Flood Insurance Transparency Act of 2021 This bill requires the Federal Emergency Management Agency (FEMA) make publicly available all data, models, assessments, analytical tools, and other information relating to the National Flood Insurance Program that is used in assessing flood risk or identifying and establishing flood elevations and premiums. This includes data relating to the risks of individual properties, loss ratio information, and current and historical policy and claims information. To accomplish this, FEMA must establish an open source data system through which all such information may be electronically accessed by the public. Further, FEMA must establish a public database that provides information regarding each community participating in the program.