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<br />SESSION WQ-OI
<br />WATER QUALITY I
<br />Moderator: Randy D. Crissman
<br />
<br />flow and Chloride Transport in the Tidal Hudson River, NY
<br />Lawrence A. Weiss. Raymond W. Schaffranek: and M. Peter deVries ...........,..1300
<br />Thenno-Hydrodynamic Modeling of the Chicago Sanirary and Ship Canal
<br />Ejaz Mohammad and Fonest M. Holly, Jr. ...... ................. ....... .....1306
<br />Salinity and Dissolved..oxygen Dynamics in a WindwDriven Estuary
<br />Jerad 0, Bales and R,G, Garrett "",.."..""....""""..",..""".." 1311
<br />Development of Long-Term Three-Dimensional Hydrodynamics in Long IsI~d Sound
<br />for Use in Waler Quality Modeling
<br />Richard A. Sclunalz. Jr. .......,..........,......,...,.................... .1316
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<br />SESSION WQ02
<br />WATER QUALITY ENHANCEMENT TECHNOLOGY
<br />Sponsor: Technical Committee on Hydrologic Transport and Dispersion
<br />Moderator: John Gulliver
<br />
<br />Modeling Ecological Impacts of DestratiflCation
<br />S, Geoffrey Schladow, O,P, Hamilloo and M, Burling"","""""""""" ,1321
<br />Design and Testing of Two Ice-Preserving Winter Lake Aeration Systems
<br />Christopher R, Ellis and Heinz G, Stefan ..",...."..,..,........,....""" _ 1326
<br />Water Quality Enhancement Technology for River-Reservoir Systems
<br />John S. Gulliver and Steven C. Wilhelms............................. _...... .1331
<br />
<br />Subject Index, , , , , , , ' , , ' , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ' , , , , , , , , , , , , , , , , 1341
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<br />AlIlhar_."""""""""""""""""""""""""""""", ,1351
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<br />BIAS IN REGRESSION ESTIMATES OF MANNING'S D
<br />KellJlt:th L. Wahl 1 , Member, ASCE
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<br />Selected equations for estimating roughness for gravel-bed sJreams were lested
<br />using a composite data sel containing much of the data used to define the equations,
<br />AU equations tested were found to significantly underestimate n for relatively low
<br />discharges, For floods about equal 10 the median annual peak discharge, Jarrett's
<br />equation overestimates n (median error = 10 percent) while the other equations rested
<br />showed no bias, Extrapolation of any of these equations 10 discharges greater than
<br />aboul 1.5 times the median annual peak discharge is presently unwlUTlUlted, The
<br />roughness of mountain streams is known to generally decrease as dischlllgC and flow
<br />depth increases, The data, however, are presently DOl available 10 leSlthe applicability
<br />of the equations 10 large flood discharges.
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<br />Introduction
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<br />Rood discharges are often detennined from indirecl measurements made after
<br />the floods have receded, These indirec1 measurements are based on hydraulic
<br />fonnulae that define the channel roughness in lel11lS of Manning's n, Traditional
<br />methods of estimating the roughness values ""1M thai the anaIysI visually estimate
<br />the influence of several factors thai affecl roughness and combine or weighl those
<br />facto" 10 estimate the roughness for the channel reach. This traditional approach is
<br />admittedly subjective, hnt is aided somewhal by the compilation by Barnes (1967) of a
<br />book of color photographs of various channels for which the roughness values have
<br />heen validated, MOSI, bol 001 all, of Barnes (1967) verifications were for at least
<br />moderate flood discharges, A recent report by Hicks and Mason (1991) presents
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<br />I. Hydrotog;st. U,S, Geo1ogiea1 survey, WRO, Lakewood, CDltndoIlO22S
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