Data importation

Data importation (Tools > Format data) and the definition of the case study area are necessary before running a simulation. After closing the software, all imported data remain and will be available for future use.

Data importation is conducted using ASCII files in ArcGIS format, with the heading shown below:

ncols ...

nrows ...

xllcorner ...

yllcorner ...

cellsize ...

NODATA_value ...

.... (data)....

Caution: the decimal symbol needs to be the same as defined in your system preferences.

It is imperative to use meters as unit for the xllcorner and yllcorner coordinates as well as for the cellsize. In addition, the corners coordinates of the grid must be a multiple of the cellsize in order to guarantee that the data are correctly superimposed. If this last point is problematic, see the FAQ. It is also necessary that all the data have the same resolution. This resolution will influence the source identification and the calculation of the spreading, and should be consistent with the studied phenomenon (see references).

Data importing and formatting are conducted in two steps:

1. The data (ASCII grids) are first imported using the button Import. The spatial domain may be as large as desired, as the study area on which the simulations are processed are determined afterwards. If the domain is very large and the import fails, see the FAQ or the preferences.

2. Then, the case study areas are defined. This step determines the sub-areas on which the simulations are processed. The size of study areas must be limited due to available memory. This creates a local grid of the digital elevation model (DEM) and a mask of the region. There are three ways to generate these data:

   • Manually using the DEM: an overview of the DEM is displayed and the boundaries are defined by clicking on the image.

   • By introducing the coordinates: boundary coordinates may be entered in a window. X corresponds to abscissa coordinates (west-east) and Y corresponds to ordinate coordinates (south-north).

   • On the basis of a mask: a mask of the area in ASCII format. The area to consider must be >=1 and the rest <=0.

   • By selecting the entire DEM: this is only possible for areas of a reasonable size.

An optional preprocessing is available for debris flows only and consist in:

1. Identifying the rivers (of any kind: from streams to large rivers): rivers can be identified based on the flow accumulation calculated in ArcGIS (the D8 is here recommended) and imported as described above. It is also possible to process the flow accumulation using an integrated routine, but this can only be done for an area of limited size. The result of this step is a mask of the pixels that are characterized by a contributing area higher than the chosen threshold.

2. Choosing the buffer zones: only source areas that are at a certain distance from the rivers will be taken into consideration. The size of the buffer (distance to drainage pixels) is to be determined. The result is a buffer mask that constraint the identification of the source areas.

When new data have been imported, the main interface must be refreshed to integrate them (View > Update).