Performance Criteria One in Ten year discharge capacity of 3468 cfs at 9.7 ft NGVD stage in L-29 4 Proportion of area with low flow velocity (<0.1 f/s) discharges within one mile of the Tamiami Trail (removed from final USACE report due to lack of modeling data). 4 Difference between average velocity in marsh and average velocity at road (velocity in marsh is assumed to be 0.024 fps). 4 Background Modified Water Deliveries Authorized by Congress 1989 1 “The overall purpose of the Modified Water Deliveries (MWD) to Everglades National Park project is to restore natural hydrologic (water) conditions in Everglades National Park, which was altered by the construction of roads, levees and canals.” –USACE 2 Analysis Spreadsheet Model Based on observation of flow threshold at EL=5.7 ft NAVD88 Flow and spreader canal water stage are considered independent parameters. Calculates average water velocity based on length of spreader canal and depth of flow over rim of canal. Back calculates stage in L-29 from culvert equation (assuming completely submerged culvert). L-29 stage used as screen to eliminate stages above operating capacity of improved roadway. Calculates Ratio of marsh velocity to spreader swale discharge velocity as a percentage. Culvert geometry was assumed to be trapezoidal with slope=3; depth=5.5ft; base= 30ft and
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