Modeling 3D Ex-Filtration Process of a Soak-Away Rain Garden ()
Abstract
This paper presents a
three-dimensional (3D) model developed using COMSOL Multiphysics to understand the 3D ex-filtration process of a
soak-away rain garden. With a design hyetograph of 3-month average rainfall
intensities of Singapore, it is found that the average vertical ex-filtration
rate that is obtained by dividing the average vertical ex-filtration (drained
through bottom of the soak-away rain garden, averaged over the simulation
period = 720 min, and expressed in m3) by the surface area of the
soak-away rain garden and the simulation time step is almost constant regardless
of increase in saturated hydraulic conductivity (K) of the in-situ soil and the surface area of
the soak-away rain garden as a percentage of catchment area. However, as depth
to groundwater table which is measured from bottom of the filter media
increases, in between 0.5 m and 1 m of depth
to groundwater table, the average vertical ex-filtration rate decreases
significantly (by around 15 - 20 mm/hr) and the decrease is almost
twice, compared with that between 1 m and 1.5 m of depth to groundwater table.
Furthermore, this study shows that for a given K of in-situ, K of filter media, and depth to groundwater table, as the
surface area of the soak-away rain garden increases, the horizontal flow
coefficient which is defined as the ratio between total horizontal ex-filtration (drained through sides of the soak-away rain
garden, summed over the simulation period, and expressed in m3) and
total vertical ex-filtration (drained through bottom of the soak-away rain
garden, summed over the simulation period, and expressed in m3) decreases.
Moreover, for a given surface area of the soak-away rain garden, K of in-situ, and depth to groundwater table,
the horizontal flow coefficient decreases as K of the filter media increases.
However, it is found that for a given surface area of the soak-away rain
garden, K of in-situ, and K of filter
media, the horizontal flow coefficient increases as depth to groundwater table
increases.
Share and Cite:
Mylevaganam, S. , Chui, T. and Hu, J. (2015) Modeling 3D Ex-Filtration Process of a Soak-Away Rain Garden.
Journal of Geoscience and Environment Protection,
3, 35-51. doi:
10.4236/gep.2015.33004.
Conflicts of Interest
The authors declare no conflicts of interest.
References
[1]
|
Allan, P.D., Robert, G.T. and William, F.H. (2010) Improving Urban Stormwater Quality: Applying Fundamental Principles. Journal of Contemporary Water Research and Education, 146, 3-10.
http://dx.doi.org/10.1111/j.1936-704X.2010.00387.x
|
[2]
|
Jia, L., David, J.S., Cameron, B. and Yuntao, G. (2014) Review and Research Needs of Bioretention Used for the Treatment of Urban Stormwater. Water, 6, 1069-1099.
http://dx.doi.org/10.3390/w6041069
|
[3]
|
Hunt, W.F., Jarrett, A.R., Smith, J.T. and Sharkey, L.J. (2006) Evaluating Bioretention Hydrology and Nutrient Removal at Three Field Sites in North Carolina. Journal of Irrigation and Drainage Engineering, 132, 600-608.
http://dx.doi.org/10.1061/(ASCE)0733-9437(2006)132:6(600)
|
[4]
|
Jones, M.P. and Hunt, W.F. (2009) Bioretention Impact on Runoff Temperature in Trout Sensitive Waters. ASCE Journal of Environmental Engineering, 135, 577-585.
http://dx.doi.org/10.1061/(ASCE)EE.1943-7870.0000022
|
[5]
|
Li, H., Sharkey, L.J., Hunt, W.F. and Davis, A.P. (2009) Mitigation of Impervious Surface Hydrology Using Bioretention in North Carolina and Maryland. ASCE Journal of Hydrologic Engineering, 14, 407-415.
http://dx.doi.org/10.1061/(ASCE)1084-0699(2009)14:4(407)
|
[6]
|
Richards, L.A. (1931) Capillary Conduction of Liquids through Porous Mediums. Journal of Applied Physics, 1, 318-333.
http://dx.doi.org/10.1063/1.1745010
|
[7]
|
COMSOL AB (2012) COMSOL Multiphysics User’s Guide (Version 4.3). Stockholm, Sweden.
|
[8]
|
COMSOL AB (2012) COMSOL Multiphysics Reference Guide (Version 4.3). Stockholm, Sweden.
|
[9]
|
Li, Q., Ito, K., Wu, Z., Lowry, C.S. and Loheide II, S.P. (2009) COMSOL Multiphysics: A Novel Approach to Ground Water Modeling. Groundwater, 47, 480-487.
http://dx.doi.org/10.1111/j.1745-6584.2009.00584.x
|
[10]
|
Chow, V.T., Maidment, D.R. and Mays, L.W. (1988) Applied Hydrology. McGraw Hill, New York.
|