Past and future perspectives upon landscape instability in Cumbria, northwest England |
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Authors: | R C Chiverrell |
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Institution: | (1) Department of Geography, University of Liverpool, Roxby Building, L69 3BX, Liverpool, UK |
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Abstract: | Geomorphic and lacustrine evidence is used to identify phases of landscape instability in Cumbria, northwest England, British
Isles. The temporal and spatial pattern of erosion is used alongside palaeovegetation data from across the region to elucidate
the causes of landscape instability in the late Holocene. The lines of evidence include changes in sediment accumulation rate
and provenance within the region’s lakes; the hillslope alluvial fan and gully incision record; the lowland fluvial geomorphic
record; and pollen analytical data for the late Holocene vegetation history. The sediment supply driven hillslope and lacustrine
records suggest that only the 1,200–800 BP and post 600–500 BP erosion episodes were both catchment-wide and directly affected
upland hillslopes, with the earlier phases after 5,200 and 3,000–1,600 BP on a lower scale and more restricted spatially.
These episodes coincide with major expansions or changes in anthropogenic activity during Neolithic, Iron Age and Romano-British,
Norse and late Medieval times. The projected future trajectories of changes in both climate (UKCIP scenarios) and landuse
(CAP reform and ESA status) appear unlikely to increase landscape instability, although a shift to greater incidence of storms
and high magnitude flood events clearly could. The past shows that the largest increases in erosion and sediment movement
occur in the wake of major intensifications in land pressure that primarily affect previously wooded or protected hillslopes,
circumstances that land management strategists should mitigate against. |
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Keywords: | Cumbria Vegetation history Hillslope instability Erosion Lacustrine sediments |
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