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river meandered in a predictable fashion, constantly eroding the bank along the outside of each meander arc and depositing new soils enriched with organic material on the inside bank (Figure 4). The high sediment trans- port combined with variation in the postflood stages from year to year created a series of terraced "bot- toms," the first bottom (lowermost terrace) being replenished and some- times leveled annually by inundation. The second and higher terraces were inundated only intermittently, ailow- Ing a slower cycle of building and destruction and, consequently, a more stable bank formation. Today, these alluvial valleys are marked by human settlements and agri- t IY ?4fYhL? Figure 4. Lower Colorado River flowing through the valley near Parker, AZ, circa 1940. Sediment is being deposited in the outer arc providing for seed- beds supporting native riparian plants and, later, saltcedar. Photo from the files of R.D. Ohmart. culture (Figure 1). The northernmost valley extends from just below Davis Dam to the head of Topock Gorge and supports the towns of Bullhead City and Needles, CA. The next valley south is the Chemehuevi, which once supported a thriving population of Native Americans but now lies com- pletely under Lake Havasu. At Parker, AZ, the valley opens again on the Arizona side and stretches south to Ehrenberg, AZ, and Blythe, CA, where the floodplain shifts to the Califor- nia side of the river and extends to the town of Palo Verde. The Palo Verde Valley was formerly named the "Great Valley of the Colorado" and was among the first to be settled and farmed. The only other broad valley is in the Yuma area, from the vicinity 5