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Water Science and Applications



  • Paleohydrology
  • Floods

Index Terms

  • 1719 History of Geophysics: Hydrology
  • 1821 Hydrology: Floods
  • 2494 Ionosphere: Instruments and techniques
  • 2447 Ionosphere: Modeling and forecasting



One-dimensional estimation techniques for discharges of paleofloods and historical floods

R. H. Webb and R. D. Jarrett

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 R. D. Jarrett (2002), One-dimensional estimation techniques for discharges of paleofloods and historical floods, in Ancient Floods, Modern Hazards: Principles and Applications of Paleoflood Hydrology, Water Sci. Appl., vol. 5, edited by P. K. House et al., pp. 111–125, AGU, Washington, D. C., doi:10.1029/WS005p0111.

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