For the purpose of insurance, a 1% annual risk of flood is categorized as high risk. It calculates out to a 26% risk of being flooded at least once in a 30 year

For the purpose of insurance, a 1% annual risk of flood is categorized as high risk. It calculates out to a 26% risk of being flooded at least once in a 30 year mortgage. "Moderate risk" is considered flooding between every 100-500 years.