Geoscience Reference
In-Depth Information
drainage model relies on the direction of slopes and gradients, which are calculated
by DEMs. For several years now the analysis of relief using information technology
(IT) methods has been the subject of the research projects of many hydrologists. In
the 1970s, DEMs (they had another name during this period) were very rarely used
because it was necessary to represent altitudes on a map and at this time this was not
possible for DEMs [LAB 76]. Some time later [DEP 91] tools used to digitize
contour lines were introduced, and these tools were seen as a leading development
of that period in time. Progress made to date in the field of remote sensing has
meant that DEMs have become increasingly available. However, several anomalies
can also occur, such as the preferred direction in which the drainage flows, and the
creation of endroheic basins, etc. It is, therefore, necessary to make more people
aware of such drainage models and to get them to use them, as well as using the
stream system that is also available. The different commands of GIS make it
possible to use such models and include flow direction, flow accumulation and flow
length, which are part of the library known as Hydro Arc View.
Figure 7.3.
A diagram showing the principles of a semi-distributed model
From this introduction it is possible to see that in order to respond to the
problems of today's society, hydrologists require precise information about water
levels for a particular point on a drainage basin's outlet. These data are very rarely
