Riparian Vegetation Recovery Patterns Following Stream Channelization: A Geomorphic Perspective

Abstract

Hundreds of kilometres of West Tennessee streams have been channelized since the turn of the century. After a stream is straightened, dredged, or cleared, basinwide ecologic, hydrologic, and geomorphic processes bring about an integrated, characteristic recovery sequence. The rapid pace of channel responses to channelization provides an opportunity to document and interpret vegetation recovery patterns relative to otherwise long—term, concomitant evolution of river geomorphology. Nearly 150 sites along 15 streams were studied in the Obion, Forked Deer, Hatchie, and Wolf River basins. Channels of these streams, except that of the Hatchie River main stem, have undergone major modifications along all or parts of their courses. This paper presents the eco—geomorphic analyses and interpretation of a large multidisciplinary study, with special reference to their interrelated hydrogeomorphic aspects of channel recovery. Quantitative plant ecological analyses were conducted to infer relative bank stability, to identify indicator recovery species, and to determine patterns of vegetation development through the course of accelerated channel evolution. Binary—discriminant and ordination analyses show that distinctive riparian—species patterns reflect a six—stage model of channel evolution and can be used to infer channel stability and hydrogeomorphic conditions. Woody vegetation initially establishes on low— and mid—bank surfaces at the same location and time that bank accretion begins, and corresponds to the site of initial geomorphic restabilization. The linkage of channel bed aggradation, woody vegetation establishment, and bank accretion all lead to recovery of the channel. Pioneer species are hardy and fast growing, and can tolerate moderate amounts of slope instability and sediment deposition; these species include river birch (Betula nigra), black willow (Salix nigra), boxelder (Acer negundo), and silver maple (Acer saccharinum). High stem densities and root—mass development appear to enhance bank stability. Tree—ring analyses suggest that on average 65 yr may be required for recovery after channelization.

CHANNEL INSTABILITY IN THE LOESS AREA OF THE MIDWESTERN UNITED STATES1

“…Silt-bedded West Tarkio Creek, southwestern Iowa and northwestern Missouri, and to a lesser extent, two sites on the South Fork Big Nemaha River, Nebraska were investigated in more detail to show typical channel changes. The sand-bedded Obion River System, West Tennessee, was studied previously (Simon, 1989a(Simon, , 1989b(Simon, , 1989cHupp, 1992;Simon and Hupp 1992;Simon, 1994).…”

Application and validation of a GIS-based stream bank stability tool for the Great Lakes region

“…Conversion of natural riparian land use to agricultural practices typically reduces the stability of stream banks (Abernethy and Rutherfurd 2001;Millar 2000;Hupp 1992Hupp , 1999Charlton et al 1978) and can cause dramatic morphologic response (Riedel et al 2006;Osman and Thorne 1988;Huang and Nanson 1998).…”

Altered hydrologic and geomorphic processes and bottomland hardwood plant communities of the lower White River Basin

“…Significant changes to the gradient, hydrology, or sediment load result in adjustment toward a new quasi-equilibrium condition (as in Knox, 2006;Hupp and others, 2009a;Hupp and others, 2015). Geomorphic adjustment at the reach and regional scale can trigger substantial changes to river-floodplain interactions and feedback mechanisms between geomorphic, hydrologic, and ecological processes (as with Hupp, 1992;Ligon and others, 1995;Knox, 2006;Hupp and others, 2009b;Osterkamp and Hupp, 2010).…”