The risk of the catastrophic flooding that struck Texas Hill Country as people slept on July 4 and left at least 120 dead was potentially underestimated by federal authorities, according to an ABC News analysis of Federal Emergency Management Agency data, satellite imagery and risk modeling.

Additional rounds of heavy rains lasting into Tuesday could produce more dangerous flooding, especially in places already saturated.

A National Weather Service flood watch forecasting heavy downpours of up to half a foot of rain was posted until Tuesday morning for a wide swath of central Texas extending from the Rio Grande east to San Antonio and Austin.