Long-term and large scale high resolution catchment modelling: Innovations and challenges arising from the NERC Land Ocean Interaction Study (LOIS)

The CAESAR (Cellular Automaton Evolutionary Slope And River) model is used to simulate the Holocene evolution of four major tributaries of the Yorkshire Ouse (The Rivers Swale, Ure, Nidd and Wharfe). Using a regular grid to represent each river catchment, the model simulates erosion and deposition for every flood over the last 9000 years driven by a land cover history derived from palynological sources and a rainfall record reconstructed from peat bog wetness indices. Results from these simulations show that all four catchments demonstrate rapid increases of sediment discharge in response to wet shifts in the climate record, and the magnitude of sediment yields are amplified after simulated catchment deforestation. However, there are some differences in sediment yield between the river catchments which are caused by sediment storage and re-mobilisation within lower gradient reaches or sub basins. This modelling study shows how it is possible to simulate the evolution of large river catchments over Holocene time scales, but highlights that there are still many problems to be overcome, especially with process representation.

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