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soil classes presented in it are the following: (1) PVd: Red
Yellow Podzolic distrophic (typic Paleudult). of very high
erosion potential. mainly when associated to Cambisol (typic
Dystrochrept): (2) LVd: Red Yellow Latosolic (typic
Haplorthox). associated to Cambisol. with no or very low
erosion potential: (3) Ac2: Alluvion, with no erosion, although
it is not appropriate to every urban land use. but with good
agricultural potential: (4) Ca: Cambisol. presenting high erosion
potential: (5) Ral5: Litosol (Orthent). associated to Cambisol.
of high crosion potential: (6) AR2: rock outcrop. in which
predominate iron layers with quartzite and “itabiritos™ rock
outcrop and which has no erosion potential but. considering its
characteristics. should not be occupied.
As with the topographic maps. the soil map was divided in
cells. and the soil classes found in each cell were stored.
Using the soil map and following the soil characteristics. each
class of it was associated to a.soil erosion potential to produce a
new map. using Arc-Info commands. The new map was
classified in five classes: (1) no erosion potential: (2) no erosion
but prohibitive urban land use: (3) low to medium erosion
potential; (4) high erosion potential: (5) rock outcrop.
The original map scale is not really appropriate in terms of
detailed information about erosion in the study area. but it was
the only one available. The map produced from it is a
generalisation of reality. neglecting important variants.
3.2.3 Establishing the Drainage and Producing the Map
of Suitability Areas to Urban Land Use: Using the drainage
map produced on the basis of the topographic map. a new map
was elaborated considering the higher or lower suitability to
urban land use. According to the Brazilian Constitution and
other information. there are in Brazil three classes of
occupation: (a) Permitted occupation - the occupation is
permitted. with no restriction. if the cell area does not have a
river or a spring: (b) Permitted occupation. with restriction -
this class considers the presence in the cell area of any sort of
river. whatever its dimension. defining restriction according to
the size of the river edge: (c) Prohibited occupation - the
occupation here is forbidden if there is one or more springs in
the cell area. or if the area is located inside a river. lake or
reservoir.
Each cell was evaluated in terms of the predominant situation.
that which characterised more than 50 percent of the cell.
3.2.4 Modelling and Producing the Physical Potential
Map: The physical potential map was produced after the
elaboration of the soil erosion. drainage. and slope maps. This
map was made in the Arc-Info Grid Module. using the "if
statement" function. so that crossing (overlay) rules were
established.
The next step was to establish the relationship among the basic
maps and define the classes of the physical potential map.
These classes were produced considering the EMPLASA
(1990) - a planning office of the Sào Paulo City. information
and the characteristics of the study area. The resulting
classification is indicated in table 1.
The potential map was superposed to the urban land-use map to
define the most problematic areas.
Table 1- Physical Potential Classes
Class Characteristic
SUITABLE AREAS e Flat to mildly sloping (< 10%). with no
river spring or even a river, and no erosion
risk:
SUITABLE AREAS. | e topography predominantly in good
WITH SOME | conditions to be occupied but having some
RESTRICTION sectors with high slope (>20%). river
spring. and moderate or severe erosion risk;
FAVOURABLE e topographic conditions not favourable
AREAS WITH | to be occupied in many hill sectors,
SEVERE presence of unstable slopes areas of
RESTRICTIONS landslides. or the potential for their
occurrence during or after construction,
which must have severe projects of
urbanization:
AREAS WITH | e flat sloping. soils with low capacity of
SEVERE supporting; Having zones of inundation:
RESTRICTIONS IN | e areas with mildly slopes. which can
DIFFERENT have problems associated to roads
SECTORS construction;
e areas with high slopes. being crossed
by rivers;
INADEQUATED e areas with slope >20%, and high
AREAS erosion risk that makes these areas
inappropriate to be occupied; some areas
have river spring. which can not be
occupied:
ROCK OUTCROP e Rock outcrop
32.5 Urban Land Use Map: The urban land-use map was
produced by means of TM/LANDSAT digital image. bands 1,
2. 3. 4. 5. and 7. located at the orbit 218/74, and obtained in
March 3. 1993. A median filter was applied to the raw image to
produce a new image with more uniform urban classes, making
it possible to have a good classified map.
The digital image was classified using the Erdas-Imagine
Maximum Likelihood classifier. the map was divided.
following the methodology of Anderson et al. (1976) in eight
classes: predominantly residential. predominantly commercial /
services/ industrial. parks. grass. exposed soil, lake. water
vegetation, other uses. After being classified. this map was
exported to Arc-Info to be superposed to the physical potential
map.
4. RESULTS AND DISCUSSION
4.1 Physical Potential Map
The physical potential map was produced after the elaboration
of the basic maps and the definition of the crossing rules. The
result is shown in figure 3. The classes obtained and respective
areas occupied by them are in figure 4.
These data show that the areas classified as severe restrictions
in different sectors are present in 41.3% (116.6 square
kilometres) of the total area. The class “favourable areas with
severe restriction” occupies 29.1% (117.4 square kilometres),
and the class “inadequated areas”. where the occupation is
prohibited. represents 20% (80.7 square kilometres) of the total
area.
International Archives of Photogrammetry and Remote Sensing. Vol. XXXII, Part 7, Budapest, 1998 219
