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Guide to Color Key: User Input Data Calculated Value Reference Data <br />Designed By: Allen. Sorenson Date: 06/16108 <br />Checked By: Date: <br />Company: Division of Minerals and Geology <br />Project Name: Monarch Quarry <br />Proiect No.: TR-01 I <br />Site Location (City/Town) Monarch Qua <br />Site Id. M2000098 <br />Step 1. Selection of basic value of n. Select a basic n value for a straight, <br />uniform, smooth channel in the natural materials involved. The conditions of <br />straight alignment, uniform cross section, and smooth side and bottom surfaces <br />without vegetation should be kept in mind. Thus, basic n varies only with the <br />material than forms the sides and bottom of the channel. Select the basic n for <br />natural or excavated charnels from Table 8.04a. If the bottom and sides of a <br />channel consist of different materials, select an intermediate value. <br />Channels in earth <br />Basic n value (n=0.020) 0.02 Table 8.04a <br />Step 2. Selection of modifying value for surface irregularity. This factor <br />is based on the degree of roughness or irregularity of the surfaces of channel <br />sides and bottom. Consider the actual surface irregularity first in relation <br />to the degree of surface smoothness obtainable with the natural materials <br />involved, and second in relation to the depths of flow expected. If the surface <br />irregularity is comparable to the best surface possible for the channel materials, <br />assign a modifying value of zero. Irregularity induces turbulence that calls for <br />increased modifying values. Table 8.04b may be used as a guide to selection <br />of these modifying values. <br />Modifying value: channel <br />surface irregularity (Severe (0.020) I 0.02 I Table 8.04b <br />This section describes a method for estimating the roughness coefficient n for <br />use in hydraulic computations associated with natural streams, floodways, and <br />excavated channels. The procedure applies to the estimation of n in Manning's <br />formula (Appendix 8.05).