(5) 
K = 0.0007,1 + n 
s* 
Table 4 shews the value of n that has been adopted in this study. 
The higher the value of De for a particular window, the higher will be the 
weight assigned. The weight assigned reflects the value of the roughness 
coefficient used. 
TABLE 4 : Value of the Roughness Coefficient 
LAND COVER 
n 
Bare 
0.0120 
Urban 
0.0600 
Grass 
0.0855 
Forest 
0.1005 
Channel Detention 
The discharge relationship in streams is calculated by the Manning 
equation: 
V = R^jft (6) 
n 
where: 
V is the mean velocity 
R is the hydraulic radius 
s is the slope 
n is the roughness coefficient. 
Values for the roughness coefficient in natural channels vary from 
0.015 to 0.15 with typical values of 0.03. The same concept is applied as 
in detention storage, a higher value of V means a higher weight assigned. 
For an area which is furthest away from a channel, lowest weight will be 
assigned. 
RISK PROBABILITY ANALYSIS 
Fran the weights assigned to the various factors, a expert ranking 
matrix system can be generated, as shown in Table 5. From the weights 
generated in the table, a test for flood prediction can be performed on a 
3x3 window of the Image. From the test, each 3x3 window of the image will 
contain a weights which reflects the probability of flood occurrence. 
Color level slicing can be performed where the value of each pixel is 
taken as the value of the weight produced. 
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