Laserfiche WebLink
<br />Stream and location: Hypothetical river in Colorado <br /> <br />Reach length: Station 0 to 570 feet, Section 1 in reach A is <br />located at station 285 feet. <br /> <br />Reach description: The main channel is composed of boulders <br />averaging 11 inches in diameter with average channel adjust- <br />ment conditions. The left overbank consists of sparse brush <br />and trees and the right bank consists of a dense stand of <br />trees, Existing channel conditions are representative of <br />study conditions. See figures 2 and 3 for the plan view and <br />cross sections. <br /> <br />Discharge and depth for the study period: The 100-year discharge <br />is 6,000 cubic feet per second, and the estimated flood depth <br />is about 7 feet. <br /> <br />Channel computation of weighted n-value: <br /> <br />Factor Value <br />Base value (no) 0,065 <br />Cross section irregularity (nl) <br /> <br />Remarks <br /> <br />Used prediction equation 6. <br /> <br />Average condition. In- <br />cluded in prediction <br />equation. <br /> <br />do. <br /> <br />do, <br /> <br />do. <br /> <br />Channel variation (n2) <br />Effects of obstructions (n3) <br />Channel vegetation (n4) <br />Degree of meandering (m) <br /> <br />1.0 <br /> <br />L / L = 1. 06 <br />m s <br /> <br /> n = (no + nl + n2 + n3 + n4) m = (0,065 + o + 0 + o + 0) 1.0 = 0.065 <br /> Overbank n-values: <br /> Subarea Value Remarks <br /> Left overbank 0.08 Used table 6, item C5. <br />I Right overbank 0,12 Used table 6, item D5, <br />I' <br /> <br />Figure 14B,--Sample of a completed roughness-coefficient <br />evaluation form for a natural flood plain. <br /> <br />49 <br /> <br />~ <br />