Bajadas (also spelled bahadas) are formed by the lateral merging and blending of a series of alluvial fans. They extend from the base of a mountain range out onto the floodplain, most frequently into an inland basin. Such a basin is also called a bolson, and these coalesced fan deposits are also called a bolson plain. A bajada can be relatively narrow, made up of two or three fans, or a broad, extensive, continuous alluvial slope consisting of many fans. If other factors are also involved, parts of the surface of an extensive bajada can take on the characteristics of a gravel plain, i.e., a pediplain. Bajadas have a progressively finer texture downslope, and they may blend into playas in the lowest parts of a basin. Because of the low, ridgelike mounds of the component fans, the surface is undulatory, and the amplitude of the undulations decreases downslope. The upper boundary of a bajada is commonly merged with a pediment slope.
Episodic flow of sediment-laden water.
Aside from being sources of engineering materials, bajadas can support foot and vehicular traffic, as well as rotary-wing aircraft operations. Fast-moving vehicles and rotary-wing aircraft can, however, cause dust and fine sand to become airborne: the lower down the slope, the greater the dust problem. The intersecting, parallel-to-subparallel channels and gravel ridges provide a grain to the surface that may affect cross-country travel. Travel parallel with the grain, i.e., going down slope or up slope, can be easier than going across the grain. Because of the undulations and numerous small channels, travel across the bajadas can be slow, particularly on the upper slopes.
Depending on the amount of relief, the channels and undulations can provide some degree of cover and concealment. The abundant loose gravel and rock fragments on the bajada are sources of secondary projectiles when hit with ordnance. Trenching is laborious, but the walls of the trench generally stand up well.
(common names are in bold): Alluvial apron, alluvial fan, alluvial plain, apron, bolson plain, debris apron, fan apron, gravel piedmont.
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