THE EFFECT OF SEDIMENT TRANSPORT AND HYDROLOGIC CONDITIONS ON WETLAND BED MORPHOLOGY

Wetlands have been historically drained for land development, recreational, and agricultural purposes. Results of these extensive usages appear as degradation of wetland features such as ridge and slough which impact wetland ecology, biology, biodiversity. An example of such degradation is seen in the Everglades wetland in southern Florida where degradation is evidenced as loss of sloughs and their connectivity in this highly controlled ecosysytem. Therefore, understanding the mechanisms involved in ridge and slough landscape formation, stability, and maintenance are crucial in wetland restoration efforts.

Previous investigations have shown that wetland patterning can be explained by positive feedback between flow, plant productivity, nutrient and sediment transport processes. Researchers have simulated sediment transport and they hypothesized that sediment transport is the key mechanism that controls initial formation and maintenance in ridge and slough. However, their findings do not account for the effect of extreme events or pulse flows during short periods of timetheir approach neither covers groundwater/surface water interaction nor the importance of sediment characteristics in ridge and slough which may affect deposition/erosion patterns.

A physically based numerical model of sediment transport has been developed as an extension to FLO – 2D integrated surface water/groundwater model. Loxahatchee Impoundment Landscape Assessment (LILA) has been selected as study are and it is located at Loxahatchee National Wild Life Refuge in Boynton Beach, Florida. The developed model has been calibrated over the area of study. Water samples were taken from several locations within a flowing macrocosm during a series of manually generated pulse flow. Suspended sediment concentration was measured in the lab. These data along with other data such as water depth and velocity, and groundwater head, were collected to support and validate the developed model.

Results from this developed model will provide an improved understanding of how wetland features such as ridges and slough may have formed and degraded that resulted from increasing human activity in wetlands over the past decades.