Nyarko, Benjamin Kofi 
  
  
  
Figure 1.7 Flood risk zones of the study area 
  
Flood risk zones of the study area 
  
  
  
  
E 
  
  
  
  
  
  
  
  
Mipoaee 1 : 1508512 
Table 1.2 Flood Risk Zone Coverage 
Flood Intensities Area 
(m?) % 
Low 2269185000 26.85 
Medium 2652485000 31.39 
High 3012897500 35.66 
Very high 515355000 6.10 
  
  
  
  
Source: Figure 1.7 
Table 1.2 shows areas that fall within the very high flood risk zone covering about 6.09 percent 
of the study area. However the combination of the very high and high-risk zones constitutes a 
total of 41.74 percent of the entire study area. Hence, the area coverage of the flood risk zone 
will expand if the rainfall intensity increases above 140.2 mm/day. 
5 SUMMARY AND CONCLUSION 
To determine flood risk zones in Accra and it environs a hydrological model (modified rational 
model) was integrated into the GIS platform, by the arithmetic overlay operation method, using 
operators such as addition and division. The results show that the delineated areas however 
experience same rainfall intensity of 140.2 mm yet the flood intensities of these areas differ. For 
instance, the high flood risk zone covers 35.66 percent of the study area, whiles the low risk zone 
covers 26.85 percent. 
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B7. Amsterdam 2000. 1047