Abstract
Most work on simulating landscape evolution has been focused at scales of about 1 Ha, there are still limitations, particularly in understanding the links between hillslope process rates and climate, soils and channel initiation. However, the need for integration with GCM outputs and with Continental Geosystems now imposes an urgent need for scaling up to Regional and Continental scales. This is reinforced by a need to incorporate estimates of soil erosion and desertification rates into national and supra-national policy. Relevant time-scales range from decadal to geological. Approaches at these regional to continental scales are critical to a fuller collaboration between geomorphologists and others interested in Continental Geosystems.
Two approaches to the problem of scaling up are presented here for discussion. The first (MEDRUSH) is to embed representative hillslope flow strips into sub-catchments within a larger catchment of up to 5,000 km2. The second is to link one-dimensional models of SVAT type within DEMs at up to global scales (CSEP/SEDWEB). The MEDRUSH model is being developed as part of the EU Desertification Programme (MEDALUS project), primarily for semi-natural vegetation in southern Europe over time spans of up to 100 years. Catchments of up to 2500 km2 are divided into 50–200 sub-catchments on the basis of flow paths derived from DEMs with a horizontal resolution of 50 m or better. Within each sub-catchment a representative flow strip is selected and Hydrology, Sediment Transport and Vegetation change are simulated in detail for the flow strip, using a 1 hour time step. Changes within each flow strip are transferred back to the appropriate sub-catchment and flows of water and sediment are then routed through the channel network, generating changes in flood plain morphology.
The CSEP/SEDWEB model uses a one-dimensional hydrological model to simulate vegetation growth from monthly climate data. Growth of semi-natural vegetation is simulated using mass balances for living biomass and soil organic matter. Erosion is estimated from the rainfall and runoff distribution, using thresholds related to the vegetation, and used to provide a climatic soil erosion potential (CSEP). Current work is integrating the CSEP with topographic data derived from a global DEM at 1 km horizontal resolution. At this scale, the sediment yield is related to local relief. There is the potential to link the model to both global tectonics, including isostatic components and flexure driven by the erosion, and to orographic rainfall schemes which respond to major changes in topography over geologic time spans.
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Kirkby, M.J. (1999). Landscape modelling at Regional to Continental scales. In: Hergarten, S., Neugebauer, H.J. (eds) Process Modelling and Landform Evolution. Lecture Notes in Earth Sciences, vol 78. Springer, Berlin, Heidelberg. https://doi.org/10.1007/BFb0009726
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DOI: https://doi.org/10.1007/BFb0009726
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