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Creases, Separatrices and Drainage Patterns


Since the end of the last century researchers have tried to characterize mathematically the special slopelines that sketch the drainage pattern of a landscape. As a result other features were also characterized: creases and separatrices.

According to Webster's dictionary, a crease is a ridge or groove produced in anything by folding. The key word of the definition is folding which, in natural language, refers to a specific and intuitive geometric aspect of a surface, locally observable. The words ridge and groove should be interpreted here merely as a distinction between convexity and concavity with respect to some singled out direction. We term as creases the ridge/valley-like structures defined according to local conditions, which basically come from analyzing the form of the surface, looking for the 'center' of anisotropic regions.

A separatrix is something that divides or separates, following Webster's dictionary, so we have to specify what separate our separatrices. As we will see, ridge-like separatrices, basically, will be separating basins (watersheds) and valley-like separatrices, basically, will be separating hills (watercourses).

Antonio Lopez
Wed Oct 8 17:04:50 MET DST 1997