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and Dry Climate) zone also known as the Savanna climate. The onset of rains is in April and the retreat 
completed in October. The rains are usually heavy thunderstorms, a factor that facilitates sheet and gully 
erosion especially on exposed inclined surfaces. 
The prominent landforms in the area include the Udi - Okigwe escarpment which trends NNE. It originates 
south of Enugu and the trends past to the west of Enugu, towards River Benue. Others are, the flat lowlying 
terrain east of the escarpment; the relatively waterless plateau, the eastern edge of which is the precipitous and 
often gullied escarpment; and the southwestern sections of the Benue Trough. This latter area include flat, 
lowlying and often waterlogged sections. The potential corridor is almost wholly underlain by weakly 
consolidated Cretaceous sandstones, mudstones, shales and calcareous rocks, arranged in N-S stratigraphic 
bands, the exception being the northeastern section (Gboko-Yandev) which is underlain by pre - Cambrian 
Basement Complex rocks. There is a close relationship between the geological formation and the 
morphological unit. Soils along the corridor appear to be closely associated with the geology and the 
topographical positions on which they are developed. Thus for example, soils on the plateau, i.e those 
developed on False Bedded Sandstones are mainly acid, have limited development of structure, and a poorly 
developed profile. Lateritic soils also occur on the plateau, but are localized. Alluvial soils are found along the 
river valleys, especially those developed on the Makurdi Shales. 
The vegetation is mainly Derived Savanna in the south (Enugu area) and southern Guinea in the north 
(Makurdi - Yandev area, Keay 1959). A notable feature of the Derived Savanna is the presence of oil palm 
(Elaeis guineesis) and trees associated with dry forests such as silk cotton tree (Ceiba pentandra) and the oil 
bean tree (Pentaclethra macrophylla). The main grass species is Andropogon tectorum. The high density of 
settlements and cultural practices within the corridor have altered the natural vegetation such that economic 
trees (including Pentaclethra sp. , Irvingia sp. , Anocardium sp) are found only around homesteads. A number 
of forest/wildlife reserves are close to the potential corridor. The most notable being the Ikwe Wildlife Reserve 
(7°25' - 7°35'N, 8°20!- 8°23'E) and the Okpobi (7°11' - 7°12'N, 8° 02!- 8°04'E ) and Enugu (6727! - 6°29'N, 
7928!-7°30'E ) Forest Reserves (see Figure 1). There are some sites of archaeological - cultural heritage 
significance in the Leja community, west of Opi (see Figure 1). These sites consist essentially of extensive 
surface scatter of massive, cylindrical shaped iron slag, and appear to be iron-working and smelting centres of 
considerable antiquity. 
  
3 METHODOLOGY 
The methodology employed is aimed at indicating potential areas of environmental impact of the construction 
and maintenance of the HVTL on the proposed corridor. Information used in the assessment was obtained 
through a combination of survey of the literature, field work, analysis of topographic maps and current SPOT 
(XS) satellite imageries. 
The fieldwork was based on the subdivision of the proposed transmission line corridor into 5 x 2 km sampling 
sites. These served as baseline survey quadrats from which information on the geology, topography, 
settlements, ecology, socio-economics and archaeological-historical-cultural elements were derived and 
described. The socio-economic conditions of the populations along the proposed corridor were determined 
mainly through structured and informal interviews and discussions with core members of each community. 
This was to ascertain their reactions to possible disruption of life and property along the proposed route of the 
new transmission lines. 
Soil samples were taken at 0 - 15 cm and 15 - 30 cm depth at each of the 20 sampling points. Soil erodibility 
along the potential corridor was assessed using Bouyoucous' (1935) Clay Ratio (CR) and Middleton's 
Dispersion Ratio (Byran, 1968). For the vegetation, the guidelines designed by Sanford and Isichei (1986) 
were adopted in describing the physiognomy, canopy structure, and the taxonomic composition of both the 
woody and herbaceous layer. 
The topographic map information were updated using ground truthed information on land use/ land cover, 
settlement, road network and stream courses/wetland obtained from classified SPOT (XS) imageries of the 
proposed corridor. Colour-coded segment maps, each corresponding to 10km x 10 km subscene imageries 
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B7. Amsterdam 2000. 29