APPENDIx D
SIZING STORM WATER DRAINAGE SYSTEMS
drainage system. Maximum allowable roof areas with
various rainfall rates are listed in Table 1101.7 and Table
1101.11, along with the required pipe sizes. Using this
method, it shall be permitted to interpolate between two
listed rainfall rate columns (inches per hour). To determine
the allowable roof area for a listed pipe size at a listed
slope, divide the allowable square feet (m2) of roof for a 1
inch per hour (in/hr) (25.4 mm/hr) rainfall rate by the listed
rainfall rate for the local area. For example, the allowable
roof area for a 6 inch (150 mm) drain at 1⁄8 inch per foot
(10.4 mm/m) slope with a rainfall rate of 3.2 in/hr (81
mm/hr) is 21 400/3.2 = 6688 square feet (621.3 m2).
D 1.0 Roof Drainage.
D 1.1 General. The rainfall rates in Table D 1.01 shall be
permitted to be used for design unless higher values are
established locally.
IN
T
D 2.0 Sizing by flow Rate.
D 2.1 General. Storm drainage systems shall be permitted
to be sized by storm water flow rates, using the gpm/square
foot of rainfall listed in Table D 1.01 for the local area.
Multiplying the listed gallons per minute (gpm)/per square
foot (L/s/m2) by the roof area being drained by each inlet (in
square feet) produces the gallons per minute (gpm) of
required flow for sizing each drain inlet. The flow rates
(gpm) shall be permitted to be added to determine the flows
in each of the drainage systems. Required pipe sizes for
various flow rates (gpm) are listed in Table 1101.7 and
Table 1101.11.
D 4.0 Capacity of Rectangular Scuppers.
D 4.1 General. Table D 4.01 lists the discharge capacity
of rectangular roof scuppers of various widths with various
heads of water. The maximum allowable level of water on
the roof shall be obtained from the structural engineer,
based on the design of the roof.
E
-P
R
D 3.0 Sizing by Roof Area.
D 3.1 General. Storm drainage systems shall be permitted
to be sized using the roof area served by each of the
TAblE D 1.01
MAxIMUM RATES Of RAINfAll fOR VARIOUS CITIES*
STATES AND CITIES
STORM DRAINAGE 60-MINUTE DURATION, 100-YEAR RETURN
(inches per hour)
(gallons per minute per square foot)
–
3.7
3.3
4.5
3.8
–
0.038
0.034
0.047
0.039
ALASKA
Aleutian Islands
Anchorage
Bethel
Fairbanks
Juneau
–
1.0
0.6
0.8
1.0
0.6
–
0.010
0.006
0.008
0.010
0.006
ARIZONA
Flagstaff
Phoenix
Tucson
–
2.3
2.2
3.0
–
0.024
0.023
0.031
ARKANSAS
Eudora
Ft. Smith
Jonesboro
Little Rock
–
3.8
3.9
3.5
3.7
–
0.039
0.041
0.036
0.038
P
R
ALABAMA
Birmingham
Huntsville
Mobile
Montgomery
UNIfORM PlUMbING CODE
291
APPENDIx D
TAblE D 1.01
MAxIMUM RATES Of RAINfAll fOR VARIOUS CITIES* (continued)
STORM DRAINAGE 60-MINUTE DURATION, 100-YEAR RETURN
STATES AND CITIES
(gallons per minute per square foot)
CALIFORNIA
Eureka
Lake Tahoe
Los Angeles
Lucerne Valley
Needles
Palmdale
Redding
San Diego
San Francisco
San Luis Obispo
–
1.5
1.3
2.0
2.5
1.5
3.0
1.5
1.5
1.5
1.5
–
0.016
0.014
0.021
0.026
0.016
0.031
0.016
0.016
0.016
0.016
COLORADO
Craig
Denver
Durango
Stratton
–
1.5
2.2
1.8
3.0
–
0.016
0.023
0.019
0.031
CONNECTICUT
Hartford
New Haven
–
2.8
3.0
GEORGIA
Atlanta
Brunswick
Macon
Savannah
Thomasville
R
P
R
DISTRICT OF COLUMBIA
Washington
–
0.029
0.031
–
3.5
3.6
–
0.036
0.037
–
4.0
–
0.042
–
4.0
4.0
4.3
4.0
4.5
5.0
4.2
4.1
–
0.042
0.042
0.045
0.042
0.047
0.052
0.044
0.043
–
3.5
4.0
3.7
4.0
4.0
–
0.036
0.042
0.038
0.042
0.042
E
-P
DELAWARE
Dover
Rehobeth Beach
FLORIDA
Daytona Beach
Ft. Myers
Jacksonville
Melbourne
Miami
Palm Beach
Tampa
Tallahassee
IN
T
(inches per hour)
HAWAII
–
–
1
Rainfall rates in the Hawaiian Islands vary from 1 ⁄2 inches per hour to 8 inches per hour, depending on location and elevation. Consult local data.
IDAHO
Boise
Idaho Falls
Lewiston
Twin Falls
292
–
1.0
1.2
1.0
1.1
–
0.010
0.012
0.010
0.011
UNIfORM PlUMbING CODE
APPENDIx D
TAblE D 1.01
MAxIMUM RATES Of RAINfAll fOR VARIOUS CITIES* (continued)
STATES AND CITIES
STORM DRAINAGE 60-MINUTE DURATION, 100-YEAR RETURN
(gallons per minute per square foot)
ILLINOIS
Chicago
Harrisburg
Peoria
Springfield
–
2.7
3.1
2.9
3.0
–
0.028
0.032
0.030
0.031
INDIANA
Evansville
Indianapolis
Richmond
South Bend
–
3.0
2.8
2.7
2.7
–
0.031
0.029
0.028
0.028
IOWA
Council Bluffs
Davenport
Des Moines
Sioux City
–
3.7
3.0
3.4
3.6
–
0.038
0.031
0.035
0.037
–
3.5
3.8
3.8
3.9
–
0.036
0.039
0.039
0.041
–
2.9
2.9
2.8
3.0
–
0.030
0.030
0.029
0.031
–
3.8
4.5
4.0
–
0.039
0.047
0.042
–
2.2
2.4
2.0
–
0.023
0.025
0.021
MARYLAND
Baltimore
Frostburg
Ocean City
–
3.6
2.9
3.7
–
0.037
0.030
0.038
MASSACHUSETTS
Adams
Boston
Springfield
–
2.6
2.7
2.7
–
0.027
0.028
0.028
MICHIGAN
Detroit
Grand Rapids
Kalamazoo
–
2.5
2.6
2.7
–
0.026
0.027
0.028
IN
T
(inches per hour)
KENTUCKY
Bowling Green
Lexington
Louisville
Paducah
MAINE
Bangor
Kittery
Millinocket
P
R
LOUISIANA
Monroe
New Orleans
Shreveport
E
-P
R
KANSAS
Goodland
Salina
Topeka
Wichita
UNIfORM PlUMbING CODE
293
APPENDIx D
TAblE D 1.01
MAxIMUM RATES Of RAINfAll fOR VARIOUS CITIES* (continued)
STORM DRAINAGE 60-MINUTE DURATION, 100-YEAR RETURN
STATES AND CITIES
(gallons per minute per square foot)
Sheboygan
Traverse City
2.1
2.2
0.022
0.023
MINNESOTA
Duluth
Grand Forks
Minneapolis
Worthington
–
2.6
2.5
3.0
3.4
–
0.027
0.026
0.031
0.035
MISSISSIPPI
Biloxi
Columbus
Jackson
–
4.5
3.5
3.8
–
0.047
0.036
0.039
MISSOURI
Independence
Jefferson City
St. Louis
Springfield
–
3.7
3.4
3.2
3.7
MONTANA
Billings
Glendive
Great Falls
Missoula
–
1.8
2.5
1.8
1.3
R
E
-P
–
0.038
0.035
0.033
0.038
–
0.019
0.026
0.019
0.014
–
3.6
3.5
2.8
–
0.037
0.036
0.029
–
1.5
1.2
1.0
–
0.016
0.012
0.010
NEW HAMPSHIRE
Berlin
Manchester
–
2.2
2.5
–
0.023
0.026
NEW JERSEY
Atlantic City
Paterson
Trenton
–
3.4
3.0
3.2
–
0.035
0.031
0.033
NEW MEXICO
Albuquerque
Carlsbad
Gallup
–
2.0
2.6
2.1
–
0.021
0.027
0.022
NEW YORK
Binghamton
Buffalo
–
2.4
2.3
–
0.025
0.024
NEVADA
Las Vegas
Reno
Winnemucca
294
P
R
NEBRASKA
Omaha
North Platte
Scotts Bluff
IN
T
(inches per hour)
UNIfORM PlUMbING CODE
APPENDIx D
TAblE D 1.01
MAxIMUM RATES Of RAINfAll fOR VARIOUS CITIES* (continued)
STATES AND CITIES
STORM DRAINAGE 60-MINUTE DURATION, 100-YEAR RETURN
(gallons per minute per square foot)
New York City
Schenectady
Syracuse
3.1
2.5
2.4
0.032
0.026
0.025
NORTH CAROLINA
Asheville
Charlotte
Raleigh
Wilmington
–
3.2
3.4
4.0
4.4
–
0.033
0.035
0.042
0.046
NORTH DAKOTA
Bismarck
Fargo
Minot
–
2.7
2.9
2.6
–
0.028
0.030
0.027
–
2.8
2.4
2.7
2.6
2.4
–
0.029
0.025
0.028
0.027
0.025
–
3.4
4.0
4.1
–
0.035
0.042
0.043
–
1.3
1.0
1.3
–
0.014
0.010
0.014
PENNSYLVANIA
Erie
Harrisburg
Philadelphia
Pittsburgh
Scranton
–
2.4
2.9
3.2
2.5
2.8
–
0.025
0.030
0.033
0.026
0.029
RHODE ISLAND
Newport
Providence
–
3.0
2.9
–
0.031
0.030
SOUTH CAROLINA
Charleston
Columbia
Greenville
–
4.1
3.5
3.3
–
0.043
0.036
0.034
SOUTH DAKOTA
Lemmon
Rapid City
Sioux Falls
–
2.7
2.7
3.4
–
0.028
0.028
0.035
IN
T
(inches per hour)
E
-P
OREGON
Medford
Ontario
Portland
P
R
OKLAHOMA
Boise City
Muskogee
Oklahoma City
R
OHIO
Cincinnati
Cleveland
Columbus
Toledo
Youngstown
UNIfORM PlUMbING CODE
295
APPENDIx D
TAblE D 1.01
MAxIMUM RATES Of RAINfAll fOR VARIOUS CITIES* (continued)
STORM DRAINAGE 60-MINUTE DURATION, 100-YEAR RETURN
STATES AND CITIES
(gallons per minute per square foot)
TENNESSEE
Knoxville
Memphis
Nashville
–
3.1
3.5
3.0
–
0.032
0.036
0.031
TEXAS
Corpus Christi
Dallas
El Paso
Houston
Lubbock
San Antonio
–
4.6
4.2
2.0
4.6
3.3
4.4
–
0.048
0.044
0.021
0.048
0.034
0.046
UTAH
Bluff
Cedar City
Salt Lake City
–
2.0
1.5
1.3
–
0.021
0.016
0.014
VERMONT
Bennington
Burlington
Rutland
–
2.5
2.3
2.4
R
–
0.026
0.024
0.025
–
0.035
0.042
0.042
0.034
–
1.0
1.0
1.0
–
0.010
0.010
0.010
–
2.9
3.0
2.7
–
0.030
0.031
0.028
WISCONSIN
Green Bay
Lacrosse
Milwaukee
Wausau
–
2.5
2.9
2.7
2.5
–
0.026
0.030
0.028
0.026
WYOMING
Casper
Cheyenne
Evanston
Rock Springs
–
1.9
2.5
1.3
1.4
–
0.020
0.026
0.014
0.015
WASHINGTON
Seattle
Spokane
Walla Walla
WEST VIRGINIA
Charleston
Martinsburg
Morgantown
E
-P
–
3.4
4.0
4.0
3.3
P
R
VIRGINIA
Charlottesville
Norfolk
Richmond
Roanoke
IN
T
(inches per hour)
2
For SI units: 1 inch per hour = 25.4 mm/h, 1 gallon per minute per square foot = 0.618 L/s/m
* The rainfall rates in this table are based on U.S. Weather Bureau Technical Paper No. 40, Chart 14: 100-Year 60-Minute Rainfall (inches).
296
UNIfORM PlUMbING CODE
APPENDIx D
TAblE D 4.01
DISChARGE fROM RECTANGUlAR SCUPPERS (gallons per minute)1,2,3,4
WATER hEAD
(inches)
WIDTh Of SCUPPER (inches)
6
12
18
24
30
36
⁄2
6
13
19
25
32
38
1
17
35
53
71
89
107
1
1 ⁄2
31
64
97
130
163
196
2
–
98
149
200
251
302
1
2 ⁄2
–
136
207
278
349
420
3
–
177
271
364
458
551
1
3 ⁄2
–
–
339
457
575
693
4
–
–
412
556
700
844
1
2
3
Head is the depth of water above bottom of the scupper opening.
The height of the scupper opening shall be not less than two times the design head.
Coordinate the allowable head of water with the structural design of the roof.
P
R
E
-P
R
4
IN
T
For SI units: 1 inch = 25.4 mm, 1 gallon per minute = 0.06 L/s
Notes:
1
Table D 4.01 is based on discharge over a rectangular weir with end contractions.
UNIfORM PlUMbING CODE
297
IN
T
R
E
-P
P
R
298
UNIfORM PlUMbING CODE