Reconstruction of historic soil erosion rates in a small lake catchment of the Melrakkaslétta peninsula of northeast Iceland using tephrochronology and ground-based LiDAR data

Abstract

Erosion rates within the small catchment of an endorheic basin located in the upper Fremridalur (NE-Iceland) were quantified using a combination of borehole data, tephrochronology, terrestrial LiDAR and GIS techniques. Despite the great distance of the study area to the volcanic centers active during the Holocene, it was possible to identify five tephra layers to be used for a dating of stratigraphical units. A continuous increase in sediment accumulation rates during the last c. 6,100 years is observed. The total volume of the sediment within the basin and the sediment yield of the catchment were determined using a digital elevation model derived from terrestrial laser scanning and a modelled layer of underlying bedrock. The sediment yield within the 426 ha catchment has risen from c. 0.172 t ha–1 yr–1 during the late subboreal period (3,830–2,855 14C BP) to c. 0.493 t ha–1 yr–1 in the subatlantic period. In order to assess the present state of the study area concerning the vegetation cover and susceptibility to further erosion, the vegetation cover was mapped and a digital relief analysis was conducted. This revealed a significant degradation of the vegetation cover with increasing elevation.