Rates and processes of lateral erosion were studied for the middle Sacramento River between Chico Landing and Colusa, Calif. , a river distance of about 50 miles which is bordered by valuable agricultural land. The study is based on comparison of maps made during 1867-1949 and on aerial photographs made during 1924-74. Meander loops migrate by downstream translation in a direction nearly perpendicular to the loop axis. Loops are cut off by straight or diagonal chutes across the meander neck. The sinuosity of the river has gradually decreased from a value of 1.56 in 1896 to 1.35 in 1974. The morphology and curvature of meander loops cut off before white settlers came to the area indicate that the river was more stable, as well as more sinuous , then than now; subsequent morphologic changes are attributed mainly to the clearing of riparian vegetation and the effects of levees in reducing the area of overflow. The bank-erosion is 1.82 acres per year per stream mile or about 15 feet per year per stream foot for the period 1896-1974. (Woodard-USGS)
