Abstract:
Dams represent a unique category of engineered infrastructure because their eventual obsolescence is determined by the geomorphological processes of erosion and sedimentation, anthropic land-use changes and natural hazards such as landslides, as well as changes on river management strategies, calling for the complete removal of dams, as seen in the Pacific Northwest. When sedimentation is controlled, water dams can have useful lives greatly exceeding any other type of engineered infrastructure. For example, Schnitter (1994) lists12 ancient dams that had operational periods exceeding 2,000 years. Four of these are still in operation, five have been rehabilitated and are operating again, and only three are no longer operational. However, absent sediment control, today’s dams and their reservoirs represent an unsustainable pattern of water resource development. Historically, sedimentation investigations have focused primarily on computing rates of sediment inflow, predicting sediment induced shifts in the stage–storage curve over time, sizing dead pools typically equivalent to 50 or 100 years of sediment storage and determining the “life of the reservoir.” Today an increasing number of dams are reaching the end of their “design life,” and their operation is increasingly affected by long-term sedimentation issues ignored at the time of construction. Some examples include Sanmenxia Dam in China, Guavio Dam in Colombia, and the Peoria Lakes in Illinois.
In this talk, the mechanics of sediment transport in lakes and reservoirs will be presented. Two modes of sediment transport, sediment in suspension by turbulence in free surface flows, and transport by sediment-laden underflows, known as turbidity currents, will be presented. The formation of deltas in reservoirs by predominantly coarser sediments and the distribution of finer sediments to deeper water, all the way to a given dam closure, will be discussed. Different transport modes and the impact sedimentation has on the morphology of deposits and distribution of sediments along a given reservoir will be considered. Erosion and sedimentation in the context of reservoir management, delta restoration and disposal of mining tailings, will also be discussed. The relevance of understanding the mechanics of sedimentation for long-term water reservoir management and preservation, provided the motivation for this seminar.
Bio:
Marcelo H. Garcia holds the M.T. Geoffrey Yeh Endowed Chair in Civil Engineering and is the Director of the Ven Te Chow Hydrosystems Laboratory. Garcia joined the faculty of the University of Illinois at Urbana-Champaign in 1990. Before Illinois, he was a Research Fellow at St. Anthony Falls Hydraulic Laboratory, University of Minnesota, where he completed his graduate studies in Civil Engineering (MS'85, PhD'89). From 2011 to 2014, he held the Chester and Helen Siess Endowed Professorship in Civil Engineering. Garcia has mentored and supported over 100 graduate students, including 42 Ph.D. doctoral students, 65 master’s students and several post-doctoral research associates. Four of his PhD students have been recognized with the prestigious Lorenz G. Straub Award for most meritorious PhD Dissertation in hydraulics, ecohydrology, geophysical fluid dynamics, or related fields. Garcia has been a member of the faculty at the University of Illinois at Urbana-Champaign for 35 years.
