Negative feedback . Excellent regulatory mechanism. The relationship is cyclical but remains within limits. When interpreting physical or human influence on a landscape you should be familiar with and look for these type of relationships. Although the patterns are difficult to map because of their fluid nature, it is apparent to most of us that humans have had and continue to have an effect on the earth's atmosphere.
Urban heat islands Shelter-belts .
Affect on wind velocity on leeward side. Pattern and change is more obvious than atmosphere. Maps not only delineate hydrographic features, they provide excellent documentation for those studying these features. Certain patterns are characteristic of human modification. Form channelization levees and dikes reclaimed and filled areas reservoirs, e.g., Lake Travis, Lake Austin , Lake Amistad subsurface maps of water table Water Quality and Availability mapping of geochemistry and water quality salinization of soils , e.g., area around Ft.