**3.5. Conclusions**

264 Cartography – A Tool for Spatial Analysis

runoff) and 3-16% (moderate runoff).

*3.4.2. Modified Fournier Index* 

rainfall.

**Erosive** 

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

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

**State Occupation Slope Soil Land Cover** 

group

gravel

and dunes

and dunes

and dunes

quartzites and Flysch

sand, sandstone gravel

sand, sandstone gravel

16-31% Flysch group Hardwood

Flysch group Agro-forestry

Dunes Permanently

Flysch group Hardwood forest

3-16% Flysch group Hardwood forest

Hardwood forest

irrigated land

Coniferous forest

Coniferous forest

Cultures /systems fragmented complex / non-irrigated arable

forest/agro forestry

Non-irrigated arable land/ forest or shrub

transition/beaches

land

vegetation

Very Low 10% 0-3% Schists, phyllites, silltites,

Low 28% 0-3% Sand, sandstone and

Moderate 44 % 3-16% Sand, sandstone, gravel

High 16% 3-16% Limestone, dolomite,

Very High 3% 21-31% Limestone, dolomite,

**Table 8.** Characterization of the erosive status.

Environmental biophysics requires knowledge of the resources and processes affecting ecological systems conservation, as well as planning and land management. In completion of the erosion cartography it was possible to develop topographic models (slope, orientation of slopes and distance to the coastline), climate (rainfall, hillshading, Modified Fournier index) and lithofaces. These models represent quantitatively the environmental variables that affect the process of erosion.

Moderate erosive status is the most frequent class in the study area. Highlands, where the soil material have moderate resistance (flysch formation) and the precipitation is higher, and the coastline, essentially composed of cliffs with low cohesive material (sand gravel), are the most sensitive areas to erosion. However, using this erosive model it is difficult to justify the risk of water erosion at the coastline. In coastal areas infiltration prevails (sand dunes) and the wind action is the most important factor in the erosion process. Therefore, in future studies, the model should be capable of including wind erosion.

The largest amount of precipitation is falling in December and January and the lowest in July and August. Through the mapping of the rainfall erosivity, it was found that the aggressiveness of rain in the coastline and in the highlands is higher in these months.
