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Showing papers on "Siltation published in 1995"


Book ChapterDOI
TL;DR: In this paper, the authors examined the relationship between stream siltation and fish community characteristics and found that fishery communities were most sensitive to siltations in some guilds while other guilds were not.
Abstract: Riparian buffer zones serve several important roles in linking a stream to its watershed. A main function is controlling the dynamics of sedimentation. This paper documents how siltation impacts fish communities and how proper riparian management can mitigate the negative effects of sedimentation. Two studies examined the relation between stream siltation and fish community characteristics. Community responses to siltation were poorly described by common structural indices. Community level responses to varying siltation were most consistently described by changes in functional characteristics of the resident fish species using a guild-based analysis. Herbivores, benthic insectivores and simple lithophilous spawners were most sensitive to siltation while other guilds were not. These results were repeatable in both intraregional comparisons among sites of similar size and character, and in interregional comparisons of streams which varied in characteristics besides siltation. This suggests the index may be useful in separating the effects of siltation from other environmental variables. A discussion of bufferstrip characteristics important in mitigating against, or preventing, excess siltation is presented.

151 citations


Journal ArticleDOI
TL;DR: In this paper, the results of a 3-year investigation at the Laboratory of Hydraulics, Hydrology, and Glaciology of the Federal Institute of Technology in Zurich are summarized.
Abstract: In alluvial rivers, suspended matter is deposited in the pore space of the riverbed during low and medium discharges, and at high flows the armor layer breaks up and the riverbed is flushed. During this cycle, the hydraulic conductivity decreases with time and then suddenly increases, so one can speak of a characteristic graph of siltation. In this paper, the results of a 3-year investigation at the Laboratory of Hydraulics, Hydrology, and Glaciology of the Federal Institute of Technology in Zurich are summarized. A wealth of long-term tests allowed the derivation of several equations concerning the siltation of riverbeds, including the reduction of the hydraulic conductivity with time, the limit of siltation, the conditions for desiltation, and the consequent increase in hydraulic conductivity. Simultaneously, the influence of the significant variables is shown. This research makes it possible to quantify the siltation process as well as the effect of specific changes in the river regime and the catchment area.

66 citations


Journal ArticleDOI
TL;DR: The chronology of near-surface sediments in Lake Illawarra has been investigated using radiocarbon dating and anthropogenically derived substances including trace metals, ash, and137Cs as discussed by the authors.
Abstract: The chronology of near-surface sediments in Lake Illawarra has been investigated using radiocarbon dating and anthropogenically derived substances including trace metals, ash, and137Cs. Sediments at depths about 1 m below the water-sediment interface ranged in age from Modern to 786 calendar years bp on the basis of radiocarbon dating ofNotospisula trigonella valves. Multiple marker (for example ash-trace metals) depth-concentration sediment profiles yielded estimates of sedimentation rate ranging from 3 to 5 mm yr−1 at Griffins Bay to more than 16 mm yr−1 at Macquarie Rivulet. Sedimentation rates of approximately 10 mm yr−1 appeared to be typical of the western and southwestern portions of the lagoon. Rates of sediment accretion, prior to catchment clearing, urbanization, and industrialization have been estimated at less than 1 mm yr−1, thus indicating a general tenfold increase in sediment accumulation adjacent to the western foreshore caused by catchment development. Accelerated sedimentation in shallow coastal lagoons constitutes significant environmental impacts including shoaling, degradation of seagrass beds, and increased turbidity with consequent loss of aesthetic appeal. Management policy should be directed at attempts to reduce the amount of sediment input by the construction of strategically placed sediment retention ponds. Siltation within the shallow embayments of Lake Illawarra could be ameliorated by a carefully planned program of dredging.

47 citations


Journal ArticleDOI
Abstract: A small number of ancient lakes (mostly >10 6 y old) scattered around the globe contain an extraordinary percentage of the world's documented freshwater biodiversity. Endemic benthic invertebrates and fish in most of these lakes today face a variety of anthropogenic threats, including damaging fishing activities, water pollution, species introductions and translocations, climate change, and watershed disturbances. Lake Tanganyika, one of the oldest and most diverse of the ancient lakes, provides a model for studying the effects on endemic faunal diversity from watershed disturbances caused by deforestation. Increased erosion rates around the northern portion of the lake are associated with substantially lower diversity levels for both benthic invertebrates and fish. Disturbance processes in the biologically complex littoral region of this lake that are related to this excess siltation include reductions in light penetration (affecting algal habitat and herbivory), reductions in habitat heterogen...

35 citations


A. Dinar, P. Seidl, H. Olem, V. Jorden, A. Duda 
01 Oct 1995
TL;DR: In this article, the authors identify vital components of the water-based ecosystem requiring special consideration to maintain biodiversity, including wetlands and marginal floodplains inextricably linked to lakes and reservoirs.
Abstract: The paper calls attention to the particular problems that lakes and reservoirs have suffered as a result of increased siltation, nutrient loading, toxics, habitat degradation, over-exploitation, and changes to marginal ecosystems. It identifies vital components of the water-based ecosystem requiring special consideration to maintain biodiversity, including wetlands and marginal floodplains inextricably linked to lakes and reservoirs.

24 citations


01 Jun 1995
TL;DR: Napa Countywide Stormwater Pollution Prevention Program (NCSPPP) www.countyofnapa.org/Stormwater or (707) 253-4823 NCSPPP wishes to thank Marin County Stormwater Program for allowing us to modify their brochure as discussed by the authors.
Abstract: Napa Countywide Stormwater Pollution Prevention Program (NCSPPP) www.countyofnapa.org/Stormwater or (707) 253-4823 NCSPPP wishes to thank Marin County Stormwater Program for allowing us to modify their brochure. Below are the minimum maintenance practices recommended by the NCSPPP to avoid or minimize pollutants discharged to waterways. By following them you can help protect water quality in our streams and comply with local, state, and federal regulations. The local agency may require additional BMPs.

9 citations


Journal ArticleDOI
Mei-e Ren1
TL;DR: In this paper, a more rational use of the river water resources should be formulated to mitigate this situation, which is suggested to mitigate the serious siltation in the river channel and river mouth.
Abstract: The Yellow River, China is noted for its extremely heavy sediment load, about 5 times that of the Mississippi and very small flow, only 8% that of the Mississippi. Owing to the construction of reservoirs and increasing withdrawal of the river water for agriculture, industry and urban water supply, the flow of the Lower Yellow River is greatly reduced causing more serious siltation in the river channel and river mouth, threaterning the stabilization of the present outlet to the sea and economic growth of the delta. It is suggested that a more rational use of the river water resources should be formulated to mitigate this situation.

7 citations


Journal ArticleDOI
01 Dec 1995-Wetlands
TL;DR: In this article, the authors studied the change in the pattern and distribution of tropical wetland vegetation in four small impoundments over a 28-year period, and found that vegetation colonization and expansion in the impoundment is a function of the reduction of water depth due to siltation accompanying increasing urbanization.
Abstract: Temporal changes in the pattern and distribution of tropical wetland vegetation in four small impoundments over a 28-year period were documented for a wetland ecosystem in the Olezoa drainage basin in Yaounde, Cameroon, West Africa. These impoundments were constructed along the Olezoa stream for the purpose of aquaculture and ranged in size from 1.4 to 3.0 ha, had depths between 200 to 400 cm, and were devoid of vegetation. Evaluation of the impoundments and the surrounding catchment was accomplished using low altitude aerial photographs for the years 1964, 1974, and 1986 and field surveys for the periods 1985 through 1992. The results reveal a progressive decline in open water surface area of the impoundments ranging from 70 to 100% due to plant colonization and expansion. Measured impoundment depths along profiles show more than 50% reduction from original depths of 300–400 cm to less than 150–200 cm in 1992. We suggest that vegetation colonization and expansion in the impoundments is a function of the reduction of water depth due to siltation accompanying increasing urbanization. During the period of evaluation, urbanization in the surrounding catchment tripled. Siltation in the impoundments resulted mainly from the accumulation of soil eroded from the upland accompanying devegetation and construction activities. The shallowing of the impoundments by siltation provided a favorable water-depth regime and substrate for colonization by aquatic and emergent wetland vegetation. Continued shallowing resulted in development of vegetation zones along a water-depth gradient, and the migration of these zones toward the interior of the impoundments. The history of degradation of the catchment area and siltation of the impoundments is thus recorded by temporal changes in vegetation.

3 citations