It has also caused damage to parts of neighbouring Oahu.
The state's Red Cross is busy delivering emergency aid to people, many of whom are in evacuatiion centres.
Record flash flooding and severe thunderstorms over the weekend turned roads to waterways and triggered mudslides, while there were widespread power and water shut downs.
In some cases access to emergency shelters was blocked.
American Red Cross Hawaii CEO Coralie Matayoshi said damage assessments were ongoing but their teams were doing what they could to assist, including providing medical aid volunteers to help in the shelters.
"We actually, on Oahu, had three destroyed homes that were completely unliveable and 26 with major damage, 96 with minor damage and 38 homes that were affected. And so we have been doing damage assessment and helping them with recovery.
"On Kaua'i its been more precarious the situation. A lot of landslides and flooding and inaccessible areas. Hundreds of people have had to be evacuated."
The Governor of Hawaii has issued an emergency proclamation for Kauai.