From: Colin Rennie To: Subject: Rivers-List: another 21st century problem Date: 05 July 2000 01:22 I would like to propose another problem for hydraulics in the 21st century that does not appear to be adequately addressed in the present list. During a season of tricky field work in flooding gravel-bed rivers, I have been reminded of what seems to me to be the essential paradox of the study of rivers: that it is too difficult and/or dangerous to sample most rivers when they are flowing at channel-forming discharges. If we are to make headway with the other problems on the list, then it is crucial that robust and accurate methods are developed to measure details of the flow and sediment transport at all relevant spatio-temporal scales. Colin Rennie Department of Civil Engineering University of British Columbia, Canada colin@civil.ubc.ca