Silenced rivers: the ecology and politics of large dams
Dam ; Environment ; Hydraulic works ; Impact study ; Political geography ; Project
Devastating critique of the environmental effects and human consequences of dams around the world. Considers the powerful political and economic interests behing large dam projects, many proposed and built for large international aid projects
Jökulhlaup initiation by ice-dam flotation : the significance of glacier debris content
Ice-dam flotation is a commonly described mechanism for the initiation of jökulhlaups (catastrophic floods)from ice-dammed lakes, but predictions of the critical lake depth required for flotation often differ from the actual lake depth at which
flotation occurs. Glacier debris content is identifed as an insufficiently recognized variable in ice-dam flotation. It is demonstrated that high debris contents could suppress flotation, and thereby affect the timing, mechanism and magnitude of catastrophic
lake drainage events. The density of the part of the glacier forming the ice dam is the key to predicting ice-dam flotation.
Formation and failure of volcanic debris dams in the Chakachatna River valley associated with eruptions of the Spurr volcanic complex, Alaska
Alaska ; Cold area ; Dam ; Glacial lake ; Holocene ; Lahar ; Mudflow ; Natural hazards ; Quaternary ; Stream ; Volcanic eruption ; Volcanism
In this paper, evidence for several episodes of debris dam formation associated with eruptions of the Spurr volcanic complex are described. Dam failure conditions and peak discharge are estimated with a dam-break model and regression equations
that relate peak discharge to dam and reservoir characteristics.
Dams, sediment sources and reservoir silting in Romania
Dams and geomorphology. Special issue
Dam ; Dammed lake ; Earth surface processes ; Hydraulic works ; Romania ; Sediment budget ; Sedimentation ; Silting ; Watershed
The AA. analyzed 138 reservoirs for which there is a determination of the silting time. They try to make a synthesis of the knowledge stage of the dam lakes silting in Romania on the basis of the relations with the territory morphodynamics
and considering the substantial accumulations of new data. The factual material that they have is structured as follows : the construction of dams and the arrangement of reservoirs in Romania; the problem of sediment sources and, the silting of reservoirs.
Geoarchaeological studies in the environs of the ancient dam of glosses, Akarnania, NW Greece
Aetolia and Acarnania ; Archaeology ; Dam ; Geoarchaeology ; Geomorphology ; Greece ; Stratigraphy
The Glosses dam (Akarnania, Northwest Greece) is one of the best preserved ancient dams in Greece. The article deals with Greece, Akarnania, geoarchaeology, morphodynamic activity and stability and alluvial fan stratigraphy. - (IfL)
River channel change following dam removal in an ephemeral stream
Australia ; Base level ; Dam ; Ephemeral stream ; Fluvial erosion ; Hydraulic works ; New South Wales ; River bed ; Stream
The aim of this study is to analyse the geomorphic responses of the ephemeral Bushrangers Creek, central western New South Wales, Australia, following the 2002 removal of 15 m high dam. Comparisons of pre- and post-dam removal survey data indicate
that there has been repeated base-level lowering upstream of the former dam site. Longitudinal profiles of the thalweg before and after dam removal show an average bed lowering of 0.5 m and reveal a 90 m long channel with a slope in excess of two-times greater
than the pre-dam removal channel has formed upstream of the former dam wall.
Shoreline erosion : a cautionary note in using small farm dams to determine catchment erosion rates
Australia ; Cattle ; Dam ; Erosion ; Erosion rate ; Gully erosion ; Hydraulic works ; Sediment transport ; Victoria ; Watershed
Data from 10 small dams in SE Australia show that shoreline erosion due to farm livestock access to the dams can account for a significant proportion (up to 85%) of sediment contained in the dam. The volumes of sediment resulting from such shoreline
erosion may be of the same order as the volumes produced by gully erosion in the dam's catchments, prompting caution in using farm dams to which livestock have access to determine small catchment erosion rates. Other issues, related to the trap efficiency
, also mean that erosion estimates based on farm dam sedimentation should be treated with caution.
The geomorphic influences of beaver dams and failures of beaver dams
Dams and geomorphology. Special issue
Biogenic process ; Dam ; Flood ; Fluvial dynamics ; North America ; Rodent ; Stream
The AA. examine the zoogeomorphological influences of the construction of beaver dams. They restrict their discussion to North America and the species C. canadensis. Removal of beavers by overtrapping in the 16th-19th centuries severely reduced
their number and the number of ponds and dams. Partial recovery of beaver populations in the 20 th century has allowed reoccupation of the entirety of the pre-contact range, but at densities of only one-tenth the numbers. During the past 20 years, numerous
cases of dams failure have been documented that resulted in outburst floods.
Hydrogeomorphic effects of beaver dams in Glacier National Park, Montana
Biogenic process ; Biogeography ; Dam ; Fluvial processes ; Montana ; National park ; Rodent ; Sediment budget ; Sedimentation ; Stream ; Stream flow ; United States of America
This study provides additional data on sedimentation and stream flow in order to better understand the efficacy of beaver dams to trap sediment and alter the flow regime of streams, respectively. Data are collected on sedimentation depth (thickness
) and volume, as well as stream velocity and discharge above and below beaver dams in eastern Glacier National Park (GNP), Montana. In addition, measurements of dam and pond morphology are examined in relation to sedimentation and flow alteration patterns.
The 1786 earthquake-triggered landslide dam and subsequent dam-break flood on the Dadu river, southwestern China
Herein the discussion is focused on 2 aspects of the conclusion. It is believed that dam overtopping was the primary cause of the Dadu river landslide dam failure, although aftershocks may have further weakened the embankment. Using physically based
The evolution of gravel bed channels after dam removal : case study of the Anaconda and Union City Dam removals
Dams and geomorphology. Special issue
Connecticut ; Dam ; Fluvial dynamics ; Gravel ; Hydraulic works ; River bed ; Sediment transport ; Stream ; United States of America
This paper describes the initial engineering analysis and design , the subsequent removal of the 2 dams, and compares observations on the transition of the upstream channels following dam removal to the initial engineering predictions and other
Stream ecosystem response to small dam removal : lessons from the Heartland
Dams and geomorphology. Special issue
Dam ; Ecosystem ; Environmental management ; Fish ; Geo-ecology ; Habitat ; Nutrient ; Riparian vegetation ; Stream ; United States of America
The AA. synthesize a series of small dam removal studies to examine how changes in channel form can affect riparian vegetation, fish, macroinvertebrates, mussels, and nutrient dynamics. Each of the ecosystem attributes responded to the disturbance
of dam removal in different ways and recovered at very different rates, ranging from months to decades. The AA. suggest that ecosystems may follow 2 trajectories of recovery following dam removal : fully recover or partially recover to pre-dam conditions.
Dam ; Flood ; Hydraulic works ; Hydrological regime ; Riparian vegetation ; Stream ; Stream flow ; United States of America
This paper presents the analysis of pre- and post-dam hydrologic changes from dams that cover the spectrum of hydrologic and climatic regimes across the United States. The overall goals are to document the type, magnitude, and direction
of hydrologic shifts because of impoundment. To assess hydrologic changes associated with dams, the AA. applied a hydrologic model, the Indicators of Hydrologic Alteration (IHA), supplemented with orientation statistics for certain hydrograph parameters
. The results indicate that the major pulse of dam construction during the previous century has modified hydrologic regimes on a nationwide scale, for large and small rivers.
Geomorphology and American dams : the scientific, social, and economic context
Dams and geomorphology. Special issue
Dam ; Decision making process ; Environmental management ; Habitat ; Hydraulic works ; Stream ; United States of America
This paper emphasizes the downstream effects of dams. In the scientific context, present research is embedded in a history of geomorphology in government service, with indistinct boundaries between basic and applied research. The federal policy
that most strongly influences present geomorphological investigations connected with dams is related to habitat for endangered species, because the biological aspects of ecosystems are directly dependent on the substrate formed by the sediments and landforms
that are influenced by dams. The economic context for research includes large amounts of public funds for river restoration, along with substantial private investments in dams. The cultural context for research is highly contentious and dominated by advocacy
Science, local knowledge and exclusionary practices : lessons from the Alta Dam case
Alta Dam ; Aménagement hydraulique ; Environnement ; Justice environnementale ; Norvège ; Politique ; Sciences ; Stratégie d'acteurs
Le projet Alta Dam en Norvège est utilisé pour illustrer comment le contrôle étatique de l'information peut engendrer une injustice environnementale au travers d'un processus d'élaboration de décision fermé et d'une marginalisation politique.
This study examines the adjustment of river systems in the Golan Heights to reservoir construction in small basaltic mountainous catchments where total water flow is impounded, and discusses comparisons with the effects of large dams on alluvial
The catastrophic drainage of a moraine-dammed lake, Khumbu Himal, Nepal : cause and consequences
Destruction in 1985 from a ruptured dam generated research on the mechanisms that triggered the event and the social and economic effects. - (D. W. Gade).
Bed stability variations after check dam construction in torrential channels (South-East Spain)
Dam ; Hydraulic works ; Longitudinal section ; Murcia ; Roughness ; Semi-arid area ; Spain ; Stream ; Torrent
The effect of check dams on the bed stability of torrential channels have been analysed in several tributary basins of the Segura and Guadalentín rivers. The AA. evaluate the impact of every check dam on the bed morphology, distinguishing
The hydrogeomorphological effects of beaver dam-building activity
In order to review the hydrogeomorphological effects of beaver dam-building activity, this article places a context on the likely distribution and magnitude of beaver activity by considering the spatial and temporal variability of distributions
which dam building has been observed to occur. The hydrogeomorphological impact of dam building is then appraised both locally and at the landscape scale.