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Surface microrelief is frequently characterized using random roughness factors (RRF) defined by Allmaras et al. (1966). Random roughness factors are usually measured using a pin roughness meter or laser. Saleh (1993) recently proposed the chain method as a relatively simple, fast, and inexpensive technique for characterizing surface microrelief. The chain method is based on the principle that as a chain of given length is placed across a surface, the horizontal distance covered by the chain will decrease as surface roughness increases. Reductions in chain length caused by surface roughness are described as Saleh roughness factors (SRF).
In this study, RRF and SRF were identified for a wide range of surface roughness conditions. The standard deviations in SRF obtained on al m2 area were reported. Regression equations were developed for estimating RRF and SRF. The equations, which include rainfall as a dependent variable, can be used for RRF varying from 2.59 to 37.23 mm (0.10 to 1.47 in.) and SRF ranging from 2.65 to 34.56. The chain method provides an easily obtained direct estimate of surface roughness.