Comment on Chain Method for Measuring Soil Roughness

where LI is the length of chain required to span roughness element(s) for a horizontal distance L2. At first glance, the procedure has appeal. It is simple to use and inexpensive and appears to give reasonable results. As ridge height increases without changing ridge spacing (LZ), the length of chain needed to span the ridge will increase; thus, it it can be seen from Eq. [l] that the calculated roughness also will increase. Similarly, if ridge height is held constant and ridge spacing is increased, roughness as calculated by Eq. [I] will decrease. However, a problem occurs when ridge height and ridge spacing vary together. When L2 and L1 vary but the ratio remains constant, Eq. [I] produces unrealistic results. For well-defined ridges, like the constructed wooden isosceles triangular ridges used by Saleh (1994), L1 can be computed directly based on the geometry of the ridges. Thus, to estimate the length of chain required to span one ridge cycle, let s he ridge spacing, which is equal to L2 for one ridge, and h he ridge height for isosceles triangular ridges (Fig. I), then