In an effort to control water pollution, the U.S. Clean Water Act of 1977 required that all new real estate developments had to detain storm water so that flow to adjoining properties was no greater than the pre-development runoff. As a result, nearly all residential developments had to construct detention or retention areas to hold excess storm water until it could be released at the pre-development flow level. Since these detention areas serve multiple residences, they are almost always designated as "common" areas. This requirement was a reason for developers to establish a homeowner association. Although these areas can be placed on an individual homeowner's lot, eliminating the need for an association, nearly all U.S. municipalities now require these areas to be part of a common area to ensure an entity, rather than an individual or the municipality itself, has maintenance responsibility. Real estate developers have frequently established homeowner associations to maintain such common areas. Having established the HOA, the developers have expanded their scope, giving them authority to regulate changes to residences, landscaping and maintenance requirements, color of houses, etc., a variety of other requirements and amenities that the developers believe will make their project more desirable to the market..