- Ohamobi, Sylvester Ikechukwu
IAPRS, Vol. XXXIII, Amsterdam, 2000
TO ‘ The landscape is divided into-three : Plateaux, Piedmont and Valleys. The soils of Sokoto area are characterized by a sandy surface
: layer and clayey subsoil layers. Because of the erosive nature of the climate (particularly rainfall ), the soils are often liable to rill A
and gully erosion. The soils of the Fadamas (seasonally flooded river valleys) are generally more fertile and less prone to erosion, but
flooding hazard is high on.them. Generally, soils of the area can be described as coarse textured, though some medium textured soils
can be found in the south-eastern part of the state. Most soils in the area are deep within the aeolian sand areas, while shallow soils
can be found in the plateaux. :
3 13° Planning and Allocation of Roads
The necessity for a rational soil interpretation system for the allocation of roads and other engineering purposes, and for collation,
storage and retrieval of relevant engineering information on regional basis has been recognized for some time. In planning and
allocation of roads, railways, pipelines and canals, it is necessary to identify specific problem areas and to locate source of natural
construction materials over long distances. This could be done by production of soil engineering maps by use of remote sensing
techniques. This could be done by production of soil or detailed information for road allocation /planning and also for location of
construction materials. It is therefore, important to document the information on the distribution of soils in an area and their properties
including groundwater conditions before any reasonable and economic allocation and design can be developed for road routes.
lation, p : x ,
n Ne . During a road route allocation stage, existing soil (figure 2) and geological maps of the area are often used fór trying to avoid
: : swampy sections and to utilize borrowed sources. The soil properties are obtained from the field measurements and laboratory tests
sm - before the final analysis for road allocation is made. E :
died Since the soils and geotechnical data required in the road allocation work are usually very large in quantity, geographic information '
vidt "s system (GIS) is used for data analysis, and these have been proved as effective for decision making in road projects. (Turner, 1988; - ;
portes, Oshima et al., 1986; Berry, 1986). i | : ;
ables : : dy : ; dis sas on ni | .
us Soil engineering interpretation for road allocation should be in a scheme that can be easily applied and interpreted by road engineers
final and planners. No special skill should be required for its implementation. The scheme should be compatible with all facilities that the
GIS should afford, so that information may be stored for future uses.
"E th Soil engineering interpretation for this study involves the use of soil and construction materials properties determined both in the
a Wu » laboratory and in the field (spatial and non-spatial database) and the modified rating tables (rule base ) which were used for
production of attribute suitability maps. : : :
orld
sa
Eris #!
[FA putt EX] pati. Ez
“| 86) puzus () pitis DS
EN pe212 pi112 vaits EZ setti
C7] pusts pi211 vaiid
Figure . 2, SOIL MAP OF THE STUDY AREA SOKOTO, NIGERIA | a
pu. 111 © Tread, pu. 211 = Escarpment. pu. 212 = Talus, Pu. 31i = slope-facet Complax, pu. 411 = Hill-val' | 4 . >
Complex, pi, 111 = upper slope, pi. 112 = Lower'slope, pi. 211 = slope-vale Complex, Va. 111 = Levee, '
Va 112 » overflow mantle, va 113." Basin Coxplex, va 114 = Channel Complex, va 115.» Plat.
2. METHODOLOGY
2.1 General t: s n ARM m : | : 0
The methodology used in this study is basically the application of remote sensing and GIS to terrain evaluation of Sokoto area. The
choice of this:method for soils and engineering properties of this area for road allocation is significant because of the sparse
»
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B7. Amsterdam 2000. 1059
