Article
WATER SCIENCE AND APPLICATION, VOL. 5, PP. 111-125, 2002
One-dimensional estimation techniques for discharges of paleofloods and historical floods
Paleoflood data in the form of paleostage indicators (PSIs) are used as estimates for maximum flood stage. Discharges for
paleofloods with PSI data can be estimated using one of the following one-dimensional flow techniques: (1) slope-conveyance
method, (2) slope-area method, (3) step-backwater method, and (4) critical-depth method. The purpose of this paper is to review
these methods, with an emphasis on their appropriateness in paleoflood studies. The step backwater and critical-depth methods
are the most commonly used in paleoflood studies, although early paleoflood work relied on the slope-conveyance method. The
underlying hydraulic theory behind these methods is similar, but each method uses different amounts of data and different
solution schemes that affect their usefulness in paleoflood studies. Each method relies on the Manning's equation, and energy
losses attributed to bed roughness are described with the Manning's n. Techniques for objectively determining Manning's n
allow minimizing this source of error, although roughness changes at the time of the paleoflood cannot be objectively calculated
but instead must be estimated. Discharge estimates in many previous paleoflood studies have been adequately documented, and
such documentation should be made in future studies to aid evaluation of the accuracy of discharge estimates.
Citation: Webb, R. H., and
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