Application of Synthetic Rainfall Data to Long-term Modelling of a Rehabilitated Landform

摘要

The ability to simulate the stability of post-mining landscapes over time scales ranging from decades to millennia is a critical element in the assessment of closure designs for uranium mines. Landscape Evolution Modelling (LEM) technologies provide a means to simulate and assess the long-term geomorphic stability of a conceptual rehabilitated landform for periods of thousands of years. However, a major issue with simulations derived from long-term modelling are the limitations associated with the data inputs. Specifically, simulations which utilise historic rainfall data only represent the variability of rainfall events that have occurred over a relatively short period. Consequently, these simulations run the risk of not accounting for the full range of rainfall variability that might be expected over an extended period of up to 10 000 years. Therefore, for this study a probabilistic approach was adopted to generate a stochastic synthetic rainfall data set to produce a series of unique rainfall scenarios, each representing a simulated period of 100 years. Importantly, utilising such an approach allows uncertainty in predictions to be better accounted for and provides a range or probability of likely outcomes.In this study, the effect of ten individual rainfall scenarios are assessed in terms of their impact on the predicted erosion and denudations rates produced by the CAESAR-Lisflood LEM for a conceptual rehabilitated landform. of the Ranger Uranium Mine (RUM) in the Northern Territory of Australia, focusing on the Corridor Creek catchment (Figure 1). While legislation requires this site to be erosionally stable for at least 1.0 000 years (Commonwealth of Australia, 1987), here the focus is on the first one hundred years of landscape evolution, as this is the period in wmieh erosion is expected to be higher, with limited vegetation cover or pedogenk development in the initial decades after rehabilitation. It is also the period where the drainage pattern is set.