Landscape evolution models provide a way to determine erosion rates and landscape stability over times scales from tens to thousands of years. The SIBERIA and CAESAR landscape evolution models both have the capability to simulate catchment-wide erosion and deposition over these time scales. They are both cellular, operate over a digital elevation model of the landscape, and represent fl uvial and slope processes. However, they were initially developed to solve research questions at different time and space scales and subsequently the perspective, detail and process representation vary considerably between the models. Notably, CAESAR simulates individual events with a greater emphasis on fl uvial processes whereas SIBERIA averages erosion rates across annual time scales. This paper describes how both models are applied to Tin Camp Creek, Northern Territory, Australia, where soil erosion rates have been closely monitored over the last 10 years. Results simulating 10 000 years of erosion are similar, yet also pick up subtle differences that indicate the relative strengths and weaknesses of the two models. The results from both the SIBERIA and CAESAR models compare well with independent fi eld data determined for the site over different time scales. Representative hillslope cross-sections are very similar between the models. Geomorphologically there was little difference between the modelled catchments after 1000 years but signifi cant differences were revealed at longer simulation times. Importantly, both models show that they are sensitive to input parameters and that hydrology and erosion parameter derivation has long-term implications for sediment transport prediction. Therefore selection of input parameters is critical. This study also provides a good example of how different models may be better suited to different applications or research questions.

The measurement and prediction of soil erosion is important for understanding both natural and disturbed landscape systems. In particular numerical models of soil erosion are important tools for managing landscapes as well as understanding how they have evolved over time. Over the last 40 years a variety of methods have been used to determine rates of soil loss from a landscape and these can be loosely categorized into empirical and physically based models. Alternatively, physically based landscape evolution models (LEMs) have been developed that provide information on soil erosion rates at much longer decadal or centennial scales, over large spatial scales and examine how they may respond to environmental and climatic changes. Both soil erosion LEMs are interested in similar outcomes (landscape development and sediment delivery) yet have quite different methodologies and parameterizations. This paper applies a LEM (the CAESAR model) for the first time at time and space scales where soil erosion models have largely been used. It tests the ability of the LEM to predict soil erosion on a 30 m experimental plot on a trial rehabilitated landform in the Northern Territory, Australia. It then continues to discuss the synergies and differences between soil erosion and LEMs.The results demonstrate that once calibrated for the site hydrology, predicted suspended sediment and bedload yields from CAESAR show a close correspondence in both volume and timing of field measured data. The model also predicts, at decadal scales, sediment loads close to that of field measured data. Findings indicate that the small-scale drainage network that forms within these erosion plots is an important control on the timing and magnitude of sediment delivery. Therefore, it is important to use models that can alter the DEM to reflect changing topography and drainage network as well as having a greater emphasis on channel processes.

No abstract

The biodiversity values of the wetlands in the Kakadu Region of northern Australia have been recognised as being of national and international signifi cance, as demonstrated through their listing by the Ramsar Convention on Wetlands. Analyses of the wetland biodiversity have resulted in the production of species list for many taxa, and some population and community-level analyses of biomass and abundance, and the mapping of habitats at multiple scales. Wetland habitats include inter-tidal mud-fl ats, mangroves, hyper-saline fl ats, freshwater fl ood plains and streams. The tidal infl uence on the saline wetlands is pronounced, as is the infl uence of the annual wet-dry cycle of the monsoonal climate on the fl ood plains and streams. The vegetation is diverse and highly dynamic with rapid turnover of organic material and nutrients. The fauna is abundant with endemism being high in some habitats. Most fauna analyses have focussed on vertebrates with a large amount of information on waterbirds and fi sh in particular. However, despite extensive effort over the past two decades much is still unknown about the biota. While the invertebrate fauna in the streams has received some attention, a large taxonomic classifi cation effort is required. The functional inter-relationships between habitats and species have largely not been assessed. Further, the ecology of many species is only cursorily known. At the same time there has been increased attention to pressures on the wetlands, such as weeds and feral animals, water pollution, and the potential impact of climate change and salinisation of freshwater habitats. Importantly, given the social context of the region, increased attention is being directed towards traditional use and management of the wetlands.

ABSTRACT1. This paper provides an introduction to Synthetic Aperture Radar (SAR) remote sensing and, in particular, the significance of long-wavelength (L-band) SAR for wetland applications relevant to the Ramsar Wetlands Convention.2. The Convention has long been a supporter of effective wetland inventory being used to support management initiatives and the wise use of all wetlands.3. Three major application areas have been identified where SAR data may constitute an important additional information source for wetland inventory and management. These comprise mapping of below-canopy inundation, monitoring of environmental disturbances and wetland inventories based on SAR mosaics. These areas have all previously been supported in general terms by formal resolutions on wetland inventory and assessment through the Convention with recognition that further technique development was required.4. The potential to make further use of remote sensing is increased through wider use of the special features of SAR in situations where other data are less suitable.5. The Japanese Advanced Land Observing Satellite (ALOS) provides an opportunity to support the Convention and its goal of wise use of all wetlands.