Default H&H or Hydrology and Hydraulic Values from SWMM5

Default H&H or Hydrology and Hydraulic Values 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 (milligrams/liter)  ug/L (micrograms/liter)  Count/L (counts/liter)
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

 dimensionless

dimensionless
    Weir
 CFS/footn
CMS/metern
Elevation
 feet
meters
Evaporation
 inches/day
millimeters/day
Flow
 CFS (cubic feet / second)  GPM (gallons / minute)
 MGD (million gallons/day)
CMS (cubic meters/second)
LPS (liters/second)
MLD (million liters/day)
Head
 feet
meters
Hydraulic Conductivity
 inches/hour
millimeters/hour
Infiltration Rate
 inches/hour
millimeters/hour
Length
 feet
meters
Manning's n
 seconds/meter1/3
seconds/meter1/3
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
Ψ
φ
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 Ψ =   suction head, in.
φ=   porosity, fraction FC =   field capacity, fraction WP =   wilting point, fraction

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

Note: The following relation between Ψ and K can be derived from this table:
                                         

A.3       NRCS Hydrologic Soil Group Definitions



Group


Meaning
Saturated Hydraulic
Conductivity
(in/hr)

A
Low runoff potential.
Water is transmitted freely through the soil. Group A soils typically have less than 10 percent clay and more than 90 percent sand or gravel and have gravel or sand textures. 

> 1.42

B
Moderately low runoff potential.
Water transmission through the soil is unimpeded. Group B soils typically have between 10 percent and 20 percent clay and 50 percent to 90 percent sand and have loamy sand or sandy loam textures.

0.57 – 1.42

Moderately high runoff potential.

C
Water transmission through the soil is somewhat restricted. Group C soils typically have between 20 percent and 40 percent clay and less than 50 percent sand and have loam, silt loam, sandy clay loam, clay loam, and silty clay loam textures.
0.06 - 0.57

High runoff potential.

D
Water movement through the soil is restricted or very restricted. Group D soils typically have greater than 40 percent clay, less than 50 percent sand, and have clayey textures.
< 0.06

Source: Hydrology National Engineering Handbook, Chapter 7, Natural Resources Conservation Service, U.S. Department of Agriculture, January 2009.

A.4       SCS Curve Numbers1

Land Use Description  

Hydrologic Soil Group
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



39



61



74



80
   Fair condition: grass cover on    50-75% of the area

49

69

79

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

Source: SCS Urban Hydrology for Small Watersheds, 2nd Ed., (TR-55), June 1986.

Footnotes:
1.  Antecedent moisture condition II.
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: 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%

0.06
   Residue cover > 20%
0.17
Range (natural) 
0.13
Grass
   Short, prairie    Dense

0.15
0.24
   Bermuda grass
0.41
Woods
   Light underbrush
   Dense underbrush

0.40
0.80

Source: McCuen, R. et al. (1996), Hydrology, FHWA-SA96-067, 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

0.012 - 0.014
- Rough forms
0.015 - 0.017
Concrete pipe
0.011 - 0.015
Corrugated-metal pipe
(1/2-in. x 2-2/3-in. corrugations) - Plain


0.022 - 0.026
- Paved invert
0.018 - 0.022
- Spun asphalt lined
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: ASCE (1982). Gravity Sanitary Sewer Design and Construction, ASCE Manual of Practice No. 60, New York, NY.

A.8          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: ASCE (1982). Gravity Sanitary Sewer Design and Construction, ASCE Manual of Practice No. 60, New York, NY.


A.9          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.

Source:   http://nepis.epa.gov/Exe/ZyPDF



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