Undoubtedly, the flood is known as a natural disaster. But in practice, the flood is considered the most terrible natural disaster in terms of mortality and financial losses. In this regard, a worrying trend is the increasing trend of mortality and flood damage in the world in recent decades. The increase in population and assets in the floodplain the changes in hydro systems and the destructive effects of human activities have been a major cause of this trend. In this chapter, due to the importance of this natural phenomenon in the ZayandehRud basin, the general study of flood and its effective factors in creating it, based on library studies and reports, and the collection of flood statistics in the basin during a 40-year period and the damage caused by this flood, has been attempted. With the causes and factors influencing the flooding and also the use of EXCEL software for various damages caused by these floods in high risk cities of this basin, has been identified. In general, the cause of many floods in the central parts of Iran, including ZayandehRud basin, is high rainfall. The causes of these rainfall are also related to the Elenino and Lenina phenomenon, as well as the passage of low pressure systems, which after affecting a large amount of steam from the Mediterranean, affect the western parts of the province that overlooks the Zagros mountains.