Numerous environmental processes affect the development and stability of playa (lakebed) surfaces. Of special significance are hydrologic processes that control the amount and flow of both surface and ground water, and climatic variations which in turn influence the hydrology. This report, in six parts, examines some aspects of the playa surface environment. Chapter 1 is an introduction. Chapter 2 describes microrelief changes that developed at Harper Playa, California, following flooding of the playa in 1965-66. Chapter 3 documents a subsurface hydrologic investigation at Rogers Playa, California. The investigation revealed that the piezometric surface has lowered into sand layers beneath the surface, and it may explain why giant desiccation fissures have formed in the surface clays. Chapter 4 describes an investigation of seven Australian playas and suggests that Australia did not undergo a pluvial period like that of the western United States. Chapter 5 describes three kavirs (playas) in northern Iran and indicates that former lakes did exist there, but not to the same extent as in the western United States. Chapter 6 examines the possibilities of observing playa surface changes from satellites, using the present remote sensor technology. It also states that Gemini color photography and high resolution vidicon (TV) imagery are currently useful. (Author)

Numerous environmental processes affect the development and stability of playa (lakebed) surfaces. Of special significance are hydrologic processes that control the amount and flow of both surface and ground water, and climatic variations which in turn influence the hydrology. This report, in six parts, examines some aspects of the playa surface environment. Chapter 1 is an introduction. Chapter 2 describes microrelief changes that developed at Harper Playa, California, following flooding of the playa in 1965-66. Chapter 3 documents a subsurface hydrologic investigation at Rogers Playa, California. The investigation revealed that the piezometric surface has lowered into sand layers beneath the surface, and it may explain why giant desiccation fissures have formed in the surface clays. Chapter 4 describes an investigation of seven Australian playas and suggests that Australia did not undergo a pluvial period like that of the western United States. Chapter 5 describes three kavirs (playas) in northern Iran and indicates that former lakes did exist there, but not to the same extent as in the western United States. Chapter 6 examines the possibilities of observing playa surface changes from satellites, using the present remote sensor technology. It also states that Gemini color photography and high resolution vidicon (TV) imagery are currently useful. (Author).

Dry lakebeds (playas) in the Mojave Desert are often hard and flat enough to serve as natural landing areas for aircraft. However, the surface physical properties of moisture, strength, and microrelief can vary with seasonal or local conditions. It is desirable to develop methods for deterining and monitoring these properties and their variations. Airborne remote sensing enables collection of data on the reflectance, temperature, and emissivity of these surfaces that can be correlated with soil parameters. Four playas in the Mojave Desert that have a variety of surface properties were investigated. Airborne spectrophotography and thermal infrared imagery were obtained by overflights. Ground photometry and measurements of surface properties were obtained. Moisture-sensitive dyes were applied to one lakebed surface to evaluate the feasibility of monitoring its dryness through color changes apparent on the aerial photography. The report describes the results of the remote-sensing investigations and the correlation of photographic and imagery interpretation with actual surface conditions.