Team Stream–Kimberly’s Group

Debris flow related to hazard mitigation in a changing climate

In experimental facilities in the CE building and at SAFL research projects include:  (1) Debris flows in a changing climate. What controls the dynamics of debris flows, and how does that vary according to the climate and changes in climate in which the landscape has evolved?  (2) Grain size distributions and particle-based pattern formation in nature.  When particles are transported down hillslopes and river channels, they tend to segregate by particle size.  For example, in debris flows, larger particles segregate toward the front and sides of debris flows, significantly influencing the dynamics and hazards.  Another example involves the formation and evolution of gravel patches along a river bed: Along a river that is typically transporting a wide distribution of particle sizes, relatively narrowly distributed patches of gravel may form along a river bed. The patches both influence the transport of gravel and provide spawning grounds for certain fish species. There is no predictive formulation for segregation in these disparate conditions. This project will focus on understanding the mechanics behind the segregation in debris flows, river beds, and in simpler systems, with an emphasis based on student background and interest.  (3) Infiltration of fines into a gravel bed. When small sized particles of diameter df are introduced onto base of larger sized particles of diameter dc, if they are sufficiently small they can travel into the pore spaces and clog them, a process called infiltration. This can critically affect fish habitat as it reduces the flow of oxygen, nutrients, and waste.  On the other hand, if they are only moderately small, the particles become a part of the surface, and often increase the mobility of the bed which can lead to bank destabilization.  This project investigates the controls on these infiltration and lubrication behaviors.