landform elements such as borrow pits, individual scrolls and oxbow lakes was compiled using LiDAR DEM. Prior to landform delineation, the LiDAR DEM required levelling to eliminate tilting in the landscape, by subtracting the floodplain trend surface from the DEM. This is particularly important in floodplains and river profiles where there can be as much as a 20 m difference between the upper and lower reaches. A best-fit trend surface, which provides an average estimation of change in slope along a single plane, was required to level the data. Once the LiDAR was levelled, an interactive contour tool in ArcGIS was used to generate graphic outlines of particular features at identified breaks in elevation using hill-shading, e.g. channel banks and dune bases. Slope and 3-D DEM visualisation also facilitated identification of these breaks. Further editing was required to assemble line work, convert it into polygons, and assign landform attributes. A greater number of landform classes were developed at this finer scale than for the regional scale. In many cases, specific landforms are characterised by particular surface materials, though sediment type can vary within a single landform class. SPOT imagery has been used to delineate surface materials. In summary, the combination of the two datasets - landforms and surface materials - has allowed for the identification of potential recharge site

The Fitzroy catchment is the largest Queensland catchment discharging to the Great Barrier Reef (GBR) lagoon. Sediments and nutrients together with anthropogenic pollutants originating upstream in the catchment are discharged from the Fitzroy River via the Fitzroy Estuary (FE) and ultimately into Keppel Bay (KB). The estuary and the bay act as natural chemical reactors where the materials delivered undergo chemical and physical transformations before some are deposited and stored in the growing deltaic and beach areas, with the remainder transported eastward to the southern zone of the GBR lagoon.

The central aim of the Comparative Geomorphology of Estuaries Project of the Coastal CRC was to improve our understanding of Australia's near-pristine estuaries. As the title implies, the project had a geomorphic focus in that a major output was mapping of geomorphic habitats of a representative selection of nearpristine estuaries from around Australia.

The release of fluid to the seabed from deeper sources is a process that can influence seabed geomorphology and associated habitats, with pockmarks a common indicator. In May 2012, Geoscience Australia led a multidisciplinary marine survey in Joseph Bonaparte Gulf, to facilitate an assessment of the potential for fluid leakage associated with geological storage of CO2 at depth within the Petrel Sub-basin. Multibeam bathymetry and backscatter mapping (652 km2), combined with acoustic sub-bottom profiling (655 line-km) and geomorphological and sediment characterisation of the seabed was undertaken. Seabed geomorphic environments identified from 2 m resolution bathymetry include carbonate banks and ridges, palaeochannels, pockmark fields and fields of low amplitude hummocks. This paper focuses on pockmarks as indicators of fluid seepage from the subsurface. Three principal pockmark morphologies (Type I, II and III) are present with their distribution non-random. Small unit (Type I) depressions occur on plains and in palaeochannels, but are most commonly within larger (Type II) composite pockmarks on plains. Type III pockmarks, intermediate in scale, are only present in palaeochannels. The timing of pockmark formation is constrained by radiocarbon dating to 14.5 cal ka BP, or later, when a rapid rise in sea-level would have flooded much of outer Joseph Bonaparte Gulf. Our data suggest the principal source of fluids to the seabed is from the breakdown of organic material deposited during the last glacial maxima lowstand of sea-level, and presently trapped beneath marine sediments. These results assist in ameliorating uncertainties associated with potential CO2 storage in this region.