"Dogs and their owners need shelter, especially on sunny summer days and they help when it rains too," Mr Gill said.
The committee had been holding training sessions on Wednesday nights for $5, as a means of improving the park's drainage and facilities.
Mr Gill was appealing for help replacing the sails.
"The dog park belongs to the whole community. Even if you don't like dogs the park will help you by allowing you to have areas where dogs cannot go. The informal training and socialising of dogs is why the owners regularly use the dog park, many of whom become friends."
Mr Gill said he was thankful for the support of Whangarei District Council and Bunnings Warehouse - the latter had offered to come and plant some trees at the park this week.
Police spokeswoman Sarah Kennett said police would like to hear from anyone with information.