60 / 2025-04-24 12:55:27

Use of a Recirculating Flume to Evaluate Fluvial Erosion of Peat

Approximately one-quarter of Ontario’s (Canada) landscape is covered with peat soils. Peat soils consist of partially decomposed organic matter derived from plant material. Construction around peat and other organic-heavy soils presents a challenge due to their lack of structure, susceptibility to erosion, and tendency to compress. These factors cause peat to be generally unsuitable for supporting structures and/or to serve as the foundation (e.g. for natural channel corridors). Fluvial erosion of peat was studied in a laboratory setting with a custom-built, small-scale recirculating flume. The flume is outfitted with time-lapse cameras, acoustic velocimetry, and optical backscatter sensors to document hydraulics and entrainment. Peat samples of varying composition were collected from multiple sites in Ontario, characterized based on their physical properties (e.g. median particle size, sample porosity, degree of consolidation), and subjected to a range of flow conditions to evaluate fluvial erosion mechanisms and thresholds. Erosion was evaluated based on the measured difference in baseline and “downstream” suspended sediment concentration within the flume in tandem with physical measurement and visual observations. Associated critical shear stresses were derived for the surface layer of the peat (i.e. representative of initial particle mobilization) and complete erosion of the peat sample for various stabilization periods. Critical shear results were compared with other laboratory and field-derived findings for peat samples or soils. Study findings were used to inform general design requirements (i.e. design-channel geometry and associated tractive force thresholds) and erosion protection requirements (i.e. additional bed and bank stabilization) for select natural channel design concepts located in peat soil conditions in Ontario, Canada.