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Post Construction BMP Selection & Design for
Public Transportation Projects
July 27, 2016
Ohio Department of Transportation 1
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BMP Design
Aids
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Rational Method
Manning’s Equation
Outlet Discharge Equations
ODOT CDSS
SCS Curve Number
Hydrograph and Pond Routing Programs
USGS StreamStats
Equations / Programs
Post Construction BMP Selection & Design for
Public Transportation Projects
July 27, 2016
Ohio Department of Transportation 2
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Training Intent
Introduction and overview of various design aids (equations and programs)
Not a detailed training on how to use each one
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Rational Method
Manning’s Equation
Outlet Discharge Equations
ODOT CDSS
SCS Curve Number
Hydrograph and Pond Routing Programs
USGS StreamStats
Equations / Programs
Post Construction BMP Selection & Design for
Public Transportation Projects
July 27, 2016
Ohio Department of Transportation 3
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Rational Method
For peak flow rate only
Q = CiA
Q: flow rate (cfs)
C: coefficient of runoff
i: rainfall intensity (in/hr)
Based on time of concentration
Sheet flow, shallow concentrated flow, and open
channel or pipe flow
A: tributary area (ac)
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Rational Method
Q = CiA
C:
Post Construction BMP Selection & Design for
Public Transportation Projects
July 27, 2016
Ohio Department of Transportation 4
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Rational Method
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Rational Method
Manning’s Equation
Outlet Discharge Equations
ODOT CDSS
SCS Curve Number
Hydrograph and Pond Routing Programs
USGS StreamStats
Equations / Programs
Post Construction BMP Selection & Design for
Public Transportation Projects
July 27, 2016
Ohio Department of Transportation 5
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Manning’s Equation
(0.15 for Vegetated Biofilter)
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Manning’s Equation
Post Construction BMP Selection & Design for
Public Transportation Projects
July 27, 2016
Ohio Department of Transportation 6
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Manning’s Equation
Program or Spreadsheet Calculation
Use bisection method (trial and error)
Inputs:
Channel geometry and slope
Manning’s roughness coefficient
Flow rate
Results:
Normal depth
Velocity
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Rational Method
Manning’s Equation
Outlet Discharge Equations
ODOT CDSS
SCS Curve Number
Hydrograph and Pond Routing Programs
USGS StreamStats
Equations / Programs
Post Construction BMP Selection & Design for
Public Transportation Projects
July 27, 2016
Ohio Department of Transportation 7
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Discharge Equations
Orifice flow
Weir flow
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Orifices
Orifices
Post Construction BMP Selection & Design for
Public Transportation Projects
July 27, 2016
Ohio Department of Transportation 8
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Weir Orifice
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Orifice Flow
Post Construction BMP Selection & Design for
Public Transportation Projects
July 27, 2016
Ohio Department of Transportation 9
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Weir Flow
L&D Vol. 2, 1102.3.4
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Rational Method
Manning’s Equation
Outlet Discharge Equations
ODOT CDSS
SCS Curve Number
Hydrograph and Pond Routing Programs
USGS StreamStats
Equations / Programs
Post Construction BMP Selection & Design for
Public Transportation Projects
July 27, 2016
Ohio Department of Transportation 10
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ODOT CDSS
CDSS is a hydraulic design software developed by ODOT
C – Culvert Design
D – Ditch Design
SS – Storm Sewer Design
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Rational Method
Manning’s Equation
Outlet Discharge Equations
ODOT CDSS
SCS Curve Number
Hydrograph and Pond Routing Programs
USGS StreamStats
Equations / Programs
Post Construction BMP Selection & Design for
Public Transportation Projects
July 27, 2016
Ohio Department of Transportation 11
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SCS Curve Number
Technical Release 55 (TR-55)
Technical Release 20 (TR-20)
Urban Hydrology for Small Watersheds
Determines runoff depth (inches)
Combines with unit hydrograph theory
Produces runoff hydrographs
Peak flow and total volume
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SCS Curve Number
CN: depth of runoff abstracted
Total P – Abstracted P = Runoff Depth
Runoff Depth * Area = Runoff Volume
NRCS unit hydrograph gives runoff volume
a shape (distribution over time)
Produces a full runoff hydrograph
Time
Runoff F
low
Rate
Post Construction BMP Selection & Design for
Public Transportation Projects
July 27, 2016
Ohio Department of Transportation 12
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SCS Curve Number
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SCS Curve Number
Post Construction BMP Selection & Design for
Public Transportation Projects
July 27, 2016
Ohio Department of Transportation 13
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SCS Curve Number
Analyses that require a full hydrograph
Pre vs. post volumes (CSO areas)
Routing a design storm through a detention
basin, bioretention cell, or infiltration trench
Still gives peak flow rate, but will likely be slightly different from Rational Method
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Rational Method
Manning’s Equation
Outlet Discharge Equations
ODOT CDSS
SCS Curve Number
Hydrograph and Pond Routing Programs
USGS StreamStats
Equations / Programs
Post Construction BMP Selection & Design for
Public Transportation Projects
July 27, 2016
Ohio Department of Transportation 14
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Hydrograph and Pond Routing
Programs
Many different programs
Different inputs
Different calculations
Different limitations
Know your tool before you use it
• Basic Pipe or Open
Channel Capacity
Calcs.
• Basin Inlet/Outlet
• Peak Flow and HGL
• Steady/Unsteady Flow
• Open Channels
• Some Sediment
Transport/Quality
• Often used in FEMA Floodplains
• Normal Gravity Sewer, Detention Pond Design
• Hydrology and Hydraulics Combined
• Rational/TR-55/SCS Hydrology
• Manning’s/Orifice/Weir Hydraulic Calcs.
• Some Quality Calculations Available
• Complex Drainage Systems that have:
• tail water, reverse flow, pump stations, surface flooding
• Horton/Green-Ampt Hydrology
• Hydrodynamic and Kinematic Wave Hydraulic Calcs.
• Detailed Quality Calculations Available
Common Hydraulics and Hydrology Software Options
Design Calculations
•Hydraflow Express
•Bentley CulvertMaster
•Bentley FlowMaster
•Urban Drainage HY22
•HY-8, ODOT CDSS
HEC
•HEC-1
•HEC-HMS
•HEC-2
•HEC-RAS
•GEO-RAS
Simple Stormwater
Routing Models
•HydraFlow Hydrographs
•HydraFlow Storm Sewers
•Bentley StormCAD
•Bentley PondPack
•HydroCAD
Robust Stormwater
Routing Models
•EPA SWMM
•Bentley CivilStorm
•AutoDesk SSA
•PCSWMM
•XP SWMM
Post Construction BMP Selection & Design for
Public Transportation Projects
July 27, 2016
Ohio Department of Transportation 15
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PondPack and HydroCAD
Inputs for runoff hydrograph
Area
Curve number, land use, or runoff coefficient
Time of concentration
Design storm frequency
Produces runoff hydrograph
Then route that hydrograph into your BMP
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PondPack and HydroCAD
Inputs for BMP
Stage vs storage curve (elevation vs. volume)
Inputs for BMP discharge
Stage vs. depth curve
Each outlet
WQ orifices
Weirs, catch basin grates
Overflow weirs
Discharge pipe
Downstream constraints (tailwater)
793
794
795
796
797
798
799
800
0 0.10.20.30.40.50.60.70.80.9 1 1.11.21.3
Ele
vatio
n (
ft)
Volume (ac-ft)
Elevation vs. Volume
Post Construction BMP Selection & Design for
Public Transportation Projects
July 27, 2016
Ohio Department of Transportation 16
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PondPack and HydroCAD
Two types of analyses
Hydrograph routing
Drawdown analysis
Split event into many
short pieces and
calculate:
Volume entering
Volume leaving
Volume and depth in basin
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PondPack and HydroCAD
Make sure you have all of the potential
discharge conveyances
Make sure the BMP storage information in
the model matches the design sheets
Make sure the modeled discharge
conveyance characteristics match the
design sheets and site, including tailwater
Make sure the results make sense
Post Construction BMP Selection & Design for
Public Transportation Projects
July 27, 2016
Ohio Department of Transportation 17
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Rational Method
Manning’s Equation
Outlet Discharge Equations
ODOT CDSS
SCS Curve Number
Hydrograph and Pond Routing Programs
USGS StreamStats
Equations / Programs
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Post Construction BMP Selection & Design for
Public Transportation Projects
July 27, 2016
Ohio Department of Transportation 18
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Rational Method
Peak flow rate only
Manning’s Equation
Flow conditions (velocity and depth) at a given flow rate
Outlet Discharge Equations
Flow rate at a given outlet shape and hydraulic head
ODOT CDSS
Hydraulic design of culverts, ditches, and storm sewers
SCS Curve Number
Full runoff hydrograph (flow rate over time and full storm volume)
Hydrograph and Pond Routing Programs
Full hydrograph, detention, peak flow rate, and draw down analyses
USGS StreamStats
Peak design storm flow rates as well as other stream statistics
Equations / Programs
Post Construction BMP Selection & Design for
Public Transportation Projects
July 27, 2016
Ohio Department of Transportation 19
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Questions ?
Jon Prier, [email protected]
614-644-1876