Since 1876, various councils have administered local areas under legislation determined by the central government. In 1989, the government reorganised local government into the current two-tier structure of regional councils and territorial authorities. The 249 municipalities that existed in 1975 have now been consolidated into 67 territorial authorities and 11 regional councils. The regional councils' role is to regulate "the natural environment with particular emphasis on resource management", while territorial authorities are responsible for sewage, water, local roads, building consents, and other local matters. Five of the territorial councils are unitary authorities and also act as regional councils. The territorial authorities consist of 13 city councils, 53 district councils, and the Chatham Islands Council. While officially the Chatham Islands Council is not a unitary authority, it undertakes many functions of a regional council.