The results of the tests showed that the roughness Manning porous concrete made of basalt with a different , it has roughness coefficient different. The Manning porous concrete used to test the coefficient of roughness of each of the basalt backlog sieve No. 4 at on the respectively to a range of coefficients. Rough roughness (Manning's, n) at the 0.020 - 0.025 and respectively porous concrete of basalt size 3/8 inch. According to the roughness coefficient (Manning's, n) is 0.028 - 0.030 and concrete's porous basalt with a half 1/2 inch the respectively of the roughness coefficient (Manning's, n) is 0.030 - 0.035
The coefficient of roughness (Manning's, n) changes also aggregates a large coefficient roughness (Manning's, n) a lot and aggregates are small, it has a coefficient roughness. (Manning's, n) at least as well. This will result in a change of roughness coefficient (Manning's, n).