The rainfall and runoff calculation methods inside InfoDrainage and how to customize them

3 min read

When it comes to evaluating drainage design software, one of the paramount requirements is that it delivers results in line with your local and regional rainfall types and runoff calculation regulations. Runoff calculations play a crucial role in optimizing drainage systems and meeting sustainability requirements, and over the years, there have been a plethora of approaches to calculating this runoff volume and corresponding flow.

For InfoDrainage, Autodesk’s drainage design software, you have the luxury of choosing from a vast number of rainfall types and runoff calculation methods. In this short blog, we’ll take a look at the various rainfall types and runoff calculation methods in InfoDrainage, and touch on a few details from tutorials.

If you’re not already an InfoDrainage user, you can download a free 30-day trial (no credit card required) and explore rainfall options in the software.

What rainfall calculation methods does InfoDrainage offer?

Rainfall data is fundamental for determining the amount of runoff generated by a storm event. Given the variable environmental and climatic conditions, rainfall types and distributions are highly regionalised. InfoDrainage incorporates all major design rainfall types, from NOAA’s rainfall in the US to FSR and FEH in the UK and ARR in Australia.

The chart below outlines all currently supported design rainfall types by region. Additionally, you can customize rainfall data by creating Intensity Duration and Frequency (IDF) tables and assigning temporal patterns to create a User Defined Rainfall. You can also leverage InfoDrainage’s Known Rainfall functionality to analyze unique hyetographs.

By giving you this flexibility, you can ensure design accuracy by using the most appropriate rainfall type and distribution for any of your projects, local or global.

RegionRainfall types in InfoDrainage
USNOAA rainfall
US, GlobalSCS Rainfall
China/CanadaChinese Rainfall (aka Chicago Rainfall)
UKFSR Rainfall
UKFEH Rainfall
AustraliaARR Rainfall

How to customize rainfall methods in InfoDrainage

If you are looking to get a better grasp of the rainfall types workflow, watch our short on-demand training module on Creating Rainfall Data. The module walks through using the Rainfall Manager to create and assign design storms for analysis in InfoDrainage.

Finally, it is worth mentioning that InfoDrainage’s Rainfall Manager enables you to create custom templates and libraries for any region around the globe. For example, you can model a known rainfall event to analyze hyetograph data and historical rain gauge data, which can be manually entered and/or imported from a wide variety of data types.  Additionally, you can build unique temporal patterns and apply them to one or more rainfall events based on a duration and a total depth (or average intensity). The Water Drop workflow video below walks you through that process.

We’re always adding new videos to the Water Drop Workflow videos playlist. Subscribe.

What runoff calculation methods does InfoDrainage offer?

Following our discussion on rainfall types and how design storms can be created, templatised, and assigned in InfoDrainage, it is only natural that we segue to a discussion on runoff methods to identify the runoff flow intended to be used for the optimal sizing of stormwater infrastructure. Typically, a portion of your rainfall will contribute to your runoff flow, and that flow can be calculated through a range of graphical and numerical methods, some more complex than others, most of which are available within InfoDrainage as summarized in the table below.

Runoff method in InfoDrainage
SWMM Method
Rational Method
Modified Rational Method
Laurenson Method
Green Roof Method
ReFH Method
ReFH2 Method
FEH Method
FSR Method
Time Area Diagram Method
Santa Barbara Unit Hydrograph Method
SCS Method (aka curve number method with calculator)
Time of Concentration Method (with calculator)

If you’re looking to dive deeper into how these rainfall types and runoff methods are leveraged inside InfoDrainage, as well as solving common drainage design challenges, Solutions Engineers Hunter Sparks and Midori Patterson discuss these concepts in a past Water Talk.

Staying up to date with InfoDrainage

Our product development teams are constantly at work adding new features and functionalities to InfoDrainage, as well as communicating with customers in multiple ways:

Food for thought: Will rainfall and runoff standards need to be adjusted for climate change?

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