A semi-permanent method for fixing sand beds in laboratory flumes

Abstract

A new flume bed-sediment hardening method employing a surficial layer of plaster of Paris coated by spar urethane has been developed and tested for sand beds. Unlike existing bed-hardening techniques, this method is gentle enough to be used in and subsequently removed from a laboratory flume made of Plexiglas, yet is durable enough to last several days under flowing water. Tests showed that artificially fixed beds withstand an estimated bed shear stress of up to 0.251 N/m² for 52 h. The effects of the hardening technique on bed roughness were evaluated. A mean absolute difference in the bed roughness estimate between fixed and loose beds of 0.166 mm was found when tested on a sand bed. Although roughness estimates seemed reasonable, standard deviations were high. Further testing under a wider range of flow conditions and sediment sizes is required to assess the effect of the hardening technique on roughness.

Keywords:

• Alluvial channel
• bed fixation
• bed hardening
• morphology
• roughness
• transitional flow

Acknowledgements

The authors would like to acknowledge funding provided through the Natural Sciences and Engineering Research Council (NSERC) Discovery Grant #298275-2004, “Acoustic measurement of bedload and turbulence for morphodynamic modelling of rivers”, and the Canadian Foundation for Innovation (CFI), New Opportunities Grant #10239, “Acoustic measurement of flow and sediment transport for river channel change”.

Additional information

Notes on contributors

Colin D. Rennie

IAHR Member, [email protected]