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, 2^nd 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