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| Harleman Lecture -
2002 'Saving Venice from the Sea' Dr. Donald R.F. Harleman Ford Emeritus Professor of Civil & Env. Engineering Massachusetts Institute of Technology
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Speaker Biography
Donald R. F. Harleman, a native of Palmerton, PA, received his B.S.C.E. degree from Penn State in 1943 and his M.S. and Sc.D. degrees in Civil Engineering in 1947 and 1950 from the Massachusetts Institute of Technology (MIT). He worked as a design engineer for Curtis-Wright Corporation in Ohio during WWII. Through 1962 he held research and faculty positions in Hydraulics at MIT, and in 1963 he became Professor of Civil Engineering. He was appointed Ford Professor of Environmental Engineering in 1975, and achieved Emeritus status in 1991. He currently holds the title of Senior Lecturer at MIT.
Dr. Harleman has been an active member of the National Academy of Engineering and is an Honorary Member of the American Society of Civil Engineers (ASCE). He has won six (6) ASCE awards, including two (2) Hilgard Hydraulic Prizes in 1971 and 1973, and a Stevens Award in 1973. The Boston Society of Civil Engineers has honored him with three (3) awards with the latest being in 1990, and he has received two (2) awards from the College of Engineering at Penn State as Outstanding Alumnus in 1979 and as an Alumni Fellow in 1987. He has served as a member of the Board of Editors of the international Journal of Hydraulic Research, and was a member and Chairman of the Executive Committee of the Hydraulics Division of ASCE in the 1960’s. He has spent residence time overseas as a visiting engineer at the Delft Hydraulics Laboratory in the Netherlands and at the International Institute for Applied Systems Analysis in Austria, as well as being a Guggenheim Fellow in the Department of Applied Mathematics and Theoretical Physics at the University of Cambridge, England. He gave the First Hunter Rouse Hydraulic Engineering Lecture for ASCE in 1980.
For ten (10) years beginning in 1973, Don Harleman was the Director of the Ralph M. Parsons Laboratory for Water Resources and Hydrodynamics. During that same period, he was the Head of the Water Resources and Environmental Engineering Division of MIT’s Department of Civil Engineering. He has a very extensive record of research, publications, and consulting on a national and international level. His current consulting takes him occasionally to Mexico, Hong Kong, Italy, and Brazil.
Don Harleman is a co-holder of two U.S. patents in hydraulics and environmental engineering. He is the co-author of the 1968 textbook Fluid Dynamics, and also the author of “Stratified Flow” in Streeter’s 1960 Handbook of Fluid Dynamics. The Donald and Martha Harleman Professorship at MIT was established in 2000 through an endowment raised by his friends and former students.
Abstract
The survival and prosperity of Venice, built on more than a hundred small islands in the middle of a large lagoon at the head of the Adriatic, during its thousand year history has been achieved by the solution of a succession of engineering “problems”.
The first problem was the physical conservation of the lagoon. Venice was never successfully invaded because the one meter average depth was too deep for armies and too shallow for navies. The lagoon was protected from silting several hundred years ago by diverting the three major rivers outside the lagoon.
The second problem was the protection from Adriatic storm waves of the thin sandy barrier on the ocean side of the lagoon. After diversion of the rivers, sediment transported from the lagoon through the three openings was insufficient to prevent erosion of the barrier. By the 18th century, construction of groins had stabilized the fragile barrier.
The third problem was a result of pumping ground water in the mainland industrial area in the 1950s. By 1975, Venice had subsided about 12 cm and pumping was stopped. This is equivalent to 300 years of natural subsidence.
The fourth problem is caused by global warming and accelerating sea level rise. Venice is the most sensitive place on earth to the impact of centimeters of tidal elevation change. Due to the combined effect of sinking and sea level rise, tides are 25 cm higher than a 100 years ago. Therefore there are more frequent floods and an increase in economic dislocation and structural damage. A predicted sea level rise of 50 cm in the next 50 to 100 years means that the City would become uninhabitable.
Following the disastrous flood of 1966 in which all of Venice was under a meter of water for 15 hours, the Consorzio Venezia Nuova (CVN) was formed and charged with protecting the city.
CVN’s proposed Venice gates are unique in that they are raised and lowered by buoyancy. Each gate module is a hollow steel box 20 m wide and long. A total of 80 gates are needed to close the three barrier openings. Normally the gates, filled with water rest horizontally on the bottom and are hinged at the seaward end. They can be raised by expelling the water by compressed air there
From the early days of planning for the protection of Venice against flooding there has been a vocal opposition to the movable gates by those who insist that more passive defenses are possible. These include permanently narrowing the width and depth of the 3 inlets and raising the level of pavements in the city—however, repeated studies have shown that these interventions cannot protect Venice against the increasing number of storm tide flooding events.
In 1996 CVN appointed an International Panel (of which I am a member) to oversee the development of an Environmental Impact Assessment for the movable gates. The Panel also strongly recommended the gates as the only viable solution. Construction cost is estimated at about 3 billion euros and construction time at 8 years.
Ultimately the Venice flood gates will have to be built, as they have been in the Netherlands and London. The Italian government has recently completed the stabilization of the foundation of the leaning tower of Pisa—Venice is incomparably more important and deserves no less.