FAQ

Question:

Does RAMMS work on a Mac?

Answer:

Yes and No. Not directly, you have to install Parallels Desktop or any other virtualization software that allows you to run Windows alongside macOS without the need to restart your computer.

Question:

I have been trying to create a new project with my DEM-Tiff-File. Unfortunately, this failed and I see one of the following errors:

• REVERSE: Subscript_index must be less than or equal to number of dimensions
• Illegal subscript range: DEM_ARR.

Answer:

There are several common reasons why a DEM might cause errors in RAMMS. Please check the following:

1. Incorrect Coordinate System:
   Your DEM may be using a geographic (spherical) coordinate system, where coordinates are in degrees (latitude/longitude). RAMMS requires DEMs to be in a projected coordinate system, such as UTM, where all units are in meters. Please reproject your DEM to UTM using a GIS tool like QGIS or ArcGIS.
2. DEM is not Elevation Data:
   Some files that appear to be DEMs are actually hillshade images or visual map layers containing RGB color values instead of elevation (Z) values. RAMMS requires a true elevation raster, where pixel values represent ground elevation in meters.
3. Corrupt or Incompatible DEM Format:
   Ensure that the DEM file is in a supported raster format (e.g., GeoTIFF) and not corrupted. You may also try re-exporting the DEM from your GIS software with clean settings.
   Solution:

Verify your DEM’s coordinate system and data type, correct any issues as described above, and then attempt to create a new project in RAMMS with the corrected DEM.

To help you get started with RAMMS, we provide a set of sample data that includes a Digital Elevation Model (DEM) and an ortho-image. These files are ideal for testing the software, learning the workflow, or running example simulations.

You can download the sample dataset here:

RAMMS Sample Data

This dataset is compatible with RAMMS and can be loaded directly through the graphical user interface.

If you need guidance on how to import and use your own terrain data, please ask Rocky, use the user manual or reach out to our support team.

Great question — and you’re absolutely right to notice the discrepancy. In classical mechanics, momentum is defined as the product of mass and velocity, with units of kg·m/s. However, in RAMMS::DEBRIS FLOW, the momentum output is simplified for performance and visualization purposes.

Since the model assumes a constant flow density and uses a uniform grid (with equal X and Y resolution), we represent momentum as the product of flow height (H) and flow velocity (V), resulting in units of m²/s. This simplification omits constant factors like density and grid area for clarity and computational efficiency.

To convert this value to physical momentum (kg·m/s), simply multiply the RAMMS output by:

• The flow density (kg/m³), and
• The square of the grid resolution (m²).

This gives you the full physical momentum:
Momentum = H × V × ρ × (grid_res)² (in kg·m/s)

This approach allows for more efficient calculations and visualization while maintaining physical consistency when properly interpreted.

Answer:

Yes, you can, but this is work in progress. Please get in contact with us and we gladly help!

October 25th 2021

Problem:

I have two tif-files, a topographic map and an orthophoto, but I don’t understand why they don’t appear in the program and why it says that it doesn’t find any map or orthophoto. What can I do?

Answer:

• Both topo map and orthophoto must be in the same coordinate system as the DEM you used to create the project in RAMMS.
• For topo map and orthophoto, you need the corresponding world-file (tfw-file) to the tif-file. Otherwise, RAMMS will not find the files.

February 2^nd 2021

Problem:

I try to run a simulation, but instead of the results, I get the following error message:

Error-Messages:
Unable to allocate memory: to make array.
Not enough space
Execution halted at: 

What is going wrong here?

Answer:

The following issues can have an influence on the memory management of RAMMS:

• Do you use a large ortho-image that you overlay? This could be the problem here. Reduce the resolution of your ortho-image and try again.
• Calculation domain: Do you use a narrow calculation domain? If not, please have a look in the manual on how to define an ideal calculation domain (for avalanche and debris flow simulations).
• Dump Step: By increasing the dump step, you decrease the amount of memory needed to open a simulation file.
• Simulation resolution: A very good (=small) simulation resolution increases the amount of memory needed to open a simulation file.

July 12th 2024

Problem:

I get an error when I try to update RAMMS (Help -> Update… -> Web Update). What is going wrong?

Answer:

This is due to the transition of RAMMS from SLF to the new WSL-Spin-off company RAMMS AG. Some links do not work anymore.

Avalanche/Debrisflow:

Please update your version by doing the following:

• Download the update from here, and unzip the file to a local directory (e.g. C:\Temp\). Beware, there is another zip-file within the downloaded zip-file, do NOT unzip this file, otherwise the update will not work.
• Then start RAMMS and choose Help -> Update… -> Install Update from local folder.
• Select your local directory from before, where you unzipped the update.
• RAMMS should now tell you, that an update is available. Do NOT let RAMMS show you the changelog document, as this link also does not work. Click No.
• In the next window, RAMMS shows you your current version, and the update version. Click Yes to update your RAMMS version.
• You successfully installed the update. Restart RAMMS to use the new version.

Rockfall:

If you still use version 1.7.65, then please download the new version from here (Downloads section at the bottom of the page). Version 1.7.65 will not be updated anymore.

If you already use the new version 1.8.10 or higher, then you can download the update manually from here, and unzip it into your installation directory (replace all files).

From version 1.8.26 on, Web Update should work again as usual.

August 19th 2024

Question:

Does RAMMS work on Windows 11?

Answer:

Yes, all modules of RAMMS run also on Windows 11!

Did you already install RAMMS?

If No, you have to download and install RAMMS first, before proceeding to the next steps!

If Yes, then do the following:

Start RAMMS for the first time, and you will see the following screen, where you have to click the upper right button, to create the license request file:

In this window, enter your name and your company name, and then click OK.

Then choose a location to save the license request file (it’s a txt-file).

An informational window will then tell you where you saved your license request file. Attach this file when ordering a license (full, demo or student license).

Problem:

I updated RAMMS::Avalanche (or Debrisflow) to version 1.8.0, but now I cannot run any simulations. RAMMS is stuck with “Create .xy-file”, see Figure 1 below.

Solution 1:

Open the “Additional Preferences” (Help -> Advanced… -> Additional Preferences… -> Edit) and check, if you have the “X64” option set to 1 (see Figure 2 below). If you do not find this option, then just add a new line (before the END tag) and enter

X64 1

Then click “Save” and “OK” and try again to run a simulation. If this does not work, then most probably some C++ libraries are missing on your system. Please see solution 2 below.
Solution 2:

• Open RAMMS
• Then use the function “Install C++ libraries” (Help -> Advanced… -> Install C++ libraries) to install the libraries (you will need Admin privileges to do that).

Question: 

I tried the new update, but when I try to open an old file, the following error message appears:

Can you help me?

Solution:

• close RAMMS
• remove this directory: “C:\Users\<your username>\.idl”    (if you specified Preferences in RAMMS, then you have to re-set them)
• now you should be able to start and use the new version. I strongly suggest only to use the new version (Rockfall) from now on. The speed of the handling is much improved, much easier to use RAMMS!
• if you again use the old version (Rockfall), then this problem could happen again…….

I made several different calculations, but the results differ only with the height of the released snow; the density doesn’t count. Did I make any mistake while modeling, or it doesen’t play a role?

Answer:

The RAMMS model (Avalanche and Debrisflow) uses depth-averaged mass and momentum conservation equations, particularly the Voellmy–Salm (VS) model. These are formulated under the assumption of a constant flow density.

“…we model as an incompressible continuum of mean constant density …”

The key point is that:

Density appears in both sides of the momentum equations (inertia and frictional terms). When these equations are written in terms of depth-averaged quantities, and the density is assumed to be constant across space and time, it can be factored out and canceled from both sides of the equations. The equations govern how the flow evolves over time, but crucially, it’s expressed in terms of velocity and height, not mass, and the density is implicitly removed.

What this means for engineers:

• When using RAMMS (Avalanche and Debrisflow), the flow density won’t affect the outcomes like runout, flowheight or velocity directly.
• The density (e.g., 300 kg/m³ for avalanches) only plays a role in output variables like impact pressure — not in the internal dynamics.

This plot combines topographic information with simulation results to show how pressure (in this example) behaves along the avalanche track. Here’s how to interpret the different elements:

• Green Line – Topography:
  This represents the ground surface elevation along the avalanche path. It is scaled on the left-hand vertical axis, in meters (m). The x-axis shows the horizontal distance along this track.
• Grey Area – Pressure Values:
  The grey shaded area shows the calculated pressure (or any other simulation result) at each point along the path. These values start from zero and are scaled according to the right-hand vertical axis, in kPa. They are plotted vertically from the baseline (zero pressure) at each x-location.
• Red Line – Scaled Pressure Superimposed on Topography:
  The red line is a scaled representation of the pressure values from the grey area, but instead of starting from zero, it is superimposed on top of the green terrain line. This means that at each location, the red line starts at the elevation given by the green line, and rises by a scaled pressure value.

Note: The red line does not represent the pressure values 1:1. Some vertical scaling is applied for visualization purposes, to make the pressure distribution easier to interpret over varying terrain. Because the topography is constantly changing in elevation, the red line appears smoother than the grey shaded profile. Local oscillations in pressure (as seen in the grey area) may not be as visible in the red line due to this elevation-based scaling.

RAMMS::Avalanche Manual

Answer

The time required to simulate an avalanche or a debris flow is a function of the finite volume grid resolution and the size of the calculation domain. Typically we use 5m resolutions and the simulations require around 10 minutes. We usually perform the initial simulations at 10 m resolution and therefore we have results in 1 or 2 minutes. When we have a solution that we like we might take a look at the problem at 2m resolution.

Answer:

In all RAMMS versions (Avalanche and Debrisflow) up to Version 1.5.01, an ENO (Essentially Non-Oscillatory) scheme was used to numerically solve the governing differential equations (Christen et al., 2010). However, the numerical solution was implemented on strictly orthogonal grids. This improves computational speed, but introduces numerical instabilities especially in steep terrain.
The new Version 1.6.20 uses the same second order ENO scheme, but now on general quadrilateral grid. This new scheme improves numerical stability, but slows the computational speed somewhat. The introduction of this stable ENO scheme allows us to use lower H_cutoff values minimizing mass loss during calculations. The standard value of H_cutoff is 0.000001 m.

Answer:

Friction parameters mu and xi are automatically calculated according to return period, avalanche volume, “track type” (flat, open slope, channelled and gully) and altitude. In the “Automatic MuXi Procedure” you can specify the altitude limits:

Altitude limit 1 is the upper limit, and altitude limit 2 the lower limit.

These limits will change the friction values according to the altitude, assuming, that the temperatures are higher in lower regions, and thus the snow characteristics are different (higher snow densities with higher temperatures, etc…).

• Upper limit: is normally below the tree line (in Switzerland, the tree line is around 1800m……we use 1500m as the upper limit)
• Lower limit: the lower limit could be seen as a “snow line”. In Switzerland this limit is normally 1000m.

Suggestions for altitude limits for different regions:

 September 2nd 2024

Answer:

Avalanches

The Voellmy model – coupled with the calibrated parameters – can be used to

• (1) predict the runout distance and
• (2) predict the maximum flow velocity of extreme, large snow avalanches.

This is one of the important research results from the Vallée de la Sionne test site. The Voellmy parameters that we recommend describe the front of a dry-snow avalanche. Because the front defines the runout distance and maximum velocity the Voellmy model will work.

However, the Voellmy model will not describe the avalanche flow behind the front, at the tail of the avalanche. Here, measurements show an increase in the friction (a rapid decrease in speed). This effect causes avalanches to elongate and eventually deposit mass. Therefore, the Voellmy model will not predict the deposition behaviour.

The Voellmy model has difficulties to predict the runout of small avalanches, which sometimes begin immediately to deposit or “to starve”. Of course, small avalanches can be modelled using higher μ and ξ values, but this is a very ad-hoc approach.

RAMMS::Rockfall Manual

October 25th 2021

Problem:

I get an error when I import the shapefile of my release areas. What is going wrong?

Answer:

The polygon shapefile most probably contains Z and M values. RAMMS does not like them 🙂
Convert the shapefile to a polygon shapefile without Z and M values, and it will work.

Idea: Calculate possible retention volume of flexible barriers, according to the document «Practical guide for debrisflow and hillslope protection nets» from WSL. Then remove retention volume (and momentum) out of the flow at the locations of flexible barriers (defined as polygon shapefiles).

To use flexible barriers (net) in the RAMMS::Debrisflow module, follow these steps:

1. Define Barrier Locations: Open an input file in RAMMS and draw polygons at the locations where you want to place the flexible barriers. You can have one or several polygons within a shapefile to represent multiple nets
2. Set Barrier Parameters: Define the width and height for each barrier in meters. The green arrow in the interface will indicate which polygon you are defining the parameters for. After setting the width and height, RAMMS will calculate the possible retention volume for the barrier. If the calculated volume is not satisfactory, you can enter a new retention volume manually
3. Check Barrier Parameters: After setting the parameters, you can right-click on the filename to view the barrier information. If you need to set new parameters, remove the existing barrier from the shapefile first.
4. Simulation: Start a simulation with the barriers in place. In the simulation, you can monitor how much volume is retained by the barriers. It is recommended to set the stop criteria to 1 percent and avoid using the Center-of-Mass stop criteria with barriers.
5. Results: After the simulation, you can check the retained volume by choosing “Barrier Retention Height” and animating the flow. The barrier information will also be added to the output log file.

These steps will help you effectively use flexible barriers in the RAMMS::Debrisflow module to simulate debris flow protection and retention scenarios. More information can be found here.

I made several different calculations, but the results differ only with the height of the released snow; the density doesn’t count. Did I make any mistake while modeling, or it doesen’t play a role?

Answer:

The RAMMS model (Avalanche and Debrisflow) uses depth-averaged mass and momentum conservation equations, particularly the Voellmy–Salm (VS) model. These are formulated under the assumption of a constant flow density.

“…we model as an incompressible continuum of mean constant density …”

The key point is that:

Density appears in both sides of the momentum equations (inertia and frictional terms). When these equations are written in terms of depth-averaged quantities, and the density is assumed to be constant across space and time, it can be factored out and canceled from both sides of the equations. The equations govern how the flow evolves over time, but crucially, it’s expressed in terms of velocity and height, not mass, and the density is implicitly removed.

What this means for engineers:

• When using RAMMS (Avalanche and Debrisflow), the flow density won’t affect the outcomes like runout, flowheight or velocity directly.
• The density (e.g., 300 kg/m³ for avalanches) only plays a role in output variables like impact pressure — not in the internal dynamics.

This plot combines topographic information with simulation results to show how pressure (in this example) behaves along the avalanche track. Here’s how to interpret the different elements:

• Green Line – Topography:
  This represents the ground surface elevation along the avalanche path. It is scaled on the left-hand vertical axis, in meters (m). The x-axis shows the horizontal distance along this track.
• Grey Area – Pressure Values:
  The grey shaded area shows the calculated pressure (or any other simulation result) at each point along the path. These values start from zero and are scaled according to the right-hand vertical axis, in kPa. They are plotted vertically from the baseline (zero pressure) at each x-location.
• Red Line – Scaled Pressure Superimposed on Topography:
  The red line is a scaled representation of the pressure values from the grey area, but instead of starting from zero, it is superimposed on top of the green terrain line. This means that at each location, the red line starts at the elevation given by the green line, and rises by a scaled pressure value.

Note: The red line does not represent the pressure values 1:1. Some vertical scaling is applied for visualization purposes, to make the pressure distribution easier to interpret over varying terrain. Because the topography is constantly changing in elevation, the red line appears smoother than the grey shaded profile. Local oscillations in pressure (as seen in the grey area) may not be as visible in the red line due to this elevation-based scaling.

Question:

I read the manual of debrisflow, but I am still confused about how to to determine the values of μ and ξ.

Answer: 

The major problem is that debris flow parameters vary strongly related to the water content. They therefore vary much more than rockfall parameters. As a first approximation we take (μ=0.2, ξ=200m/s2) which represents the friction of a standard, granular debris flow (say water content of about 30 percent). If you have flows with more water I would suggest using lower mu values (μ between 0.05 and 0.2). A μ of 0.05 is for highly saturated flows (water content > 50 percent). Some possible xi values are provided in the figure below:

RAMMS::Debrisflow Manual

Answer:

Erosion is explained in on this page.

Answer:

Debris flow

The “best” constitutive model for debris flows is still a very open question in the scientific community. We recommend using the Voellmy model until a better model is found. Voellmy basically has only two parameters and after some calibration a useful solution can usually be found. With Voellmy one can control the flow velocity (parameter xi) and runout distance (mu).

One reason Voellmy is useful is that it only requires two parameters to calibrate. The turbulent term dominates the frictional behavior when the flow is moving rapidly and the Coulomb term is dominant when the flow is moving slowly, allowing the model to be approximately calibrated to observations of flow velocity and the stopping location of the flow front.

Finding the “right” debris flow model is more difficult than finding the “right” snow avalanche model because debris flows are two component systems (fluid, solid). Much of the behaviour of a debris flow — including the stopping process — involves the interaction between the fluid-solid components. Thus, without a two component model, it will be unlikely that we are able to model all aspects of debris flows. The Voellmy model mixes the two components and therefore models the debris flow when the components volumes are constant and well mixed. This assumes, of course, that the relative portions of solid and fluid remain the same, from head to tail of the event. This is hardly true

Answer:

There are several good reasons:

Firstly, hazard mitigation experts are often interested in the flow behaviour only near the fan. Calculating the movement of the debris flow in the torrent is a time consuming and often useless task. Therefore using a hydrograph can often cut calculation times dramatically.

Another reason is that it is impossible to describe the initial conditions of debris flows as a “block release”. There are cases where block release is a good approximation of reality (e.g. dam breaks), but, in general, it does not accurately reflect the starting conditions of flows from intense precipitation.

Read this publication for more information on this issue:
Deubelbeiss, Y.; Graf, C., 2013: Two different starting conditions in numerical debris-flow models – case study at Dorfbach, Randa (Valais, Switzerland)

Problem: My debris flow simulation takes ages to calculate. I use a 0.5m resolution. Do you have any suggestions on how to speed up my simulation? And sometimes I get this error message:

Error-Messages:
Unable to allocate memory: to make array.
Not enough space
Execution halted at:  RAMMS_OPENBINARYOUTPUT 2237                    

Answer:

There are several important issues that affect your simulation speed and also your (RAMMS) memory management:

1. Dump Step: By increasing the dump step (when starting a simulation, e.g. 10s instead of 5s), you decrease the amount of memory needed to open a simulation file.
2. Calculation domain: Do you use a narrow calculation domain? If not, please have a look in the manual (section 3.5.4) on how to define an ideal calculation domain.
3. Simulation resolution: A very good (=small) simulation resolution increases the amount of memory needed to open a simulation file.
4. Do you use a large ortho-image that you overlay? This could also be a memory problem. Reduce the resolution of your ortho-image (do not forget to change the .tfw file too) and try again.

August 26th 2024

Problem: What data do I need to model a debrisflow using a hydrograph?

Answer: You only need the hydrograph for the debris flow itself, not for the river flow from before or after the event. RAMMS can only predict the runout of debris flows (not the flood flows before or after the debris flow).

1. The easiest way to run RAMMS using an input hydrograph is to start with an estimate of the total volume of the debris flow, which you may be able to estimate using other engineering methods or based on estimates from previous events in the area. When you enter this into the 3-point hydrograph table in the “Release Tab”, RAMMS will then propose a maximum discharge based on a semi-analytical relationship in the literature (as described in the handbook, from Figure 2 in Rickenmann (1999, Empirical Relationships for Debris Flows).
2. If you only have an estimate of the maximum discharge, but not the total event volume, you could use the Rickenmann (1999) curve (mentioned above) and your maximum-expected discharge value to estimate the total debris-flow volume. You could do this either with the graph in Rickenmann (1999) or you could do this iteratively in RAMMS by adjusting the total volume until it matches your predicted maximum discharge value. This will give you the standard three-point hydrograph.
3. If you have information that you trust regarding the expected duration of the peak discharge, you could also manually edit the hydrograph table.

As a reminder, the hydrograph volume in RAMMS (as well as the block release volume) is the sum of both the water and the sediment in the debris flow, not the pure-water discharge, so depending on the methods you are using, you may need to increase the volume of the flow to include the sediment in the flow, depending on your expected sediment concentration. To a first approximation, debris flows are roughly half water and half sediment (by volume), but you may already have a better estimate of the expected properties of the debris flows you are modelling.

Only Swiss customers have to pay the Swiss taxes (MwSt).

Yes, you can 🙂

When you select products in the shop, add them to the cart, then view the cart and proceed to checkout. There you will find the option to pay by credit card:

August 26th 2024