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Understanding post-mining landforms: Utilising pre-mine geomorphology to improve rehabilitation outcomes
- Lowry, J.B.C., Narayan, M., Hancock, G.R., Evans, K.G.
- Geomorphology 2019 v.328 pp. 93-107
- environmental factors, landscapes, particle size, pollution load, rain, ravines, sediment transport, sediment yield, simulation models, topography, vegetation cover, watersheds
- Post-mining landscapes are required to geomorphically and ecologically integrate with the surrounding undisturbed environment. To understand the pre- and post-mining landscape, models can be used to guide rehabilitation strategies. This is particularly important where an absence exists of pre-mine (predisturbance) data regarding the landscape system. In particular, geomorphic evolution may be simulated with tools such as landform evolution models (LEMs). In this study, we use the CAESAR-Lisflood LEM to assess how a pre-mine landscape may evolve over 1000 years and compare it to the evolution of a catchment representing a rehabilitated post-mining landscape. Environmental conditions such as rainfall, vegetation cover, and surface particle size characteristics were varied through a series of model simulations to determine their impact on the different landforms. We compared the outputs of the model simulations – specifically, sediment loads, denudation rates, and extent, depth, and distribution of gullies – from the undisturbed, pre-mine landform and the disturbed, post-mine landform. Under all scenarios simulated, much greater erosion occurred on the post-mine landform, producing sediment yields and denudation rates that were higher than the undisturbed pre-mine landform by up to an order of magnitude. The results showed that the presence/absence of vegetation and variations in rainfall amount and intensity could influence erosion rates, sediment yields, and gully depths between the two primary scenarios. However, the parameters that most influenced landscape evolution over centennial time scales were the particle size classes used to represent the surface conditions in the simulations, and the topographic characteristics of the catchments on the pre- and post-mine landforms. The model outputs reinforce the expectation that a pre-mining landscape will experience less erosion and sediment transport than a post-mining landscape.