URBAN SWALES

1
URBAN SWALES STORMWATER ON COLLINGWOOD AVE.
GLENCOVE RD. SYRACUSE, NY SERVICE LEARNING
PROJECT Deborah Ketola, Todd Cridge Dr. T.
Endreny. FEG 340 Engineering Hydrology
Hydraulics Course, 207 Marshall Hall, SUNY
College of Environmental Science and Forestry,
Syracuse, NY
Introduction Urban areas must better manage
stormwater to reduce stresses on sewer systems.
In Syracuse NY, the sewers are under capacity for
the stormwater loads, creating combined sewer
overflows (CSO) that discharge pollutants into
Onondaga Creek. A regional treatment facility
(RTF) and sub-surface storage system have been
proposed to handle CSO discharges, which would
later send wastes to the METRO for full
treatment. Our design objective was to prioritize
community concerns about neighborhood disruption
of the RTF and examine ecologically based
alternatives to reduce stormwater runoff and thus
CSO discharges. We considered an alternative
design of a small foot-print swale lined with
Bermuda grass. This design focused on the
Syracuse Eastwood area along South Collingwood
Avenue and Glencove Road. It was found that a
swale design would meet the constraints, size at
69 m long, have an average velocity of 0.12 m/s,
and adequately reduce runoff for the small
contributing area during 10-year through 100 year
rainfall year events

• Methods
• Design
• The velocity that we calculated was 0.12 m/s for
  this channel.
• The maximum velocity that we will allow from this
  swale is 0.3 m/s.
• Any velocity greater than this will uproot the
  Bermuda grass in the swale.
• We will be using a Bermuda grass of approximately
  6cm in height with a roughness factor of D
  (n.04).
• This number is used in the Manning equation and
  it takes into account the roughness coefficient
  which helps to reduce the flow of the storm
  water.

Figure 4 Erosion Factors
Figure 2 Storm Discharges for different
intensity storms April, 2003

• Methods
• Sizing
• To ensure that this flow velocity is not exceeded
  a slope of no more than 0.5.
• The below equation is used to find the bottom
  width and the depth of the trapezoidal swale
• From this a bottom width (Bw) of 0.25 m (9 in)
  and a depth of flow of 0.053 m (2in) are
  derived.
• This equation also takes into account the slope
  of the area which will be no more than 0.5.

Figure 5 Retardance Factors
Figure 1 Stormwater swale in a residential
neighborhood

• Conclusions
• This design will greatly reduce runoff from
  residential, industrial, and commercial
  neighborhoods
• Increase the quality of the groundwater
• Slow down the rapid flow of the stormwater
• Reduce the pollutants as well as control
  flooding during flood events
• Maximize infiltration and provides storage
• Cost effective to build and maintain
• Relatively easy to maintain

• Design of a Swale
• To design a swale for the purpose of
• Trapping pollutants
• Promote infiltration of the surface water
• Reduce the flow velocity of the storm runoff
  water
• This swale is to be designed to
• Discourage long standing water
• Promote infiltration into the ground
• The sizing of this swale was based on the
  equation QCiA
• Where
• C (catchment coefficient) 1 This assumes no
  infiltration into the soil (a unit-less number)
• i (intensity) 1.0 in/hr (for the 10 year 2
  hour storm)
• A (area) 45000 sq.ft.
• This results in a runoff discharge (Q) of
  0.03cms.
• The total length of the swale is to be 69.28 m
  (211.17 ft) which will fit into the area.

References SUNY ESF ERE596URH, Dr. Endreny's
Lecture, WEFs Urban Runoff Quality
Text. http//www.nscc.govt.nz/Waterinfo/stormwater
/images/img-swale4.jpg. www.ridgesanctuary.org/ima
ges/ BlindBridg23.jpg.
Figure 3 Syracuse Eastwood area along South
Collingwood Avenue and Glencove Road, Picture
taken by D. Ketola, April 2003.