Date of Award

Fall 2004

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Ocean & Earth Sciences

Program/Concentration

Geology

Committee Director

G. Richard Whittecar

Committee Member

Donald J. P. Swift

Committee Member

Joseph H. Rule

Committee Member

W. L. Daniels

Call Number for Print

Special Collections LD4331.G4 D47 2004

Abstract

The hydrology of wetlands, particularly how wetland soils collect, store, and redistribute water strongly affects how wetland systems function. In created wetlands, construction processes and materials influence the hydrology and consequently, the potential for successful reestablishment of target vegetation communities. During .2002- 2004, the Virginia Department of Transportation constructed large mitigation wetlands on two different Quaternary aged surfaces with very similar hydrogeomorphic conditions. The Sandy Bottom Nature Park site (SBNP) located in Hampton, VA and rests on the sandy loam Tabb Formation while the Charles City Wetland site (CCW) lies on the older and clay-rich Shirley Formation. This study documents and synthesizes stratigraphic and soil permeability data with biweekly and hourly hydrologic data collected from piezometer nests located in the constructed and surrounding natural wetlands at both locations in order to understand the influences of different construction practices on the hydrology of these mitigation wetlands. The clay-rich soils at the CCW natural and constructed sites displayed both endoaquic and epiaquic conditions that varied spatially and temporally as a result of the removal of the A-horizon and the exposure of the expansive clay-containing Btg-horizon. The newly constructed CCW wetland had a much faster response to precipitation than the natural wetland because the combination of moderately expansive clay soils and unusually dry weather resulted in extensive soil cracking on the newly graded surface at all but the wettest areas. The SBNP wetland site, constructed by filling in an existing lake with a variety of sediment types, contained extensive finer-grained layers that were tightly compacted during construction. These compacted layers impeded vertical flow and resulted in epiaquic conditions that were never observed in the surrounding natural wetland formed on loamy sediments.

The data collected during this study show that several factors can affect the hydrology of both natural and constructed pocosin wetland sites. Significant climatic influences include evapotranspiration, seasonal precipitation variations, and diurnal barometric pressure fluctuations. Geologic factors include landscape position, regional aquifer characteristics, stratigraphic variations in shallow sediments and soils, and both primary and secondary porosity. Construction practices affect hydrology via scraping surface soils, layering and compaction of sediments, deep ripping, and the addition and mixing of organic material into the final wetland surface.

Rights

In Copyright. URI: http://rightsstatements.org/vocab/InC/1.0/ This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).

DOI

10.25777/wfv1-tv73

Download

Share

COinS