Mountains build alluvial fans as sediment-bearing streams wash eroded material out of the higher parts of the range and deposit it around the mountain’s base. The overlapping consolidated alluvial fans creates a slope habitat of more water permeable material and deeper soils which provide optimum conditions for the Sonoran Desert plant life. These slopes, known as bajadas, display the local Sonoran Desert growth at its highest degree of development. These photos are from the lower slopes of the Santa Catalina Mountains, Arizona.