PESERA PEAT: a fluvial erosion model for blanket peatlands
In peatlands, fluvial erosion can lead to a dramatic decline in hydrological function, major changes in the net carbon balance and loss of biodiversity. Climate and land management change are thought to be important influences on rates of peat erosion. However, sediment production in peatlands is different to that of other soils and no models of erosion specifically for peatlands currently exist. Hence, forecasting the influence of future climate or spatially distributed management interventions on peat erosion is difficult. The PESERA GRID model was substantially modified in this study to include dominant blanket peat erosion processes. In the resulting fluvial erosion model, PESERA PEAT, freeze thaw and desiccation processes were accounted for by a novel sediment supply index as key features of erosion. Land management practices were parameterized for their influence on vegetation cover, biomass and soil moisture condition. PESERA PEAT was numerically evaluated using available field data from four blanket peat covered catchments with different erosion conditions and management intensity. PESERA PEAT was found to be robust in modelling fluvial erosion in blanket peat. A sensitivity analysis of PESERA PEAT showed that modelled sediment yield was more sensitive to vegetation cover than other tested factors such as precipitation, temperature, drainage density and ditch/gully depth. Two versions of PESERA PEAT, equilibrium and time series, produced similar results under the same environmental conditions, facilitating the use of the model at different scales. The equilibrium model is suitable for assessing the high resolution spatial variability of average monthly peat erosion over the study period across large areas (national or global assessments) while the time series model is appropriate for investigating continuous monthly peat erosion throughout study periods across smaller areas or large regions using a coarser spatial resolution. PESERA PEAT will therefore support future investigations into the impact of climate change and management options on blanket peat erosion at various spatial and temporal scales.