This file contains information on each grid of the watershed as well as how the grids are connected in a hydrological manner. It is based on the WATFLOOD map file and can be created using the Green Kenue software. Please refer to the Preparing the MESH Drainage Database File page for further information.
Information about the various attributes can be found in the Green Kenue (GK) manual. Please note that the attribute names are sometimes different in the GK manual, but you should be able to figure out which name in the manual corresponds to the name in this file. When time and priority permits, we will update this documentation to be more complete. Some information about the river classification attribute (IAK) is located below the example file shown next.
The following lines show a sample MESH drainage database file.
- IAK - River Classification
With respect to the five river classes, unfortunately we don't provide much guidance and don't have many tools to assist with identifying different river classes and with actually changing the drainage database file. In the creation of the drainage database file with Green Kenue and BSN.exe, all grid squares are given a default value of 1. If you open the drainage database file in Green Kenue, bring it into a 2D view, right click and select "properties", then look at the "Data" tab, the 8th attribute (IAK), is the river classification. The default value for this attribute is 1.
Now comes the hard part, deciding how to determine your river classes and changing the attributes in the drainage database file. I'll address each one of these separately:
1) How to determine your river classes
There are a number of ways to do determine river classes. Some people provide different river classes to each of the sub-basins they're considering. This only really works if you're dealing with 5 or less relatively homogeneous basins (in terms of river roughness), but it is an option. Others have looked at physiographic properties like soil type to come up with a classification. And others still have looked at streamflow responses to determine a classification. Or you could also provide values based on the number of channels that cross a grid square (channel density, the 10th property in the "Data" tab - Chnl). You may also develop your own ideas about how to determine the river classes that is different.
2) Changing the attributes in the drainage database file
This is usually a tedious process and a number of us have discussed developing a tool to do it, but such a tool hasn't been developed. You could manually change the drainage database file or cut and paste the IAK block of the drainage database file into a text editor or excel and then paste it back into the file. The extra complication with this method is that the r2c file looks inverted in a text editor or excel. So if you invert the array so it looks okay in the editor, you'll need to invert it again before pasting it back into the r2c drainage database file.
Another option (if you classify based on channel density), is to copy and paste the Chnl block of numbers into the IAK part of the drainage database file. This is fast and easy technically, but may not be appropriate for your basin.
Another easy, but much slower process, is to change each grid square individually in Green Kenue. You would have to open the drainage database file in Green Kenue, go to the "Data" tab, and then change the grid squares by double clicking, then right clicking and selecting "Edit" to change the IAK property for that grid square. This can be sped-up by viewing the IAK attribute in the 2D view, using <Shift>-Double-click for the grid squares that you want to change, then right-clicking and selecting "edit" to change the values.
2.1) Email from Kurt Kornelsen - June 18, 2013
I've been going through my drainage files and assigning River Classes (for which I partially have to use Green Kenue). After to much clicking, I was reading your wiki for some advice on doing this and I found an easier way of assigning IAK in Green Kenue than shift+click that I thought I would share. Under the 'Edit' menu you can 'Select > Items in Polygon'. A polygon can either be created by making a 'New Closed Line' or by importing a shapefile. Then you can right click and 'Edit Selected Cell(s)' as before. Saved me lots of time.