Designing Dry Swales for Stormwater Quality Improvement Using the Aberdeen Equation

W. F. Hunt, E. A. Fassman-Beck, S. A. Ekka, K. C. Shaneyfelt, A. Deletic

Research output: Contribution to journalArticle

Abstract

This case study presents a semiempirical method for designing water quality swales to treat stormwater runoff that is an alternative to current mostly anecdotal design approaches. Water quality swales are intended to reduce pollutant concentrations; they are not just flow conveyance systems. The design presented herein is a two-part process: (1) hydraulic design, and (2) treatment design. A hydraulic design feature unique to water quality swales includes maximum flow depths typically lower than grass height. Frequency analysis is used to estimate the water quality design storm intensity, and the design peak flow rate is estimated using the Rational method. Subsequently, Manning's equation is used to determine the swale cross-section and slope. A relatively high roughness coefficient (n=∼0.35) is applied because the water is not intended to overtop the vegetation. This case study used the Aberdeen equation to calculate pollutant removal efficiencies if particle-size information was available. The method was applied to field-monitored swales in Auckland, New Zealand and Knightdale, North Carolina, US, and was found to accurately predict sediment capture. The conceptual approach presented here can be used to estimate reductions in total suspended solids by swales. However, the method needs to be validated with appropriate monitoring data in estimating removal of metals and other particulate-bound pollutants, but it is not applicable to the dissolved fraction of pollutants.

Original languageEnglish (US)
Article number05019004
JournalJournal of Sustainable Water in the Built Environment
Volume6
Issue number1
DOIs
StatePublished - Feb 1 2020

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stormwater
water quality
hydraulics
pollutant removal
pollutant
frequency analysis
peak flow
roughness
cross section
particle size
grass
runoff
method
vegetation
metal
sediment

All Science Journal Classification (ASJC) codes

  • Water Science and Technology
  • Management, Monitoring, Policy and Law

Cite this

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Designing Dry Swales for Stormwater Quality Improvement Using the Aberdeen Equation. / Hunt, W. F.; Fassman-Beck, E. A.; Ekka, S. A.; Shaneyfelt, K. C.; Deletic, A.

In: Journal of Sustainable Water in the Built Environment, Vol. 6, No. 1, 05019004, 01.02.2020.

Research output: Contribution to journalArticle

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