Question

To spell the word occurrence, why is the final consonant doubled before adding the suffix?

Answer 1

The answer to your question would be that to spell the word occurrence, the final consonant is doubled before adding the suffix because the stress is on the second syllable of the base word ending in consonant+ vowel + consonant.

You should always double the r for words of more than one syllable when the final r is preceded by a vowel. The following ones are other examples of this rule: concurrence, deterrent and referral.

Answer 2

 Because the stress is on the second syllable of the base word ending in consonant + vowel + consonant. its what separates the U from the E so it dos'nt make the word sound like (oh-cure-ence)