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Modeling hydrologic connectivity and virtual fish movement across a large Southeastern floodplain, USA

Meitzen, Kimberly M., Kupfer, John A., Gao, Peng
Aquatic sciences 2018 v.80 no.1 pp. 5
ecosystems, fish, floodplains, geographic information systems, hydrology, lakes, models, rivers, travel, United States
Lateral hydrologic connectivity between a river and its floodplain is important for exchanges of organisms and materials that support healthy, functioning riverine ecosystems. We use a GIS-based distance, cost-weighted spatial model to measure the possible pathways and travel durations for fish migrating from a mainstem river channel to ten different floodplain lakes during a range of discharge magnitudes. We modeled routes of movement and fish swim times for five discharges that ranged from 140 to 1585 m³ s⁻¹ and represented a gradient of hydrologic connectivity. Hydrologic travel pathways included perennial floodplain channels (tributaries and permanent lakes) and intermittently active floodplain channels (channels re-occupying abandoned meander segments, meander-scrolls, batture channels, and crevasses). The different hydrologic pathways made available during the different discharge magnitudes were represented using spatially-variable, raster-based cost surfaces. Fish swim times and route of movement varied with discharge magnitude and lake location. Two distinct patterns emerged between the fish swim times and routes of movement. One group of five floodplain lakes experienced very little change in the route or rate of fish movement with increasing discharge, while another group of five lakes exhibited significant decreases in swim time with increasing discharge. These responses indicate the importance of managing for flood pulses of various magnitudes that hydrologically connect the river and floodplain through different pathways, enabling dynamic spatial and temporal exchanges of organisms and materials.