Appendix A - Useful Tables

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 Weir	dimensionless CFS/foot	dimensionless CMS/meter
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/meter^1/3	seconds/meter^1/3
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
*Resolution	feet	Meter
*Seepage	in/hr	mm/hr

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.

A.3 NRCS Hydrologic Soil Group Definitions

Group	Meaning	Saturated HydraulicConductivity(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.	≥ 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

A.4 SCS Curve Numbers

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 90
Meadow Good condition	30	58	71	78
Wood or forest land Thin stand, poor cover, no mulch Good cover	45 25	66 55	70 77	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
Residential Average lot size (% Impervious) 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.	98	98	98	98
Streets and roads Paved with curbs and storm sewers Gravel Dirt	98 76 72	98 85 82	98 89 87	98 91 89

Land Use Description

Hydrologic Soil Group

Cultivated land

Without conservation treatment

With conservation treatment

Pasture or range land

Poor condition

Good condition

Meadow

Good condition

Wood or forest land

Thin stand, poor cover, no mulch

Good cover

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

Commercial and business areas (85% impervious)

Industrial districts (72% impervious)

Residential

Average lot size (% Impervious)

1/8 ac or less (65)

1/4 ac (38)

1/3 ac (30)

1/2 ac (25)

1 ac (20)

Paved parking lots, roofs, driveways, etc.

Streets and roads

Paved with curbs and storm sewers

Gravel

Dirt

A.5 Depression Storage

Surface Type	Depth of 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% Residue cover > 20%	0.06 0.17
Range (natural)	0.13
Grass Short, Prairie Dense Bermuda grass	0.15 0.24 0.41
Woods Light underbrush Dense underbrush	0.40 0.80

Source: 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: 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.

A.10 Culvert Code Numbers

Circular Concrete

1 Square edge with headwall

2 Groove end with headwall

3 Groove end projecting

Circular Corrugated Metal Pipe

4 Headwall

5 Mitered to slope

6 Projecting

Circular Pipe, Beveled Ring Entrance

7 45 deg. bevels

8 33.7 deg. Bevels

Rectangular Box; Flared Wingwalls

9 30-75 deg. wingwall flares

10 90 or 15 deg. wingwall flares

11 0 deg. wingwall flares (straight sides)

Rectangular Box;Flared Wingwalls and Top Edge Bevel:

12 45 deg flare; 0.43D top edge bevel

13 18-33.7 deg. flare; 0.083D top edge bevel

Rectangular Box, 90-deg Headwall, Chamfered / Beveled Inlet Edges

14 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)

Rectangular Box, Skewed Headwall, Chamfered / Beveled Inlet Edges

17 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

Rectangular Box, Non-offset Flared Wingwalls, 3/4" Chamfer at Top of Inlet

21 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

Rectangular Box, Offset Flared Wingwalls, Beveled Edge at Inlet Top

24 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

Corrugated Metal Box

27 90 deg headwall

28 Thick wall projecting

29 Thin wall projecting

Horizontal Ellipse Concrete

30 Square edge with headwall

31 Grooved end with headwall

32 Grooved end projecting

Vertical Ellipse Concrete

33 Square edge with headwall

34 Grooved end with headwall

35 Grooved end projecting

Pipe Arch, 18" Corner Radius, Corrugated Metal

36 90 deg headwall

37 Mitered to slope

38 Projecting

Pipe Arch, 18" Corner Radius, Corrugated Metal

39 Projecting

40 No bevels

41 33.7 deg bevels

Pipe Arch, 31" Corner Radius, Corrugated Metal

42 Projecting

43 No bevels

44 33.7 deg. bevels

Arch, Corrugated Metal

45 90 deg headwall

46 Mitered to slope

47 Thin wall projecting

Circular Culvert

48 Smooth tapered inlet throat

49 Rough tapered inlet throat

Elliptical Inlet Face

50 Tapered inlet, beveled edges

51 Tapered inlet, square edges

52 Tapered inlet, thin edge projecting

Rectangular

53 Tapered inlet throat

Rectangular Concrete

54 Side tapered, less favorable edges

55 Side tapered, more favorable edges

56 Slope tapered, less favorable edges

57 Slope tapered, more favorable edges

A.11 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, sq. cut end	0.5
Headwall or headwall and wing-walls:
Socket end of pipe (groove-end)	0.2
Square-edge	0.5
Rounded (radius = D/12)	0.2
Mitered to conform to fill slope	0.7
*End-Section conforming to fill slope	0.5
Beveled edges, 33.7⁰ or 45⁰ bevels	0.2
Side- or slope-tapered inlet	0.2
Pipe or Pipe-Arch. Corrugated Metal
Projecting from fill (no headwall)	0.9
Headwall or headwall and wing-walls 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, 33.7⁰or 45⁰ 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
Rounded on 3 edges to radius of D/12 or B/12;or Beveled edges on 3 sides	0.2
Wingwalls at 30⁰ to 75⁰ to barrel:
Square-edged at crown	0.4
Crown edge rounded to radius of D/12; or Beveled top edge	0.2
Wingwall at 10⁰to 25⁰ 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

*Note: "End Sections conforming to fill slope," made of either 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 in their design have a superior hydraulic performance. These latter sections can be designed using the information given for the beveled inlet.

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