Date of Award

Spring 1986

Project Type

Dissertation

Program or Major

Earth Sciences

Degree Name

Doctor of Philosophy

Abstract

Storms are important aperiodic events, which intensify erosional processes over short time periods. The effect of rain on the shallow intertidal water column was the focus of this study. The literature was extensively reviewed to identify parallel research in other scientific disciplines, which could be used to understand how raindrops may be acting as a sediment resuspension mechanism. Single-drop and multi-drop laboratory studies were conducted on the initiation of motion of sediment. Results indicate single vortex rings in a quiescent environment can initiate motion of sand-sized noncohesive sediment in all water depths tested, up to and including 22.5 cm. Multidrop experiments (with estuarine muds) indicated that rain can resuspend cohesive sediment at an average rate of 2.8 gm/m('2)/hr in water depths to 8 cm. Insitu experiments were conducted to compare the magnitude of rain resuspension with wind wave and boat wake effects. Rain effects were observed in water depths less than 7 cm. In these water depths wind effects were decreasing, because the shallow water dampened out the larger waves. Observations during two storms illustrated the problem of isolating rain resuspension from wind wave resuspension.

The ability of drops to form vortex rings was utilized in a mixing test of aquaculture tanks used in toxicity testing. Drop-formed vortex rings were more effective in oxygenating the tanks than air bubbling at the strengths typically used for the tests.

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