Paper Number: EP21D-2277 Development of ‘Debris Library’ and ‘GSSHA’ linkage-architecture for non- Newtonian sediment fluid flow Nawa Raj Pradhan1, Ian Eli Floyd1, Ronald Heath1, Charles W. Downer1, Stanford Gibson2, Gary Brown1, Steve Turnbull1, Jose M. Paredez3. 1 U.S. Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory, Vicksburg, Mississippi 2 US Army Corps of Engineers, Hydrologic Engineering Center, Davis, CA 3 US Army Corps of Engineers, Los Angeles District, CA Introduction 2018 AGU Fall Meeting, Washington D.C., 10-14 December The assumption of a Newtonian fluid flow condition, (a linear stress-strain relationship) fails for sediment laden fluids with higher volumetric concentrations. As sediment concentrations increase, they begin to influence the fluid properties, which alters the stress-strain relationship. The ‘Debris Library’ assigns a stress-strain relationship that is appropriate for non-Newtonian, sediment laden fluid flow conditions. The Gridded Surface Subsurface Hydrologic Analysis (GSSHA) model is a fully coupled overland/in-stream model with the SEDLIB library for the in- stream sediment flux formulations. In this study, we developed a linkage-architecture to pass the GSSHA computed flow velocity, depth and concentration to Debris Library and to pass the Debris Library computed internal shear stresses back to GSSHA. Both Debris Library and SEDLIB are model independent libraries that can be implemented in any H&C code (for example, another effort in this work unit involves the implementation of Debris Library into HEC-RAS) GSSHA/SEDLIB Coupling GSSHA / SEDLIB Result GSSHA/SEDLIB GSSHA (parent code) generates and transports the overland sediment flux as lateral input to channel. The SEDLIB library GSSHA is a multidimensional modeling technology that integrates computes the and deposition processes of multi grains and surface and subsurface flow for accurate watershed simulation. bed layers in every GSSHA channel computational unit. GSSHA, in GSSHA can be used as an episodic or continuous model where soil turn, routes the channel sediment concentration using an advection surface moisture, levels, stream interactions, and dispersion equation, with the SEDLIB source/sink contributions. constituent fate are continuously simulated. Sediment Library (SEDLIB) is an in-stream sediment process library SEDLIB PARENT CODE SEDLIB-LINK that includes detailed descriptions of sediment processes including • Pass parent code Bed Dynamics bed dynamics such as erosion, layering, armoring, sorting, and (GSSHA) (GSSHA) Goodwin Creek Experimental Watershed. • Overland sediment hydrodynamics • Sediment flux percolation, along with sediment suspension and deposition. detachment by and sediment (erosion and raindrop impact and concentrations at deposition) overland flow a node/cell to • Particle sorting Debris Library • Overland sediment SEDLIB • Bed displacement routing with • Pass bed • Bed layer updating The ‘Debris Library’ computes internal shear stresses along with deposition. sediment fluxes other variables like mixed density and viscosity under non • Lateral sediment flux and bed input to channel displacements Newtonian sediment laden fluid flow condition. This study • In-stream from SEDLIB to developed a linkage-architecture to pass the GSSHA computed flow hydrodynamics parent code velocity, depth and concentration to Debris Library and to pass the (GSSHA) Debris Library computed internal shear stresses back to GSSHA. Improvement in simulated sedograph with in-stream Schematic of GSSHA SEDLIB coupling/linkage. sediment process library linkage. GSSHA/Debris Library/SEDLIB Linkage GSSHA/Debris Library Test Case Architecture Development

SedimentSediment Detachment detachment A contrived test case, as well as an Experimental Shear stress, Viscosity, UWmixture , FVhindered (a)Raindropa) Sediment detachment detachment by ‘Raindrops’ b)(b)Surface Sediment detachment runoff by ‘Surface detachment Runoff’ Watersheds for calculating non-Newtonian fluid flow Velocity, depth, concentration Sediment ‘transport capacity’ of GSSHA / Debris Lib Link with Debris Library is being developed.

Overland sediment ‘transport / routing’ Debris Lib

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b) bed load b) bed

overland

lateral input to lake to input lateral

input to input

lateral input to channel to input lateral

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input to channel input GSSHA Overland Hydrodynamics

Suspended Suspended

sediment flux ‘ flux sediment

a)

sediment flux ‘ flux sediment

Lake Lake

Overland sediment flux ‘ flux sediment Overland

Lake Lake

Overland sediment flux ‘ flux sediment Overland GSSHA / Debris Lib Link GSSHAGSSHA ChannelChannel Hydrodynamics Hydrodynamics GSSHASEDLIB SEDLIB-LINK-Link Velocity, depth, concentration

Shear stress, Viscosity, UWmixture , FVhindered SEDLIBSEDLIB SEDLIB-CORE Schematic of GSSHA Debris lib and SEDLIB-PROCESS Debris library non Newtonian sediment laden fluid flow formulation. SEDLIB linkage architecture. Debris flows in Santa Barbara county. Source: Santa Barbara County