TABLE 3 : Weights Assigned Due to 
Interception 
Land Cover 
Weights 
Forest 
5 
Grass 
10 
Urban 
15 
Bare 
20 
Depression Storage 
The irregular features of the land surface are filled with water 
during rainfall and which does not run off but infiltrates or evaporates. 
Land tillage, loading and housing construction, swamp drainage, the 
construction of terraces, etc. tend to change the natural depression. The 
greater the depression storage, the lesser the overland flow, and it is 
assumed that the lower the flood potential. If the depressions are 
sufficiently large, such as swamps in upland basin, it tend to regulate 
the water yield and provide a supply for stream flow. 
In this paper it is assumed that the natural depression storage 
ranges from 1 mm to 50 mm. For sloping ground it is assumed that the 
depression storage increase by 50 mm and 75 mm if on fairly flat ground. 
Detention Storage 
The amount of water detained on the land surface that provides the 
head for overland flow is directly associated with the roughness and 
condition of the land surface. Overland flow is, in general, more 
pronounced in arrid conditions. 
The equation used to study the relation between the surface detention 
and overland flow is: 
De = Klqc 
(4) 
where: 
De is the detention volume under equilibrium conditions. 
K is a coefficient. 
1 is the length of flow. 
qc is the discharge per unit width of equilibrium. 
The value K depends on the rainfall intensity (I), the slope surface 
(S) and a roughness factor (n), that is : 
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