Prev Topic Home Up Next Topic

HydroCAD Stormwater Modeling - Since 1986

Rainfall Tables

Rainfall Distribution Tables

Click for complete self-training materialsHydroCAD provides several options for defining the rainfall distribution to be used with the SCS or SBUH runoff procedures.

Most projects will use one of the predefined rainfall distributions listed below.  The most common are the SCS/NRCS rainfalls listed at the top of the table.  The easiest way to use these distributions is to define your rainfall events using the built-in event lookup table.

With HydroCAD-10, you can also generate a synthetic rainfall distribution based on local precipitation frequency data.  Details here.

For special applications, you can create a custom rainfall table by hand.

Predefined Rainfall Distributions

The following predefined rainfall distributions are included with the latest HydroCAD release or available for download from this page.

Rainfall Name(s) Comments
Type I 24-hr
Type IA 24-hr
Type II 6-hr
Type II 12-hr
Type II 24-hr
Type III 6-hr
Type III 12-hr
Type III 24-hr
Original SCS/NRCS distributions still used for many projects in the United States.  Supplied as polynomial curves for optimum results over the widest range of Tc values.  The 6 and 12 hour durations were added in HydroCAD-9.1
Type I 24-hr Tabular
Type IA 24-hr Tabular
Type II 6-hr Tabular
Type II 12-hr Tabular
Type II 24-hr Tabular
Type II 48-hr Tabular
Type III 24-hr Tabular
Tabular versions of original SCS/NRCS distributions.  Recommended only for direct TR-20 comparisons.  Available by download only.  Right-click any item and save to your HydroCAD\Rainfall folder.
Type II FL 24-hr Modified Type II storm used by Southwest Florida Water Management District and Saint Johns County, Florida.
Type IIA CS 24-hr Modified Type IIA storm for Colorado Springs, Colorado.  Added in HydroCAD 6.1
Type B 6-hr Same as the Emergency Spillway distribution (ESH), but preset to a duration of 6 hours.   Added in HydroCAD-10 build-4.
Type NM 24-hr NRCS New Mexico rainfall distributions.  Added in HydroCAD 10.0 build 20.
MSE 1-6 NRCS Atlas 14 rainfall distributions.  (MSE 3/4 added in HydroCAD-10.00 build 14, MSE 1/2/5/6 added in build 21)
NOAA A/B/C/D NRCS Atlas 14 rainfall distributions for Mid-Atlantic states based on NOAA data.  (Added in HydroCAD-10.00 build 14 and fully implemented in the event lookup table in build 21)
NRCC A/B/C/D NRCS Atlas 14 rainfall distributions for Northeast states based on NRCC data.  (Added in HydroCAD-10.00 build 14 and fully implemented in the event lookup table in build 21)
Nevada North/South/West NRCS Atlas 14 rainfall distributions for Nevada
(Added in HydroCAD-10.00 build 14)
CA 1-6 NRCS Atlas 14 rainfall distributions for California.  (Added in HydroCAD-10.0 build 21)
NRCS Atlas 14 rainfall distributions for the Pacific Islands.  (Added in HydroCAD-10.0 build 21)
PR_VI Puerto Rico/Virgin islands 1/6/12/24-hour 1Q/4Q rainfall distributions.  (Added in HydroCAD-10.0 build 21)
"Chicago Storm" This term refers to a technique for using IDF coefficients to define a mass curve.  This is illustrated in the "Sample D" rainfall table and discussed in the rainfall.txt file.
SFWMD 24-hr
SFWMD 72-hr
Southern Florida Water Management District
FDOT 1/2/4/8/24-hr
FDOT 3/7/10-day
Florida Department of Transportation
Orange County, Florida
  6-hour  24-hour 
Use with 10, 25, or 100 year depth.
Added in HydroCAD-10 build-2.
SJRWMD 96-hr Saint John's River Water (Florida) management District 96-hour rainfall based on the SCS Type II 24-hour rainfall according to Section 14.2 of the MSSW Handbook.  Provided in half hour increments as described in MSSW, or tenth hour increments for greater accuracy and consistency with the Type II storm on which it is based.  Added in HydroCAD-10 build-2.
Spillway Emergency SCS Emergency Spillway Hydrograph (ESH, a.k.a Type B).
Spillway 1-day 10-day SCS Principal Spillway Hydrograph (PSH)
Constant Intensity Usable at any duration.  Added in HydroCAD 7.0.
Sample A (intensity curve)
Sample B (smoothed curve)
Sample C (mass curve)
Sample D ("Chicago" storm)
Sample E (Incremental rainfall depths)
Sample F (Incremental depths @ uneven times)
Sample G (Cumulative depths @ uneven times)
Fictional rainfall examples that may be used as the basis for custom storms.

Samples F and G were added in HydroCAD 10.1

Auckland 24-hr Design storms for Auckland, New Zealand, includes TP108 data and projected future rainfall.  Added in HydroCAD 10.1
Austin 3-hr Design storms for Austin, Texas, for return periods of 2, 5, 10, 25, 50, & 100 years.
TX-TCEQ-PMP Texas Dam Safety Program, TCEQ PMP rainfall events for durations of 1, 2, 3, 4, 5, 6, 12, 24, 48-72 hours.  (Added in HydroCAD-10.0 build 21)
Calgary 24-hr Calgary Canada Stormwater Manual, 2000 (includes event definitions)
Added in HydroCAD-10.
Charlotte 6-hr 2-yr and 10-yr "Balanced Storms" for Charlotte, NC.
25, 50, and 100-yr storms added in HydroCAD 10 build 11.
Charlotte 24-hr 1-yr storm for Charlotte, NC, added in build 23.
Colorado Springs 2-hr Colorado Springs, CO, 2-hour rainfall, added in build 23
Edmonton 4-hr and 24-hr Edmonton Canada Design Standards, 2008 (includes event definitions)
4-hr Chicago-style and 24-hr Huff, added in HydroCAD-10 build 8.
E-WA Short
E-WA Long Region 1-4
Eastern Washington State.  Added in HydroCAD 7.1
Fayette-01 (originally Fayette) Lexington-Fayette, KY 2001,  5-hr 1995, 6-hr 10/100-yr, 18-hr 1992
Separate "Fayette" files added in HydroCAD 7.0.
Consolidated into single "Fayette-01" file in HydroCAD 10.00 build 21
(Combines Fayette05 and Fayette09)
Lexington-Fayette, KY 2005,  6-hr 10/100-yr, 24-hr 10/100-yr
Separate "Fayette05" tables implemented in HydroCAD 7.1.
Consolidated into single "Fayette-05" file in HydroCAD 10.00 build 21
and including 1-hr 1/10/100-year storms from Fayettte09 (removed).
Fayette-16 Lexington-Fayette, KY 2016 - latest rainfall data
5-hr 1995, 6-hr 10/100-yr, 24-hr 10/25/100-yr, 24-hr 2006
Added in HydroCAD-10.0 build 21
Halifax 24-hr Halifax Canada rainfall distributions 2018
24-hr Chicago-style  2/5/10/25/100, Added in HydroCAD 10.1
Huff 0-10sm
Huff 10-50sm
Huff 50-400sm
Illinois Huff distributions from ISWS Bulletin-71 & Circular-173.  Supplied for 1st, 2nd, 3rd, and 4th quartiles.
Huff B70 0-10sm Updated Illinois Huff distributions from ISWS Bulletin-70.  Supplied for 1st, 2nd, 3rd, and 4th quartiles.  Added in HydroCAD-10.
Huff B75 0-10sm Updated Illinois Huff distributions from ISWS Bulletin-75.  Supplied for 1st, 2nd, 3rd, and 4th quartiles.  Added in HydroCAD-10.1-5a.
Indy Huff 24-hr Variation of the Huff distributions from Indianapolis Stormwater Manual 5/10/95.
Indy Huff Indianapolis SQU Guide 7/20/06.  1st, 2nd, 3rd, 4th quartiles.
Indy Huff 2011 Updated 2011 Indy Huff distributions added in HydroCAD-10 build 21.
Indy Huff South Bend Porter County Indiana, 1st, 2nd, 3rd, 4th quartiles.
Added in HydroCAD-10 build 11.
Indy Huff Evansville Huff distributions for Evansville added in HydroCAD-10 build 23.
Indy Huff Fort Wayne Huff distributions for Fort Wayne added in HydroCAD-10 build 21.
LA County DPW 24-hour
LA County DPW 96-hour
Los Angeles County DPW 2006 Hydrology Manual, using 10%+40%+35%+100% depths.  Added in HydroCAD-10.
NJ DEP 2-hr New Jersey DEP Water Quality Storm.  Added in HydroCAD 7.1
Ohio PMP 6-hr and 24-hr Ohio PMP rainfall distributions (2013 Memo).  Added in HydroCAD 10.1 build 2.
RSA 24-hr  (Type 1, 2, 3, 4) "Chicago" style rainfalls for Republic of South Africa.  Added in HydroCAD-10.  Rainfall type and depth maps: 1MB PDF
Salt Lake County 3-hour 10-year and 100-year Farmer-Fletcher distributions for Salt Lake County Utah.
Added in HydroCAD-10 build 16.
San Diego 6-hr
San Diego 24-hr
San Diego Country, CA.  Added in HydroCAD 6.1.
San Luis Obispo 24-hr
  Type U and D
  2, 10, 25, 50, and 100 year
San Luis Obispo, CA, upper and lower watersheds.  Added in HydroCAD-10.
Seattle 24-hr Seattle, Washington, Flow Control Technical Requirements Manual, November 2000.
SEWRPC SE Wisconsin 90th Percentile storm (added in HydroCAD-7.0)
SE Wisconsin 2006 storm (added in HydroCAD-10.0 build 14)
Shelbyville Shelbyville, IN uses standard Huff distributions, above.
St. George 3-hr 10-yr and 100-yr Farmer-Fletcher distributions for St George Utah.
Added in HydroCAD 10.1-5a.
Thurston 24-hr (1/2 to 100-yr) 
Thurston 24-hr 1990
Thurston 7-day 100-yr
Thurston County, Washington.


If you need a rainfall that is not listed here, you can create a custom rainfall table or download local rainfall data.

[Home]   [Support] 
Copyright 2020 HydroCAD Software Solutions LLC (privacy)   (legal notices)