Long-term change in storm hydrographs in response to peatland vegetation change

SummaryThe runoff from blanket peatland catchments tends to be dominated by flashy stormflows. However, it is not known whether changes in vegetation cover influence the nature of stormflow hydrographs from blanket peatlands. This is important since degraded peatlands are of concern to restoration bodies who seek to understand the wider impacts of restoration investment on ecosystem services. This paper tests the hypothesis that peak flows are significantly higher and lag times shorter at the catchment scale when blanket peat vegetation cover is reduced. Storm hydrograph data from the 1950s to the present day are analysed from a blanket peat catchment in northern England. The proportion of the catchment that was vegetated appears to have declined between the early 1950s and mid 1970s and then increased again to the present day. The changes in the proportion of bare peat over the catchment are coincident with changes in storm hydrographs. Hydrographs were significantly peakier with higher peaks per unit of rainfall (0.40 m3 mm−1 compared with 0.27 m3 mm−1) and narrower hydrograph shapes during the more eroded periods in the catchment and less so as the site has revegetated. Mean peak storm discharge was also significantly higher during the most eroded period. Thus, for the first time we have found evidence in a blanket peat headwater catchment that vegetation cover influences river flow response to rainfall.