Hydraulic Resistance in Grass Swales Designed for Small Flow Conveyance
Publication: Journal of Hydraulic Engineering
Volume 131, Issue 1
Abstract
Grass swales, originally used for erosion control in agricultural settings, are now widely employed in urban environments as an effective best management practice for controlling pollutants in stormwater runoff. In particular, vegetated swales are quite successful in removing heavy metal concentrations when the depth of flow is small relative to grass height. However, guidance materials currently available for design of vegetated channels focus on larger depths of flow (large flow conveyance/erosion control), and for such conditions the hydraulic resistance exerted by the vegetation can be significantly different than that observed when the depth of flow is small (remediation). Utilizing a series of laboratory channels, small-flow retardance curves have been developed in the present work for Bluegrass, Centipede, and Zoysia grass species. These “small-flow” curves extend the well-known Stillwater versus diagram by approximately 1 order of magnitude, to smaller values of . Experimental results should provide valuable design guidance to those faced with the need to hydraulically design a swale intended for shallow depths of flow.
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Acknowledgments
This research was conducted as a part of a larger effort focused on innovative technologies for removal of metals in urban runoff, sponsored by the Water Environment Research Foundation (WERF). The financial support provided by WERF is gratefully acknowledged.
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© 2004 ASCE.
History
Received: Sep 15, 2003
Accepted: Aug 5, 2004
Published online: Jan 1, 2005
Published in print: Jan 2005
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