Graduation Year

2007

Document Type

Thesis

Degree

M.S.E.S.

Degree Granting Department

Civil and Environmental Engineering

Major Professor

Mark A. Ross, Ph.D.

Co-Major Professor

Mahmoud Nachabe, Ph.D.

Committee Member

Kenneth Trout, Ph.D.

Committee Member

G. Ladde, Ph.D.

Keywords

hydrology, time series, frequency analysis, spectral analysis, power spectrum density

Abstract

Wetlands are nominally characterized by, vegetation, presence of saturated soils and/or period and depth of standing water (inundation). Wetland hydroperiod, traditionally defined by the period or duration of inundation, is considered to control the ecological function and resultant plant community. This study seeks to redefine "hydroperiod" to incorporate both surface and subsurface water-level fluctuations, to identify predominant hydroperiod of different wetland types, and to find the range of the water-level fluctuations during the predominant hydroperiod durations. The motivation being that wetland ecological condition is controlled not just by the period of inundation but also by the proximity and depth to water-table and period of water-level fluctuation. To accomplish this, a frequency distribution analysis of water-table and stage levels in wetlands is performed. The conclusions of this study suggest a need to rethink current definitions and methodologies in determining hydroperiod. Redefining wetland hydroperiod taking into consideration depth to water-table, namely water-level periods and depths below ground surface, may also aid in the understanding of how fluctuations in water-levels in a wetland affect plant ecology.

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