#INFOSWMM

APPENDIX A – Useful Tables in InfoSWMM and InfoSWMM SA from SWMM5

APPENDIX A – Useful Tables in InfoSWMM and InfoSWMM SA from SWMM5

A.1 Units of Measurement

Parameter US CUSTOMARY SI/METRIC
Area (Subcatchment) acres Hectares
Area (Storage Unit) square feet square meters
Area (Ponding) square feet square meters
Capillary Suction inches millimeters
Concentration mg/L

ug/L

Count/L

mg/L

ug/L

Count/L

Decay Constant (Infiltration) 1/hours 1/hours
Decay Constant (Pollutants) 1/days 1/days
Depression Storage inches millimeters
Depth feet meters
Diameter feet meters
Discharge Coefficient

Orifice

Weir

dimensionless

CFS/footn

dimensionless

CMS/metern

Elevation feet meters
Evaporation inches/day millimeters/day
Flow CFS

GPM

MGD

CMS

LPS

MLD

Head feet meters
Hydraulic Conductivity inches/hour millimeters/hour
Infiltration Rate inches/hour millimeters/hour
Length feet meters
Manning’s n dimensionless dimensionless
Pollutant Buildup mass/length

mass/acre

mass/length

mass/hectare

Rainfall Intensity inches/hour millimeters/hour
Rainfall Volume inches millimeters
Slope (Subcatchments) percent percent
Slope (Cross Section) rise/run rise/run
Street Cleaning Interval days days
Volume cubic feet cubic meters
Width feet meters

A.2 Soil Characteristics

Soil Texture Class K Y f FC WP
Sand 4.74 1.93 0.437 0.062 0.024
Loamy Sand 1.18 2.40 0.437 0.105 0.047
Sandy Loam 0.43 4.33 0.453 0.190 0.085
Loam 0.13 3.50 0.463 0.232 0.116
Silt Loam 0.26 6.69 0.501 0.284 0.135
Sandy Clay Loam 0.06 8.66 0.398 0.244 0.136
Clay Loam 0.04 8.27 0.464 0.310 0.187
Silty Clay Loam 0.04 10.63 0.471 0.342 0.210
Sandy Clay 0.02 9.45 0.430 0.321 0.221
Silty Clay 0.02 11.42 0.479 0.371 0.251
Clay 0.01 12.60 0.475 0.378 0.265

K = saturated hydraulic conductivity, in/hr

Y = suction head, in.

f = porosity, fraction

FC = field capacity, fraction

WP = wilting point, fraction

Source: Rawls, W.J. et al., (1983). J. Hyd. Engr., 109:1316.

Rossman, L.A. (2005). Storm Water Management Model User’s Manual. Version 5.0, Environmental Protection Agency, National Risk Management Research Laboratory, Cincinnati, OH.

A.3 NRCS Hydrologic Soil Group Definitions

Group Meaning Saturated Hydraulic

Conductivity

(in/hr)

A Low runoff potential. Soils having high infiltration rates even when thoroughly wetted and consisting chiefly of deep, well to excessively drained sands or gravels. ³ 0.45
B Soils having moderate infiltration rates when thoroughly wetted and consisting chiefly of moderately deep-to-deep, moderately well to well-drained soils with moderately fine to moderately coarse textures. E.g., shallow loess, sandy loam. 0.30 – 0.15
C Soils having slow infiltration rates when thoroughly wetted and consisting chiefly of soils with a layer that impedes downward movement of water, or soils with moderately fine to fine textures. E.g., clay loams, shallow sandy loam. 0.15 – 0.05
D High runoff potential. Soils having very slow infiltration rates when thoroughly wetted and consisting chiefly of clay soils with a high swelling potential, soils with a permanent high water table, soils with a clay-pan or clay layer at or near the surface, and shallow soils over nearly impervious material. 0.05 – 0.00

Source: Rossman, L.A. (2005). Storm Water Management Model User’s Manual. Version 5.0, Environmental Protection Agency, National Risk Management Research Laboratory, Cincinnati, OH.

A.4 SCS Curve Numbers1

Hydrologic Soil Group
Land Use Description A B C D
Cultivated land

Without conservation treatment

With conservation treatment

72

62

81

71

88

78

91

81

Pasture or range land

Poor condition

Good condition

68

39

79

61

86

74

89

80

Meadow

Good condition

30 58 71 78
Wood or forest land

Thin stand, poor cover, no mulch

Good cover2

45

25

66

55

77

70

83

77

Open spaces, lawns, parks, golf courses, cemeteries, etc.

Good condition: grass cover on

75% or more of the area

Fair condition: grass cover on

50-75% of the area

39

49

61

69

74

79

80

84

Commercial and business areas (85% impervious) 89 92 94 95
Industrial districts (72% impervious) 81 88 91 93
Residential3

Average lot size (% Impervious4)

1/8 ac or less (65)

1/4 ac (38)

1/3 ac (30)

1/2 ac (25)

1 ac (20)

77

61

57

54

51

85

75

72

70

68

90

83

81

80

79

92

87

86

85

84

Paved parking lots, roofs, driveways, etc.5 98 98 98 98
Streets and roads

Paved with curbs and storm sewers5

Gravel

Dirt

98

76

72

98

85

82

98

89

87

98

91

89

1. Antecedent moisture condition II; Source: SCS Urban Hydrology for Small Watersheds, 2nd Ed., (TR-55), June 1986.

2. Good cover is protected from grazing and litter and brush cover soil.

3. Curve numbers are computed assuming that the runoff from the house and driveway is directed toward the street with a minimum of roof water directed to lawns where additional infiltration could occur.

4. The remaining pervious areas (lawn) are considered to be in good pasture condition for these curve numbers.

5. In some warmer climates of the country a curve number of 95 may be used.

A.5 Depression Storage

Impervious surfaces 0.05 – 0.10 inches
Lawns 0.10 – 0.20 inches
Pasture 0.20 inches
Forest litter 0.30 inches

Source: Rossman, L.A. (2005). Storm Water Management Model User’s Manual. Version 5.0, Environmental Protection Agency, National Risk Management Research Laboratory, Cincinnati, OH.

ASCE, (1992). Design & Construction of Urban Stormwater Management Systems. New York, NY.

A.6 Manning’s n – Overland Flow

Surface n
Smooth asphalt 0.011
Smooth concrete 0.012
Ordinary concrete lining 0.013
Good wood 0.014
Brick with cement mortar 0.014
Vitrified clay 0.015
Cast iron 0.015
Corrugated metal pipes 0.024
Cement rubble surface 0.024
Fallow soils (no residue) 0.05
Cultivated soils

Residue cover < 20%

Residue cover > 20%

0.06

0.17

Range (natural) 0.13
Grass

Short, prarie

Dense

Bermuda grass

0.15

0.24

0.41

Woods

Light underbrush

Dense underbrush

0.40

0.80

Source: Rossman, L.A. (2005). Storm Water Management Model User’s Manual. Version 5.0, Environmental Protection Agency, National Risk Management Research Laboratory, Cincinnati, OH.

McCuen, R. et al. (1996). Hydrology. FHWA-SA-96-067, Federal Highway Administration, Washington, DC.

A.7 Manning’s n – Closed Conduits

Conduit Material Manning n
Asbestos-cement pipe 0.011 – 0.015
Brick 0.013 – 0.017
Cast iron pipe

– Cement-lined & seal coated

0.011 – 0.015
Concrete (monolithic)

– Smooth forms

– Rough forms

0.012 – 0.014

0.015 – 0.017

Concrete pipe 0.011 – 0.015
Corrugated-metal pipe

(1/2-in. x 2-2/3-in. corrugations)

– Plain

– Paved invert

– Spun asphalt lined

0.022 – 0.026

0.018 – 0.022

0.011 – 0.015

Plastic pipe (smooth) 0.011 – 0.015
Vitrified clay

– Pipes

– Liner plates

0.011 – 0.015

0.013 – 0.017

Source: Rossman, L.A. (2005). Storm Water Management Model User’s Manual. Version 5.0, Environmental Protection Agency, National Risk Management Research Laboratory, Cincinnati, OH.

ASCE (1982). Gravity Sanitary Sewer Design and Construction,. ASCE Manual of Practice No. 60, New York, NY.

A.8 Water Quality Characteristics of Urban Runoff

Constituent Event Mean Concentrations
TSS (mg/L) 180 – 548
BOD (mg/L) 12 – 19
COD (mg/L) 82 – 178
Total P (mg/L) 0.42 – 0.88
Soluble P (mg/L) 0.15 – 0.28
TKN (mg/L) 1.90 – 4.18
NO2/NO3-N (mg/L) 0.86 – 2.2
Total Cu (ug/L) 43 – 118
Total Pb (ug/L) 182 – 443
Total Zn (ug/L) 202 – 633

Source: U.S. Environmental Protection Agency. (1983). Results of the Nationwide Urban Runoff Program (NURP), Vol. 1, NTIS PB 84-185552), Water Planning Division, Washington, DC.

A.9 Manning’s n – Open Channels

Channel Type Manning n
Lined Channels
– Asphalt 0.013 – 0.017
– Brick 0.012 – 0.018
– Concrete 0.011 – 0.020
– Rubble or riprap 0.020 – 0.035
– Vegetal 0.030 – 0.40
Excavated or dredged
– Earth, straight and uniform 0.020 – 0.030
– Earth, winding, fairly uniform 0.025 – 0.040
– Rock 0.030 – 0.045
– Unmaintained 0.050 – 0.140
Natural channels (minor streams, top width at flood stage < 100 ft)
– Fairly regular section 0.030 – 0.070
– Irregular section with pools 0.040 – 0.100

Source: Rossman, L.A. (2005). Storm Water Management Model User’s Manual. Version 5.0, Environmental Protection Agency, National Risk Management Research Laboratory, Cincinnati, OH.

ASCE (1982). Gravity Sanitary Sewer Design and Construction, ASCE Manual of Practice No. 60, New York, NY.

A.10 Culvert Codes

Conduit and Head Treatment Culvert Code
Circular Concrete (HDS-5 Chart 1)
– Square edge with headwall 1
– Groove end with headwall 2
– Groove end projecting 3
Circular Corrugated Metal Pipe (HDS-5 Chart 2)
– Headwall 4
– Mitered to slope 5
– Projecting 6
Circular Pipe, Beveled Ring Entrance (HDS-5 Chart 3)
– 45 deg. Bevels 7
– 33.7 deg. Bevels 8
Rectangular Box; Flared Wingwalls (HDS-5 Chart 8)
– 30-75 deg. wingwall flares 9
– 90 or 15 deg. wingwall flares 10
– 0 deg. wingwall flares (straight sides) 11
Rectangular Box;Flared Wingwalls and Top Edge Bevel (HDS-5 Chart 9)
– 45 deg flare; 0.43D top edge bevel 12
– 18-33.7 deg. flare; 0.083D top edge bevel 13
Rectangular Box, 90-deg Headwall, Chamfered / Beveled Inlet Edges (HDS-5 Chart 10)
– chamfered 3/4-in. 14
– beveled 1/2-in/ft at 45 deg (1:1) 15
– beveled 1-in/ft at 33.7 deg (1:1.5) 16
Rectangular Box, Skewed Headwall, Chamfered / Beveled Inlet Edges (HDS-5 Chart 11)
– 3/4" chamfered edge, 45 deg skewed headwall 17
– 3/4" chamfered edge, 30 deg skewed headwall 18
– 3/4" chamfered edge, 15 deg skewed headwall 19
– 45 deg beveled edge, 10-45 deg skewed headwall 20
Rectangular Box, Non-offset Flared Wingwalls, 3/4" Chamfer at Top of Inlet (HDS-5 Chart 12)
– 45 deg (1:1) wingwall flare 21
– 8.4 deg (3:1) wingwall flare 22
– 18.4 deg (3:1) wingwall flare, 30 deg inlet skew 23
Rectangular Box, Offset Flared Wingwalls, Beveled Edge at Inlet Top (HDS-5 Chart 13)
– 45 deg (1:1) flare, 0.042D top edge bevel 24
– 33.7 deg (1.5:1) flare, 0.083D top edge bevel 25
– 18.4 deg (3:1) flare, 0.083D top edge bevel 26
Corrugated Metal Box (HDS-5 Charts 16, 17, 18 and 19)
– 90 deg headwall 27
– Thick wall projecting 28
– Thin wall projecting 29
Horizontal Ellipse Concrete (HDS-5 Chart 29)
– Square edge with headwall 30
– Grooved end with headwall 31
– Grooved end projecting 32
Vertical Ellipse Concrete (HDS-5 Chart 30)
– Square edge with headwall 33
– Grooved end with headwall 34
– Grooved end projecting 35
Pipe Arch, Corrugated Metal (HDS-5 Chart 34)
– 90 deg headwall 36
– Mitered to slope 37
– Projecting 38
Pipe Arch, 18" Corner Radius, Structural Plate (HDS-5 Chart 35)
– Projecting 39
– No bevels 40
– 33.7 deg bevels 41
Pipe Arch, 31" Corner Radius, Structural Plate (HDS-5 Chart 36)
– Projecting 42
– No bevels 43
– 33.7 deg. bevels 44
Arch, Corrugated Metal (HDS-5 Charts 41, 42 and 43)
– 90 deg headwall 45
– Mitered to slope 46
– Thin wall projecting 47
Circular Culvert (HDS-5 Chart 55)
– Smooth tapered inlet throat (Concrete) 28
– Rough tapered inlet throat (Corrugated Metal) 49
Elliptical Inlet Face (HDS-5 Chart 56)
– Tapered inlet, beveled edges 50
– Tapered inlet, square edges 51
– Tapered inlet, thin edge projecting 52
Rectangular (HDS-5 Chart 57)
– Tapered inlet throat 53
Rectangular Concrete, Face Control (HDS-5 Charts 58 and 59)
– Side tapered, less favorable edges 54
– Side tapered, more favorable edges 55
– Slope tapered, less favorable edges 56
– Slope tapered, more favorable edges 57

Source: Rossman, L.A. (2009). Storm Water Management Model User’s Manual. Version 5.0, Environmental Protection Agency, National Risk Management Research Laboratory, Cincinnati, OH.

Federal Highway Administration (2005). Hydraulic Design of Highway Culverts, Publication No. FHWA-NHI-01-020 (HDS-5).

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