Faculty Profile


  • Ph.D., Environmental Engineering Science, California Institute of Technology, 1977.
  • M.S., Environmental Engineering Science, California Institute of Technology, 1972.
  • S.M., Mechanical Engineering, Massachusetts Institute of Technology, 1970.
  • B.Sc. (Eng), Mechanical Engineering, First Class Honors, Imperial College of Science and Technology, 1968.

Dr. Roberts’ professional interests are in environmental fluid mechanics, particularly its application to the engineering design of water intakes and ocean outfalls for disposal of wastewaters and desalination brine, and density-stratified flows in lakes, estuaries, and coastal waters. This includes mixing and dynamics of natural water bodies, mathematical modeling of water quality, field studies, and laboratory studies of turbulent mixing.

He is an authority on the fluid mechanics of outfall diffuser mixing and the development and application of mathematical models of wastewater fate and transport. He has extensive international experience in marine wastewater disposal including the design of ocean outfalls, review of disposal schemes, numerical modeling, and the design and analysis of oceanographic field study programs. Dr. Roberts has lectured widely on outfall design and is presently Co-Chairman of the IAHR/IWA Committee on Marine Outfall Systems.

Dr. Roberts’ mathematical models and methods have been adopted by the U.S. EPA and are widely used around the world. He is a regular lecturer at workshops for the U.S. EPA on mixing zone analyses and on the use of mathematical models and outfall design for the Pan American Health Organization. He has developed innovative experimental techniques for research on diffuser mixing processes using three-dimensional laser-induced fluorescence and has published extensively in this area. For this research he was awarded the Collingwood Prize of ASCE in 1980 and was UPS Foundation Visiting Professor at Stanford University in 1993-94. He is presently one of only two Distinguished Scholars in the National Ocean and Atmospheric Administration (NOAA) Oceans and Human Health Initiative (OHHI) in which he is conducting research on the hydrodynamic aspects of bacterial and pathogen transport in coastal waters.

Dr. Roberts holds a professional engineering (PE) license.


  • Environmental fluid mechanics, mixing and dynamics of rivers, lakes, coastal waters, and estuaries
  • Outfalls for wastewater discharge
  • Mathematical models of wastewater fate and transport
  • Oceanographic field programs and data interpretation


  • Appointed to and Chairman of “Expert Panel on Fate and Effects of Brine Discharge” State of California Water Resources Control Board, October 2011 -
  • Distinguished Scholar, NOAA Oceans and Human Health Initiative, 2006-2008
  • UPS Foundation Visiting Professor, Stanford University, 1993-94
  • Member of the Hydrologic Transport and Dispersion Committee, ASCE, 1988 to present.
  • Fellow, American Society of Civil Engineers
  • Adjunct Professor of Oceanography, Skidaway Institute of Oceanography, Georgia
  • Associate Editor, Journal of Hydraulic Engineering, 1987 to 1992
  • Chairman of the ASCE Hydraulics Division Research Committee, 1986-1987
  • Co-Chairman, IAHR/IWA Committee on Marine Outfall Systems
  • Registered Professional Engineer number GA 12476, Georgia, United States
  • 1980 Collingwood Prize of ASCE for paper: "Line Plume and Ocean Outfall Dispersion"
  • 1999-2000 Outstanding Interdisciplinary Activity Award, School of CEE (with Don Webster).


  • Gandhi, V. N., Roberts, P. J. W., and Kim, J.-H. (2013). "Visualizing and Quantifying Dose Distribution in a UV Reactor Using Three-Dimensional Laser-Induced Fluorescence." ES&T, 46(24), 13220-13226.
  • Nekouee, N., Roberts, P. J. W., Schwab, D. J., and McCormick, M. J. (2013). "Classification of Buoyant River Plumes from Large Aspect Ratio Channels." J. Hydraul. Eng., 139(3), 296-309.
  • Tian, X., and Roberts, P. J. W. (2011). "Experiments on Marine Wastewater Diffusers with Multiport Rosettes." J. Hydraul. Eng., 137(10), 1148-1159.
  • Roberts, P. J. W., Hunt, C. D., Mickelson, M. J., and Tian, X. (2011). "Field and Model Studies of the Boston Outfall." J. Hydraul. Eng., 137(11), 1415-1425.
  • Tian, X., and Roberts, P. J. W. (2011). "Experiments on Marine Wastewater Diffusers with Multiport Rosettes." J. Hydraul. Eng., 137(10), 1148-1159.
  • Abessi, O. and Roberts, P. (2014). "Multiport Diffusers for Dense Discharges." J. Hydraul. Eng., 10.1061/(ASCE)HY.1943-7900.0000882 , 04014032.
  • Roberts, P.J.W. (2013). “Ocean Outfalls.” In Handbook of Environmental Fluid Dynamics, Volume Two. H. J. Fernando, Ed., CRC Press: 229-242.
  • Roberts, P.J.W. et al. (2010). “Marine Wastewater Outfalls and Treatment Systems.” International Water Association, London.
  • Roberts, P.J.W., and Webster, D.R. (2002). "Turbulent Diffusion," in Environmental Fluid Mechanics - Theories and Applications, H. Shen, Ed., ASCE, Reston, Va.
  • Ettema, R., Arndt, R., Roberts, P.J.W., and Wahl, T. (2000). Hydraulic Modeling: Concepts and Practice, ASCE, Reston, Virginia.
  • Roberts, P.J.W. (2014). "Topics in Environmental Hydraulics,” Keynote presentation at 7th International Symposium on Environmental Hydraulics, ISEH2014, Nanyang Technological University, Singapore, January 7 – 11, 2014.
  • Roberts, P.J.W. (2014). " Methods of Brine Disposal from Seawater Desalination,” Keynote presentation at International Conference on “Desalination, Environment And Marine Outfall Systems” to be held from 13-16 April 2014 at Sultan Qaboos University (SQU), Muscat, Oman.
  • Roberts, P.J.W. (2013). "Mixing of Brine Discharges,” Keynote address at the Workshop “Seawater Intakes and Desalination Brine/Wastewater Outfalls: Coastal Environmental Impacts in the Gulf Collaboration Region.” King Abdullah University of Science and Technology (KAUST), Saudi Arabia, October 6 – 9, 2013.
  • Nemlioglu, S., and Roberts, P. J. W. (2011). "Three Dimensional Analyses of Inclined Dense Jets under Counter and Co-flow Conditions." International Symposium on Outfall Systems, Mar del Plata, Argentina May 15-18, 2011, IWA.
  • Roberts, P.J.W. (2010). "Issues in Marine Wastewater Disposal." 44th Annual Congress, Ottawa, Canada, May 31 - June 4, 2010, Canadian Meteorological and Oceanographic Society.