Centennial time scale impacts using stochastically generated rainfall - assessing sediment output from a post-mining catchment

Rainfall intensity and temporal distribution have a major influence on soil erosion, sediment delivery and landscape evolution. Long-term reliable rainfall data is needed is to understand soil erosion rates and landscape evolution. For many parts of the world rainfall data may not exist locally or may be of insufficient quality (e.g. incomplete or only cover a short time period) and therefore has to be inferred from nearby sites. Further, there is also the question of whether the current climate (and rainfall pattern) is representative of longer term trends, particular into the future under a warming climate scenario. Using reliable rainfall data computer based landscape evolution models can provide insight into both erosion rates and process (i.e. sheetwash, rill, gully erosion). Of particular interest here are mining landscapes. Mining disturbs large areas to access minerals and upon completion of the resource extraction the disturbed area is re-engineered. The landscape once created will remain part of the surrounding landscape system for the foreseeable future. Therefore, understanding the hydrological and erosional behavior of such landscapes is vital so that any issues design can be corrected. It is also vital that these landscapes be evaluated not just for current climate but for how different rainfall patterns may affect erosion and landscape evolution. Here we assess a proposed post-mining landform using existing rainfall data from established weather stations and secondly create stochastically generated rainfall time series based on this rainfall data. The rainfall data is then used in a landscape evolution and sediment transport model. It was found that each rainfall data set produces differences in the position of rills and gullies. Each rainfall scenario also produces a unique pattern of sediment output that suggests non-linear processes. Therefore each rainfall data set produces unique patterns of erosion, deposition and catchment sediment output. Importantly, this method provides a statistical approach to quantify sediment transport and landform evolution.