Geography Reference
In-Depth Information
Table 8 shows that most representative classes have low risk (28%) and moderate risk (44%)
of soil erosion, usually on the highlands or at the coastal areas. The coastline consists mainly
of cliffs with non-cohesive materials (sand and gravel). In the highlands the material is more
resistant (Flysch group from lower Alentejo) but the amount of rainfall is higher and the
steep slopes favour soil erosion processes. Soils with material from class D (soil or poorly
resistant or deeply altered rocks) and E (soils or sediments that are poorly cohesive or
detritus materials) are the most representative, with slopes ranging between 0-3% (slow
runoff) and 3-16% (moderate runoff).
3.4.2. Modified Fournier Index
All study areas, classified according to CORINE - CEC (1992), present values of
MFI
of low
risk (71%) and moderate risk (29%) of erosion, which means a small aggressiveness of
rainfall.
Erosive
State
Occupation
Slope
Soil
Land Cover
Very Low
10%
0-3%
Schists, phyllites, silltites,
quartzites and Flysch
group
Hardwood forest
Dunes
Permanently
irrigated land
Low
28%
0-3%
Sand, sandstone and
gravel
Coniferous forest
3-16%
Flysch group
Hardwood forest
Moderate
44 %
3-16%
Sand, sandstone, gravel
and dunes
Coniferous forest
Flysch group
Hardwood forest
High
16%
3-16%
Limestone, dolomite,
sand, sandstone gravel
and dunes
Cultures /systems
fragmented complex
/ non-irrigated arable
land
16-31%
Flysch group
Hardwood
forest/agro forestry
Very High
3%
21-31%
Limestone, dolomite,
sand, sandstone gravel
and dunes
Non-irrigated arable
land/ forest or shrub
vegetation
transition/beaches
Flysch group
Agro-forestry
Table 8.
Characterization of the erosive status.
