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<br />Scope: Perform model runs for the 10-, 50-, 100-, and 500-year tributary peak <br />hydrographs to support the USACE’s physical and numeric modeling of the Maple River <br />Aqueduct Structure. Provide modeling results to USACE. <br />IV. ADDITIONAL ASSISTANCE FOR THE MAPLE RIVER AQUEDUCT PHYSICAL MODEL <br />Scope: Additional assistance includes participating in bi-weekly conference calls, <br />providing additional technical information and support from Feasibility Study team to <br />USACE’s physical modeling team, and attending a four-day value-based design <br />charrette. <br />V. UNSTEADY HEC-RAS MODELING OF EXISTING PMF INFLOWS <br />Background: The existing Probably Maximum Flood (PMF) was developed almost <br />30 years ago (1984) and is based on simple hydrologic routing that likely does not <br />account for the full effects of floodplain storage and cross-basin flow that occurs <br />upstream of Fargo-Moorhead. USACE has updated the unsteady HEC-RAS model <br />upstream of the unsteady HEC-RAS model currently being used for the FMMFRM project <br />so that it has the extents and connections necessary to model the PMF event. The <br />portion of the FMMFRM unsteady HEC-RAS model from Abercrombie, ND (the upstream <br />extents of the unsteady HEC-RAS model being used for the FMMFRM study) through <br />Fargo-Moorhead has been added to the upstream model to create the unsteady HEC- <br />RAS model required for this PMF analysis. To avoid confusion, the unsteady HEC-RAS <br />model being used for the PMF analysis will be referred to as the “Upstream” model, <br />while the unsteady HEC-RAS model generally being used for most of the FMMFRM study <br />will be referred to as the “FMMFRM” model. <br />To get an idea of how much the PMF might change, the Corps and the Project Sponsor <br />previously decided that it would be useful to investigate routing the existing PMF <br />inflows using the Upstream model. The Corps has set up the Upstream model with the <br />proper inflows. <br />Scope: <br />a) Perform a technical review of the model <br />b) Address the instability issues related to running the model with very large inflows <br />c) Produce final model runs using the 1984 hydrology that provide the PMF at the <br />Fargo gage. <br />Deliverables: <br />a) Draft unsteady HEC-RAS models. <br />b) Draft technical memorandum (hard copy and electronic). <br />c) Final unsteady HEC-RAS input and output files for the PMF event. <br />d) Final technical memorandum. <br />Phase 2 - Numerical Modeling Scope: <br />a) Set Up Unsteady HEC-RAS Model for New PMF Inflows <br />USACE has developed a number of new inflow locations for the unsteady HEC-RAS <br />model that are associated with HMS output hydrographs. These inflow locations <br />have been provided separately in an HEC-RAS unsteady flow data file. Develop a <br />draft unsteady HEC-RAS model with updated inflow locations. If requested, modify <br />names of certain reaches and storage areas to be consistent with the final unsteady <br />HEC-RAS model used for the PMF flow routing. <br /> <br />Deliverables: <br />i. Draft unsteady HEC-RAS model with updated inflow locations. <br />HMG_TO9-A13_Long.docx 7 <br />DR <br />A <br />F <br />T <br /> <br />3/6 <br />/ <br />2 <br />0 <br />1 <br />5 <br />