Biological and Agricultural Engineering has an enormous amount of applications, as we’ve learned in past months. But in this month’s Biological and Agricultural Engineering Online Blog, we look at just one more way BAE impacts the world around us.
We spoke to Dr. Celso Castro-Bolinaga, a former hydraulic project engineer from Venezuela who is now an assistant professor here at NC State. He told us more about his particular area of research and expertise: sediment transport.
We understand that your experience and research is focused on sediment transport in streams. Can you explain what that is and why it is an important research focus in Biological and Agricultural Engineering?
CCB: Sediment transport refers to the movement of a wide range of grain sizes due to the forces exerted by the flowing water, in which coarser particles move near the channel bed by rolling, saltation (hopping) or sliding, and finer particles are carried out in suspension by the turbulence of the flow.
Understanding how sediment transport occurs is important because this phenomenon governs the morphology of rivers, defining the channel slope, width and planform as well as the roughness and grain-size distribution of the bed material. Additionally, excess sediment in watercourses may cause severe channel deposition, which can increase flood frequency; damage of infrastructure, such as bridges or culverts; impairment of water quality; and degradation of aquatic and riparian ecosystems.
What got you interested in studying in sediment transport, and how did you enter the field?
CCB: I got interested in this field after the Vargas disaster that occurred in my home country, Venezuela, in December 1999. During this event, a large number of rainstorm-induced landslides along the Cordillera de la Costa released massive amounts of sediment to downstream channels, inundating and destroying coastal communities and causing a significant loss of lives. I was shocked by how effortlessly the flow could entrain rather large boulders and deposit them much farther downstream.
However, it was not until 2010, when I joined the Baker Environmental Hydraulic Laboratory led by Dr. Panos Diplas at Virginia Tech that I had the opportunity to start doing research in the area of sediment transport. I was then reassured I wanted to dedicate my career to this field.
What are the implications of sediment transport in streams? Why might future students want to continue this research?
CCB: Sediment transport influences many physical, environmental and ecological aspects of rivers. Therefore, understanding the fundamental mechanisms that govern this phenomenon is important for the identification, quantification and management of problems caused by sedimentation processes. Nowadays, with changing climatic conditions affecting both the magnitude and frequency of hydrologic events, the occurrence of hazards, such as sediment pulses (e.g. generated by landslides, dam removals projects or mining-related activities), is expected to become more common in river corridors. As a result, current knowledge of how these sediment-flow hazards propagate downstream under extreme flooding conditions must be advanced.
Why are dams installed in streams, and what are the impacts to local ecosystems when they are installed?
CCB: There are many reasons why dams are constructed, including flood control, water supply, irrigation, navigation, recreation, and energy production among others. However, despite the benefits associated with these applications, dams introduce a barrier that disrupts the natural flow regime of rivers, impacting the transport of sediment downstream and the movement of various species in both directions. The construction of dams affects physical, environmental and biological aspects of in-stream habitats and, therefore, causes an adjustment of surrounding ecosystems to the presence of the structure over time.
What reasons may there be for a dam to be removed, and what are the impacts to local ecosystems?
CCB: Dams are typically removed because their reservoirs have filled with sediment; the structure has exceeded its life expectancy or become unsafe, or as part of a stream restoration strategy. Dam removal is also associated with physical, environmental, and biological impacts to surrounding and downstream ecosystems due to the release, for instance, of large amounts of sediments, contaminants or nutrients that can degrade water quality.
How long does it take for the ecosystem to realize these impacts?
CCB: It varies. The temporal scale of the impacts associated with dam removal primarily depends on the characteristics of the river corridor and the watershed; the size of the dam; the volume of water and sediment impounded in the reservoir; and the grain-size distribution of this sediment. As a result, there is a great deal of uncertainty when it comes to predicting how ecosystems will respond to dam removal and how long the impacts are going to persist.
What kinds of technology do you use for your study?
CCB: My research primarily focuses on the development and application of numerical models. Therefore, an important part of what I do relies on having powerful workstations that can quickly process data and execute models. I also employ state-of-the-art field equipment to characterize flow and sediment transport conditions in the natural settings. These types of measurements are important for the validation and calibration of the numerical models.
What is your educational and professional background?
CCB: I received my Ph.D. and M.S. in Civil Engineering from Virginia Tech in August of 2016 and December of 2012, respectively. I completed my undergraduate studies in January of 2009 at Universidad Católica Andrés Bello (UCAB) in Caracas, Venezuela, where I then worked for nearly two years as a hydraulic project engineer in a private consulting firm. During this period, I was involved in a variety of projects, such as evaluating the hydraulic capacity and operation of agricultural irrigation canals and developing flood inundations maps. I joined the Department of Biological and Agricultural Engineering at NC State in November of 2016 as an assistant professor.
What is the most exciting aspect about sediment transport in streams?
CCB: The most exciting aspect is the dynamism of the water flow-sediment transport phenomena, which dictates how watercourses adapt to enhanced hydrologic events and natural or anthropogenic disturbances. Current river engineering problems are rather challenging since they require a solid fundamental understanding of how the different mechanisms that govern the aforementioned phenomena interact, coupled with sustainable solutions that are based on adaptation, mitigation, and resilience.
Thanks, Dr. Castro-Bolinaga!
Check back each month as we take a new look at Biological and Agricultural Engineering and the research and innovation being done in this exciting field.