This value may be satisfactory for many computations of discharge. However, more precise values are given in the accompanying table, which shows values derived from tables and graphs published by the Federal Highway Administration for culvert design and that apply to both annular and spiral corrugations, as noted in the table. Values from this table should be used by U.S.JGeological Survey offices in computation of discharge through culverts. Experimental data show a slight lowering of the n value as pitch increases. The n values for these three types of corrugation are also given in the table.
Multiplate construction is used with both steel and aluminum.
Tests show somewhat higher n values for this metal and type of construction than for riveted construction. The n values for various diameters of pipe are given in the following table.