Calculate Topographic Wetness Index and Create a Processing Tool in QGIS

In this video you'll derive the Topographic Wetness Index (TWI) from a DTM using the PCRaster Tools plugin in QGIS. Next, you'll see how we can write a Python script that does the same. Finally you'll see how to develop a Processing Tool and share it with others through the QGIS Resource Sharing plugin.

0:00 Introduction and theory
1:06 Calculate slope fraction
1:52 Calculate flow direction (LDD)
2:07 Calculate flow accumulation
3:16 Calculate cell area
3:48 Calculate TWI with Raster Calculator
5:20 Calculate TWI with Python script
9:50 Install Resource Sharing plugin
11:08 Create QGIS Processing Script

#QGIS #PCRaster #PyQGIS

[sanjoybarman]

Please make a tutorial on ''Shannon's entropy'' for

[staycherry]

Dear Hans, thank You very much for your videos! They help a lot!
Please, could You show how to make a map of total mean annual soil erosion during snowmelt? Based on the map of the flow accumulation or the flow length... Can it be done with PCRaster?

[MadhurimaB-sb]

Hi Hans. what do we do when the slope has zero values? how can we remove them?

[RubenThe]

Hello Hans, my TWI.map looks very different from your's. It is very pixely and i cant detect a clear pattern. In the video you said there could be isseus because of values of zeros in the slope map. Well, my layer has some zeros but I'm not sure how to fix them. Best regards, Ruben

[StefanvanGestel]

When using lddcreate it just calculates into infinity and I have to kill the qgis process using task manager. Any idea what could be going on? Using some AHN4 tiles which I merged together as DEM.