For the definition of HRU (Hydrological response units), the parameter slope can be classified into maximum of 5 classes. Depending on the definition the results will vary.

Is there a commonly used method to decide on the intervals of such classifications?

In literature, many different classifications are used. Most of the times, no information on how the classes were created is given.

How can I find out what makes sense the most?

Example FAO

0-7 7-15 15-20 20-25 25-30 30-100

Example ArcGIS

In ArcGIS, the slope can be classified with different algorithms. For my watershed, the Natural Invertall (Jenks-Caspell-Algoritm) creates the classes

0-5 5-12 12-20 20-30 30-100

Standard deviation

0-4 4-13 13-22 22-31 31-100


Someone asked the similar question in Google Group: https://groups.google.com/forum/#!topic/swat-cup/vS8QDE5eyag

While the definition of different classification should be available online. http://pro.arcgis.com/en/pro-app/help/mapping/layer-properties/data-classification-methods.htm

I think the real problem is what portion of the data the model output is sensitive to. Based on the description of these method, I think the Natural breaks (Jenks) should be used in most cases because "Class breaks are identified that best group similar values and that maximize the differences between classes." so it could preserve the most spatial variability in the dataset.

  • thanks for the comment. I ended up using the natural breaks with the same thoughts as you stated. – loloj0 Nov 28 '18 at 9:46

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