Critical specific stream power in gravel-bed rivers

• Published in: Geomorphology (Amsterdam, Netherlands) Vol. 69; no. 1; pp. 92 - 101
• Main Authors: Petit, F., Gob, F., Houbrechts, G., Assani, A.A.
• Format: Journal Article Web Resource
• Language: English
• Published: Amsterdam Elsevier B.V 01-07-2005; Elsevier; Elsevier Science Bv
• Subjects: Bgi / Prodig; Earth sciences; Earth sciences & physical geography; Earth, ocean, space; Exact sciences and technology; Fluvial forms and processes; Freshwater; Geomorphology; Geomorphology, landform evolution; Gravel bed river; Marine and continental quaternary; Physical geography; Physical, chemical, mathematical & earth Sciences; Physique, chimie, mathématiques & sciences de la terre; Sciences de la terre & géographie physique; Sediment transport; Specific stream power; Surficial geology; Tracer pebbles; Belgium; Ardennes; Western Europe; Ardenne; Tracer pebbles; Gravel bed river; Specific stream power; Sediment transport; experimental studies; rivers; stream transport; pebbles; Europe; streams; boulders; grains; bedforms; gravel; drainage basins; grain size; shear stress; modern; bedload; Sediment transport Tracer pebbles; landform evolution; energy; Sediment load; Tracer; Shear stress; Hydrological regime; Hydrodynamics; Stream
• ISSN: 0169-555X; 1872-695X; 1872-695X
• DOI: 10.1016/j.geomorph.2004.12.004

Experiments with marked pebbles were carried out on different sized rivers of the Belgian Ardenne (catchment areas varying from less than 1 km
2 to 2700 km
2). Specific stream power required to cause bedload movement was evaluated and critical values were obtained. Three types of relationship between critical specific stream power (
ω
0) and grain size (
D) were established. The values for
ω
0 in the largest river (the Ourthe) were the lowest and were close to the values obtained for mountainous rivers carrying large boulders. In medium sized rivers (catchment area between 40 and 500 km
2), the critical unit stream power was higher. It is likely that it is due to the bedform's greater resistance. This resistance would use up some of the energy that can cause movement and transport of bedload. The amount of resistance of the bedform can be expressed as bedform shear stress (
τ″), determined by the relationship between grain shear stress (
τ′—that determines movement and transport of the bedload) and the total shear stress (
τ). This ratio varies between 0.4 and 0.5 in the medium sized rivers, compared to 0.7 in the Ourthe. In headwater streams (less than 20 km
2), there is greater loss of energy due to bedform resistance (
τ′/
τ<0.3). Critical specific stream power is higher in this third type of river than in the other two.