ALPMON FINAL REPORT - ARC systems research

Contract ENV4-CT96-0359 ALPMON
2.3.4.3 Applied Methods
2.3.4.3.1 Overview of the FSTAB Erosion Risk Model
The erosion model, called FSTAB (Fuzzy Stability) is composed by two sub-models, DA (Discriminant
Analysis) and SCS-CN (Soil Conservation Service – Curve Number), running in parallel to account for
the different factors influencing soil erosion processes and slope instability. The DA sub-model,
specifically built for this study on statistical basis, accounts for static factors affecting mass erosion
while the SCS-CN sub-model, an already available and well known potential infiltration and runoff
model, accounts for the dynamic effects of rainfalls. These sub-models run independently using a
shared database of geographically referenced information on land cover, soil, geology, geomorphology
and climate. The output from the two sub-models are integrated in an inference engine, based on fuzzy
logic, which gives a reasoned erosion risk index, called MEHI (Mass Erosion Hazard Index). The
inference engine, for the assessment of global risk, uses a set of predefined decision rules.
Land Cover
Slope
Soil/Debris Depth
Soil/Debris Type
Impermeable Subsoil
DA sub-model
Stability index based on
classification of present stability
degree and derived from
discriminant analysis. It
accounts for static conditions.
Curve Number (depends on Land Cover,
Pedology, Geology)
Critical Rainfall Volume
FSTAB Model
Slope natural instability risk
based on fuzzy inference
system.
Inference Engine
Based on Fuzzy Logic and a
set of predefined decision
rules.
SCS-CN sub-model
Runoff/Infiltration potential. It
accounts for dynamic conditions
due to extreme hydrologic
events.
DA Index Infiltration Potential Index (INF)
Mass Erosion Hazard Index (MEHI)
Figure 9: Overview of the FSTAB Erosion Risk Model
JR, RSDE, ALU, LMU, Seibersdorf, WSL 45