The river Ganges is bottled each year, but severe floods are relatively rare. Long-term monitoring of water levels in the river have shown that there is some relationship between the force of floods and their recurrence intervals, namely, raising almost proportional to the logarithm of time. Therefore, it is unlikely that a flood of 50-year cycle was repeated in the annual range. This idea can be invaluable when planning construction of river valleys. Although the economic importance of the area flooded during the annual floods of the Ganges, there is no doubt, it is clear that economically disadvantageous, for example, to build a house for up to 100 years of existence, in a part of the plain, which is flooded every 20 years. Therefore, when planning the development of floodplain areas or use of their lands should take into account the interval flood recurrence. But in the UK border danger zone is generally carried out at the level of the flood of 1947 caused by the melting of snow; This level corresponds to a height of floods that may be a time of 100-200 s.