Flow-R is software for rapid, reliable, and user-friendly propagation modeling of natural hazards. Flow-R allows rapid assessment of the propagation area based on several published empirical run-out models at local and regional scales. It is optimized for regional susceptibility mapping of gravitational hazards, such as:

  • Debris flows
  • Rockfalls
  • Rock avalanches
  • Shallow landslides
  • Snow avalanches

Flow-R supports susceptibility mapping to depict areas prone to natural hazards. These maps are, therefore, an essential tool for land-use planners to identify quickly and efficiently settlements, infrastructure, and communication networks potentially threatened by natural hazards.


Probabilistic approach

Flow-R uses a probabilistic approach to model the propagation of gravitational hazards from user-defined source areas. It results in the total perimeter encompassing all possible propagations, which leads to susceptibility maps that are similar to the reach probability used in hazard mapping.

Wide range of algorithms

Flow-R includes a wide range of algorithms for the lateral spreading of a mass movement coupled with several simple friction models that control the run-out distance of the flow.

Realistic propagations

Up to date with recent academic research, Flow-R has demonstrated the capability to model reliable and realistic propagations for different gravitational hazards on various scales.

Effect of protection forest & mitigation measures

The protective effect of forests or other mitigation measures can be assessed by spatial variations of the travel angle.

Flexible input data

The choices of the datasets and the algorithms are open to the user, which makes it compliant with various applications and available datasets. Required input data are a Digital Elevation Model and a raster file with the source areas prepared in any GIS software. All common types of raster files are supported by Flow-R.

Data export

The generated output files are saved as raster files or shapefiles for further treatment with any standard GIS tool.


Fast and versatile software for gravitational hazards run-out assessment

Wide range of implemented algorithms

  • Control of the lateral spreading of a mass movement with various direction algorithms
  • Assessment of the runout distance using simple frictional models
  • Persistence functions reproducing the inertia of a mass flow
  • An algorithm for rock avalanches allows going up on the opposite side of the slope

Optimized algorithms for large study areas

  • Computationally efficient: about 45× faster than previous versions (Flow-R 0.9.x)
  • Multi-threaded processing
  • Efficient memory handling that facilitates working with unrestricted spatial extents
  • Runs on 64-bit Windows

Multiple runs

  • A queue system allows starting multiple consecutive runs
  • An unlimited number of runs in the queue for the Flow-R Pro version (limited to three runs in the Lite and Trial versions)
  • Facility to abort, pause or resume runs

Graphical user interface

  • Easy configuration of model runs
  • All parameters in a single window

Flexible input data

  • Flow-R requires only a Digital Elevation Model and user-defined source areas as input files
  • Flow-R supports all common raster file types
  • Automatic regridding of the source areas in case of differences in raster cell size
  • Simple data importation and model setup
  • Optional raster file providing the travel angles to account for protection forest and other mitigation measures

Created output files

  • Susceptibility maximum: The maximum of susceptibility values from all propagations passing through a given cell
  • Susceptibility sum: The sum of susceptibility values from all propagations passing through a given cell
  • Total extent: The overall extent of all propagations
  • Number of propagations: The total number of source cells contributing to a given cell
  • Velocity: The maximum of the velocity values from all propagations passing through a given cell
  • Energy: The maximum of the energy values from all propagations passing through a given cell for a unitary mass of 1 kg
  • Propagation polygons: Polygon of the propagation extent of each source cell
  • Results are exported as raster files in GeoTIFF format or as polygons in shapefile
  • Optional compression of output raster files


Flow-R comes in two versions: Flow-R Pro & Flow-R Lite

Flow-R Pro Flow-R Lite
All algorithms available
Efficient multi-threaded computation
Efficient memory management
All common raster file types as input
Automatic regridding of source areas
Maximum size of the study area unlimited 5 million DEM cells*
Filter source areas based on cell values customizable** fixed (> 0)
Output types all limited***
Maximum number of runs in queue unlimited 3

* or 500 km² for a DEM with a cell size of 10 m; ** =, >, <, ≥ or ≤ any value; *** limited to susceptibility (max and sum), velocity and energy.


Trial version

The full-featured demo version is valid for 30 days and restricted to non-commercial applications. Furthermore, the size of the study area is restricted to 0.5 million cells (or 50 km² for a DEM with a cell size of 10 m) and the queue is limited to three runs.


Flow-R Pro and Flow-R Lite are available in different license types and pricing plans: monthly and yearly subscriptions or perpetual purchase, as well as personal and flexible (floating) licenses.

Monthly subscription Yearly subscription Perpetual license
Flow-R Pro Personal 150 EUR 500 EUR 1000 EUR
Flow-R Pro Flexible 220 EUR 750 EUR 1500 EUR
Flow-R Lite Personal 60 EUR 200 EUR 400 EUR
Flow-R Lite Flexible 100 EUR 350 EUR 700 EUR

Taxes may still be added. The tax rate depends on your country tax rules, entered tax identification number (e.g. VAT ID), and selected purchase method. Discounts for multiple licenses (3+: 5%, 5+: 10%). Personal: Installation on a single computer. Flexible (floating): Installation on multiple computers with concurrent use. Perpetual license: With updates for the current major version. It is possible to add restrictions based on IP ranges. Please contact the support.


Terranum offers 60% discount for academic institutions and proposes a special education pack with 50 pro flexible licences.

Program participants must agree to use the software for educational and research purposes only. Please complete this form to determine your eligibility for the academic version of Flow-R and then to access the dedicated offers.



Download files for a hands-on tutorial

Useful links

Support: https://support.terranum.ch
Subscription management and billing: https://terranum.onfastspring.com/account
Licenses management: https://licenses.terranum.ch/
Report a bug: https://bugs.terranum.ch
Suggest improvement or a new feature: https://suggest.terranum.ch

Scientific reference

Horton P, Jaboyedoff M, Rudaz B and Zimmermann M: Flow-R, a model for susceptibility mapping of debris flows and other gravitational hazards at a regional scale. Natural Hazards Earth System Sciences, 13, 869-885, 2013, doi:10.5194/nhess-13-869-2013

Release notes

v2.1.0 – 2023-11-30

  • The runout distance was underestimated for directions other than the cardinal and diagonal ones. The new version corrects this bias and the runout distance now better corresponds to the real reach angle values. Therefore, the runout distances are now slightly longer than in previous versions.
  • Adding offline license activation.
  • Improving computation speed.
  • Improving the compression of the output files.
  • Setting the straight patterns avoidance as an option.
  • Default to per-machine installation.
  • The support for irregular grids has been removed.
  • The multi-threaded export has been removed (was causing issues in resulting files).
  • Make license reloading easier.
  • Fixed: using Perla’s model along with the direction memory was failing.
  • Fixed: some propagations were missing in the output files.
  • Fixed: the run cancellation was not working properly.

v2.0.9 – 2021-12-22

  • Adding the projection information to the produced shapefile.
  • A shift between the DEM and the sources is now allowed to a certain extent.
  • Cells defined as nodata were not properly assigned when regridding.
  • Data export failed in some cases (error message saying that the resulting raster data could not be loaded)
  • Various bug fixes

v2.0.8 – 2021-09-10

  • The rock avalanches could crash when reaching the DEM border.

v2.0.7 – 2021-07-02

  • Adding option for license borrowing.

v2.0.6 – 2021-05-06

  • Some options were not correctly saved in the parameters file.
  • The “cosinus” weight option has been renamed to “cosine”.
  • An unnecessary warning for raster sources extent has been removed.
  • Adding support for different decimal separators.

v2.0.5 – 2021-02-23

  • Some letters had font issues. The fonts have been updated.

v2.0.4 – 2021-02-15

  • Underscores are now used in resulting file names instead of hyphens.

v2.0.3 – 2021-01-20

  • An issue with the direction memory raised warnings.

v2.0.2 – 2020-12-21

  • The update link on the main interface did not work.

v2.0.1 – 2020-12-15

  • The license key is now partly censored.

v2.0.0 – 2020-12-10

  • Initial release.


Flow-R was originally developed at the University of Lausanne. Terranum is now in charge of its development and provides related support in various domains:

Specific development

There may be situations where Flow-R needs to be modified in order to meet the requirements of a certain project, or to model a specific behaviour. We are ready to make the necessary adjustments in Flow-R in order to meet your needs.

Nation scale modeling

Although Flow-R is optimized for regional applications, nation scale modeling requires a significant amount of processing time. Terranum possesses a cluster in order to perform intensive calculations.


We have now various experiences using Flow-R in different conditions, with varying data quality and for multiple hazards. Being the editor of the model, we also know perfectly the behaviour of the different algorithms.


Having some help when starting using Flow-R is a time saving option. We have some courses ready and will be happy assisting you.


Rockfall propagation in Flow-R

Introduction of a variable travel angle in Flow-R in order to take into account the effect of forests on rockfall propagation

2014 | Canton of Fribourg, Switzerland

Indicative hazard mapping (Fribourg)

Indicative hazard mapping of debris-flows, snow avalanches, rockfalls and landslides for the Canton de Fribourg

2014-2015 | Canton of Fribourg, Switzerland

Snow Avalanche Runout Computation

Investigation on DEM resolutions effects on the processing of the Norwegian snow avalanche susceptibility maps using α⁄β and Perla's models implemented in RAS and Flow-R

2015 | NVE, Norvège