During 1967-71, 15,800 acres of flood-plain vegetation were cleared from a 26-mile reach of the Gila River valley and a 9-mile reach of the San Carlos River valley. Both areas are on the San Carlos Apache Indian Reservation, Arizona. The area cleared in the Gila River valley included the Gila River Phreatophyte Project and the clearing was conducted as prescribed by the experimental design of that research program. Establishment of replacement vegetation was attempted on the cleared areas with indifferent success.
The report outlines methods used to remove the vegetation and to discourage its subsequent regrowth. Costs of the clearing operation are given by vegetation type, and descriptions of the procedures used for establishing new vegetation are given.
Clearing and subsequent maintenance of parts of the flood plain were hampered by channel clogging and subsequent flooding of adjacent areas. Part of the area selected for clearing lies within the San Carlos Reservoir. The wide range of water level in the reservoir further aggravated maintenance of an inflow channel. Both draglines and a dredge were used to open a channel to the reservoir. Because the flow of the Gila River is intermittent, vegetation becomes established in the channel at the head of the reservoir during periods of no flow. The report concludes that the presence of the vegetation promotes silt deposition and further clogging. Inflow channel maintenance is a persistent problem that will require well-planned repetitive clearing of vegetation at the head of the reservoir.
