Geography Reference
In-Depth Information
6.3.7. GLA Method
The GLA (
G
eologisches
L
andesamt
)
Method, first proposed by Hoelting
et al. (1995), is based on a point count system similar to the DRASTIC
method. The GLA method was further developed by Goldscheider (2000) into
the PI-method within the framework of the European COST 620.
Satellite
Imagery
Geomorphology
Soil Properties
SRTM DEM
Data
Geology
Processing of Input Data in Geographical Information System
Geomorphological
Classification
Land Use/Land
Cover Map
Lithological
Map
Soil Map
Slope Map
Protective Cover
Rating (P)
Infiltration Rating (I)
Karst Rating
(K)
Epikarst Rating (E)
Computation of EPIK Vulnerability Index by Weighted Linear Combination Technique
Figure 8. Flowchart showing step-by-step methodology for applying GIS-based EPIK
method.
Unlike the DRASTIC, the GLA-method only takes the unsaturated zone
into consideration. Attenuation processes in the saturated zone are not
included in the vulnerability concept.
Perhaps, consideration of only unsaturated zone is the major reason that
the method could not get wide popularity and applicability.
In this method, the degree of vulnerability is specified according to the
protective effectiveness of the soil cover and the unsaturated zone. Six
parameters
considered
for
the
assessment
of
the
overall
protective
effectiveness are as follows (Hoelting et al., 1995):
Parameter 1: S- effective field capacity of the soil (rating for FCe in mm
down to 1 m depth)
Parameter 2: W- percolation rate
Parameter 3: R- rock type
Parameter 4: T- thickness of soil and rock cover above the aquifer
