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HydroCAD® Stormwater Modeling - Since 1986
Rainfall Tables
Rainfall Distribution Tables
HydroCAD 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.
TIM lwu-u)
A mass curve indicates the cumulative
rainfall depth at anytime during the storm.
Rainfall Name(s1
Comments
Type 124-hr
Type IA 24-hr
Type II 6-hr
Type If 12-hr
Original SCS/NRCS distributions still used for many projects in the United States.
Type If 24-hr
Supplied as polynomial curves for optimum results over the widest range of Tic values.
Type III 6-hr
The 6 and 12 hour durations were added in HydroCAD-9.1
Type III 12-hr
Type III 24-hr
Type 124-hr Tabular
Type IA 24-hr Tabular
Tabular versions of original SCS/NRCS distributions. Recommended only for direct TR-20
Type II 6-hr Tabular
comparisons. Available by download only. Right -click any item and save to your
Type II 12-hr Tabular
folder.
Type II 24-hr To bu IS
Type II 48-hr Tabular
Latest "version 2" tables from WinTR-55 2.0 are also available here:
_Type 11124 -hr Tabular
Type I Type IA Type II Type III
Type If FL 24-hr
Modified Type It 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.
CA 1-6
NRCS Atlas 14 rainfall distributions for California. (Added in HydroCAD-10.0 build 21)
HI 1-6 ME1MI
NRCS Atlas 14 distributions for Hawaii, as published in WinTR-55 v2, and added in
HydroCAD 10.2-4b.
MSE 1-6
Atlas 14 rainfall distributions for midwest and southeast states developed by NRCS.
(MSE 3/4 added in HydroCAD-10.00 build 14, MSE 1/2/5/6 added in build 21)
NO 1/2/3/4 NEWI
Atlas 14 distributions for North Dakota, developed by NRCS and published in WinTR-55
v2. Originally named 1_NO, 2_NO, etc. Added in HydroCAD 10.2-4b.
Atlas 14 rainfall distributions for Mid -Atlantic states developed by NRCS based on NOM
NOM A/B/C/D
data. (Added in HydroCAD-10.00 build 14 and fully implemented in the event lookup
table in build 21)
Atlas 14 Volume 10 rainfall distributions for Northeastern states, developed by NRCS and
NOM10 A/e/C/D
published in WinTR-55 v2 as N10_A, N10_3, etc. Added in HydroCAD 10.2-4b.
Supersedes NRCC distributions (below.)
Atlas 14 rainfall distributions for Northeast states developed by NRCS using NRCC data
NRCC A/B/C/D
and published in WinTR-55 as SIR A, NR_B, etc. (Added in HydroCAD-10.00 build 14 and
fully implemented in the event lookup table in build 21
2ON