A7 — Reference Tables

What you'll do

Look up a parameter value before you type it into an editor: a hydraulic conductivity for a soil texture, a curve number for a land use, a Manning's n for a channel lining, a culvert code for a conduit, a standard pipe size for a cross-section.

These are starting values drawn from the published literature. They are a place to begin a calibration, never a substitute for one.

Where to find it

Each table feeds a specific editor:

Table	Typed into
Units of Measurement	everywhere — set by [OPTIONS] FLOW_UNITS; see 18 — Simulation Options
Soil Characteristics	the Green-Ampt page of the Infiltration editor, 13 — Hydrology: Rain Gages, Subcatchments, LID, Snow, Groundwater and RDII
NRCS Hydrologic Soil Group Definitions	choosing a curve-number row below
SCS Curve Numbers	the Curve Number page of the Infiltration editor, 13 — Hydrology: Rain Gages, Subcatchments, LID, Snow, Groundwater and RDII
Depression Storage	subcatchment D-Store Imperv and D-Store Perv, 13 — Hydrology: Rain Gages, Subcatchments, LID, Snow, Groundwater and RDII
Manning's n — Overland Flow	subcatchment N-Imperv and N-Perv, 13 — Hydrology: Rain Gages, Subcatchments, LID, Snow, Groundwater and RDII
Manning's n — Closed Conduits	conduit Roughness, 14 — Hydraulics: Nodes, Links, Cross-Sections, Streets, Inlets and Controls
Manning's n — Open Channels	conduit Roughness and transect roughness, 14 — Hydraulics: Nodes, Links, Cross-Sections, Streets, Inlets and Controls
Water Quality Characteristics of Urban Runoff	land-use build-up and wash-off, 16 — Water Quality, Reaction Systems, Water Age and Heat
Culvert Code Numbers	conduit Culvert Code, 14 — Hydraulics: Nodes, Links, Cross-Sections, Streets, Inlets and Controls
Culvert Entrance Loss Coefficients	conduit Entry Loss Coeff., 14 — Hydraulics: Nodes, Links, Cross-Sections, Streets, Inlets and Controls
Standard Elliptical Pipe Sizes	the Cross-Section editor, 14 — Hydraulics: Nodes, Links, Cross-Sections, Streets, Inlets and Controls
Standard Arch Pipe Sizes	the Cross-Section editor, 14 — Hydraulics: Nodes, Links, Cross-Sections, Streets, Inlets and Controls

Step-by-step

Units of Measurement

The unit system follows [OPTIONS] FLOW_UNITS. Choosing a US flow unit (CFS, GPM, MGD) puts every quantity in the US customary column; choosing an SI flow unit (CMS, LPS, MLD) puts them in the SI column. Property rows in the Properties panel and the Attribute Table carry the active unit as a suffix, so the label you see reflects this table rather than needing to be looked up.

Parameter	US customary	SI metric
Area (subcatchment)	acres	hectares
Area (storage unit)	square feet	square metres
Area (ponding)	square feet	square metres
Capillary suction	inches	millimetres
Concentration	mg/L · µg/L · #/L	mg/L · µg/L · #/L
Decay constant (infiltration)	1/hours	1/hours
Decay constant (pollutants)	1/days	1/days
Depression storage	inches	millimetres
Depth	feet	metres
Diameter	feet	metres
Discharge coefficient — orifice	dimensionless	dimensionless
Discharge coefficient — weir	CFS/footⁿ	CMS/metreⁿ
Elevation	feet	metres
Evaporation	inches/day	millimetres/day
Flow	CFS · GPM · MGD	CMS · LPS · MLD
Head	feet	metres
Hydraulic conductivity	inches/hour	millimetres/hour
Infiltration rate	inches/hour	millimetres/hour
Length	feet	metres
Manning's coefficient (n)	seconds/metre^(1/3)	seconds/metre^(1/3)
Pollutant buildup	mass/length · mass/acre	mass/length · mass/hectare
Rainfall intensity	inches/hour	millimetres/hour
Rainfall volume	inches	millimetres
Slope (subcatchments)	percent	percent
Slope (cross-section)	rise/run	rise/run
Street cleaning interval	days	days
Volume	cubic feet	cubic metres
Width	feet	metres

Flow units: CFS = cubic feet/second · GPM = gallons/minute · MGD = million gallons/day · CMS = cubic metres/second · LPS = litres/second · MLD = million litres/day.

Soil Characteristics

Green-Ampt parameters by soil texture class.

Soil texture class	K (in/hr)	ψ (in)	φ (fraction)	FC (fraction)	WP (fraction)
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).

These columns map onto the Green-Ampt page of the Infiltration editor: K is Conductivity, ψ is Suction Head, and φ − FC gives the Initial Deficit for a soil drained to field capacity. FC and WP are also the aquifer's Field Capacity and Wilting Point in 13 — Hydrology: Rain Gages, Subcatchments, LID, Snow, Groundwater and RDII.

A useful relation derived from this table is ψ = 3.23 · K⁻⁰·³²⁸ (R² = 0.9), with K in in/hr and ψ in inches.

Source: Rawls, W. J. et al. (1983). Journal of Hydraulic Engineering, 109:1316.

NRCS Hydrologic Soil Group Definitions

Group	Meaning	Saturated hydraulic conductivity (in/hr)
A	Low runoff potential. Water is transmitted freely through the soil. Typically less than 10 % clay and more than 90 % sand or gravel; gravel or sand textures.	> 1.42
B	Moderately low runoff potential. Water transmission is unimpeded. Typically 10–20 % clay and 50–90 % sand; loamy sand or sandy loam textures.	0.57 – 1.42
C	Moderately high runoff potential. Water transmission is somewhat restricted. Typically 20–40 % clay and less than 50 % sand; loam, silt loam, sandy clay loam, clay loam and silty clay loam textures.	0.06 – 0.57
D	High runoff potential. Water movement is restricted or very restricted. Typically more than 40 % clay and less than 50 % sand; clayey textures.	< 0.06

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

SCS Curve Numbers

Runoff curve numbers for antecedent moisture condition II.

Land use description	A	B	C	D
Cultivated land — without conservation treatment	72	81	88	91
Cultivated land — with conservation treatment	62	71	78	81
Pasture or range land — poor condition	68	79	86	89
Pasture or range land — good condition	39	61	74	80
Meadow — good condition	30	58	71	78
Wood or forest land — thin stand; poor cover; no mulch	45	66	77	83
Wood or forest land — good cover¹	25	55	70	77
Open spaces; lawns; parks; golf courses; cemeteries — good condition (grass on 75 % or more)	39	61	74	80
Open spaces; lawns; parks; golf courses; cemeteries — fair condition (grass on 50–75 %)	49	69	79	84
Commercial and business areas (85 % impervious)	89	92	94	95
Industrial districts (72 % impervious)	81	88	91	93
Residential² — 1/8 ac or less (65 % impervious)	77	85	90	92
Residential² — 1/4 ac (38 % impervious)	61	75	83	87
Residential² — 1/3 ac (30 % impervious)	57	72	81	86
Residential² — 1/2 ac (25 % impervious)	54	70	80	85
Residential² — 1 ac (20 % impervious)	51	68	79	84
Paved parking lots; roofs; driveways³	98	98	98	98
Streets and roads — paved with curbs and storm sewers³	98	98	98	98
Streets and roads — gravel	76	85	89	91
Streets and roads — dirt	72	82	87	89

¹ Good cover is protected from grazing; litter and brush cover the soil. ² Assumes 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. The remaining pervious area is treated as good pasture. ³ In some warmer climates a curve number of 95 may be used.

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

Depression Storage

Surface type	Depression storage (inches)
Impervious surfaces	0.05 – 0.10
Lawns	0.10 – 0.20
Pasture	0.20
Forest litter	0.30

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

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
Cultivated soils — residue cover > 20 %	0.17
Range (natural)	0.13
Grass — short; prairie	0.15
Grass — dense	0.24
Grass — Bermuda	0.41
Woods — light underbrush	0.40
Woods — dense underbrush	0.80

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

Manning's n — Closed Conduits

Conduit material	n
Asbestos-cement pipe	0.011 – 0.015
Brick	0.013 – 0.017
Cast iron pipe — cement-lined and seal-coated	0.011 – 0.015
Concrete (monolithic) — smooth forms	0.012 – 0.014
Concrete (monolithic) — rough forms	0.015 – 0.017
Concrete pipe	0.011 – 0.015
Corrugated-metal pipe — plain	0.022 – 0.026
Corrugated-metal pipe — paved invert	0.018 – 0.022
Corrugated-metal pipe — spun asphalt lined	0.011 – 0.015
Plastic pipe (smooth)	0.011 – 0.015
Vitrified clay — pipes	0.011 – 0.015
Vitrified clay — liner plates	0.013 – 0.017

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

Manning's n — Open Channels

Channel type	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.

Water Quality Characteristics of Urban Runoff

Constituent	Event mean concentration
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 (µg/L)	43 – 118
Total Pb (µg/L)	182 – 443
Total Zn (µg/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.

Culvert Code Numbers

A conduit becomes a culvert when its Culvert Code is set. The code selects an FHWA HDS-5 inlet-control nomograph; leave it blank for an ordinary conduit. The Properties panel offers these as a grouped list, so you normally pick a description rather than type a number.

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

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

Culvert Entrance Loss Coefficients

Type of structure and design of entrance	Coefficient
Pipe; concrete
Projecting from fill; socket end (groove-end)	0.2
Projecting from fill; square cut end	0.5
Headwall or headwall and wingwalls — socket end of pipe (groove-end)	0.2
Headwall or headwall and wingwalls — square-edge	0.5
Headwall or headwall and wingwalls — rounded (radius = D/12)	0.2
Headwall or headwall and wingwalls — mitered to conform to fill slope	0.7
Headwall or headwall and wingwalls — end section conforming to fill slope	0.5
Headwall or headwall and wingwalls — beveled edges; 33.7° or 45° bevels	0.2
Headwall or headwall and wingwalls — side- or slope-tapered inlet	0.2
Pipe or pipe-arch; corrugated metal
Projecting from fill (no headwall)	0.9
Headwall or headwall and wingwalls; square-edge	0.5
Mitered to conform to fill slope; paved or unpaved slope	0.7
End section conforming to fill slope	0.5
Beveled edges; 33.7° or 45° bevels	0.2
Side- or slope-tapered inlet	0.2
Box; reinforced concrete
Headwall parallel to embankment (no wingwalls) — square-edged on 3 edges	0.5
Headwall parallel to embankment (no wingwalls) — rounded on 3 edges to radius of D/12 or B/12; or beveled edges	0.2
Wingwalls at 30° to 75° to barrel — square-edged at crown	0.4
Wingwalls at 30° to 75° to barrel — crown edge rounded to radius of D/12; or beveled top edge	0.2
Wingwalls at 10° to 25° to barrel — square-edged at crown	0.5
Wingwalls parallel (extension of sides) — square-edged at crown	0.7
Side- or slope-tapered inlet	0.2

End sections conforming to fill slope, in metal or concrete, are the sections commonly available from manufacturers. From limited hydraulic tests they are equivalent in operation to a headwall in both inlet and outlet control. Some end sections incorporating a closed taper have superior hydraulic performance; design those using the information given for the beveled inlet.

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

Standard Elliptical Pipe Sizes

Set a cross-section to HORIZ_ELLIPSE or VERT_ELLIPSE and give it a size code instead of explicit dimensions.

The minor axis is the maximum width of a vertical ellipse and the full depth of a horizontal ellipse; the major axis is the maximum width of a horizontal ellipse and the full depth of a vertical ellipse.

Code	Minor axis (in)	Major axis (in)	Minor axis (mm)	Major axis (mm)
1	14	23	356	584
2	19	30	483	762
3	22	34	559	864
4	24	38	610	965
5	27	42	686	1067
6	29	45	737	1143
7	32	49	813	1245
8	34	53	864	1346
9	38	60	965	1524
10	43	68	1092	1727
11	48	76	1219	1930
12	53	83	1346	2108
13	58	91	1473	2311
14	63	98	1600	2489
15	68	106	1727	2692
16	72	113	1829	2870
17	77	121	1956	3073
18	82	128	2083	3251
19	87	136	2210	3454
20	92	143	2337	3632
21	97	151	2464	3835
22	106	166	2692	4216
23	116	180	2946	4572

Source: Concrete Pipe Design Manual, American Concrete Pipe Association, 2011.

Standard Arch Pipe Sizes

Set a cross-section to ARCH and give it a size code. The 102 codes run consecutively across the five families below — a code is unique across the whole set, not per family.

Concrete arch pipes

Code	Rise (in)	Span (in)	Rise (mm)	Span (mm)
1	11	18	279	457
2	13.5	22	343	559
3	15.5	26	394	660
4	18	28.5	457	724
5	22.5	36.25	572	921
6	26.625	43.75	676	1111
7	31.3125	51.125	795	1299
8	36	58.5	914	1486
9	40	65	1016	1651
10	45	73	1143	1854
11	54	88	1372	2235
12	62	102	1575	2591
13	72	115	1829	2921
14	77.5	122	1969	3099
15	87.125	138	2213	3505
16	96.875	154	2461	3912
17	106.5	168.75	2705	4286

Corrugated steel; 2⅔ × ½ in corrugation

Code	Rise (in)	Span (in)	Rise (mm)	Span (mm)
18	13	17	330	432
19	15	21	381	533
20	18	24	457	610
21	20	28	508	711
22	24	35	610	889
23	29	42	737	1067
24	33	49	838	1245
25	38	57	965	1448
26	43	64	1092	1626
27	47	71	1194	1803
28	52	77	1321	1956
29	57	83	1448	2108

Corrugated steel; 3 × 1 in corrugation

Code	Rise (in)	Span (in)	Rise (mm)	Span (mm)
30	31	40	787	1016
31	36	46	914	1168
32	41	53	1041	1346
33	46	60	1168	1524
34	51	66	1295	1676
35	55	73	1397	1854
36	59	81	1499	2057
37	63	87	1600	2210
38	67	95	1702	2413
39	71	103	1803	2616
40	75	112	1905	2845
41	79	117	2007	2972
42	83	128	2108	3251
43	87	137	2210	3480
44	91	142	2311	3607

Structural plate; 18 in corner radius

Code	Rise (in)	Span (in)	Rise (mm)	Span (mm)
45	55	73	1397	1854
46	57	76	1448	1930
47	59	81	1499	2057
48	61	84	1549	2134
49	63	87	1600	2210
50	65	92	1651	2337
51	67	95	1702	2413
52	69	98	1753	2489
53	71	103	1803	2616
54	73	106	1854	2692
55	75	112	1905	2845
56	77	114	1956	2896
57	79	117	2007	2972
58	81	123	2057	3124
59	83	128	2108	3251
60	85	131	2159	3327
61	87	137	2210	3480
62	89	139	2261	3531
63	91	142	2311	3607
64	93	148	2362	3759
65	95	150	2413	3810
66	97	152	2464	3861
67	100	154	2540	3912
68	101	161	2565	4089
69	103	167	2616	4242
70	105	169	2667	4293
71	107	171	2718	4343
72	109	178	2769	4521
73	111	184	2819	4674
74	113	186	2870	4724
75	115	188	2921	4775
76	118	190	2997	4826
77	119	197	3023	5004
78	121	199	3073	5055

Structural plate; 31 in corner radius

Code	Rise (in)	Span (in)	Rise (mm)	Span (mm)
79	112	159	2845	4039
80	114	162	2896	4115
81	116	168	2946	4267
82	118	170	2997	4318
83	120	173	3048	4394
84	122	179	3099	4547
85	124	184	3150	4674
86	126	187	3200	4750
87	128	190	3251	4826
88	130	195	3302	4953
89	132	198	3353	5029
90	134	204	3404	5182
91	136	206	3454	5232
92	138	209	3505	5309
93	140	215	3556	5461
94	142	217	3607	5512
95	144	223	3658	5664
96	146	225	3708	5715
97	148	231	3759	5867
98	150	234	3810	5944
99	152	236	3861	5994
100	154	239	3912	6071
101	156	245	3962	6223
102	158	247	4013	6274

Source: Modern Sewer Design, 4th ed., American Iron and Steel Institute, Washington, DC, 1999.

Tips and gotchas

• The values are US customary as published. The unit suffix on a property row follows [OPTIONS] FLOW_UNITS, so in an SI project you must convert before typing. SWMMVis does not convert a value you paste from this appendix.
• Curve numbers here are for antecedent moisture condition II. The engine adjusts for AMC I and III internally; do not pre-adjust the number you enter.
• A culvert code overrides the ordinary conduit head-loss path. Setting it on a conduit that is not actually a culvert will change the answer. Clear the field rather than setting it to 0.
• Elliptical and arch size codes are alternatives to explicit dimensions, not additions to them. Supplying a code makes the geometry columns read-only.
• Arch codes are global, not per family. Code 45 is a structural-plate section, not the forty-fifth concrete arch.
• These tables are pinned to their sources where the source is code rather than literature: scripts/manual_docs_audit.py culvert-codes checks the culvert table against src/ui/properties/culvertcodes.cpp, and pipe-sizes checks the elliptical and arch counts against the engine's xsect_tables.hpp.

Related

• 13 — Hydrology: Rain Gages, Subcatchments, LID, Snow, Groundwater and RDII — infiltration, subcatchment and aquifer parameters
• 14 — Hydraulics: Nodes, Links, Cross-Sections, Streets, Inlets and Controls — conduits, cross-sections, transects and culverts
• 16 — Water Quality, Reaction Systems, Water Age and Heat — pollutants, land uses and wash-off
• A9 — Object Property Index — which chapter documents which object property
• 18 — Simulation Options — where FLOW_UNITS is set