Article

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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    • "Therefore, traditional research of meandering rivers is receiving new impulse from river managers who demand models of possible development trajectories of newly formed (revitalised) meandering channels where only straightened channelized streams existed for many decades. In this context, with regard to meandering river research, the key questions that need to be addressed are: (1) how do bank erosion and channel migration affect production of aquatic and semi-terrestrial habitats in oodplains (e.g. through cut oos and oxbow lake formation ) [15] [16] [17]?; (2) how should channel migration zones be delimited to mitigate the connicts between the dynamic changes of meandering channels and economic activities, typically arable land erosion and disruption of transportation infrastructure [18] [19] [20]?; (3) what controls channel migration rates of meandering rivers [21] [22] [23]? In the Czech Republic, as a consequence of riverstraightening practices, meandering reaches of large lowland rivers have almost completely disappeared. "
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    ABSTRACT: Freely meandering (quasi)natural reaches of lowland rivers represent a rare phenomenon in Central Europe. Increasing attention is currently being paid to the dynamics of quasi-natural (artificially influenced) meandering rivers as this attention represents the basic prerequisite for the development of appropriate restoration strategies on regulated rivers. This study focused on a 5.5 km long reach of the Morava River in the Strážnické Pomoraví region, Czech Republic that is characterised by quasi-natural evolution after substantial engineering adjustments were made in the first decades of the twentieth century. Based on Geographic Information Systems (GIS) analysis of aerial photographs, the spatio-temporal dynamics of bank erosion and accretion rates were quantitatively described and variables that control channel migration rates were identified. High rates of lateral shifts were localised in high sinuosity segments (sinuosity 1.17-2.37), whereas segments with very low rates were straight or formed into slightly curved bends (sinuosity 1.05-1.18). As a key factor, engineering works that influenced local river bed slope and induced a dramatic increase in bank erosion rates were identified. River engineering works induced a dramatic increase in bank erosion rate (2.19 m/year for 1938-53 and 1.47 m/year for 1953-63). An interval of approximately 25 years was needed before the erosion rates dropped back to values documented before river regulation (0.35-1.09 m/year for 1841-1938). Other important controlling variables included radius of curvature, frequency and magnitude of floods and, locally, river bank material properties and floodplain land cover.
    Full-text · Article · Nov 2015 · Open Geosciences
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    • "The erosion and deposition of sediment by fluvial bank erosion plays a pivotal role in maintaining the ecological and geomorphological diversity of fluvial channels [Florsheim et al., 2008; Camporeale et al., 2013]. Previous research has shown how the rate at which sediment is exhumed from floodplains by the processes of bank failure, sediment entrainment, and transportation has far reaching implications for geomorphology, ecology, infrastructure management, and nutrient and contaminant tracking [e.g. "
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    ABSTRACT: The three-dimensional flow field near the banks of alluvial channels is the primary factor controlling rates of bank erosion. Although submerged slump blocks and associated large-scale bank roughness elements have both previously been proposed to divert flow away from the bank, direct observations of the interaction between eroded bank material and the 3-D flow field are lacking. Here we use observations from multibeam echo sounding, terrestrial laser scanning, and acoustic Doppler current profiling to quantify, for the first time, the influence of submerged slump blocks on the near-bank flow field. In contrast to previous research emphasizing their influence on flow diversion away from the bank, we show that slump blocks may also deflect flow onto the bank, thereby increasing local shear stresses and rates of erosion. We use our measurements to propose a conceptual model for how submerged slump blocks interact with the flow field to modulate bank erosion.
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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.
    Full-text · Article · Aug 2015
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