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2 <br /> Task 1.2 Field Data Sampling Plan <br /> A cursory review of the existing data and information indicates that there may be a data <br /> gap for modeling sediment transport.WEST will develop a field data sampling plan that <br /> is designed to collect site-specific data for the modeling of hydrodynamics and sediment <br /> transport of the Snohomish River in the vicinity of Outfall 025. Such data may include <br /> bed material sampling,velocity,bedload,and suspended sediment concentration and will <br /> include hydrographic cross section survey to fill the gap between existing bathymetry <br /> data and overbank LiDAR topographic data. We assume that URS will implement the <br /> plan to collect the required data. <br /> Task 2 Geomorphic Assessment <br /> Task 2.1 Site Geomorphic Review <br /> WEST Consultants will use and evaluate any existing geomorphic information(studies, <br /> historic aerial photos,etc.)to evaluate the potential for migration of the channel in the <br /> bridge reach. This will not be a detailed quantitative analysis,but an assessment of the <br /> channel characteristics and the potential for channel migration within the river reach near <br /> Outfall 025. <br /> Task 3 Development of 2-D Sediment Transport Model <br /> • <br /> Task 3.1 Field Reconnaissance <br /> A field visit to the location of Outfall 025 will be conducted by WEST personnel. <br /> Task 3.2 Hydrology <br /> We propose to predict sedimentation patterns and volumes for a range of hydrologic <br /> conditions. They may include the following: <br /> • Up to three short-term significant flood events <br /> • Low,average, and high annual events <br /> • Up to a 30-year long-term period of record <br /> WEST will analyze the flow and stage record to define an actual simulation period for <br /> each hydrologic condition. _ <br /> Task 3.3 Update the FIS UNET model to an unsteady HEC RAS Hydraulic Model <br /> As described previously,we propose to develop a site-specific 2-D hydrodynamic and <br /> sediment transport model of the Snohomish River in the vicinity of Outfall 025. <br /> Boundary conditions required in the 2-D model will be provided by the results from an <br /> HEC-RAS model,which was recently converted by WEST from the FIS UNET model. <br /> The HEC-RAS model will be reviewed and calibrated to available observed data. <br /> WEST scope and costs for Outfall 025 Hydrodynamic and Sediment Transport Modeling 4 <br /> 10/15/2013 <br /> 35 <br />