Flow Resistance in Broad Shallow Grassed Channels

by Cheng-lung Chen, (M.ASCE), Prof. of Civ. and Environmental Engrg.; Utah Water Research Lab., Utah State Univ., Logan, Utah,

Serial Information: Journal of the Hydraulics Division, 1976, Vol. 102, Issue 3, Pg. 307-322

Document Type: Journal Paper


Resistance to sheet flows over natural turf surface is investigated experimentally. The formulation of a functional relationship between the resistance coefficient and controlling parameters for shallow flows over various turf surfaces is essential to the mathematical modeling of the rainfall-runoff process and sediment yield from a watershed which may consist of various vegetated surfaces. An analysis of results obtained from laboratory experiments for laminar flow on Kentucky Blue grass and Bermuda grass surfaces reveals that a relationship exists between the Darcy-Weisbach friction coefficient, Reynolds number, and bed slope. A further analysis of previous investigators' experimental results for flow on various smooth and rough surfaces under or no rainfall leads to the qualitative determination of a general trend of the resistance relationship for shallow flows over such dense turf surfaces as affected by bed slope, raindrop impact, and roughness size.

Subject Headings: Overland flow | Flow resistance | Hydraulic roughness | Vegetation | Channel flow | Load and resistance factor design | Sheet flow | Slopes

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