EARTH SURFACE PROCESSES AND LANDFORMS Earth Surf. Process. Landforms (2017) Copyright © 2016 John Wiley & Sons, Ltd. Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/esp.4100 Oblique aggradation: a novel explanation for sinuosity of low-energy streams in peat-filled valley systems Jasper H.J. Candel,1* Bart Makaske,1 Joep E.A. Storms2 and Jakob Wallinga1 1 Soil Geography and Landscape group, Wageningen University, P.O. Box 47, 6700AA Wageningen, The Netherlands 2 Faculty of Civil Engineering and Geosciences, Delft University of Technology, P.O. Box 5048, 2628CN Delft, The Netherlands Received 1 July 2016; Revised 2 December 2016; Accepted 7 December 2016 *Correspondence to: Jasper Candel, Wageningen University, Soil Geography and Landscape group, P.O. Box 47, 6700AA Wageningen, The Netherlands. E-mail:
[email protected] This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. ABSTRACT: Low-energy streams in peatlands often have a high sinuosity. However, it is unknown how this sinuous planform formed, since lateral migration of the channel is hindered by relatively erosion-resistant banks. We present a conceptual model of Holocene morphodynamic evolution of a stream in a peat-filled valley, based on a palaeohydrological reconstruction. Coring, ground-penetrating radar (GPR) data, and 14C and OSL dating were used for the reconstruction. We found that the stream planform is partly inherited from the Late-Glacial topography, reflecting stream morphology prior to peat growth in the valley. Most impor- tantly, we show that aggrading streams in a peat-filled valley combine vertical aggradation with lateral displacement caused by at- traction to the sandy valley sides, which are more erodible than the co-evally aggrading valley-fill.