Precious Eureka D. Flores
(Precious Eureka D. Flores)
Marla C. Maniquiz-Redillas
(Marla C. Maniquiz-Redillas)
Jevelyn Ann S. Tobio
(Jevelyn Ann S. Tobio)
김이형
(Lee-Hyung Kim)
†
Copyright © 2015, Korean Society on Water Environment
Key words(Korean)
Hydrologic effect, Low impact development, Peak flow, Rainfall, Runoff
1. Introduction
Urbanization is the continuous development of urban areas that has long been perceived
as one of the adverse force affecting natural hydrologic cycle and stream ecosystem
(McCuen, 1998). The major hydrologic effects of urbanization include the high fraction of precipitation
converted to surface runoff, decreased in the lag time between rainfall and runoff,
increase in peak flow magnitudes and reduced groundwater recharge capabilities (Hsu et al., 2000; Jacobson, 2011; Shaw, 1994; Shuster et al., 2005). Several studies indicated and examined the specific hydrologic effects of an urbanized
area. According to Rose and Peters (2001), the peak flows in an urbanized area were most likely 30% to more than 100% greater
than the non-urbanized land use. In addition, Cook and Dickinson (1985) has examined the hydrologic response of urbanization and found out that regardless
of rainfall intensity or duration, the runoff coefficient increased by at least 50%,
and the lag time of concentration and peak flow was decreased by three-fold. Likewise,
urban development contributes substantial amount of washed-off pollutants into the
receiving waters which cause water quality degradation (Kim and Lee, 2005; Lee et al., 2007; Lee et al., 2008; Maniquiz et al., 2012).
Currently, the integration and linking of both the ecosystem and landscape planning
is being considered to address the growing concern in water quantity and quality management
(Hatt et al., 2007). In Korea, the Ministry of Environment has funded several projects related to the
management of stormwater runoff and one of these is the application of low impact
development (LID) technologies in the urban landuses. LID is an approach that manages
stormwater by promoting the natural movement of water within the watershed, thus maintaining
or restoring the watershed’s hydrologic and ecological functions (Coffman, 2000; Davis, 2008). There are many practices that have been used in LID such as bioretention facilities,
rain gardens, vegetated rooftops, rain barrels, permeable pavements, etc. Two of the
most common LIDs implemented in urban landuses in Korea were infiltration trench and
bioretention. The infiltration trench mainly captures and temporarily holds stormwater
runoff prior to groundwater recharge (U.S. EPA, 1999). On the other hand, bioretention incorporate trees and other gardening plants to
regulate and treat runoff from an impervious surface (Davis et al., 2009). Hood et al. (2007) reported that after the application of common LID technologies on a residential area,
the start of runoff-to-peak flow time was increased by almost 30% and peak flow was
reduced for an estimate of 80%. This research was conducted to evaluate the hydrologic
effects of the infiltration trench (IT) and tree box filter (TBF) employed in LID
for the management of stormwater runoff in a road and parking lot landuse inside a
university campus.
2. Materials and Method
2.1. Description of the LID Sites
The two LID sites were located inside the Kongju National University campus grounds
in Cheonan City, South Korea (36°51'1.11"N, 127°9'0.23"E). Fig. 1 shows the hydrologic conditions before and after the application of LID, and the
schematic diagrams of the two technologies employed in LID. In the pre-existing condition
the stormwater runoff flows to the paved road and impervious parking lot which is
directly discharged to the drainage system increasing the amount of runoff volume
and flow peaks during storm events. The two technologies namely the infiltration trench
and tree box filter employed in LID were constructed to provide hydrologic benefits
such as runoff volume and peak flow reduction; and help restore the natural circulation
system lost due to the impervious surfaces. The infiltration trench, with a surface
area and storage volume of 5.0 m2 and 3.85 m3, respectively was constructed to manage stormwater runoff from a 520 m2 paved road with a 2.5% slope. The tree box filter, about half the size of the infiltration
trench has a surface area of 1.5 m2 and storage volume of 0.56 m3 drains the runoff from a 450 m2 parking lot with a 0.33% slope. The surface area of the infiltration trench and tree
box filter were only less than 1% of the total catchment area, and the storage volume
was approximately 60% of the total volume.
Fig. 1.
Hydrologic condition before and after LID with the schematic diagrams of the infiltration
trench and tree box filter utilized in LID.
The infiltration trench and tree box filter have pre-treatment component that captures
and temporarily holds stormwater runoff, infiltration capability for ground water
recharge and utilized filter media that aid in the filtration and storage of stormwater
runoff. Although smaller than the infiltration trench, the tree box filter can perform
additional hydrologic benefit such as evapotranspiration and plant uptake to regulate
runoff from an impervious area.
2.2. Storm Event Monitoring
A total of 13 storm events were monitored in the infiltration trench from July 2010
to April 2014 and nine storm events in the tree box filter from July 2010 to July
2014. The rainfall data for all the storm events were obtained from the Korean Meteorological
Association (KMA). Flow measurements were manually conducted at the inflow and outflow
units of the infiltration trench and tree box filter in five minute interval from
the start until the end of runoff/outflow. The flow rates were calculated as the volume
of runoff collected in a graduated container or volumetric flask per unit time.
3. Results and Discussion
3.1. Hydrologic Characteristics
The rainfall frequency distribution in the LID sites for the monitoring period of
2010 to 2013 indicates that the total annual rainfall was highly variable for each
year, smallest being 768 mm in 2013 and highest in 2012 with 2,212 mm (Fig. 2). In low rainfall year, the proportion of storms 15 mm or less accounts for 45% of
the total annual rainfall; whereas in high rainfall years, it accounts for only 20%.
Since most of the storms that occurs in Korea (more than 70%) falls to the category
of low-intensity rainfall (15 mm or less) Maniquiz (2012) several stormwater management technologies were designed to control these most frequent
storms. But as can be seen, a greater variation in rainfall distribution pattern has
occurred recently due to climate change (e.g., occurrence of large storms greater
than 70 mm) making it more difficult to select appropriate rainfall conditions for
LID.
Fig. 2.
Rainfall frequency distribution on the site, 2010 to 2013.
The relationships of the runoff volume, average and peak flows before and after LID
application are shown in Fig. 3. It was observed that the amount of runoff was greater than the storage capacity
of the infiltration trench and tree box filter in 77% and 56% of storm events, respectively.
Although there was a dominance of low rainfall storm events that were monitored, the
runoff was fairly captured in the infiltration trench and tree box filter with an
average runoff coefficient of 0.87 and 0.50, respectively.
Fig. 3.
Volume, average and peak flows before and after LID.
The rainfall that occurred in the paved road was effectively converted into stormwater
runoff due to a steeper slope and lesser runoff interceptors (e.g. overhanging vegetation,
parked vehicles, etc.) in the infiltration trench site that also resulted to higher
rate of flows compared to the impervious parking lot in the tree box filter site.
On average, the peak flows reached up to fourfold the average flows before LID. Apparently,
the trendlines generated from the linear regression have high coefficient of determination
(R2), and fall below the 1:1 line suggesting the hydrologic improvement contributed upon
the application of the infiltration trench and tree box filter.
3.2. Changes in the Hydrologic Balance
The contribution of the infiltration trench and tree box filter on the hydrologic
balance after LID was exemplified by the reduction in runoff volume (Table 1). The runoff before LID was completely discharged to sewers and possibly could lead
to local flooding of transport systems and pollution to receiving waters during intense
storm events. But after LID, the runoff was partially reduced by means of the combined
processes of infiltration for groundwater recharge, retention for temporary storage
of runoff, filtration and evapotranspiration that were provided by the infiltration
trench and tree box filter. On average, the infiltration trench was able to reduce
almost half the runoff generated from the paved road. The tree box filter only reduced
20% of the runoff but still satisfactory considering its small storage capacity compared
to the catchment area that it drains.
Table 1.
Hydrologic balance before and after LID
It was observed that hydrologic parameters such as rainfall depth and rainfall intensity
were factors that affect the runoff before LID and highly significant at the infiltration
trench site than the tree box filter site (Fig. 4). When the rainfall depth was doubled, the difference in the amount of runoff volume
before and after LID was increased by twofold in magnitude in the infiltration trench
and about 115% in the tree box filter. As greater amount of runoff was generated in
the infiltration trench than the tree box filter; the reduction in runoff volume before
and after LID in the infiltration trench site was still evident (1 m3) even for rainfall as small as 5 mm. However, in the case of tree box filter it requires
at least 15 mm of rainfall in order to reduce at least 0.5 m3 of runoff.
Fig. 4.
Runoff volume as a function of rainfall and average rainfall intensity before and
after LID.
It can be seen that as the rainfall increased, the volume reduction was becoming more
apparent. For instance, when the rainfall was 10 mm, almost 65% reduction was observed
in the infiltration trench site; however, as the rainfall was further increased to
30 mm, almost 90% reduction was achieved. In the tree box filter site, only 15% volume
reduction was attained for 25 mm rainfall and could only reached 50% when the rainfall
depth was 45 mm. Similar observations were found in the case of rainfall intensity;
the more intense rainfall, the greater amount of runoff was generated and also reduced.
However, the influence of rainfall intensity in the volume reduction was not as prominent
as the rainfall due to the lower correlation observed.
3.3. Changes in the Magnitude, Frequency and Duration of Average and Peak Flows
Based on Davis (2008), the peak flow reduction was an important parameter for quantifying the hydrologic
impact of a particular stormwater management practice for LID. Fig. 5 shows the relationship of peak flows with the rainfall and rainfall intensity before
and after LID application. Before LID, the peak flows in the infiltration trench site
were 50 to 87% greater than the magnitude of peak flows in the tree box filter site
that resulted due to a higher ground slope in the paved road (90% greater than the
parking lot slope) further promoting the surface runoff. The rainfall intensity showed
a more apparent influence on the peak flow reduction compared to rainfall particularly
in the infiltration trench site. For every unit increase in rainfall intensity, the
average reduction in peak flow after LID was approximately 30% in the infiltration
trench while only more than 5% in the tree box filter. The average monitored rainfall
intensity on the sites (infiltration trench, 2.67 mm/hr and tree box filter, 3.7 mm/hr)
resulted to lower the peak flow by 2.2 and 0.9 m3/hr for infiltration trench and tree box filter, respectively. Although the value
was lower in the tree box filter site, the peak flow was reduced by 5% greater than
the infiltration trench site.
Fig. 5.
Peak flows as a function of rainfall and average rainfall intensity before and after
LID.
After LID, the minimum peak flow was reduced by 15% for infiltration trench at 3 mm
rainfall; while 26% for tree box filter at the smallest rainfall of 1 mm. As the rainfall
increases so as the peak flows; the reduction in peak flows after LID was becoming
more evident. The maximum monitored peak flow before LID (infiltration trench, 16
m3/hr and tree box filter, 8 m3/hr) was reduced by 58% and 32% in the infiltration trench and tree box filter sites,
respectively. Based on the regression analyses, insignificant increase in peak flow
reduction was observed when rainfall was 40 and 30 mm for infiltration trench and
tree box filter, respectively indicating that the maximum possible peak flow reduction
was attainable at about 61% for infiltration trench and 33% for tree box filter.
Compared in Fig. 6 were the hydrographs for the infiltration trench and tree box filter for the same
storm event that happened on August 10, 2010. It was observed that the flows resembled
the rainfall distribution pattern but with a slight delay in the peaks due to surface
runoff, typical in urban land use characterized by high impervious surfaces. After
LID, both sites exhibited a delay (lag time) or reduction in the magnitude, frequency
and duration of flow peaks as the rainfall progress. Apparently, in the infiltration
trench the average flows were greatly reduced; while the tree box filter was able
to reduce the peak flows even not reducing a huge amount of runoff volume. Comparing
the two, it was revealed that the infiltration trench having a larger storage capacity
and subjected to high runoff and flows was able to perform more efficiently than the
tree box filter. However, considering the catchment area of the infiltration trench
that was only 13% larger than the tree box filter, the current storage capacity of
the tree box filter could be maximize when applied to a smaller catchment.
Fig. 6.
Hydrographs for August 10, 2010 storm event at the (a) infiltration trench and (b)
tree box filter.
4. Conclusion
Continuing urbanization imposed significant strains to the environment alongside with
the climate change necessitating a need for a more sustainable stormwater practices
like LID. In this research, the infiltration trench and tree box filter were utilized
to implement the LID principle of restoring the hydrologic functions in urban catchments.
Based on the results, it was found out that the magnitude of runoff and peak flows
was dependent on the landuse characteristics such as imperviousness, slope, runoff
interceptors, and most importantly the rainfall amount and intensity. After the application
of infiltration trench and tree box filter, hydrological improvement was observed
in the sites specifically changes in the hydrologic balance (runoff was reduced),
magnitude, frequency and duration of peak flows. The runoff reduced in the sites were
assumed to be infiltrated into the soil providing groundwater recharge, retained in
the facility for temporary storage, or used by the plants.
Findings revealed that rainfall was the limiting factor in volume reduction and rainfall
intensity in peak flow reduction indicating that as the rainfall increases so as the
runoff volume, and as the rainfall intensity increases so as the peak flows; the reduction
in runoff volume and peak flows after LID was becoming more evident. In the infiltration
trench, the runoff volume and average flows were greatly reduced; while the tree box
filter was still able to reduce the peak flows even not reducing a huge amount of
runoff volume.
Comparing the two LID sites, the infiltration trench was able to perform more efficiently
than the tree box filter due to higher runoff coefficient at the infiltration trench
and larger storage capacity set against the catchment area. However, the capability
of the tree box filter can be maximized when applied to a smaller catchment area.
Consequently, the site selection for LID application should prioritize the sites subjected
to high amount of runoff and it is recommended that the rainfall distribution pattern
must be considered to select appropriate rainfall conditions for LID.
Acknowledgements
The funding for this research was financially supported by Construction Technology
Innovation Program under the grant of Korea Agency for Infrastructure technology Advancement
(KAIA) in the Ministry of Land, Infrastructure and Transport (Code#’12 CTIP C03, Development
of LID technology) in Korea. The authors were grateful for their support.
References
Coffman L., 2000, Low Impact Development Design Strategies, An Integrated Approach,
Coffman, L. (2000). Low Impact Development Design Strategies, An Integrated Approach,
EPA 841-B-00-003, Department of Environmental Resources, Programs and Planning Division,
Prince’s George County, Maryland.
Cook D. J., Dickinson W. T., 1985, The Impact of Urbanization on the Hydrologic Response
of the Speedvale Experimental Basin, Ontario-A case study, Cook, D. J. and Dickinson,
W. T. (1985). The Impact of Urbanization on the Hydrologic Response of the Speedvale
Experimental Basin, Ontario-A case study, in Proceedings, 1985 International Symposium
on Urban Hydrology, Hydraulic Infrastructures and Water Quality Control.
Davis A., 2008, Field performance of Bioretention: Hydrology impacts, Journal of Hydrologic
Engineering, Davis, A. (2008). Field performance of Bioretention: Hydrology impacts,
Journal of Hydrologic Engineering, 13(2), pp. 90-95., Vol. 13, No. 2, pp. 90-95
Davis A. P., Hunt W. F., Traver R. G., Clar M., 2009, Bioretention Technology: Overview
Practice and Future Needs, Journal of Environmental Engineering, Davis, A. P., Hunt,
W. F., Traver, R. G., and Clar, M. (2009). Bioretention Technology: Overview Practice
and Future Needs, Journal of Environmental Engineering, 135(3), pp. 109-117., Vol.
135, No. 3, pp. 109-117
Hatt B. E., Fletcher T. D., Delatic A., 2007, Treatment Performance of Gravel Filter
Media: Implications for Design and Application of Stormwater Infiltration Systems,
Water Research, Hatt, B. E., Fletcher, T. D., and Delatic, A. (2007). Treatment Performance
of Gravel Filter Media: Implications for Design and Application of Stormwater Infiltration
Systems, Water Research, 41(12), pp. 2513-2541., Vol. 41, No. 12, pp. 2513-2541
Hood M. J., Clausen J. C., Warner G. S., 2007, Comparison of Stormwater Lag Times
for Low Impact and Traditional Residential Development, Journal of the American Water
Resources Association, Hood, M. J., Clausen, J. C., and Warner, G. S. (2007). Comparison
of Stormwater Lag Times for Low Impact and Traditional Residential Development, Journal
of the American Water Resources Association, 43(4), pp. 1036-1046., Vol. 43, No. 4,
pp. 1036-1046
Hsu M. H., Chen S. H., Chang T. J., 2000, Inundation Simulation for Urban Drainage
Basin with Stormwater Sewer System, Journal of Hydrology, Hsu, M. H., Chen, S. H.,
and Chang, T. J. (2000). Inundation Simulation for Urban Drainage Basin with Stormwater
Sewer System, Journal of Hydrology, 234, pp. 21-37., Vol. 234, pp. 21-37
Jacobson C. R., 2011, Identification and Quantification of the Hydrological Impacts
of Imperviousness in Urban Catchments: A Review, Journal of Environmental Management,
Jacobson, C. R. (2011). Identification and Quantification of the Hydrological Impacts
of Imperviousness in Urban Catchments: A Review, Journal of Environmental Management,
92, pp. 1438-1448., Vol. 92, pp. 1438-1448
Kim L. H., Lee S., 2005, Char Characteristics of Washed-off Pollutants and Dynamic
EMCs in a Parking Lot and a Bridge during Storms, Journal of Korean Society on Water
Environment, Kim, L. H. and Lee, S. (2005). Char Characteristics of Washed-off Pollutants
and Dynamic EMCs in a Parking Lot and a Bridge during Storms, Journal of Korean Society
on Water Environment, 21(3), pp. 372-379. [Korean Literature], Vol. 21, No. 3, pp.
372-379
Lee S. Y., Lee E., Kim C., Son H., Maniquiz M., Son Y., Kang H., Kim J., Kim L. H.,
2007, Characteristics of Wash-off Metal Pollutants from Highway Toll-Gate Area, Journal
of Korean Society on Water Environment, Lee, S. Y., Lee, E., Kim, C., Son, H., Maniquiz,
M., Son, Y., Kang, H., Kim, J., and Kim, L. H. (2007). Characteristics of Wash-off
Metal Pollutants from Highway Toll-Gate Area, Journal of Korean Society on Water Environment,
23(6), pp. 945-950. [Korean Literature], Vol. 23, No. 6, pp. 945-950
Lee S. Y., Lee E., Maniquiz M. C., Kim L. H., 2008, Determination of Pollutant Unit
Loads from Various Transportation Landuses, Journal of Korean Society on Water Environment,
Lee, S. Y., Lee, E., Maniquiz, M. C., and Kim, L. H. (2008). Determination of Pollutant
Unit Loads from Various Transportation Landuses, Journal of Korean Society on Water
Environment, 24(5), pp. 543-549. [Korean Literature], Vol. 24, No. 5, pp. 543-549
Maniquiz M. C., 2012, Low Impact Development (LID) Technology for Urban Stormwater
Runoff Treatment-Monitoring, Performance and Design, PhD Thesis, Maniquiz, M. C. (2012).
Low Impact Development (LID) Technology for Urban Stormwater Runoff Treatment-Monitoring,
Performance and Design, PhD Thesis, Kongju National University: Department of Civil
and Environmental Engineering, Cheonan City, South, Korea.
Maniquiz M. C., Kim L. H., Lee S., Choi J., 2012, Flow and Mass Balance Analysis of
Eco-bio Infiltration Systems, Frontiers of Environmental Science and Engineering,
Maniquiz, M. C., Kim, L. H., Lee, S., and Choi, J. (2012). Flow and Mass Balance Analysis
of Eco-bio Infiltration Systems, Frontiers of Environmental Science and Engineering,
6(5), pp. 612-619., Vol. 6, No. 5, pp. 612-619
McCuen R. H., 1998, Hydrologic Analysis and Design, McCuen, R. H. (1998). Hydrologic
Analysis and Design, 2nd edition, Prentice Hall: Upper Saddle River: New Jersey, pp.
814., pp. 814
Rose S., Peters N. E., 2001, Effects of Urbanization on Streamflow in the Atlanta
Area (Georgia, USA): A Comparative Hydrological Approach, Hydrological Processes,
Rose, S. and Peters, N. E. (2001). Effects of Urbanization on Streamflow in the Atlanta
Area (Georgia, USA): A Comparative Hydrological Approach, Hydrological Processes,
15, pp. 1441-1457., Vol. 15, pp. 1441-1457
Shaw E. M., 1994, Hydrology in Practice, Shaw, E. M. (1994). Hydrology in Practice,
3rd edition, Chapman & Hall: London, pp. 569., pp. 569
Shuster W. D., Bonta J., Thurston H., Warnemuende E., Smith D. R., 2005, Impacts of
Impervious Surface on Watershed Hydrology: A Review, Urban Water Journal, Shuster,
W. D., Bonta, J. Thurston, H., Warnemuende, E., and Smith D. R. (2005). Impacts of
Impervious Surface on Watershed Hydrology: A Review, Urban Water Journal, 2(4), pp.
263-275., Vol. 2, No. 4, pp. 263-275
1999, Stormwater Technology Fact Sheet: Infiltration Trench, Office of Water,, United
States Environmental Protection Agency (U.S EPA). (1999). Stormwater Technology Fact
Sheet: Infiltration Trench, Office of Water, Washington DC. EPA 832-F-99-019.