Friction Factors in Coastal Flooding

by B. A. Christensen, Univ of Florida, Gainesville, United States,
T. Y. Chiu, Univ of Florida, Gainesville, United States,
John C. Dorman, Univ of Florida, Gainesville, United States,

Document Type: Proceeding Paper

Part of: Engineering Hydrology


As the world's coastal zones are being developed and the coastal population increases, coastal flooding, or rather the prediction of its extent and frequency of occurrence, becomes a more and more urgent factor in the existence of all coastal nations. Flooding of coastal regions may be caused by tropical storms and hurricanes creating the flood wave, and/or by the excessive precipitation that usually accompanies such meteorological phenomena. It is basically a stochastic event the extent of which may be evaluated by the numerical integration of the differential equations governing unsteady wind induced surface flow in the ocean near the shoreline and over low coastal regions. Such numerical models can predict flood depths and flow velocities for chosen astronomical tides and wind configurations thereby making possible a rational evaluation of risks and of the needed insurance and evacuation requirements. A term of some importance in the governing differential equations is the shear term that reduces flow depths and velocities. This shear term is proportional to a friction factor and the local velocity head. The friction factors characteristic of horizontal and vertical obstructions are considered separately. Also the influence of sediment suspended by the high shear stresses is discussed.

Subject Headings: Shear stress | Friction | Coastal environment | Floods | Flood frequency | Ocean waves | Fluid flow | Fluid velocity

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