摘要:

AbstractThe diverse Upper Rhine floodplains (with regard to geomorphology, hydrology, vegetation, and fauna) have undergone far‐reaching changews over the last 170 years, intensified from 1955 to 1977, especially as a result of water engineering measures.Far‐reaching and serious distrubances of the ecological balance (flood problems, lowering of the water table, etc.) and the drastic reduction of biotic communities, as well as the increasing demands of society, call for a newly oriented policy with regard to the future development of the Upper Rhine floodplains. This should be based on a critical review of the recent history of the landscape and a recognition of the ecological importance of these floodpla

ISSN:0886-9375    

DOI:10.1002/rrr.3450050102

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe impact of an arterial drainage scheme on the water balance of a 200 km2catchment in Northern Ireland is quantified. Monitored changes in groundwater storage act as an independent check on conclusions about storage change derived from measurements of surface hydrology. Three subcatchments of the study area and one other independent experimental catchment constitute controls against which the impact of arterial drainage can be assessed. Fiver years' predrainage data and three years' post‐drainage data are examined.Stream flow from the floodplain area of the catchment has increased, especially low flows. Catchment water‐tables, however, as monitored in floodplain transects and disused farm wells have not been drawn down. Any immediate drainage benefits deriving directly from arterial drainage are difficult to detect. Groundwater evidence indicates that the likely source of the excess discharge is an underlying gravel aquifer that has been punctured by the deeper arterial chan

ISSN:0886-9375    

DOI:10.1002/rrr.3450050103

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractRiver engineering works have recently been carried out on the upper River Wharfe (U.K.) in order to reduce the flood risk and resore land drainage beween Hubberholme and Kettlewell. As the river is located in a National Park, great care had to be exercised to limit the degree of interference and to ensure that an environmentally acceptable solution was adopted.Increased flood risk can be partially attributed to afforestation in the headwaters of the Wharfe. Improved drainage prior to planting has lead to an apparent increase in the mangitude and frequency of flooding and an increase in sediment yield.The works were to remedy both problems and were designed in consultation with a range of conservation and amenity organizations. First, a bed load trap was constructed on the Wharfe to curtail the sediment supply to the flood prone reach and prevent further aggradation. Second, limited dredging was carried out near tributary junctions to improve land drainage on the floodplain. Third, the dredged material was used to form the core of the raised banks.The engineering works were carred out between 1985‐87. Since completion in August 1987 the flood banks have been overtopped only twice which compares with the previous record of thirty‐two times per year. No significant erosion or deposition has occurred and the gravel trap is performing according to expectations; being half full after two and a half years of operation. Although stocks of mature trout were displaced by bed workings, there are now signs of a recov

ISSN:0886-9375    

DOI:10.1002/rrr.3450050104

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractAs government and organizations responsible for river mangement throughout the World become increasingly aware of the need to reconcile engineering objectives with nature conservation, alternative strategies for river management such as channel restoration are likely to continue to be developed and applied to particular areas.Based on the experiences of 15 restoration projects in Denmark and Britain the criteria which determine the success of such projects are outlined. The essential precursor to a successful restoration project is a thorough feasibility and planning study. The type of restoration work included in a project is constrained by a variety of factors, including the physcial environment and the project objectives. The detailed design needs to be tailored to the individual river reaches under consideration. Project planning should consider the timing and supeervision of construction and make recommendations on the nature of maintenance. A management plan is desirable and post‐project appraisal is essetnial to evaluate the long‐term hydraulic and environmental performances. These criteria have been applied to two recent projects carried out on the River Lambourn in Berkshire, England, and on the Elbaek in central Jutland, Denm

ISSN:0886-9375    

DOI:10.1002/rrr.3450050105

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe Rhine may provide a classical example of faunistic changes due to Man‐made stress. Formerly a salmonid river, it was transformed into a ship‐canal. Steadily increasing pollution culminated in the 1960s and 1970s. An improvement of water quality in the 1980s was followed by an increase in abundance of several species and faunal diversity. Originally 47 species inhabited the Rhine; at present 40 indigenous and 15 introduced species live in the river, seven have vanished or have not been observed so far. Recent setabacks, like the Sandoz Accident in 1986 failed to eliminate any taxon. Protection of the indigenous fauna is to be linked with conservation of remaining environmental diversity, ecotechnical improvements, and new strategies in fishery management, which do not merely support only economic spec

ISSN:0886-9375    

DOI:10.1002/rrr.3450050106

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe Dutch section of the Lower Rhine is highly modified by regulating measures, such as the construction of weirs and the closure of estuarine river mouths, which seriously affect sedimentation of suspended material. During 1987 the fate of plankton communities in this part of the Rhine was investigated. Water samples were taken fortnightly at the German‐Dutch border and in the main branch of the Rhine, just before it debouches into the North Sea. Dry weights of suspended matter, bacterial numbers, phytoplankton biomass (as chlorophylla) and zooplankton composition and biovolumes were determined, and, at two occasions, phytoplankton composition and biovolumes as well. Supended matter and bacteria disappeared during transport in the Rhine Delta. phytoplankton biomass (primarily diatoms) showed typical spring and summer peaks and also decreased in the investigated river reach. In contrast, zooplankton developed a higher biomass due to an increase in the numbers of rotifers, crustaceans, and molluscan larvae, whereas arcellas and ciliates decreased in numbers.It is concluded that the Rhine, after flowing more than 800 km, meets in its delta the proper conditions for a true plankton community to develop: settling and trophic interactions become of increasing importance in determining the structure of plankton communitie

ISSN:0886-9375    

DOI:10.1002/rrr.3450050107

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractGerman politicians have promised that the River Rhine will be sufficiently restored within twelve years to permit salmon to live there again. Obviously the large rivers in Central Europe are more isolated from each other than smaller streams, and communities donating potential colonizers (if they exist at all) are further apart for possibly restored large rivers than for smaller streams. Thus, recovery can be expected to be faster in small streams than in big rivers after restoration (or reduction of detrimental human influence). Therefore, two restoration projects in German lowland streams, which differ in their degree of isolation, can serve as an indicator to the time periods which couldat leastbe expected for the recovery of Central European rivers.Under optimal conditions (almost completely intact communities upstream and downstream of a 400 m restored reach) in North Germany, sufficient recovery of benthic macroinvertebrate fauna could be achieved in relatively short periods. However, in a rather isolated stream reach in the Upper Rhine valley (closest intact lotic ecosystems of a comparable type were found 20‐25 km away) a sufficient recovery of benthic macroinvertebrate fauna was not achieved within five years after restoration, although there was high diversity of physical habitats and the water quality was acceptable (except for two oil accidents in the fourth and the fifth year).Hence, we conclude that recovery of a large Central European river ecosystem like the Rhine, which has lost a large number of its former species and is more isolated than small streams, will require more than twelve years to reach a state significantly different from the present on

ISSN:0886-9375    

DOI:10.1002/rrr.3450050108

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThis paper describes a study of a river regulated by past engineering schemes carried out for land drainage purposes: the River Welland in the East Midlands of England. Benthic invertebrate family richness and total biomass was measured in riffles, pools, and runs separately and then related to the frequency of these physical parameters. Changes which have occurred as a consequence of (a) loss of channel length through meander cut‐offs and (b) alteration of substrate characteristics through dredging and lowering of the river bed, were quantified. Riffles comprised 20‐30 per cent of the channel in reaches not seriously altered by engineering; elsewhere dredging has reduced or eliminated riffles and pools, leaving uniform sandy runs as the dominant channel feature. Riffles, pools, and runs all contribute to overall ecological value but the riffle and pool biotopes supported higher macroinvertebrate biomass and family richness. We show that proposals for river management that address the ecological needs of invertebrate communities can thus be expressed as numerical recommendations for maintaining or enhancing the key physical features of a river. In consequence, conservation recommendations can be simplified and considered in the same form as the engineering requirements of land drain

ISSN:0886-9375    

DOI:10.1002/rrr.3450050109

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

ISSN:0886-9375    

DOI:10.1002/rrr.3450050101

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY