Geography Reference
In-Depth Information
silts and shales) which, because of its layered structure, hamper the infiltration of surface
runoff. On the other hand the vegetation is typically mediterranean, composed by
quercĂ­neas and sclerophyllous over Eutric Leptosol. Therefore on more rugged slopes, there
is little capacity for water storage, making it difficult to sustain the vegetation. Furthermore,
poor agricultural practices have been destroying the natural vegetation, causing in the rainy
season a deterioration of these soils and turning them into skeletal. So the predictable risk of
erosion ranges from moderate to high.
The flat plains are the second class of the highest representation (25.3%), distributed on the
littoral, next to the Ria Formosa and along the leeward coast. These flat surfaces, with less
dense dendritic drainage systems, are composed mainly of alluvium, sand dunes and
pebbles (slightly cohesive soils and sediments). This system flows in parallel form to the
arms of the estuary and may be subject to flooding. These areas are fluvisol, luvisols and
cambisols and are fertile for agriculture. They have dense vegetation, with orchards and
complex cultural systems providing a low or moderate risk of soil erosion.
Area
(km 2 )
Class
Subclass
Code
Plains
Flat plains
11a 11b 11c 11d
142.93
Nearly flat plains
12a 12b 12c 12d
65.92
Smooth plains
13a 13b 13c 13d
16.04
Slightly irregular plains
21a 21b 21c 21d
27.51
Irregular plains
22a 22b 22c 22d
52.62
Very irregular plains
23a 23b 23c 23d
23.97
Plateaus
Low Plateaus
14c 14d 24c 24d
0.52
Plateaus
15c 15d 25c 25d
0.02
Plains with hills
Plains with low hills
14a 14b 24a 24b
0.63
Plains with hills
15a 15b 25a 25b
0.01
Open hills
Very low open hills
31a 31b 31c 31d
3.84
Low open hills
32a 32b 32c 32d
32.33
Localized open hills
33a 33b 33c 33d
37.38
Moderate open hills
34a 34b 34c 34d
3.48
High open hills
35a 35b 35c 35d
0.13
Hills
Very low hills
41a 41b 41c 41d
2.22
Low hills
42a 42b 42c 42d
46.44
Localized hills
43a 43b 43c 43d
226.67
Moderate hills
44a 44b 44c 44d
128.85
High hills
45a 45b 45c 45d
14.45
Table 4. Classification of 20 classes of landforms and their cover area (Ria Formosa).
2.5. Conclusions
Using an automatic hierarchical method for classification the Ria Formosa drainage basin
has been subdivided in twenty landforms. The area included in each class is characterized
Search WWH ::




Custom Search