Showing papers on "River engineering published in 2002"

Learning from the past: palaeohydrology and palaeoecology

Abstract: Attempts to increase European biodiversity by restoring rivers and floodplains are based on inadequate data on natural systems. This is particularly the case for NW European rivers because all catchments have been impacted by agriculture and river engineering. If river restoration is to have an ecological, as opposed to `cosmetic' design basis then baseline models are required. However, this poses three questions; (a) what is the natural river-floodplain state, (b) how can it be defined and modelled and (c) can this state be recreated today? The first two questions can only be addressed by using palaeohydrological and palaeoecological data. A second and equally vital consideration is the stability/instability of any restored system to change in external forcing factors (e.g. climate) and in this context it may not be realistic to expect baseline models to provide equilibrium solutions but instead to define process-form domains. Over the last two decades evidence has accumulated that the natural state of lowland rivers in much of NW Europe was multi rather than single thread-braided, anastomosing or anabranching. Until recently our knowledge of floodplain palaeoecology was generally derived from pollen diagrams, which have source-area of problems and lack of taxonomic specificity. The precision and breadth of palaeoecological reconstruction (including richness and structure) has been greatly increased by the use of multiple palaeo-indicators including macrofossils, diatoms and beetles. The dynamics of small to medium sized, low-energy, predeforestation floodplains were dominated by disturbance (windthrow, beavers, etc.) and large woody debris. In order to compare the hydrogeomorphological basis of floodplain ecology, both temporally and spatially, a simple index of fluvial complexity is presented. Palaeoecological and geomorphological investigations have the potential to provide in-depth models of the natural range of channel conditions and sensitivity to external change that can be used to provide a scientific basis for floodplain restoration. There is also the possibility that floodplain-channel restoration may be a valuable tool in the mitigation of future geomorphological change forced by climatic instability.

Recent flood disasters in China

Abstract: In 1996 and 1998 several devastating floods occurred on the Yangtze, Yellow, Haihe and Songhua Rivers in China. Flood disasters are now happening more frequently than in the past, due to the fact that economic development is changing the river discharge and the flood control system has not matched the change. In recent years it has been found that small floods cause high stage and extreme damage on the Yellow and Yangtze Rivers, which is due to the non-integrated water and sediment management. On the Yellow River a flood in 1996 with a return period of two years caused the highest recorded stage in history and resulted in huge economic losses because the high rate of siltation and the increasing water diversion from the river had greatly reduced the flood discharge capacity of the river channel. In the Haihe River basin a 1-in-50-year flood in 1996 claimed fewer lives and less damage than in earlier times thanks to artificial drainage canals built in the 1960s and 1970s, which increased the capacity of th...

Analytical solution of non-homogeneous wave equation

Abstract: Models for shallow water wave processes are routinely applied in coastal, estuarine and river engineering practice, to problems such as flood waves, tidal circulation, tsunami penetration, and stor...

Benthic and hyporheic habitats of a large lowland river (Elbe, Germany): influence of river engineering.

Abstract: Benthic and hyporheic habitats of a large lowland river (Elbe, Germany): influence of river engineering.

A finite volume method for numerical modeling of 2-D flow and sediment movements on unstructured grids

Abstract: Based on the algorithm frame of finite volume on unstructured grids, by introducing upwind decomposition of flow and sediment numerical fluxes in the normal direction to and across each side of cells, a 2 D finite volume method for flow and sediment movements is established, including exchange modes between suspend sand and bed sand, and sediment carrying capacity formula of different grain The algorithm is used to simulate the numerical value on flow and sediment transport and riverbed deformation It is proved that this algorithm can reflect the dynamic process of flow and sediment transport and river bed deformation, and that the precisions satisfy the analytic need of the river engineering.

Three-dimensional mathematical model and its application in the neighborhood of the Three Gorges Reservoir dam in the Yangtze River

Abstract: The calculation of flow and sediment transport is one of the most important tasks in river engineering. The task is particularly difficult because a number of complex physical phenomena should be accounted for more realistically in a model with a predictive power. Three-dimensional calculations of river flow and suspended sediment transport are performed in this paper with application in the Three Gorges Reservoir in the Yangtze River. A period of 76 years after the dam is built is simulated and the results are compared with laboratory measurements obtained by Tsinghua University whereby the model is verified and calibrated. Generally speaking, the calculated results agree well with the experiments, demonstrating that the present model can be used for flow and sediment transport prediction in rivers.

STORM-Rhine: Simulation Tool for River Management

Abstract: The Simulation Tool for River Management (STORM), based on the River Rhine case, aims to provide insight into river and floodplain management, by (1) raising awareness of river functions, (2) exploring alternative strategies, (3) showing the links between natural processes, spatial planning, engineering interventions, river functions and stakeholder interests, (4) facilitating the debate between different policy makers and stakeholders from across the basin and (5) enhancing co-operation and mutual understanding. The simulation game is built around the new concepts of “Room for the River”, Flood Retention Areas, Resurrection of former River Channels and “Living with the Floods”. The Game focuses on the Lower and Middle Rhine from the Dutch Delta to Maxau in Germany. Influences from outside the area are included as scenarios for boundary conditions. The heart of the tool is the hydraulic module, which calculates representative high- and low waterlevels for different hydrological scenarios and influenced by river engineering measures and physical planning in the floodplains. The water levels are translated in flood risks, navigation potential, nature development and land use opportunities in the floodplain. Players of the Game represent the institutions: National, Regional, Municipal Government and Interest Organisations, with interests in flood protection, navigation, agriculture, urban expansion, mining and nature. Players take typical river and floodplain engineering, physical planning and administrative measures to pursue their interests in specific river functions. The players are linked by institutional arrangements and budgetary constraints. The game particularly aims at middle and higher level staff of local and regional government, water boards and members of interest groups from across the basin, who deal with particular stretches or functions of the river but who need (1) to be better aware of the integrated whole, (2) to understand the interests and considerations of others and (3) to experience the mutual benefits of co-operation. There is potential for using the game as one of the tools in support of interactive formulation of policy and participatory decision-making in actual plans.

Discussion of ''Impact of Turbidity Currents on Reservoir Sedimentation'' by

Abstract: This paper deals with an important topic in river engineering: the turbidity current-induced sedimentation in reservoirs. Combining in situ measurements, laboratory-scale modeling, and computer simulation, this study is certainly of significance to river engineers. This discussion is to seek further clarification of several major issues of the study in question.

Woolston New Weir and River Mersey Diversion

Abstract: The Woolston Weir and River Mersey Diversion project involved provision of a new hydraulic control structure, diversion channel and ancillary works on the River Mersey, near Warrington, for the Manchester Ship Canal Company. The weir is a substantial structure, nearly 80 m wide. It includes the largest low-head, air-regulated siphon weir to date in the UK, with nine bays, each 4 m width, plus 17·8 m wide ‘ogee’-type weirs either side, and a fishpass. Design involved extensive physical and numerical modelling. The weir was built in dewatered open cut in difficult ground, within a new channel some 600 m length cutting across an ancient loop in the Mersey. The scheme has provided an economic means of closely controlling a wide range of flows, for flood and navigation purposes, consistent with a pleasant river environment.

Impacts of river-engineering practices on the conservation interest and water quality in the Land Yeo, england

Abstract: The environmental quality of many rivers on the Somerset Levels and Moors has been reduced because of past river-engineering practices and changes in land use. A new holistic and restorative approach to river management is now helping to improve the quality of aquatic ecosystems. This paper presents the results of a study which assessed the impact of past river and floodplain management on the Land Yeo, Somerset, with the objective of recommending measures for future management. The main findings are that (a) the ecological interest of the river has been reduced due to channel re-sectioning and flow diversion, and (b) the flow diversion is also causing water-quality problems such as dissolved-oxygen reduction. Most of this degradation could be reversed by the adoption of a number of channel and riparian-enhancement measures and by revising the annual maintenance programme.