Morgan Goranflo, TVA River Operations (retired contractor)

Abstract: TVA is completing a systematic re-evaluation of extreme event flooding for its system of dams and reservoirs. A hydrologic analysis for each of the 49 projects is being conducted to determine the projects’ adequacy to safely pass the inflow design flood (IDF). For high hazard dams, TVA has adopted the probable maximum flood (PMF) as the IDF, while adopting a lesser flood (maximum probable flood) for significant and low hazard dams. These results also play a critical role in evaluating the extreme external flood hazard at three nuclear plants sited along TVA reservoirs.
     TVA’s River Forecast Center (RFC) is responsible for developing daily operating plans for all TVA reservoirs on a 24/7 basis and issuing river forecasts and warnings during all flood events. The RFC uses RiverWare as its primary river scheduling tool for most of its reservoirs. TVA is currently recalibrating its sloped-power reservoirs along the Tennessee River to better replicate the results of more robust finite-difference modeling performed as part of the PMF analyses, and to incorporate these results into the operational RiverWare model. Several refinements have been made to the RiverWare model recently to expedite the use of RiverWare for this type of modeling, and the results thus far indicate that RiverWare can be used satisfactorily for daily forecasting for all ranges of flow possibilities for the TVA system.