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Watters and Stanley Center for Limnology, University of Wisconsin, 680 N. Park St., Madison, WI USA Abstract: While some aspects of peatlands are well-studied, understanding of their drainage systems’ hydrology and geomorphology is quite limited. This paper attempts to describe some of the basic attributes of peatland stream channels, and asks whether their form and the mechanisms behind their development represent a significant departure from self-forming alluvial streams. We use three approaches to attempt to better understand these poorly studied systems: an examination of the geomorphology of Allequash Creek, Wisconsin; a survey of aerial photographs of similar peatland-stream complexes in northern Wisconsin; and a review of the existing literature on peat-influenced and wetland channels. Distinct channel features of Allequash Creek include absence of mineral substrates, low width:depth ratio, presence of lateral pool-like structures along the channel margin, long straight reaches, and acute-angle bends. Similar planform features were also observed in other peat streams in northern Wisconsin. Further, the lateral location of the thalweg was apparently independent of planform or cross-sectional form, and no-flow zones often occurred along both edges of channel cross-sections. Collectively, these features represent a distinct departure from characteristic forms of alluvial channels. Deep peat samples from Allequash Creek and aerial photographs from other sites indicate that these streams represent remnant lake systems whose basins filled with peat. Thus, we suggest that the processes responsible for peatland channel form are largely governed by groundwater hydrology and the biology of peat accumulation and decomposition. In this manner, biological forces – not just physical drivers – are central to the understanding of peatland stream geomorphology. |
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