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7721 7°25E 
6°31'N | — 
  
  
  
  
  
  
  
  
  
. Figure 2: Classified SPOT XS and Topographical Information of Subscene 4 (Ngwo Ukana Segment) 
All the soils sampled are potentially erodible given the clay ratio and the dispersion ratio. Thus, areas of significant 
potential environmental impact will be those locations having sufficient available slope. Moreover during 
construction activities, heavy vehicles would create artificial furrows along tyre tracks in which runoff can 
concentrate, thus facilitating gullying and erosion which could lead to loss of farmland, destruction of property and 
reduction of a scenic environment into badland topography. 
Of the various stages involved in EIA, emphasis is on impact identification and impact magnitude prediction. 
In order to have visual bases for the routing, the corridor was. modelled using cross profiles (Figure 3). 
Information included in this model to enhance understanding of the rationale for impact assessment are those 
on geology, soil, drainage, land use/land cover, erodibility, slope class and indemnity class. The impact 
magnitude map was derived from the integration of the result of three erodibility classes (1,2,3); three slope 
classes (1,2,3); and three indemnity classes with the magnitude of class number corresponding with magnitude 
of impact (see Figure 4). Indemnity is defined in terms of economic, social or environmental cost of potential 
impact in a given area. 
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B7. Amsterdam 2000. 31