Thanos Papanicolaou
IIHR - Hydroscience & Engineering, The University of Iowa

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Application Note: 2D Hydrodynamic Sediment Transport
   
Two-dimensional models: Since the early 1990s, there has been a shift in computational research towards 2-D models.  Most of the 2-D models are currently available to the hydraulic engineering community as interface-based software in order to allow easy data input and visualization of results.  This added capability has made these models user friendly and popular.  2-D models are depth-averaged models that can provide spatially varied information about water depth and bed elevation within rivers, lakes and estuaries and the magnitude of depth-averaged streamwise and transverse velocity components.  Most of 2-D models solve the depth-averaged continuity and Navier-Stokes equations along with the sediment mass balance equation via the methods of finite-difference, finite-element or finite-volume.
   
Black Lake simulation: Black Lake, located in the southern region of Alaska, USA has historically been a significant juvenile salmon habitat.  More recently, increase sediment transport down the Alec River system has forced a change in the sediment inflow to Black Lake.  Over the past 50 years, the Alec River has carried enough sediment to build a sandbar across a portion of the lake and effectively reduce the recirculation in the lake.  This sandbar has also caused a major shift in flow from the North Channel of the Alec River to the South Channel near the lake outlet, the bypassing most of the lake water.  This reduced volume and circulation poses a severe threat to juvenile salmon and overall salmon population in the region.  Numerical flow and sediment simulation in the Alec River and Black Lake system utilized here to predict future changes based on recent field data.  Two models were used in combination to produce an overall picture of the system.  First, the Steep Stream Sediment Transport 1D (3ST1D) model was used to predict the flow and sediment transport from the Alec River to the lake.  Then, the commercial SMS package was used to model the lake.  Using the results of the 3ST1D as inputs for the SMS model, it was possible to examine the velocity vectors, recirculation patterns, and shear stresses in the lake.  The resulting sediment transport parameters were examined in order to predict further development of the sandbar.