From: Roger Bettess To: Subject: Rivers-List: River engineering problems for 21st Century Date: 25 June 2000 08:24 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. Disclosure to parties other than addressees through for example forwarding, copying, printing, distribution etc requires HR Wallingford's specific consent. HR Wallingford is not liable for unauthorised disclosures nor for subsequent actions or omissions in reliance upon them. If you have received this message in error please notify us immediately and destroy all copies of it."