PIPING, A GEOMORPHIC AGENT IN LANDFORM DEVELOPMENT OF THE DRYLANDS

Abstract

In certain arid and semiarid lands, piping is a major factor in the erosion process and thus in the shaping of land forms. Piping, sometimes called natural tunneling, is the development of internal drainage tubes in silty soils or weakly consolidated siltstone, claystone, or similar bedrock. It is fairly widespread over dry areas of the earth, and in some places has created serious erosion problems. Nonetheless, piping is scarcely mentioned in scientific literature and no references to this phenomenon have been found in available textbooks on geomorphology, geology, physiography, soils, or in scientific or popular encyclopedias. In the United States piping is commonest in denuded heavy-soils areas of the dry West where gullying, or arroyo development, has made possible the development of steep-gradient subsurface drainage. However, not all piping is related to gullies. In the Navajo Country piping is not uncommon on residual hills or mounds in the Chinle and Moenkopi Formations of the Painted Desert of Arizona. Here crowns of many hills are miniature karsts. Much of the precipitation upon these hills runs into them, not down over their sides, and eventually discharges by seeps or tiny wet-weather springs in drainage courses at or near the bases of the hills. Commonly the subsurface drainage courses (pipes) show meanders just as surface streams often do, and natural bridges on a miniature scale are numerous in piped areas. /Author/