Downstream effects of dams on alluvial rivers

Williams, Garnett P.; Wolman, M. Gordon

doi:10.3133/pp1286

Cited by 774 publications

(602 citation statements)

References 24 publications

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“…Several studies have analysed the response of rivers to human impact, showing that remarkable channel changes generally take place, such as vertical adjustment, changes in channel width and pattern (e.g. Leopold, 1973;Gregory and Park, 1974;Williams, 1978;Petts, 1979;Williams and Wolman, 1984;Andrews, 1986;Knighton, 1991;Collier et al, 1996;Petit et al, 1996;Kondolf, 1997). These changes are generally much larger than those that could be expected from natural channel evolution, although in some cases also natural phenomena, such as large floods, fires and volcanic eruptions, or short-term climatic fluctuations (e.g.…”

Section: Introductionmentioning

confidence: 97%

“…Numerous examples in the literature report how bed-level changes at a site are best described mathematically by non-linear functions, where adjustments occur rapidly, immediately after the disturbance, and then slow and become asymptotic (Graf, 1977;Williams and Wolman, 1984;Simon and Hupp, 1986). Few examples of bed-level adjustments at a site are available for Italian rivers.…”

Section: Temporal Trends Of Channel Adjustmentsmentioning

confidence: 99%

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Morphological response to river engineering and management in alluvial channels in Italy

2003

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In response to various types of human disturbance, most Italian rivers have experienced considerable channel adjustment during the last centuries and in particular in the last decades. This paper reviews all existing published studies and available data, and aims to reconstruct a general outline of the main channel adjustments that have occurred in Italian rivers during the past 100 years.Two main types of channel adjustment have been recognized: (a) incision, which is commonly on the order of 3 -4 m, but in some cases is even more than 10 m; (b) narrowing, with channel width reduction up to 50% or more. In some reaches, these adjustments have led to changes in channel pattern in particular from braided to wandering.Such channel adjustments are due to several types of human intervention, particularly sediment extraction, dams and channelization. A strong temporal relationship (specifically, short reaction times) between human disturbance and channel adjustment can be inferred, but trends of adjustment are available for only a few rivers (e.g. the Po, the Arno and the Piave Rivers). These trends show that incision and/or narrowing are more intense immediately after the disturbance and then slow and become asymptotic; the same trends also suggest that larger rivers could have longer relaxation times.The results of this study are synthesised in a general classification scheme that summarises the main styles of adjustment observed in Italian rivers. According to the scheme, braided rivers adjust through prevalent narrowing with varying rates of incision, whereas single-thread rivers adjust mainly through a more pronounced incision accompanied by various amounts of narrowing. The scheme, representing initial and final (present) morphologies and not including intermediate stages of channel adjustment, will need to be tested on the basis of more detailed data to have a wider application both to the Italian context and to fluvial systems elsewhere, affected by similar types of human disturbance causing a reduction of sediment supply. D

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Section: Introductionmentioning

confidence: 97%

Section: Temporal Trends Of Channel Adjustmentsmentioning

confidence: 99%

Morphological response to river engineering and management in alluvial channels in Italy

2003

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“…Sometimes certain terrestrial species may adapt to these conditions of excessive hydromorphy (Riis et al, 2001;Bernez et al, 2004). However, when the hydrological impacts of dams result in a significant decrease in flood and low water discharges, the low flow channel may be invaded by non-aquatic vegetation, reducing its width (Williams and Wolman, 1984;Chang and Crowley, 1997;Friedman et al, 1998). On the other hand, when www.elsevier.com/locate/aquabot Aquatic Botany 85 (2006) [112][113][114][115][116][117][118][119][120] the discharge increases downstream from the dam, channel widening generally results (Church, 1995), which causes riparian vegetation to recede (Dominick and O'Neill, 1998).…”

Section: Introductionmentioning

confidence: 99%

The relation between geomorphological features and species richness in the low flow channel of the Warche, downstream from the Bütgenbach dam (Ardennes, Belgium)

Assani¹,

Petit²,

Leclercq³

2006

Aquatic Botany

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The Butgenbach dam, built on the Warche River (Ardennes, Belgium) in 1931 brought about two major changes: a significant reduction in the frequency and magnitude of the minimum discharges during the growing season (April-September) and the formation of numerous new geomorphological features (islets, pebble bars and rock outcrops) in the low flow channel. These changes have lead to an increase in the number of vascular plants downstream from the dam. Between 1994 and 1997, 74 species (bryophytes and phanerogams) were found downstream from the dam and 12 species were identified upstream. Downstream, most of the species are typical of damp semi-natural grasslands and of the banks of the Haute Ardennes-environments both characterised by oligotrophy. Euryoecious species (with a wide ecological range) and nitrophile species (that indicate pollution of the Warche from urban effluents and agricultural fertilisers) are also present. However, the distribution of plant species in the low flow channel is very heterogeneous. The number of species varies from one geomorphological unit to another. Species are more numerous on islets (54 species) than on rock outcrops (35 species) and gravel bars (28 species). On the islets, the number of species present varies in accordance with the degree of erosion. The islets that are most eroded and those that are least eroded display a poor range of flora. The degree of erosion influences the depth of silt, pebbles and litter on the islets. With regard to rock outcrops, the wealth of flora present depends on the form they take. Stratified outcrops are richer in flora than protruding outcrops. The number of plant species present on gravel bars depends on the frequency and the scale of remobilisation of pebbly material by floods. Following large floods, the vegetation cover and the number of different species decreases. But, if the sites remain stable, the number of species first of all increases, only then to decrease due to the proliferation of competitive species such as Phalaris arundinacea L. The ranges of species found on the different geomorphological features do not display a high degree of similarity. Canonical correlation analysis reveals that the density and the total number of species on geomorphological features are most strongly influenced by the proportion of fine particulates (<2 mm). #

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“…Quantifying the historical water and sediment inputs to a river reach and identifying the resulting responses can aid in understanding the changes induced by dam construction. Williams and Wolman (1984) highlighted the necessity of understanding the unregulated water and sediment regimen as well as changes caused by flow regulation. Such understanding can provide opportunities to differentiate between natural and anthropogenic induced changes.…”

Section: Introductionmentioning

confidence: 99%

“…Studies of regulated rivers have revealed varying responses including narrowing, widening, degradation, and aggradation occurring at different temporal scales (Williams and Wolman, 1984;Collier et al, 1996;Friedman et al, 1998;Xu, 1997). Friedman et al (1998) Received on May 21, 2005.…”

Section: Introductionmentioning

confidence: 99%

Stream restoration and environmental river mechanics

Juliën¹,

Richard

Albert

2005

International Journal of River Basin Management

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The impact of construction of dams and reservoirs on alluvial rivers extends both upstream and downstream of the dam. Downstream of dams, both the water and sediment supplies can be altered leading to adjustments in the river channel geometry and ensuing changes in riparian and aquatic habitats. The wealth of pre and post-regulation data on the Middle Rio Grande, New Mexico, provides an excellent case study of river regulation, channel adjustments, and restoration efforts. Cochiti Dam was constructed on the main stem of the Rio Grande in 1973 for flood control and sediment retention. Prior to dam construction, the Rio Grande was a wide, sandy braided river. Following dam construction, the channel bed degraded and coarsened to gravel size, and the planform shifted to a more meandering pattern. Ecological implications of the geomorphic changes include detachment of the river from the floodplain, reduced recruitment of riparian cottonwoods, encroachment of non-native saltcedar and Russian olive into the floodplain and degraded aquatic habitat for the Rio Grande silvery minnow. Recent restoration strategies include removal of non-native riparian vegetation, mechanical lowering of floodplain areas, and channel widening.

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Downstream effects of dams on alluvial rivers

Cited by 774 publications

References 24 publications

Morphological response to river engineering and management in alluvial channels in Italy

Morphological response to river engineering and management in alluvial channels in Italy

The relation between geomorphological features and species richness in the low flow channel of the Warche, downstream from the Bütgenbach dam (Ardennes, Belgium)

Stream restoration and environmental river mechanics

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