The increasing number of dams built in the last century has underlined the necessity of these constructions to the all-round development of a country. The advent of rock mechanics, engineering geology and a better understanding of materials have made it possible to construct higher and larger dams and to tackle more difficult sites. The assumptions and risks used in the theory of dam design include such unpredictable events as earthquakes, floods, and geological faults or soft seams, which may be either underestimated or completely missed during initial exploration. Incidents relating to dams are manageable at an early stage, whereas accidents, which are largely unforeseen, result in unexpected behaviour of dams and in catastrophic failures. Investigations conducted to determine the cause of a failure may not reveal the true sequence of events, while expert analyses are often controversial. From the dams that do not fail, of course, we learn nothing. Systematically monitoring the dam’s behaviour from the potential risk stage to the accident event, would allow a hazard-management programme to be implemented, minimising loss of life and property, and provide useful data.
Have reservoir fisheries been successul in replacing river fisheries? Which migration mitigation measures exist and how effective are they? What is the information base and capacity required for effective management of fisheries through a dam projcet cycle? What are the existing criteria and guidelines concerning dams and fisheries? The four papers presented in this publication address major fishery issues in relation to dams as identified by the World Commission on Dams (WCD) and FAO for the purpose of WCD's global reviews on "Dams and Development".
Dealing with dam types such as gravity, counterfort and arch, this guide examines construction techniques, their development over the years, and their merits and demerits. As well as providing citations of dams, patents and codes, the text presents comparative data on world dams, updated to 1991.
In 1996 the World Bank Operations Evaluation Department completed an internal review of 50 large dams funded by the World Bank. IUCN-The World Conservation Union and the World Bank agreed to jointly host a workshop in April 1997 to discuss the findings of the review and their implications for a more in-depth study. The workshop broke new ground by bringing together representatives from governments, the private sector, international financial institutions and civil society organizations to address three issues: critical advances needed in knowledge and practice, methodologies and approaches required to achieve these advances, and proposals for a follow-up process involving all stakeholders.