From: Zhao-Yin Wang To: Roger Bettess ; Subject: Rivers-List: Problems for 21st Century Date: 09 July 2000 06:10 Dear river researchers I was interested in the discussion on the river engineering problems for 21 century. I would like to say "thanks" for Roger initiating the discussion. Nevertheless, the list of Roger is not well prepared and most of the problems are not so challenging as "Century Problems". Only the 8th problem could be a century problem, as Bram van Prooijen indicated. Klaus Jorde and Michel Leclerc have posed very challenging problem-eco-hydraulics. I suggest the following list of river problems for 21 century: 1. Analytical solution of the Navier-Stokes equation (8th problem in Roger's list) Note: A friend of mine, Prof. Gao Ge has recently approached the problem by taking average over positive and negative fluctuating velocities. The results are very promising and even the bursting process can be numerically shown by using the solution. I believe that the problem plagued scientists for 150 years will be completely solved in 21 century. 2. Analytical solution of movement of solid particles in turbulent flow of water, e.g. sediment motion in open channel flow. 3. River eco-system and response to any human activities. (1) Establish a mathematical framework to take all geomorpho-physico-chemico-ecological processes of the river system into account simultaneously, which is able to describe the complexity and all chain reactions of various elements. (2) Provide solutions of response of the river eco-system to any interruption by human activities. 4. Land creation. All the most productive land were created by river sedimentation. On the one hand, dam construction and flood control reduced and even stopped the natural process. On the other hand, increasing population pressure requires more and more land. How to utilize river sediment for land creation but avoid any damage to the safety of economy and society? (Dutch people created the Netherlands. This is a good solution but their experiences can not be repeated everywhere). 5. Water resources. River runoff will still be the major water resources in the new century.Integrated river water management system is required to meet the water demands for production and human life, sediment transportation, navigation, river ecology, environment, recreation and aesthetics. 6. Hyperconcentrated rivers. The Yellow River has flooded for thousands years and killed millions people. Although the river is confined within the grand levee for 50 years, the flooding threat is increasing because the river bed is more than 10 meters higher than the surrounding ground and is known as suspension river. The river bed is still rising at a rate of 10-15 cm/year and will become "heaven river". A solution must be searched in the new century. And the solution will be also useful for other hyperconcentrated rivers like Bramaputra River. 7. New flood control strategies. Many environmentalists are strongly against dam construction, especially on the large rivers like the Yangtze River in China, because the impoundment of the river will impact the environment and ecology greatly. American people are discussing decommission of dams and renaturalization of rivers. The dam construction has been slowed down. Nevertheless, flood control for safety of the densely populated lower river reaches requires a reservoir to clip the flood peak. Alternative flood control strategies are needed in the new century. 8. Dynamics of fluvio-morphology and unsteady sediment transport. Although many empirical formulas describing various aspects of the river morphology, such as river profile, width-depth ratio, regime theory, a mathematical framework giving the dynamical mechanism of the fluvio- process is to be developed, which should be able to describe the morphological process with unsteady sediment transport. 9. Sediment transportation under action of flow, tide and waves in coastal areas. Great efforts have been made for sediment transportation in the coastal and estuarine areas, useful sediment transportation formulas are to be developed, especially those for silt coast. The following equations or formulas are yet to be achieved for both sand beach and silt coast: (1) coast scour under action of waves, tidal current and river flows; (2) on-shore and off- shore transportation rate of sediment; (3) long-shore sediment transportation, for sand beach and silt coast, the late is related to the law of the turbidity belt. 10. Dynamics of vegetation cover development-soil erosion by wind and flow-climate change. with my best regards Yours sincerely Zhao-Yin Wang Prof. Dr. Tsinghua University & International Research and Training Center on Erosion and Sedimentation, Beijing China Editor of "International Journal of Sediment Research" -----Original Message----- 发件人: Roger Bettess 收件人: rivers-list@iahr.org 日期: 2000年6月25日 15:27 主题: Rivers-List: River engineering problems for 21st Century >Introduction > >At the opening of the 20th century the mathematician David Hilbert published >a list of problems. They were what he considered to be the major problems >facing mathematicians at that time, covering all fields of mathematics. He >also thought that all the problems were soluble within the time span of the >century. By the end of the 20th century all but one of these problems had >been solved. Recently a group of mathematicians have published a new list >of problems for the 21st century. I thought that it would be an interesting >exercise to produce a list of major problems for river engineering for the >21st century. > >The rules are only that there should be no more than 12 problems, so any >proposal which would bring the number of problems to more than 12 must >include a proposal for which of the other problems should be removed from >the list. As we all have up to 100 years to answer them, they should be >suitably challenging and general. To initiate the discussion Professor >Knight from the University of Birmingham and myself have combined our >suggestions which are given below. Members of Rivers-list are invited to >respond with their own proposals. The hope is that the process should be a >converging one rather than diverging. > >Problems > >1 Determination of the conveyance of a section of arbitrary shape. >As plan form may be significant this may have to be re-posed using 'reach' >rather than 'section' > >2 Representation of turbulence > An adequate description of turbulence is required > >3 Determination of the discharge coefficient for a structure of arbitrary >shape > >4 An accurate sediment transport theory >In the 20th century it seemed that no theory could reliably break the >barrier of providing predictions within a factor of 2 about 70% of the time. >We need more accurate theories or an explanation of why they cannot be >achieved. > > 5 Prediction of local and general scour > >6 A theoretical justification for Regime theory > >7 Determination of the dominant physical processes responsible for the plan >form of rivers > >8 Analytical solutions to the Navier-Stokes equations > >9 Effect of cross-sectional shape on resistance coefficients in >open channel flow > >10 Suitable strategies for modelling overbank flow in >natural rivers with floodplains. > >11 Strategies for raising the awareness of society to the value of >hydraulics engineers. > >12 Any comments on the book "Issues and directions in hydraulics" >[Eds Nakato & Ettema, Balkema, 1996]? > >Roger Bettess >HR Wallingford > > >"Faxes and emails are used by HR Wallingford as a >convenience for confidential, and often legally >privileged, business communications both within >the firm and with Clients. 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