Modelling LIDs using PCSWMM and EPA SWMM5

March 28, 2012

Presented by: Rob James (CHI)

Credit to: Lewis Rossman (US EPA)

1977SWMM ported to minicomputer

1981EPA SWMM 3released

1984PCSWMM released1st PC versionFORTRAN

1988EPA SWMM 4released

2004EPA SWMM 5released

1991PCSWMM4First GUI versionBASIC

1995PCSWMM ‘95First 32-bit Windowsversion - Visual Basic

1998PCSWMM ’98First GIS-based versionVisual Basic

2002PCSWMM 2002Genetic algorithmbased calibration

IBM PC/AT Intel 80-486 IBM PowerPC Intel Pentium III Intel Quad Core

1993SWMM-USERSlistserv

2007PCSWMM.NETFirst multi-threadedversion - C#, .NET 3.5

2010-2011PCSWMM 2011• Real-time flood

forecasting• Integrated 2D

modeling• French, Spanish,

Chinese language versions

Intel i7

Processing power increase over the history of PCSWMM

100,000,000

TIMES

PCSWMM`s computational grid at CHI

1,000,000,000,000

FLOPS

So how much is 1 trillion floating point operations?

1 x 60s x 60m x 2100h x 40y

302,400,000

1,000,000,000,000= 0.03%

PCSWMM: Spatial DSS for EPA SWMM5

PCSWMM: Spatial DSS for EPA SWMM5

PCSWMM/SWMM5 LID toolbox

• Physically-based processes

• Flexible components

• SWMM Version 5.0.022

• Simplifies the modeling of:– Lot level implementations

– Watershed scale or city master planning

– Single event

– Continuous

– Performance degradation

Examples of SWMM5 LID controls

Vegetative Swale Rain Garden

Street Planter

Rain Barrel

Porous Pavement Infiltration Trench

EPA SWMM5 LID toolkit: follows the methodology of PCSWMM for PP

Conceptual Model of an LID Process

Surface Zone

Soil Zone

Storage Zone

Runon

Infiltration

Percolation

Infiltration

Overflow

Underdrain

ET

Flow Balance Equations

11101 qfeqt

d

pfeft

D 212

3333 qfeft

dp

Surface d1

Soil

Storage d3

q0

f1

fp

f3

q1

q3

e1, e2, e3

D2

Infiltration Flux

Classical Green-Ampt Eqn: (depth d is normally ignored) F

dKf sat

))((1

0

2

4

6

8

10

12

14

0 5 10 15 20 25 30

Time (minutes)

Infi

ltra

tio

n R

ate

(in

/hr)

depth included depth ignored

0

1

2

3

4

5

6

7

0 50 100 150 200 250 300 350 400

Time (minutes)

Po

nd

ed

Dep

th (

inch

es)

depth included depth ignored

Effect of ponded depth (d) on infiltration rate (Ksat = 0.5 in/hr)

DKf p

)(1)(

Rate of percolation (fp) through the unsaturated soil zone as a function of moisture content ( is described by Darcy’s Law:

))(exp( HCOKK sat

))(exp(135 PCOFC

K = hydraulic conductivity, = capillary tension, = porosity, FC = field capacity, and HCO and PCO are coefficients.

Percolation Flux

Outflow Fluxeso Flux rates are functions of zone’s water depth (d)

o Surface zone

– Overland flow using Manning’s formula

Q = (1.49/n)AR2/3S1/2 where A and R depend on d

– Overflow using the weir equation

Q = CWL(d)1.5

o Storage zone underdrain flow

Q = CD(d)

n = Manning’s roughness, A = flow area, R = hyd. radius, S = surface slope, L = length of weir crest, and Cw, CD, and are coefficients.

Representing Different LID Alternatives

LID Alternative Zones Processes (besides ET)

Rain Barrel Surface,

Storage

Surface Overflow

Storage Underdrain Flow

Porous Pavement Surface,

Storage

Surface Overland Flow

Storage Infiltration*

Infiltration Trench Surface,

Storage

Surface Overflow

Storage Infiltration

Vegetative Swale Surface Surface Overland Flow

Surface Infiltration

Bioretention Cell Surface,

Soil,

Storage

Surface Overflow

Soil Infiltration

Soil Percolation

Storage Infiltration*

*May also include storage underdrain flow

Bio-retention cell – ‘Street Planter’

LID example: Valleyfield, PQ

• New residential development to include 22 boulevard planters

• Reduce minor system inflow

• Reduce pollutant loading

Boulevard Planters

Alternate designs

Valleyfield, Quebec – LID retrofit example

Bio-retention cell to be installed in typical residential neighbourhood

PCSWMM LID representation

PCSWMM LID representation: surface

PCSWMM LID representation: surface storage

PCSWMM LID representation: soil

PCSWMM LID representation: storage

PCSWMM LID representation: tile drain

Continuous LID analysis

Continuous LID analysis: small events

Continuous LID analysis: large events

Continuous LID analysis: clogging potential

Enabling continuous LID analysis: Rainfall Processing with PCSWMM

Runoff for 1-inch, 6-hr Event

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00

Ru

no

ff (

cfs

)

No Planters 3 Planters 5 Planters

Rossman (2009)

Effect of Number of Planters

0

10

20

30

40

50

60

70

80

90

0 1 2 3 4 5 6

Number of Planters

Perc

en

t R

un

off

Rossman (2009)

36

Loss of Stored Water Over Time

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0 10 20 30 40 50

Time (hrs)

Losses (in/hr) Storage Depth (ft)

Rossman (2009)

Runoff With No Planters

Elapsed Time (days)

400350300250200150100500

Ru

no

ff (

CF

S)

0.8

0.6

0.4

0.2

0.0

Runoff With Five Planters

Elapsed Time (days)

400350300250200150100500

Ru

no

ff (

CF

S)

0.8

0.6

0.4

0.2

0.0

Long Term Performance

Rossman (2009)

Olds College Demonstration Project

Olds College: lot-level analysis

Olds College: subcatchments

Olds College : roof to cistern

Olds College: roof to landscaping

Olds College : absorbent landscaping

Olds College: bio-retention area

Olds College : parking lot 2

Olds College: oil & grit separator

Olds College: parking lot 2

Olds College: permeable pavement

Olds College: wet pond

Olds College: Irrigation

Continuous simulation of re-use

Irrigation

If the rainfall in the preceding two days is more than 10 mm, irrigation is delayed.

Irrigation

• Rule 1IF SIMULATION MONTH = 5AND SIMULATION DAY = 6AND NODE SU_RG DEPTH = 0AND NODE SU DEPTH > 2THEN PUMP P1 SETTING = 1

• Rule 2IF SIMULATION MONTH = 6AND SIMULATION DAY = 3AND NODE SU_RG DEPTH = 0AND NODE SU DEPTH > 2THEN PUMP P1 SETTING = 1

• Rule 3IF SIMULATION MONTH = 6AND SIMULATION DAY = 6AND NODE SU_RG DEPTH = 0AND NODE SU DEPTH > 2THEN PUMP P1 SETTING = 1.5ELSE PUMP P1 STATUS = OFF

Single event LID analysis: detention pond sizing

Design storm analysis: pond sizing no LIDs

Design storm analysis: pond sizing with LIDs

PCSWMM/SWMM5 LID modeling

• Physically-based processes

• Flexible components

• SWMM Version 5.0.022

• Simplifies the modeling of:– Lot level implementations

– Watershed scale or city master planning

– Single event

– Continuous

– Performance degradation