Document Type

Thesis - University Access Only

Award Date

1998

Degree Name

Master of Science (MS)

Department / School

Civil and Environmental Engineering

Abstract

Because of historical events to contain and drain the Florida Everglades, most of the flow through the Everglades is currently controlled by canals, levees, and spillways. This analysis focuses on two major Water Conservation Areas, WCA-3A and WCA-3B. Currently, WCA-3A and WCA-3B are separated by the L-67 levees, with WCA-3B being essentially isolated hydrologically. With WCA-3B being isolated from the system, this disrupts the historical flow pattern through the Everglades. This study concentrates on what conditions would be created if levee gaps were constructed between WCA-3A and WCA-3B to restore the natural flow through the Everglades. The numerical model Finite Element Surface-Water Modeling System: Two Dimensional Flow in a Horizontal Plane (FESWMS) was utilized to determine the volume of flow through the levee gaps and the water surface elevations in WCA-3B. The numerical study investigated a wide range of inflow conditions and water surface elevations in WCA-3A and at the outflows ofWCA-3B. The Everglades National Park's (ENP) major objectives for this analysis were to determine which conditions would allow approximately 50 percent of the inflow into the L-67 canal to flow through the levee gaps and which conditions would maintain a water surface elevation of approximately 8.5 feet in WCA-3B. Four major conditions were considered. The first condition was the baseline condition. In this condition, two 20 foot rectangular gaps were located at the outflows of WCA-3B to allow a natural flow of water from WCA-3B to the ENP. Several general conclusions were made from the baseline condition. First, it was found that increasing the inflow into the system and the water surface elevation in the L-67 canal resulted in an increase in both the flow through the levee gaps and the water surface elevation in WCA- 3 B. Also, it was found that by increasing the flow resistance in WCA-3B, the flow through the levee gaps decreased resulting in a higher water surface elevation in WCA-3B. Finally, it was found that the tail water levels at the outflows of WCA-3B only had a small effect upon the flow through the levee gaps. The second condition analyzed was the high crest weir condition. In this condition, two 20 foot wide broad-crested weirs were located at the outflows of WCA- 3 B. The weir crest elevations were 5 feet NGVD. It was determined that the discharge through the levee gaps decreased substantially and the water surface elevations throughout WCA-3B increased significantly when the weirs were located at the outflows ofWCA-3B. Therefore, it was concluded that weirs should not be located at the outflows ofWCA-3B or the weir crest elevation should be lowered. The third condition was the low weir crest condition. This condition was similar to the high crest weir condition except that the crest elevations of the weirs were lowered to O feet NGVD. It was found that the discharge through the levee gaps increased considerably and the water surface elevation in WCA-3B decreased significantly after the weir crest elevations were lowered. Finally, an increased levee gap width condition was considered. The increased levee gap width condition was the same as the low weir crest condition except the width of the levee gaps was increased from 1000 feet to 2000 feet. From this condition, it was determined that the discharge through the levee gaps increased substantially without raising the water surface elevation in WCA-3B significantly when the levee gaps width was increased. Overall, it was concluded that it would be difficult to meet both of the ENP's objectives of having 50 percent of the inflow into the L-67 canal flow through the levee gaps and maintaining a water surface elevation of 8.5 feet in WCA-38. Although most of the conditions allowed 50 percent of the inflow to flow through the levee gaps, the water surface elevation in WCA-3B would probably be above 8.5 feet in WCA-3B. However, the two conditions that would come the closest to meeting the ENP' s objectives would be the low weir crest condition and the increased levee gap width condition.

Library of Congress Subject Headings

Groundwater flow -- Florida -- Everglades National Park

Levees -- Florida -- Everglades National Park

Format

application/pdf

Number of Pages

207

Publisher

South Dakota State University

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