Geoscience Reference
In-Depth Information
Modelling of erosion processes most often includes creating mathematically-
expressed models that make use of knowledge about soil erosion as a natural
phenomenon. Therefore, there are models of various types (Voženílek, 1999):
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deterministic models based on analytical-physical knowledge;
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conceptual models emphasizing the impact of topography on erosion and accu-
mulation of material;
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empirical-statistical models based on laboratory methods of determining values
and on the importance of input factors.
The connection of some models to GIS technologies enables them to become
part of more comprehensive optimisation models (methodology), especially in rela-
tion to spatial optimisation of land structure. The efficiency of these models can
also enhance their interconnection (within GIS) with models of other geomorpho-
logic processes which interact with water erosion (creep, etc.). A number of models
(e.g. CREAMS, ANSVERS, SMODERP, etc.) enable modelling of soil erosion on
individual slopes or in very small river basins. In these models the impact of relief
representation on the modelling results can be seen via the models' factors.
14.5 Conclusions
The issue of relief expression for the purposes of modelling physical geographic
phenomena of land deserves constant attention, especially because of the impact of
different approaches when incorporating quantities related to relief, which is most
often the creation and use of digital relief models. Inaccuracies that arise during
the process of relief modelling are reflected further in the modelling results. Even
when using one set of source maps DEMs of various qualities can be generated due
to different input parameters. These then lead to deviations of various significance
when used in computer models of physical geographic phenomena.
The extent of errors increases primarily with the increasing segmentation of
relief. Firstly, there are errors (differences) arising from expression in 2D or 3D.
Secondly, there are errors in the quality of the DEM which influences the derived
parameters. Low segmentation of relief, to which also small slope inclination of
the land can correspond, leads to negligible deviations measured in 2D and 3D.
However, with increasing inclination the value measured in 3D can be up to double;
in that case the results of models of physical geographic phenomena are influenced
more considerably. When assessing DEM quality using basic statistical characteris-
tics or RMSE it is also possible to observe the following trend: errors (differences)
arising from the use of different interpolation methods (and different setting of their
parameters) compared to reference data decrease from more segmented to less seg-
mented relief types, which is conditioned by the decreasing spread of values of
elevation.
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