A knowledge based system as decision support for landscape management in catchments
Mariusz Merta1, Christina Seidler1, Silvie Bianchin2
1Internationales Hochschulinstitut Zittau, Markt 23, D-02763 Zittau
1IÖZ TU Bergakademie Freiberg, Leipziger Str. 29, 09599 Freiberg
Keywords: expert system, plant root system, vegetation influence on the soil, land use changes
Introduction
One of the fundamental qualities of landscapes is the regulation of runoff. Runoff generation
processes are strongly influenced by soil and vegetation. Close cooperation with ecologists enables
the upgrading of the system and affords scenario analysis with different vegetation types. These
reveal the effects of land use changes on runoff generation and, coupled with a precipitation-runoffmodel, on the shape of the flood wave. Thus, an instrument is created providing a basis of land use
planning, flood protection and nature conservation.
Material and methods
The required subdivision should be realized by methods of Artificial Intelligence because our
knowledge about the runoff processes is gained to a considerable extent by empirical knowledge
containing significant uncertainties. Therefore an expert system (XPS) was developed named XPS
FLAB as an instrument of regionalization in order to identify process-related spatial units with a
dominant runoff generation process (Fig.1). A major emphasis was put on quick runoff components.
Basics for the knowledge-based system XPS FLAB are general available information like maps of soil
types, geological formations, land use, stream network, digital elevation model (Peschke et al., 1999;
Merta et al., 2003). The XPS is the module of qualitative evaluation and classification of landscape
elements. In a first step, the system indicates dominant processes under given conditions.
Figure 1: Structure of the Expert System FLAB (areas of equal runoff processes)
Results and discussion
Information about the soils are necessary in order to derive the rules for the expert system. Since soil
properties are strongly influenced by the plant root system (porosity, hydraulic conductivity, storage
capacity, macropores etc.), a visual assessment procedure was developed to characterize the
attributes of root systems (depth, intensity) for a soil profile and applied to root distrubtion pictures of
various soil profiles. This procedure requires knowledge about the vegetation type and the species
composition (dominant species). By means of this scheme new rules on the impact of root systems on
the soil were derived and integrated in the XPS FLAB. The improved system allows considering the
vegetation’s influence on the runoff processes in more detail.
The description in Table 1 exemplifies possible modifications of the soil properties by the vegetation.
This information is the basis to derive new rules. Together with the already integrated information on
the different soil types, this results in new soil properties. Thus a better assessment of the vegetation
influence on the runoff generation processes is achieved.
1
The WBS FLAB was used in the small subcatchment Weißbach (Eastern Ore Mountains). Results
show that overland flow from areas with small infiltration intensity (precipitation intensity has to be
greater than infiltration rate) and interflow components predominate in this region (Fig. 2a).
Table 1: Relevance of root density for soil properties
Class of roots
Low roots density without
rough roots
Medium root density few
rough roots
Sandy soils
Cohesive soils
without modification
without modification
slightly increasing storage capacity
no change of conductivity
High root density many
rough roots
increasing storage capacity
no change of conductivity
slightly increasing of conductivity
no change of storage capacity
growing part of macropores
no change of storage capacity
increasing of conductivity
This subdivision agrees with hydrological measurements, detailed knowledge of the area and results
of modelling with the precipitation-runoff-model WaSim-ETH. Figure (2b) demonstrates the pattern of
runoff processes for the land use scenario. The whole catchment was afforested except the
settlements. The overland flow disappears. Interflow seems to be the most important runoff generation
process. But a general afforestation does not always reduce floods, especially when the soils are
shallow and skeleton-rich. They have only a small storage capacity. The quality of the model results
depends strongly on the resolution and the precision of the input data.
Figure 2: Spatial distribution of runoff generation processes in the Weißbach subcatchment, resulting
from the application of the Expert system FLAB. (a) Current situation, (b) land use scenario –
afforestation all surfaces apart from building area.
The XPS is a combination of strongly abstracted process modelling and the use of comprehensive
experimental experience (expert knowledge). The connection of both offers the possibility of
sophisticated analysis of spatial hydrological responses and of a catchment discretization concerning
the runoff generation processes. The area-related identification of runoff components characterizes
also spatial origins of water and transport paths, thus, being an important base to consider processes
of matter transport.
References
Merta, M., Seidler, Ch., Hellie, F., Uhlenbrook, S., Tilch, N., Zillgens, B. & Kirnbauer, R. (2003): Das
Wissensbasierte System FLAB als Instrument zur prozessbezogenen Raumgliederung von
mesoskaligen Einzugsgebieten. In: Kleeberg, H.-B. (Hrsg.): Forum für Hydrologie und
Wasserbewirtschaftung, Heft 04.03, Band 1: Klima – Wasser – Flussgebietsmanagement – im Lichte
der Flut, S. 171-178
Peschke, G., Etzenberg, C., Müller, G., Töpfer, J. & Zimmermann, S. (1999): Das Wissensbasierte
System FLAB – ein Instrument zur rechnergestützten Bestimmung von Landschaftseinheiten mit
gleicher Abflussbildung. IHI Schriften, Heft 10, Internationales Hochschulinstitut Zittau.
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