event) compared to the current hydrograph. With 32 similar total areas of land-cover change, the size of randomly located 33 patches of changed cover had no effect on peak flow for patch sizes up to 34 40000 m 2 . However, cover changes on gentle slope areas generally resulted 35 in a larger change in peak flow when compared with the same changes on 36 steeper slopes. Considering all results for the same proportion of catchment 37 area that undergoes change, land-cover change along narrow riparian buffer 38 strips had the highest impact on river flow. Thus, the protection and 39 revegetation of damaged riparian areas in upland peat catchments may be 40 highly beneficial for flood management.

8There is global concern about headwater management and associated 9 impacts on river flow. In many wet temperate zones peatlands can be found 10 covering headwater catchments. In the UK there is major concern about how 11 environmental change, driven by human interventions, has altered the 12 surface cover of headwater blanket peatlands. However, the impact of such 13 land-cover changes on river flow is poorly understood.

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Upland agricultural land management activities such as grazing, vegetation burning and bare ground restoration impact hydrological elements of headwater catchments, many of which may be important for downstream flood peaks (e.g. overland flow and soil water storage). However, there is poor understanding of how these management practices affect river flow peaks during high magnitude rainfall events. Using the distributed TOPMODEL, spatial configurations of land management were modelled to predict flood response in an upland catchment which contains different regions operating subsidised agricultural stewardship schemes. Heavy grazing leading to soil compaction and loss of vegetation cover in stewardship regions covering 79.8% of the catchment gave a 42 min earlier flow peak which was 82.2% higher (under a 1-hr 15 mm storm) than the current simulated hydrograph. Light grazing over the same regions of the catchment had much less influence on river flow peaks (18 min earlier and 32.9% increase). Rotational burning (covering 8.8% of the catchment), most of which is located in the headwater areas, increased the peak by 3.2% in the same rainfall event. Vegetation restoration with either Eriophorum or Sphagnum (higher density) in bare areas (5.8%) of the catchment provided a reduction of flood peak (3.9% and 5.2% in the 15 mm storm event); while, the same total area revegetated with Sphagnum in riparian regions delivered a much larger decrease (15.0%) in river flow peaks. We show that changes of vegetation cover in highly-sensitive areas (e.g. near-stream zones) generate large impacts on flood peaks. Thus it is possible to design spatially distributed management systems for upland catchments which This article is protected by copyright. All rights reserved. reduce flood peaks while at the same time ensuring economic viability for upland farmers.