Description of flow through a natural wetland using dye tracer tests

A series of dye tracer tests was performed to determine average flow veloci ties through various segments of a natural wetland located in Westchester, NY. The wetland was divided into segments using the US Fish and Wildlife Se rvice's National Wetlands Inventory (NWI) classification scheme and mapped using a Global Positioning System (GPS). During different levels of flow, d ye was pumped into the headwaters of the wetland. The dye was collected wit h auto samplers at several sampling stations located at the transition zone s between wetland segments. Results indicate a significant difference in fl ow characteristics between two classification types, scrub-shrub and emerge nt. High data variability was found for samples collected furthest from the dye injection point. Velocities observed for the scrub-shrub-classified se gment ranged from 1.11 to 23.08 m/min; for the emergent-classified segment, velocities ranged from 1.54 to 7.68 m/min. Differences in the velocities b etween the two wetland types can be attributed to sinuosity of the stream c hannels and vegetation in the Rood plain associated with each type of wetla nd. Results have been used to develop a model to simulate flow through a na turally occurring wetland and could be used to improve design parameters fo r natural wetland restoration. (C) 2001 Elsevier Science B.V. All rights re served.