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<br />i. Update HEC-RAS unsteady flow model geometry to reflect most current layout of <br />the Maple River Aqueduct and Spillway being used by the physical modeling team. <br />The Maple River overbank berms near the structure will also be updated. Using the <br />latest project designs, update the layouts and inlet structure geometry for the Rush <br />and Lower Rush Rivers, as well as Drain 30. <br />a. Update HEC-RAS unsteady flow existing conditions and project <br />conditions for the 10-, 50-, 100-, and 500-year Red River peak events. <br />No diversion gate optimizations will be conducted, as this will be <br />completed as part of the Phase 8 model updates. <br />b. Update HEC-RAS unsteady flow existing conditions and project <br />conditions for the 10-, 50-, 100-, and 500-year Tributary peak events. <br />No diversion gate optimizations will be conducted, as this will be <br />completed as part of the Phase 8 model updates. <br />VI. Deliverables: <br />a. Updated phase 7.1 model for the Red River peak flood events, including the 10-, 2-, <br />1-, 0.2-percent chance events and the 103kcfs and PMF flood events for both <br />existing conditions and with-project conditions. <br />b. Updated phase 7.1 tributary peak flow models with geometry developed in Task 1, <br />for the 10-, 2-, 1-, 0.2-percent chance flood events for both existing conditions and <br />with-project conditions. <br />c. Higher volume sensitivity analysis: <br />d. Updated phase 7.0 model. <br />J. UPDATE PMF WITH REVISED DISTRIBUTION OF SNOWMELT RUNOFF: <br />I. Background: <br />a. Initial results from the current PMF study for the USGS Gage at Fargo, ND indicate <br />that the peak flow is about 25% higher than what was determined during the 1985 <br />study. Comparisons with the 1985 study indicate that the Wild Rice, North Dakota <br />basin requires further investigation. Contributing drainage area for the PMF also <br />requires further investigation. Two HMS model runs (two storm centerings) are <br />available from the USACE St. Paul District for each of the eight sub-basins that are <br />included in the PMF study. The HMS models that were used in the initial PMF work <br />were modified from the Phase 1 HMS final product by peaking unit hydrograph <br />parameters for each subbasin, re-incorporating the entire drainage area, and <br />extending several storage outflow relationships that were exceeded with the <br />magnitude of discharges generated from the PMF simulations. <br />b. It has been proposed that GIS can be used in conjunction with the HMS models to <br />better estimate the amount of runoff occurring during a PMF event. The GIS/HMS <br />effort would determine areas that contribute runoff, areas that do not contribute <br />runoff, and areas that partially contribute runoff for the events investigated. <br />II. Scope: <br />a. Discuss the GIS/HMS effort with USACE before proceeding with this work. <br />b. Update the USACA-provided HMS model runs in conjunction with the GIS/HMS- <br />based runoff-determination effort. Determine the order of HMS model simulations <br />and account for the breakout flows between the various models. Coordinate <br />between the HMS model simulations and RES-SIM with USACE. Save Reservoir <br />inflows for Traverse and Orwell in DSS and submit to USACE for simulation. <br />Forward the regulated flow DSS records for inclusion into the RAS Model. <br />HMG_TO9-A13_Long.docx 13 <br />DR <br />A <br />F <br />T <br /> <br />3/6 <br />/ <br />2 <br />0 <br />1 <br />5 <br />