ANALYZING GROUNDWATER FLOW TO AID IN WETLAND MITIGATION

Robert Riberty and Duke Ophori

Department of Earth and Environmental Studies

Montclair State University

Upper Montclair, New Jersey 07043

Phone: (973) 655 7558/Fax: (973) 655 4072

Email: Ophorid@mail.montclair.edu

 

Wetlands are important natural resources having numerous values, including flood protection, erosion control, fish and wildlife habitat, water quality control, recreation, and groundwater recharge and discharge. This resource is being lost due to extensive conversion of wetlands to other uses, such as cropland, residential housing, commercial and industrial development, and highways. In some parts of the United States, 14 to 50 percent of wetlands have been lost to highway and urban development in the past four decades. The significance of this loss has led to the proposition of a “no net loss of wetland” approach for mitigating wetland destruction. However, it is unclear whether current methods of site selection are suited to meeting this goal of wetland mitigation. It is important to understand the functions of wetlands for mitigation to be successful. The recharge-discharge functions of a wetland are closely tied with factors like wetland type, geographic location, season, soil type, water-table location, and precipitation. A classification of wetlands, using these factors, helps in gaining a better understanding of the functions of a particular wetland.

            In this study, a potential wetland mitigation site in the Atlantic Coastal Plain in central New Jersey is characterized in order to determine the prevailing functions. At the site, construction of a highway is planned that would result in the loss of part of the wetland. Investigation showed that the existing wetland is a water-table type, located topographically in the midline regions of the site, and is underlain by type II geologic materials. It is therefore in direct hydraulic connection with, and functions to discharge groundwater from, the aquifer. Groundwater flow at the site was simulated to gain a better understanding of the interaction between the wetland and the aquifer, and to evaluate the possible effects of a created wetland designed for on-site mitigation. The pre and post-construction flow patterns indicate that changes to the existing flow systems will result in a loss in natural discharge despite enhancing groundwater discharge. The net effect of the wetland mitigation at the site will be to decrease the available wetland habitat contrary to the goals of wetland mitigation.