Bank Erosion as a Desirable Attribute of Rivers

[ "Joan L. Florsheim (e-mail: ) are with the Department of Geology at the University of California at Davis."]
BioScience (Impact Factor: 5.38). 05/2008; 58(Jun 2008):519-529. DOI: 10.1641/B580608

ABSTRACT Bank erosion is integral to the functioning of river ecosystems. It is a geomorphic process that promotes riparian vegetation succession and creates dynamic habitats crucial for aquatic and riparian plants and animals. River managers and policymakers, however, generally regard bank erosion as a process to be halted or minimized in order to create landscape and economic stability. Here, we recognize bank erosion as a desirable attribute of rivers. Recent advances in our understanding of bank erosion processes and of associated ecological functions, as well as of the effects and failure of channel bank infrastructure for erosion control, suggest that alternatives to current management approaches are greatly needed. In this article, we develop a conceptual framework for alternatives that address bank erosion issues. The alternatives conserve riparian linkages at appropriate temporal and spatial scales, consider integral relationships between physical bank processes and ecological functions, and avoid secondary and cumulative effects that lead to the progressive channelization of rivers. By linking geomorphologic processes with ecological functions, we address the significance of channel bank erosion in sustainable river and watershed management.

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    • "Hooke (1979) has also asserted river discharge, rainfall and soil moisture conditions as the most significant variables of bank erosion while discussing river bank erosion across Devon, Great Britain. Similarly, riparian vegetal cover, its type, distribution and principally the root density have been believed to exert noteworthy impacts on bank stability and resistance (Hickin, 1984; Knighton, 1984; Madej et al., 1994; Beeson and Doyle, 1995; Millar, 2000; Micheli and Kirchner, 2002; Simon and Collison, 2002; Micheli et al., 2004; Pollen and Simon, 2005; Bartley et al., 2008; Florsheim et al., 2008; Harden, 2013; Rosgen, n.d.). It has been observed that, river banks with healthy riparian vegetation are less affected by bank erosion than those lacking sufficient vegetal cover. "
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    ABSTRACT: Bank erosion as a natural agent of channel change owes special attention in geosciences arena. Indeed it is not only a process behind riverine dynamics but also is a quagmire for the river engineers, watershed planning agencies and especially to the co-existing human communities. An attempt has been made to reveal the processes and trends of riverbank erosion and channel width adjustments for the middle and lower course of the Duduya river belonging to the fertile North Bengal plains (with portions of upper reach fall within the highly dynamic Sub-Himalayan piedmont) of northern parts of West Bengal for a span of 24 years (1990-2014) primarily based on field observations along with the aid of Geographic Information System (GIS). Investigations cleared it out that the bank erosion trend was erratic. Recent bank erosion rate (5.99 meters/year during 2009-14) has shown signs of gradual decline from its earliest records (7.94 meters/year during 1990-2001). Primarily, riverbank composition, riparian vegetation and seasonal discharge variations have been found as the significant controllers of the bank erosion processes along with certain moderating effects of human interventions. Similarly, channel width adjustments were also been random, tended towards expansion along lower courses while headed for contraction along the middle one, guided predominantly by the opposite processes of erosion-deposition.
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    • "Our results indicate that the use of alternatively bioengineered bank protection measures at such sections may contribute to effective ecological status improvement. Bioengineered bank protection measures already combine technical requirements of erosion control with ecological requirements of habitat heterogeneity by, e.g., the use of CWD, of brushwood or vegetation mattresses, or by vertical woven stems (Florsheim et al. 2008, SEPA 2008). At natural shore sections which undergo cliff erosion , this erosion might be regarded as part of the natural morphodynamic processes. "
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    ABSTRACT: Lakeshores suffer substantially from anthropogenic, hydromorphological degradation which affects habitat diversity and the diversity of benthic invertebrates colonizing the littoral zone. Therefore, in lakes subjected to multiple human uses, successful lakeshore restoration requires an adaptive restoration strategy targeting crucial habitat types for sensitive invertebrate groups that indicate a ‘good’ ecological status according to the EU Water Framework Directive. Hence, we studied the effects of crucial habitat structures, such as the reed belt and coarse woody debris (CWD), on invertebrate assemblages and ecological status. In order to assess the effect of a key human disturbance on those habitats, we generated waves by experimental boat passages and recorded wave heights behind reed belt patches of varying width. Based on critical shear stress values found in former studies that affect invertebrates, results showed that minimum reed belt widths of 27– 32 m are needed to protect invertebrates from typical ship-induced wave action. Results from another field study showed that exposed CWD at shoreline sections with artificial shoreline protection by concrete walls and rip-rap indicated that the addition of CWD positively affected invertebrate communities at degraded lakeshore sections. When compared with previous assessments of ecological status, the ecological status already improved from ‘moderate’ to ‘good’ when the proportion of CWD among other littoral habitats reached 5 % to 15 %. Our study thus provides a general approach to estimate minimum restoration requirements depending on specific human pressures. Furthermore, we could demonstrate that even small proportions of specific littoral habitats at degraded shores significantly improve site-specific ecological status.
    Fundamental and Applied Limnology / Archiv für Hydrobiologie 05/2015; 186(4):323-332. DOI:10.1127/fal/2015/0647 · 1.08 Impact Factor
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    • "Ecological restoration projects sometimes employ revegetation by sowing or planting native species to rebuild the soil of disturbed land (Vander Mijnsbrugge et al. 2010; Kaase and Kat 2012) to control bank erosion, because riparian vegetation enhances bank stability by the root network stabilizing the soil (Florsheim et al. 2008; Lennox et al. 2011). Revegetation of riparian zones is also motivated for improving water quality, nutrient cycling, water temperature (stream shading) and for creating instream habitat (Bernhardt et al. 2005; Sudduth et al. 2007; Kaase and Kat 2012). "
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    ABSTRACT: Many streams that were channelized to facilitate timber floating in northern Sweden, have in recent years been restored by returning coarse sediment (cobbles and boulders) to the channel and reconnecting riparian with instream habitats. We asked if such restoration measures affect germination and survival of plants in the riparian zone, and if such potential effects depend on location in the catchment. We used a paired site approach, comparing the performance of Helianthus annuus (sunflower) phytometers (seeds and seedlings) in the riparian zone in channelized versus restored river reaches along climate and stream size gradients in the Vindel River catchment in northern Sweden. Phytometer survival, substrate availability, and soil nutrient content in large streams were enhanced by restoration, but overall, phytometer performance was negatively related to the length of the growing season, i.e. phytometers grew best at high altitudes and short growing seasons. This result may have been caused by less competition from the shorter and sparser neighbouring vegetation at these sites or to more frequent flooding events, enhancing retention of organic matter. Soil nutrient levels were lowest close to the coast and in large streams, probably due to deposition of mineral sediment. The higher availability of riparian habitat at restored than at channelized sites suggests that plant species richness and abundance may potentially increase after restoration. Seedling transplantation seems to be a preferable revegetation measure, because phytometer seedlings established better than seeds and survival was significantly higher at restored sites. The good plant performance at sites with short growing seasons and high altitudes suggests that, with limited resources, restoration measures should first be located to such sites.
    Plant Ecology 03/2015; 216(3). DOI:10.1007/s11258-015-0450-3 · 1.46 Impact Factor
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