Kimberly M. Meitzen

Shaping the Physical Template: Biological, Hydrological, and Geomorphic Connections in Stream Channels

Abstract Stream channels are scaled to the amount of water and sediment they convey. The amount and size of bed sediment, composition of bank material, type of channel vegetation (both riparian and in-stream), and valley morphology (slope and width) influence channel size and shape. Interactions and feedbacks among these six bio-hydro-geomorphic controls dictate channel stability and how channels respond to changes in the environment. In this chapter, we use these six interdependent variables as context in which to demonstrate how connections among hydrology, geomorphology, and vegetation; (1) set the range of variability in channel morphology; (2) understand disturbance-recovery regimes in streams; (3) illustrate how bio-hydro-geomorphic templates influence important abiotic components of stream ecosystems; and (4) present management strategies that incorporate bio-hydro-geomorphic connections. Finally, we discuss some of the important challenges that lay ahead in connecting fluvial geomorphology and stream ecology.

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

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 1585xa0m3xa0s−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.

A classic examination of fluvial processes and forest patterns: Victor Ernest Shelford’s (1954) ‘Some Lower Mississippi Valley Flood Plain Communities: Their Age and Elevation’. Ecology 35(2): 126–142.1

The study of the interaction between fluvial processes and forest community patterns owes elements of its origins to the research of Shelford (1954) on the Mississippi River valley. Shelford (1954) is a classic for many reasons; three highlighted here are its role of establishing a methodology for applying historical resources for long-term research studies, its influence on developing conceptual models of forest succession relative to multiple controlling factors, and its recognition of the rapid and extensive impact of human activities on altering natural land-cover patterns and the important role of analog forests for management and conservation. References to Shelford (1954) within the literature have increased every year since its publication and I believe its presence among varied disciplines will continue.