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<br />proper model modifications and to determine the impacts of the updated <br />geometry. If the modifications affect the 50-yr model results, complete the 100-yr, <br />500-yr, SPF, and PMF model runs to determine the impact of the updated <br />geometry. If the modifications do not affect the 50-yr model results, the updated <br />100-yr, 500-yr, SPF, and PMF model runs will be made under a future authorization. <br />Develop flooded outline polygons and depth grids for the 10-yr, 20-yr, 50-yr, 100-yr, <br />500-yr, SPF, and PMF events. <br />b) 20-year Existing Conditions Modeling: Develop 20-year Existing Conditions models <br />and provide floodplain mapping for the Staging Area. <br /> <br />Deliverables: <br />a) Preliminary unsteady HEC-RAS models. <br />b) Final unsteady HEC-RAS input and output files. <br />c) 20-year existing conditions model results. <br /> <br />VIII. MAPLE RIVER AQUEDUCT FLOW ANALYSIS <br />a) Conduct modeling of Maple River flows across the proposed Maple River Aqueduct <br />and into the Risk Reduction Area. <br />i. Use the latest HEC-RAS model for the FMMFRM Project and the best <br />available topographic data. <br />ii. The study area is the area within the Risk Reduction Area that is affected <br />by the flow coming across the Maple River Aqueduct. <br />iii. Account for coincident flows on the Sheyenne River and other local drains <br />and ditches. <br />iv. Select Maple River design flows such that insurable structures in the Risk <br />Reduction Area, and within the expected future 1% Maple River floodplain, <br />are minimally affected by the Maple River design flows and the coincident <br />flows on the Sheyenne River and the other local drains and ditches in the <br />Risk Reduction Area. <br />b) Establish Maple River design flows across the Maple River Aqueduct for the 1% and <br />0.2% flood events. <br />c) Recommend a maximum Maple River flow across the Maple River Aqueduct for the <br />Standard Project Flood (SPF) event. <br />Deliverables: <br />a) Preliminary unsteady HEC-RAS models. <br />b) Final unsteady HEC-RAS input and output files. <br />c) 20-year existing conditions model results. <br />d) Final Technical Memorandum. <br />IX. UPDATE HEC-RAS MODELS – MAPLE RIVER AQUEDUCT AND REACH 6 BRIDGE <br />a) Modify the unsteady-flow HEC-RAS model to reflect the lateral structure and <br />spillway changes recommended by the Maple River aqueduct study team. <br />b) Update the flow profile information (1% and 0.2% chance events, and 103,000 cfs <br />event) needed for the bridge design effort, using the current Phase 7 unsteady-flow <br />HEC-RAS model as the source of the geometry for the steady-flow HEC-RAS model. <br />Continue to use the bridge design criteria provided in MFR-005 (General Bridge Re- <br />Assessment for the Diversion from Inlet to Outlet) to determine the low-chord <br />elevation and hydraulic opening of bridges in the Diversion Channel. <br />c) Update the HEC-RAS model geometry: (i) to be consistent with survey and <br />topography dates collected, (ii) to reflect proposed changes to the Maple River <br />natural channel, (iii) to reflect the proposed revised location of the spillway into the <br />HMG_TO9-A13_Long.docx 9 <br />DR <br />A <br />F <br />T <br /> <br />3/6 <br />/ <br />2 <br />0 <br />1 <br />5 <br />