Date of Award

Spring 2012

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Civil/Environmental Engineering

Committee Director

David R. Basco

Committee Member

John M. Klinck

Committee Member

Jaewan Yoon

Abstract

The correlation of the morphological changes to the coast and storm characteristics is among interests of coastal engineers. Better understandings of a storm's potential forces ultimately lead engineers to safer designs and minimize the damages. Therefore, a need to quantify the storm potential forces to a storm parameter is evident. The desired storm parameter is to consider all the relative physical factors and is to present realistic results that then can be proven by actual nature response.

The concept of Coastal Storm Impulse (COSI) parameter was first introduced by Basco and Klentzman (2006) and is based on the conservation of horizontal momentum to combine storm surge, wave dynamics, and currents over the storm duration and here is referred to as original COSI parameter. The COSI parameter consists of three components of wave, surge and current momentum. The current momentum is not considered in the original COSI parameter since it was not significant in compare to the wave and surge momentum (Klentzman, 2007). It is not considered in this dissertation for the Modified COSI parameter in order to keep the consistency of the analysis.

In this dissertation, steps have been taken to examine and to redefine the criterion of storm definition, wave momentum and surge momentum in order to improve shortcomings of original COSI parameter. For the Modified COSI parameter, the estimation of wave momentum integrated over the water depth and averaged over the wave period utilizing nonlinear (Fourier) wave theory is introduced for the first time. A computer FORTRAN code developed within the Hydraulic and Coastal Group in the Department of Civil Engineering at University of California, Berkeley is used to develop a set of empirical formulas to estimate the wave momentum. Also, the importance of tides in beach stability has been noted and is considered by applying water elevations above Mean High Water (MHW) to obtain the storm surge momentum. The Modified COSI Parameter introduced here is sum of the wave momentum and the surge momentum. For a "storm event" it was assumed that the wave height will stay at or above 1.6 meter for 12 hours to have a chance to ride on the high tide and it is based on a tidal cycle of approximately 12 hours. The data set for year 1994-2003 at USACE Field Research Facility (FRF), Duck, NC, has been reanalyzed based on the new methodology and criterion set forth in this dissertation. This new approach has produced 148 storms in compare to 160 storms from original COSI results (Klentzamn, 2007) over the period of 10 years the data (1994-2003). The analyses of the 10-year data (1994-2003) show a better proportionality of the wave momentum (60%) and the storm surge momentum (40%) to the total momentum. In general the average wave momentum resulting from empirical formulation introduced in this dissertation is in average 10 times smaller than the maximum wave momentum from Hughes (2004) formulation.

DOI

10.25777/7vfg-d989

ISBN

9781267425294

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