Urban growth and the water regimen

Abstract

The continuing growth and concentration of population and industry in urban and suburban areas in recent decades has caused a complex merging of social, economic, and physical problems, The interrelationships of man and his use and development of the^land and water resources is a particularly significant aspect of urbanization, but there has been relatively little study to date of the effect of urban man upon natural hydrologic conditions. As urban man changes an area from one of field and forest to one of buildings and streets, he covers land where water once entered the soil, and thus creates or aggravates problems of drainage, including storm-water runoff. As he requires increasing amounts of water for home and factory, he drills deeper wells, and builds longer aqueducts and larger dams and reservoirs. As he disposes of unwanted waste materials, he either treats them by using water or pollutes the receiving body of water. As he dredges and deepens coastal streams carrying salt water, and as he pumps greater quantities of water from wells in coastal areas, he increases the likelihood of salt-water contamination. These and many other urban effects upon hydrology deserve increasing study if we are to provide for the best use of the water and land resources available to the Nation's urban centers. THE HYDROLOGIC IMPACT OF URBANIZATION The growth of urban areas in the United States is one of the major sociologic trends of our times. The growth of population in city and suburb during the past half century (fig. 1) has been tremendous and the trend is continuing. At the same time, the social, political, and economic problems resulting from this growth have become increasingly complex. Basic to many of these problems is man's need for land and water, and his effect upon these resources as he occupies and builds, with ever-increasing density, upon land once occupied only by field or forest. This report is a preliminary appraisal of some of the effects of urban man's activities upon his water resources as they occur both on and beneath the surface of the ground. Urbanization may be defined as the process of change in land occupancy and use resulting from conversion of rural lands to suburban, industrial, and urban communities. The obvious effects are to A-l A-2 HYDROLOGIC EFFECTS OF URBAN GROWTH 140 i i i i i i i i i i 185