Bio-retention basin
design calculation
summary
CALCULATION SUMMARY
Calculation Task
Outcome
Check
Catchment characteristics
Catchment area
Ha
Catchment land use (i.e. residential, commercial etc.)
Storm event entering inlet
yr ARI
Conceptual Design
Bioretention area
Filter media saturated hydraulic conductivity
Extended detention depth
m²
mm/hr
mm
1 Verify size for treatment
Bioretention area to achieve water quality objectives
Total suspended solids
% of catchment
Total phosphorus
% of catchment
Total nitrogen
% of catchment
Bioretention area
Extended detention depth
REVISION DATE >> 7 MAY 2014
m²
m
Townsville City Plan Table SC6.4.3.9.10
2 Determine design flow
Time of concentration
Refer to SC6.4.4.4 Stormwater drainage design and QUDM
minutes
Identify rainfall intensities
Minor storm (I1-5 year ARI)
mm/hr
Major storm (I 50 year ARI)
mm/hr
Design runoff coefficient
Minor storm (C1-5 year ARI)
Major storm (C 50 year ARI)
Peak design flows
Minor storm (1-5 year ARI)
m³/s
Major storm (50 year ARI)
m³/s
3 Design inflow system
Adequate erosion and scour protection?
Coarse sediment fore bay required?
Volume (Vs)
m³
Area (As)
m²
Depth (D)
m
Minor storm flow width
m
*Check flow widths in upstream channel
CHECK ADEQUATE LANES TRAFFICABLE
*Kerb opening width
Kerb opening length
m
4 Specify bioretention media characteristics
Filter media hydraulic conductivity
Filter media depth
mm/hr
mm
Saturated zone required
Saturated zone depth
REVISION DATE >> 7 MAY 2014
mm
Townsville City Plan Table SC6.4.3.9.10
Drainage layer media (sand or fine screenings)
Drainage layer depth
mm
Transition layer (sand) required
Transition layer depth
mm
Flow capacity of filter media
m³/s
5 Under-drain design and capacity checks
Perforations inflow check
Pipe diameter
mm
Number of pipes
Capacity of perforations
m³/s
CHECK PERFORATION CAPACITY > FILTER MEDIA CAPACITY
CHECK SATURATED ZONE WEIR/UP TURNED PIPE CAPACITY FILTER
MEDIA CAPACITY
Perforated pipe capacity
Pipe capacity
m³/s
CHECK PIPE CAPACITY > FILTER MEDIA CAPACITY
6 Check requirement for impermeable lining
Soil hydraulic conductivity
mm/hr
Filter media hydraulic conductivity
mm/hr
MORE THAN 10 TIMES HIGHER THAN IN-SITU SOILS?
7 Size overflow pit
System to convey minor floods (2-5yr ARI)
LxW
8 Verification checks
Velocity for minor storm (<0.5m/s)
m/s
Velocity for major storm (<2.0m/s)
m/s
Treatment performance consistent with Step 1
*Relevant to streetscape application only
REVISION DATE >> 7 MAY 2014
Townsville City Plan Table SC6.4.3.9.10