A comparative contribution of the sea level oscillations of various time scales (long-term, seasonal, synoptic, and mesoscale) to the formation of the Neva River floods is estimated. The identification of the Neva River flood waves as the long gravity ones existing nowadays is called in question. The comparison of estimated characteristics of flood waves with the theoretical variance relations of different types of long waves is carried out. This comparison as well as the results of analysis of meteorological information and numerical experiments carried out before on the basis of the hydrodynamic model of the Baltic Sea demonstrate that the Neva River flood waves are identified as the forced baroclinic topographic waves generated as a result of the resonance between the anemobaric forces in atmospheric cyclones and low-frequency eigenmodes of the open Baltic Sea-Gulf of Finland system.